update version

This reverts commit 5bb52fbd8c.

.github/FUNDING.yml

@@ -0,0 +1 @@
+custom: https://yggverse.github.io/#donate

.github/workflows/build.yml

@@ -0,0 +1,31 @@
+name: Build
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+env:
+  CARGO_TERM_COLOR: always
+  RUSTFLAGS: -Dwarnings
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: Run rustfmt
+      run: cargo fmt --all -- --check
+    - name: Update packages index
+      run: sudo apt update
+    - name: Install system packages
+      run: sudo apt install -y libglib2.0-dev
+    - name: Run clippy
+      run: cargo clippy --all-targets
+    - name: Build
+      run: cargo build --verbose
+    - name: Run tests
+      run: cargo test --verbose

Cargo.toml

@@ -1,19 +1,20 @@
 [package]
 name = "ggemini"
-version = "0.1.1"
-edition = "2021"
+version = "0.20.1"
+edition = "2024"
 license = "MIT"
 readme = "README.md"
-description = "Glib-oriented client for Gemini protocol"
-keywords = ["gemini", "gemini-protocol", "gtk", "gio", "client"]
-categories = ["development-tools", "network-programming"]
+description = "Glib/Gio-oriented network API for Gemini protocol"
+keywords = ["gemini", "titan", "glib", "gio", "client"]
+categories = ["development-tools", "network-programming", "parsing"]
 repository = "https://github.com/YGGverse/ggemini"
 
 [dependencies.gio]
 package = "gio"
-version = "0.20.4"
+version = "0.21.0"
+features = ["v2_70"]
 
 [dependencies.glib]
 package = "glib"
-version = "0.20.4"
+version = "0.21.0"
 features = ["v2_66"]

README.md

@@ -1,7 +1,77 @@
 # ggemini
 
-Glib-oriented client for [Gemini protocol](https://geminiprotocol.net/)
+![Build](https://github.com/YGGverse/ggemini/actions/workflows/build.yml/badge.svg)
+[![Documentation](https://docs.rs/ggemini/badge.svg)](https://docs.rs/ggemini)
+[![crates.io](https://img.shields.io/crates/v/ggemini.svg)](https://crates.io/crates/ggemini)
+
+Glib/Gio-oriented network API for [Gemini protocol](https://geminiprotocol.net/)
 
 > [!IMPORTANT]
 > Project in development!
->
+>
+
+GGemini (or G-Gemini) library written as the client extension for [Yoda](https://github.com/YGGverse/Yoda), it also could be useful for other GTK-based applications dependent of [glib](https://crates.io/crates/glib) / [gio](https://crates.io/crates/gio) (`2.66+`) backend.
+
+## Requirements
+
+<details>
+<summary>Debian</summary>
+<pre>
+sudo apt install libglib2.0-dev</pre>
+</details>
+
+<details>
+<summary>Fedora</summary>
+<pre>
+sudo dnf install glib2-devel</pre>
+</details>
+
+## Install
+
+```
+cargo add ggemini
+```
+
+## Usage
+
+* [Documentation](https://docs.rs/ggemini/latest/ggemini/)
+
+### Example
+
+``` rust
+use gio::*;
+use glib::*;
+
+use ggemini::client::{
+    connection::{request::{Mode, Request}, Response},
+    Client,
+};
+
+fn main() -> ExitCode {
+    Client::new().request_async(
+        Request::Gemini { // or `Request::Titan`
+            uri: Uri::parse("gemini://geminiprotocol.net/", UriFlags::NONE).unwrap(),
+            mode: Mode::HeaderOnly // handle content separately (based on MIME)
+        },
+        Priority::DEFAULT,
+        Cancellable::new(),
+        None, // optional auth `GTlsCertificate`
+        None, // optional TOFU `GTlsCertificate` array
+        |result| match result {
+            Ok((response, _connection)) => match response {
+                Response::Success(success) => match success.mime().unwrap().as_str() {
+                    "text/gemini" => todo!(),
+                    _ => todo!(),
+                },
+                _ => todo!(),
+            },
+            Err(_) => todo!(),
+        },
+    );
+    ExitCode::SUCCESS
+}
+```
+
+## Other crates
+
+* [ggemtext](https://github.com/YGGverse/ggemtext) - Glib-oriented Gemtext API

src/client.rs

@@ -1,10 +1,115 @@
+//! High-level client API to interact with Gemini Socket Server:
+//! * https://geminiprotocol.net/docs/protocol-specification.gmi
+
 pub mod connection;
 pub mod error;
-pub mod response;
-pub mod socket;
 
+pub use connection::{Connection, Request, Response};
 pub use error::Error;
-pub use response::Response;
-pub use socket::Socket;
 
-// @TODO
+use gio::{Cancellable, SocketClient, SocketProtocol, TlsCertificate, prelude::SocketClientExt};
+use glib::Priority;
+
+// Defaults
+
+pub const DEFAULT_TIMEOUT: u32 = 30;
+pub const DEFAULT_SESSION_RESUMPTION: bool = false;
+
+/// Main point where connect external crate
+///
+/// Provides high-level API for session-safe interaction with
+/// [Gemini](https://geminiprotocol.net) socket server
+pub struct Client {
+    is_session_resumption: bool,
+    pub socket: SocketClient,
+}
+
+impl Default for Client {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Client {
+    // Constructors
+
+    /// Create new `Self`
+    pub fn new() -> Self {
+        // Init new socket
+        let socket = SocketClient::new();
+
+        // Setup initial configuration for Gemini Protocol
+        socket.set_protocol(SocketProtocol::Tcp);
+        socket.set_timeout(DEFAULT_TIMEOUT);
+
+        // Done
+        Self {
+            is_session_resumption: DEFAULT_SESSION_RESUMPTION,
+            socket,
+        }
+    }
+
+    // Actions
+
+    /// Make new async request to given [Uri](https://docs.gtk.org/glib/struct.Uri.html),
+    /// callback with new `Response`on success or `Error` on failure
+    /// * compatible with user (certificate) and guest (certificate-less) connection types
+    pub fn request_async(
+        &self,
+        request: Request,
+        priority: Priority,
+        cancellable: Cancellable,
+        client_certificate: Option<TlsCertificate>,
+        server_certificates: Option<Vec<TlsCertificate>>,
+        callback: impl FnOnce(Result<(Response, Connection), Error>) + 'static,
+    ) {
+        // Begin new connection
+        // * [NetworkAddress](https://docs.gtk.org/gio/class.NetworkAddress.html) required for valid
+        //   [SNI](https://geminiprotocol.net/docs/protocol-specification.gmi#server-name-indication)
+        match request.to_network_address(crate::DEFAULT_PORT) {
+            Ok(network_address) => {
+                self.socket
+                    .connect_async(&network_address.clone(), Some(&cancellable.clone()), {
+                        let is_session_resumption = self.is_session_resumption;
+                        move |result| match result {
+                            Ok(socket_connection) => {
+                                match Connection::build(
+                                    socket_connection.clone(),
+                                    network_address,
+                                    client_certificate,
+                                    server_certificates,
+                                    is_session_resumption,
+                                ) {
+                                    Ok(connection) => connection.clone().request_async(
+                                        request,
+                                        priority,
+                                        cancellable,
+                                        move |result| {
+                                            callback(match result {
+                                                Ok(response) => Ok(response),
+                                                Err(e) => Err(Error::Request(connection, e)),
+                                            })
+                                        },
+                                    ),
+                                    Err(e) => {
+                                        callback(Err(Error::Connection(socket_connection, e)))
+                                    }
+                                }
+                            }
+                            Err(e) => callback(Err(Error::Connect(network_address, e))),
+                        }
+                    })
+            }
+            Err(e) => callback(Err(Error::NetworkAddress(e))),
+        }
+    }
+
+    // Setters
+
+    /// Change glib-networking `session-resumption-enabled` property (`false` by default)
+    /// * [Gemini specification](https://geminiprotocol.net/docs/protocol-specification.gmi#client-certificates)
+    /// * [GnuTLS manual](https://www.gnutls.org/manual/html_node/Session-resumption.html)
+    pub fn set_session_resumption(&mut self, is_enabled: bool) {
+        self.is_session_resumption = is_enabled
+    }
+}

src/client/connection.rs

@@ -1,3 +1,172 @@
-pub mod input_stream;
+pub mod error;
+pub mod request;
+pub mod response;
 
-// @TODO
+pub use error::Error;
+pub use request::{Mode, Request};
+pub use response::Response;
+
+use gio::{
+    Cancellable, IOStream, NetworkAddress, SocketConnection, TlsCertificate, TlsClientConnection,
+    prelude::{IOStreamExt, OutputStreamExtManual, TlsCertificateExt, TlsConnectionExt},
+};
+use glib::{
+    Bytes, Priority,
+    object::{Cast, ObjectExt},
+};
+
+#[derive(Debug, Clone)]
+pub struct Connection {
+    pub network_address: NetworkAddress,
+    pub socket_connection: SocketConnection,
+    pub tls_client_connection: TlsClientConnection,
+}
+
+impl Connection {
+    // Constructors
+
+    /// Create new `Self`
+    pub fn build(
+        socket_connection: SocketConnection,
+        network_address: NetworkAddress,
+        client_certificate: Option<TlsCertificate>,
+        server_certificates: Option<Vec<TlsCertificate>>,
+        is_session_resumption: bool,
+    ) -> Result<Self, Error> {
+        Ok(Self {
+            tls_client_connection: match new_tls_client_connection(
+                &socket_connection,
+                Some(&network_address),
+                server_certificates,
+                is_session_resumption,
+            ) {
+                Ok(tls_client_connection) => {
+                    if let Some(ref c) = client_certificate {
+                        tls_client_connection.set_certificate(c);
+                    }
+                    tls_client_connection
+                }
+                Err(e) => return Err(e),
+            },
+            network_address,
+            socket_connection,
+        })
+    }
+
+    // Actions
+
+    /// Send new `Request` to `Self` connection using
+    /// [Gemini](https://geminiprotocol.net/docs/protocol-specification.gmi) or
+    /// [Titan](gemini://transjovian.org/titan/page/The%20Titan%20Specification) protocol
+    pub fn request_async(
+        self,
+        request: Request,
+        priority: Priority,
+        cancellable: Cancellable,
+        callback: impl FnOnce(Result<(Response, Self), Error>) + 'static,
+    ) {
+        let output_stream = self.stream().output_stream();
+        // Make sure **all header bytes** sent to the destination
+        // > A partial write is performed with the size of a message block, which is 16kB
+        // > https://docs.openssl.org/3.0/man3/SSL_write/#notes
+        output_stream.clone().write_all_async(
+            Bytes::from_owned(request.header()),
+            priority,
+            Some(&cancellable.clone()),
+            move |result| match result {
+                Ok(_) => match request {
+                    Request::Gemini { mode, .. } => match mode {
+                        Mode::HeaderOnly => Response::header_from_connection_async(
+                            self,
+                            priority,
+                            cancellable,
+                            |result, connection| {
+                                callback(match result {
+                                    Ok(response) => Ok((response, connection)),
+                                    Err(e) => Err(Error::Response(e)),
+                                })
+                            },
+                        ),
+                    },
+                    // Make sure **all data bytes** sent to the destination
+                    // > A partial write is performed with the size of a message block, which is 16kB
+                    // > https://docs.openssl.org/3.0/man3/SSL_write/#notes
+                    Request::Titan { data, mode, .. } => output_stream.write_all_async(
+                        data,
+                        priority,
+                        Some(&cancellable.clone()),
+                        move |result| match result {
+                            Ok(_) => match mode {
+                                Mode::HeaderOnly => Response::header_from_connection_async(
+                                    self,
+                                    priority,
+                                    cancellable,
+                                    |result, connection| {
+                                        callback(match result {
+                                            Ok(response) => Ok((response, connection)),
+                                            Err(e) => Err(Error::Response(e)),
+                                        })
+                                    },
+                                ),
+                            },
+                            Err((b, e)) => callback(Err(Error::Request(b, e))),
+                        },
+                    ),
+                },
+                Err((b, e)) => callback(Err(Error::Request(b, e))),
+            },
+        )
+    }
+
+    // Getters
+
+    /// Get [IOStream](https://docs.gtk.org/gio/class.IOStream.html)
+    /// * compatible with user (certificate) and guest (certificate-less) connection type
+    /// * useful to keep `Connection` reference active in async I/O context
+    pub fn stream(&self) -> IOStream {
+        self.tls_client_connection.clone().upcast::<IOStream>()
+        // * also `base_io_stream` method available @TODO
+    }
+}
+
+// Tools
+
+/// Setup new [TlsClientConnection](https://docs.gtk.org/gio/iface.TlsClientConnection.html)
+/// wrapper for [SocketConnection](https://docs.gtk.org/gio/class.SocketConnection.html)
+/// using `server_identity` as the [SNI](https://geminiprotocol.net/docs/protocol-specification.gmi#server-name-indication)
+fn new_tls_client_connection(
+    socket_connection: &SocketConnection,
+    server_identity: Option<&NetworkAddress>,
+    server_certificates: Option<Vec<TlsCertificate>>,
+    is_session_resumption: bool,
+) -> Result<TlsClientConnection, Error> {
+    match TlsClientConnection::new(socket_connection, server_identity) {
+        Ok(tls_client_connection) => {
+            // Prevent session resumption (certificate change ability in runtime)
+            tls_client_connection.set_property("session-resumption-enabled", is_session_resumption);
+
+            // Return `Err` on server connection mismatch following specification lines:
+            // > Gemini servers MUST use the TLS close_notify implementation to close the connection
+            // > A client SHOULD notify the user of such a case
+            // https://geminiprotocol.net/docs/protocol-specification.gmi#closing-connections
+            tls_client_connection.set_require_close_notify(true);
+
+            // [TOFU](https://geminiprotocol.net/docs/protocol-specification.gmi#tls-server-certificate-validation)
+            tls_client_connection.connect_accept_certificate(move |_, c, _| {
+                server_certificates
+                    .as_ref()
+                    .is_none_or(|server_certificates| {
+                        for server_certificate in server_certificates {
+                            if server_certificate.is_same(c) {
+                                return true;
+                            }
+                        }
+                        false
+                    })
+            });
+
+            Ok(tls_client_connection)
+        }
+        Err(e) => Err(Error::TlsClientConnection(e)),
+    }
+}

src/client/connection/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Request(glib::Bytes, glib::Error),
+    Response(crate::client::connection::response::Error),
+    TlsClientConnection(glib::Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Request(_, e) => {
+                write!(f, "Request error: {e}")
+            }
+            Self::Response(e) => {
+                write!(f, "Response error: {e}")
+            }
+            Self::TlsClientConnection(e) => {
+                write!(f, "TLS client connection error: {e}")
+            }
+        }
+    }
+}

src/client/connection/input_stream.rs

@@ -1,4 +0,0 @@
-pub mod byte_buffer;
-pub use byte_buffer::ByteBuffer;
-
-// @TODO

src/client/connection/input_stream/byte_buffer.rs

@@ -1,86 +0,0 @@
-pub mod error;
-
-pub use error::Error;
-
-use gio::{prelude::InputStreamExt, Cancellable, InputStream};
-use glib::{object::IsA, Bytes};
-
-pub const DEFAULT_CAPACITY: usize = 0x400;
-pub const DEFAULT_CHUNK_SIZE: usize = 0x100;
-pub const DEFAULT_MAX_SIZE: usize = 0xfffff;
-
-pub struct ByteBuffer {
-    bytes: Vec<Bytes>,
-}
-
-impl ByteBuffer {
-    /// Create dynamically allocated bytes buffer from `gio::InputStream`
-    ///
-    /// Options:
-    /// * `capacity` bytes request to reduce extra memory overwrites (1024 by default)
-    /// * `chunk_size` bytes limit to read per iter (256 by default)
-    /// * `max_size` bytes limit to prevent memory overflow (1M by default)
-    pub fn from_input_stream(
-        input_stream: &InputStream, // @TODO
-        cancellable: Option<&impl IsA<Cancellable>>,
-        capacity: Option<usize>,
-        chunk_size: Option<usize>,
-        max_size: Option<usize>,
-    ) -> Result<Self, Error> {
-        // Create buffer with initial capacity
-        let mut buffer: Vec<Bytes> = Vec::with_capacity(match capacity {
-            Some(value) => value,
-            None => DEFAULT_CAPACITY,
-        });
-
-        // Disallow unlimited buffer, use defaults on None
-        let limit = match max_size {
-            Some(value) => value,
-            None => DEFAULT_MAX_SIZE,
-        };
-
-        loop {
-            // Check buffer size to prevent memory overflow
-            if buffer.len() > limit {
-                return Err(Error::Overflow);
-            }
-
-            // Continue bytes reading
-            match input_stream.read_bytes(
-                match chunk_size {
-                    Some(value) => value,
-                    None => DEFAULT_CHUNK_SIZE,
-                },
-                cancellable,
-            ) {
-                Ok(bytes) => {
-                    // No bytes were read, end of stream
-                    if bytes.len() == 0 {
-                        break;
-                    }
-
-                    // Save chunk to buffer
-                    buffer.push(bytes);
-                }
-                Err(_) => return Err(Error::Stream),
-            };
-        }
-
-        // Done
-        Ok(Self { bytes: buffer })
-    }
-
-    /// Get link to bytes collected
-    pub fn bytes(&self) -> &Vec<Bytes> {
-        &self.bytes
-    }
-
-    /// Return a copy of the bytes in UTF-8
-    pub fn to_utf8(&self) -> Vec<u8> {
-        self.bytes
-            .iter()
-            .flat_map(|byte| byte.iter())
-            .cloned()
-            .collect()
-    }
-}

src/client/connection/input_stream/byte_buffer/error.rs

@@ -1,4 +0,0 @@
-pub enum Error {
-    Overflow,
-    Stream,
-}

src/client/connection/request.rs

@@ -0,0 +1,122 @@
+pub mod error;
+pub mod mode;
+
+pub use error::Error;
+pub use mode::Mode;
+
+// Local dependencies
+
+use gio::NetworkAddress;
+use glib::{Bytes, Uri, UriHideFlags};
+
+/// Single `Request` implementation for different protocols
+pub enum Request {
+    Gemini {
+        uri: Uri,
+        mode: Mode,
+    },
+    Titan {
+        uri: Uri,
+        data: Bytes,
+        /// MIME type is optional attribute by Titan protocol specification,
+        /// but server MAY reject the request without `mime` value provided.
+        mime: Option<String>,
+        token: Option<String>,
+        mode: Mode,
+    },
+}
+
+impl Request {
+    // Getters
+
+    /// Generate header string for `Self`
+    pub fn header(&self) -> String {
+        match self {
+            Self::Gemini { uri, .. } => format!("{uri}\r\n"),
+            Self::Titan {
+                uri,
+                data,
+                mime,
+                token,
+                ..
+            } => {
+                let mut header = format!(
+                    "{};size={}",
+                    uri.to_string_partial(UriHideFlags::QUERY),
+                    data.len()
+                );
+                if let Some(mime) = mime {
+                    header.push_str(&format!(";mime={mime}"));
+                }
+                if let Some(token) = token {
+                    header.push_str(&format!(";token={token}"));
+                }
+                if let Some(query) = uri.query() {
+                    header.push_str(&format!("?{query}"));
+                }
+                header.push_str("\r\n");
+                header
+            }
+        }
+    }
+
+    /// Get reference to `Self` [Uri](https://docs.gtk.org/glib/struct.Uri.html)
+    pub fn uri(&self) -> &Uri {
+        match self {
+            Self::Gemini { uri, .. } => uri,
+            Self::Titan { uri, .. } => uri,
+        }
+    }
+
+    /// Get [NetworkAddress](https://docs.gtk.org/gio/class.NetworkAddress.html) for `Self`
+    pub fn to_network_address(&self, default_port: u16) -> Result<NetworkAddress, Error> {
+        match crate::gio::network_address::from_uri(self.uri(), default_port) {
+            Ok(network_address) => Ok(network_address),
+            Err(e) => Err(Error::NetworkAddress(e)),
+        }
+    }
+}
+
+#[test]
+fn test_gemini_header() {
+    use glib::UriFlags;
+
+    const REQUEST: &str = "gemini://geminiprotocol.net/";
+
+    assert_eq!(
+        Request::Gemini {
+            uri: Uri::parse(REQUEST, UriFlags::NONE).unwrap(),
+            mode: Mode::HeaderOnly
+        }
+        .header(),
+        format!("{REQUEST}\r\n")
+    );
+}
+
+#[test]
+fn test_titan_header() {
+    use glib::UriFlags;
+
+    const DATA: &[u8] = &[1, 2, 3];
+    const MIME: &str = "plain/text";
+    const TOKEN: &str = "token";
+
+    assert_eq!(
+        Request::Titan {
+            uri: Uri::parse(
+                "titan://geminiprotocol.net/raw/path?key=value",
+                UriFlags::NONE
+            )
+            .unwrap(),
+            data: Bytes::from(DATA),
+            mime: Some(MIME.to_string()),
+            token: Some(TOKEN.to_string()),
+            mode: Mode::HeaderOnly
+        }
+        .header(),
+        format!(
+            "titan://geminiprotocol.net/raw/path;size={};mime={MIME};token={TOKEN}?key=value\r\n",
+            DATA.len(),
+        )
+    );
+}

src/client/connection/request/error.rs

@@ -0,0 +1,16 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    NetworkAddress(crate::gio::network_address::error::Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::NetworkAddress(e) => {
+                write!(f, "Network Address error: {e}")
+            }
+        }
+    }
+}

src/client/connection/request/mode.rs

@@ -0,0 +1,6 @@
+/// Request modes
+pub enum Mode {
+    /// Request header bytes only, process content bytes manually
+    /// * useful for manual content type handle: text, stream or large content loaded by chunks
+    HeaderOnly,
+}

src/client/connection/response.rs

@@ -0,0 +1,146 @@
+pub mod certificate;
+pub mod error;
+pub mod failure;
+pub mod input;
+pub mod redirect;
+pub mod success;
+
+pub use certificate::Certificate;
+pub use error::{Error, HeaderBytesError};
+pub use failure::Failure;
+pub use input::Input;
+pub use redirect::Redirect;
+pub use success::Success;
+
+use super::Connection;
+use gio::{Cancellable, IOStream};
+use glib::{Priority, object::IsA};
+
+const HEADER_LEN: usize = 1024;
+
+/// https://geminiprotocol.net/docs/protocol-specification.gmi#responses
+pub enum Response {
+    Input(Input),             // 1*
+    Success(Success),         // 2*
+    Redirect(Redirect),       // 3*
+    Failure(Failure),         // 4*,5*
+    Certificate(Certificate), // 6*
+}
+
+impl Response {
+    /// Asynchronously create new `Self` for given `Connection`
+    pub fn header_from_connection_async(
+        connection: Connection,
+        priority: Priority,
+        cancellable: Cancellable,
+        callback: impl FnOnce(Result<Self, Error>, Connection) + 'static,
+    ) {
+        header_from_stream_async(
+            Vec::with_capacity(HEADER_LEN),
+            connection.stream(),
+            cancellable,
+            priority,
+            |result| {
+                callback(
+                    match result {
+                        Ok(buffer) => match buffer.first() {
+                            Some(b) => match b {
+                                b'1' => match Input::from_utf8(&buffer) {
+                                    Ok(input) => Ok(Self::Input(input)),
+                                    Err(e) => Err(Error::Input(e)),
+                                },
+                                b'2' => match Success::from_utf8(&buffer) {
+                                    Ok(success) => Ok(Self::Success(success)),
+                                    Err(e) => Err(Error::Success(e)),
+                                },
+                                b'3' => match Redirect::from_utf8(&buffer) {
+                                    Ok(redirect) => Ok(Self::Redirect(redirect)),
+                                    Err(e) => Err(Error::Redirect(e)),
+                                },
+                                b'4' | b'5' => match Failure::from_utf8(&buffer) {
+                                    Ok(failure) => Ok(Self::Failure(failure)),
+                                    Err(e) => Err(Error::Failure(e)),
+                                },
+                                b'6' => match Certificate::from_utf8(&buffer) {
+                                    Ok(certificate) => Ok(Self::Certificate(certificate)),
+                                    Err(e) => Err(Error::Certificate(e)),
+                                },
+                                b => Err(Error::Code(*b)),
+                            },
+                            None => Err(Error::Protocol(buffer)),
+                        },
+                        Err(e) => Err(e),
+                    },
+                    connection,
+                )
+            },
+        )
+    }
+}
+
+// Tools
+
+/// Asynchronously read header bytes from [IOStream](https://docs.gtk.org/gio/class.IOStream.html)
+///
+/// Return UTF-8 buffer collected
+/// * requires `IOStream` reference to keep `Connection` active in async thread
+fn header_from_stream_async(
+    mut buffer: Vec<u8>,
+    stream: impl IsA<IOStream>,
+    cancellable: Cancellable,
+    priority: Priority,
+    callback: impl FnOnce(Result<Vec<u8>, Error>) + 'static,
+) {
+    use gio::prelude::{IOStreamExt, InputStreamExtManual};
+    stream.input_stream().read_async(
+        vec![0],
+        priority,
+        Some(&cancellable.clone()),
+        move |result| match result {
+            Ok((bytes, size)) => {
+                if size == 0 {
+                    return callback(Ok(buffer));
+                }
+                if buffer.len() + bytes.len() > HEADER_LEN {
+                    buffer.extend(bytes);
+                    return callback(Err(Error::Protocol(buffer)));
+                }
+                if bytes[0] == b'\r' {
+                    buffer.extend(bytes);
+                    return header_from_stream_async(
+                        buffer,
+                        stream,
+                        cancellable,
+                        priority,
+                        callback,
+                    );
+                }
+                if bytes[0] == b'\n' {
+                    buffer.extend(bytes);
+                    return callback(Ok(buffer));
+                }
+                buffer.extend(bytes);
+                header_from_stream_async(buffer, stream, cancellable, priority, callback)
+            }
+            Err((data, e)) => callback(Err(Error::Stream(e, data))),
+        },
+    )
+}
+
+/// Get header bytes slice
+/// * common for all child parsers
+fn header_bytes(buffer: &[u8]) -> Result<&[u8], HeaderBytesError> {
+    for (i, b) in buffer.iter().enumerate() {
+        if i > 1024 {
+            return Err(HeaderBytesError::Len);
+        }
+        if *b == b'\r' {
+            let n = i + 1;
+            if buffer.get(n).is_some_and(|b| *b == b'\n') {
+                return Ok(&buffer[..n + 1]);
+            }
+            break;
+        }
+    }
+    Err(HeaderBytesError::End)
+}

src/client/connection/response/certificate.rs

@@ -0,0 +1,111 @@
+pub mod error;
+pub mod not_authorized;
+pub mod not_valid;
+pub mod required;
+
+pub use error::Error;
+pub use not_authorized::NotAuthorized;
+pub use not_valid::NotValid;
+pub use required::Required;
+
+const CODE: u8 = b'6';
+
+/// 6* status code group
+/// https://geminiprotocol.net/docs/protocol-specification.gmi#client-certificates
+pub enum Certificate {
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-60
+    Required(Required),
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-61-certificate-not-authorized
+    NotAuthorized(NotAuthorized),
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-62-certificate-not-valid
+    NotValid(NotValid),
+}
+
+impl Certificate {
+    // Constructors
+
+    /// Create new `Self` from buffer include header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        match buffer.first() {
+            Some(b) => match *b {
+                CODE => match buffer.get(1) {
+                    Some(b) => match *b {
+                        b'0' => Ok(Self::Required(
+                            Required::from_utf8(buffer).map_err(Error::Required)?,
+                        )),
+                        b'1' => Ok(Self::NotAuthorized(
+                            NotAuthorized::from_utf8(buffer).map_err(Error::NotAuthorized)?,
+                        )),
+                        b'2' => Ok(Self::NotValid(
+                            NotValid::from_utf8(buffer).map_err(Error::NotValid)?,
+                        )),
+                        b => Err(Error::SecondByte(b)),
+                    },
+                    None => Err(Error::UndefinedSecondByte),
+                },
+                b => Err(Error::FirstByte(b)),
+            },
+            None => Err(Error::UndefinedFirstByte),
+        }
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty (not provided by server)
+    pub fn message(&self) -> Option<&str> {
+        match self {
+            Self::Required(required) => required.message(),
+            Self::NotAuthorized(not_authorized) => not_authorized.message(),
+            Self::NotValid(not_valid) => not_valid.message(),
+        }
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return children `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        match self {
+            Self::Required(required) => required.message_or_default(),
+            Self::NotAuthorized(not_authorized) => not_authorized.message_or_default(),
+            Self::NotValid(not_valid) => not_valid.message_or_default(),
+        }
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        match self {
+            Self::Required(required) => required.as_str(),
+            Self::NotAuthorized(not_authorized) => not_authorized.as_str(),
+            Self::NotValid(not_valid) => not_valid.as_str(),
+        }
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        match self {
+            Self::Required(required) => required.as_bytes(),
+            Self::NotAuthorized(not_authorized) => not_authorized.as_bytes(),
+            Self::NotValid(not_valid) => not_valid.as_bytes(),
+        }
+    }
+}
+
+#[test]
+fn test() {
+    fn t(source: &str, message: Option<&str>) {
+        let b = source.as_bytes();
+        let c = Certificate::from_utf8(b).unwrap();
+        assert_eq!(c.message(), message);
+        assert_eq!(c.as_str(), source);
+        assert_eq!(c.as_bytes(), b);
+    }
+    // 60
+    t("60 Required\r\n", Some("Required"));
+    t("60\r\n", None);
+    // 61
+    t("61 Not Authorized\r\n", Some("Not Authorized"));
+    t("61\r\n", None);
+    // 62
+    t("61 Not Valid\r\n", Some("Not Valid"));
+    t("61\r\n", None);
+}

src/client/connection/response/certificate/error.rs

@@ -0,0 +1,40 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    FirstByte(u8),
+    NotAuthorized(super::not_authorized::Error),
+    NotValid(super::not_valid::Error),
+    Required(super::required::Error),
+    SecondByte(u8),
+    UndefinedFirstByte,
+    UndefinedSecondByte,
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::FirstByte(b) => {
+                write!(f, "Unexpected first byte: {b}")
+            }
+            Self::NotAuthorized(e) => {
+                write!(f, "NotAuthorized status parse error: {e}")
+            }
+            Self::NotValid(e) => {
+                write!(f, "NotValid status parse error: {e}")
+            }
+            Self::Required(e) => {
+                write!(f, "Required status parse error: {e}")
+            }
+            Self::SecondByte(b) => {
+                write!(f, "Unexpected second byte: {b}")
+            }
+            Self::UndefinedFirstByte => {
+                write!(f, "Undefined first byte")
+            }
+            Self::UndefinedSecondByte => {
+                write!(f, "Undefined second byte")
+            }
+        }
+    }
+}

src/client/connection/response/certificate/not_authorized.rs

@@ -0,0 +1,79 @@
+pub mod error;
+pub use error::Error;
+
+/// [Not Authorized](https://geminiprotocol.net/docs/protocol-specification.gmi#status-61) status code
+pub const CODE: &[u8] = b"61";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "Certificate is not authorized";
+
+/// Hold header `String` for [Not Authorized](https://geminiprotocol.net/docs/protocol-specification.gmi#status-61) status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct NotAuthorized(String);
+
+impl NotAuthorized {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty (not provided by server)
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let na = NotAuthorized::from_utf8("61 Not Authorized\r\n".as_bytes()).unwrap();
+    assert_eq!(na.message(), Some("Not Authorized"));
+    assert_eq!(na.message_or_default(), "Not Authorized");
+    assert_eq!(na.as_str(), "61 Not Authorized\r\n");
+    assert_eq!(na.as_bytes(), "61 Not Authorized\r\n".as_bytes());
+
+    let na = NotAuthorized::from_utf8("61\r\n".as_bytes()).unwrap();
+    assert_eq!(na.message(), None);
+    assert_eq!(na.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(na.as_str(), "61\r\n");
+    assert_eq!(na.as_bytes(), "61\r\n".as_bytes());
+
+    // err
+    assert!(NotAuthorized::from_utf8("62 Fail\r\n".as_bytes()).is_err());
+    assert!(NotAuthorized::from_utf8("62 Fail\r\n".as_bytes()).is_err());
+    assert!(NotAuthorized::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(NotAuthorized::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/certificate/not_authorized/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/certificate/not_valid.rs

@@ -0,0 +1,79 @@
+pub mod error;
+pub use error::Error;
+
+/// [Not Valid](https://geminiprotocol.net/docs/protocol-specification.gmi#status-62) status code
+pub const CODE: &[u8] = b"62";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "Certificate is not valid";
+
+/// Hold header `String` for [Not Valid](https://geminiprotocol.net/docs/protocol-specification.gmi#status-62) status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct NotValid(String);
+
+impl NotValid {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty (not provided by server)
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let nv = NotValid::from_utf8("62 Not Valid\r\n".as_bytes()).unwrap();
+    assert_eq!(nv.message(), Some("Not Valid"));
+    assert_eq!(nv.message_or_default(), "Not Valid");
+    assert_eq!(nv.as_str(), "62 Not Valid\r\n");
+    assert_eq!(nv.as_bytes(), "62 Not Valid\r\n".as_bytes());
+
+    let nv = NotValid::from_utf8("62\r\n".as_bytes()).unwrap();
+    assert_eq!(nv.message(), None);
+    assert_eq!(nv.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(nv.as_str(), "62\r\n");
+    assert_eq!(nv.as_bytes(), "62\r\n".as_bytes());
+
+    // err
+    // @TODO assert!(NotValid::from_utf8("62Fail\r\n".as_bytes()).is_err());
+    assert!(NotValid::from_utf8("63 Fail\r\n".as_bytes()).is_err());
+    assert!(NotValid::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(NotValid::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/certificate/not_valid/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/certificate/required.rs

@@ -0,0 +1,79 @@
+pub mod error;
+pub use error::Error;
+
+/// [Certificate Required](https://geminiprotocol.net/docs/protocol-specification.gmi#status-60) status code
+pub const CODE: &[u8] = b"60";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "Certificate required";
+
+/// Hold header `String` for [Certificate Required](https://geminiprotocol.net/docs/protocol-specification.gmi#status-60) status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct Required(String);
+
+impl Required {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty (not provided by server)
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let r = Required::from_utf8("60 Required\r\n".as_bytes()).unwrap();
+    assert_eq!(r.message(), Some("Required"));
+    assert_eq!(r.message_or_default(), "Required");
+    assert_eq!(r.as_str(), "60 Required\r\n");
+    assert_eq!(r.as_bytes(), "60 Required\r\n".as_bytes());
+
+    let r = Required::from_utf8("60\r\n".as_bytes()).unwrap();
+    assert_eq!(r.message(), None);
+    assert_eq!(r.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(r.as_str(), "60\r\n");
+    assert_eq!(r.as_bytes(), "60\r\n".as_bytes());
+
+    // err
+    assert!(Required::from_utf8("62 Fail\r\n".as_bytes()).is_err());
+    assert!(Required::from_utf8("62 Fail\r\n".as_bytes()).is_err());
+    assert!(Required::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(Required::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/certificate/required/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/error.rs

@@ -0,0 +1,70 @@
+use std::{
+    fmt::{Display, Formatter, Result},
+    str::Utf8Error,
+};
+
+#[derive(Debug)]
+pub enum Error {
+    Certificate(super::certificate::Error),
+    Code(u8),
+    Failure(super::failure::Error),
+    Input(super::input::Error),
+    Protocol(Vec<u8>),
+    Redirect(super::redirect::Error),
+    Stream(glib::Error, Vec<u8>),
+    Success(super::success::Error),
+    Utf8Error(Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Certificate(e) => {
+                write!(f, "Certificate error: {e}")
+            }
+            Self::Code(b) => {
+                write!(f, "Unexpected status code byte: {b}")
+            }
+            Self::Failure(e) => {
+                write!(f, "Failure error: {e}")
+            }
+            Self::Input(e) => {
+                write!(f, "Input error: {e}")
+            }
+            Self::Protocol(..) => {
+                write!(f, "Protocol error")
+            }
+            Self::Redirect(e) => {
+                write!(f, "Redirect error: {e}")
+            }
+            Self::Stream(e, ..) => {
+                write!(f, "I/O stream error: {e}")
+            }
+            Self::Success(e) => {
+                write!(f, "Success error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}
+
+#[derive(Debug)]
+pub enum HeaderBytesError {
+    Len,
+    End,
+}
+
+impl Display for HeaderBytesError {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Len => {
+                write!(f, "Unexpected header length")
+            }
+            Self::End => {
+                write!(f, "Unexpected header end")
+            }
+        }
+    }
+}

src/client/connection/response/failure.rs

@@ -0,0 +1,89 @@
+pub mod error;
+pub mod permanent;
+pub mod temporary;
+
+pub use error::Error;
+pub use permanent::Permanent;
+pub use temporary::Temporary;
+
+pub enum Failure {
+    /// 4* status code group
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#temporary-failure
+    Temporary(Temporary),
+    /// 5* status code group
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#permanent-failure
+    Permanent(Permanent),
+}
+
+impl Failure {
+    // Constructors
+
+    /// Create new `Self` from buffer include header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        match buffer.first() {
+            Some(b) => match b {
+                b'4' => match Temporary::from_utf8(buffer) {
+                    Ok(input) => Ok(Self::Temporary(input)),
+                    Err(e) => Err(Error::Temporary(e)),
+                },
+                b'5' => match Permanent::from_utf8(buffer) {
+                    Ok(failure) => Ok(Self::Permanent(failure)),
+                    Err(e) => Err(Error::Permanent(e)),
+                },
+                b => Err(Error::Code(*b)),
+            },
+            None => Err(Error::Protocol),
+        }
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty
+    pub fn message(&self) -> Option<&str> {
+        match self {
+            Self::Permanent(permanent) => permanent.message(),
+            Self::Temporary(temporary) => temporary.message(),
+        }
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return children `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        match self {
+            Self::Permanent(permanent) => permanent.message_or_default(),
+            Self::Temporary(temporary) => temporary.message_or_default(),
+        }
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        match self {
+            Self::Permanent(permanent) => permanent.as_str(),
+            Self::Temporary(temporary) => temporary.as_str(),
+        }
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        match self {
+            Self::Permanent(permanent) => permanent.as_bytes(),
+            Self::Temporary(temporary) => temporary.as_bytes(),
+        }
+    }
+}
+
+#[test]
+fn test() {
+    fn t(source: String, message: Option<&str>) {
+        let b = source.as_bytes();
+        let i = Failure::from_utf8(b).unwrap();
+        assert_eq!(i.message(), message);
+        assert_eq!(i.as_str(), source);
+        assert_eq!(i.as_bytes(), b);
+    }
+    for code in [40, 41, 42, 43, 44, 50, 51, 52, 53, 59] {
+        t(format!("{code} Message\r\n"), Some("Message"));
+        t(format!("{code}\r\n"), None);
+    }
+}

src/client/connection/response/failure/error.rs

@@ -0,0 +1,28 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code(u8),
+    Permanent(super::permanent::Error),
+    Protocol,
+    Temporary(super::temporary::Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code(b) => {
+                write!(f, "Unexpected status code byte: {b}")
+            }
+            Self::Permanent(e) => {
+                write!(f, "Permanent failure group error: {e}")
+            }
+            Self::Protocol => {
+                write!(f, "Protocol error")
+            }
+            Self::Temporary(e) => {
+                write!(f, "Temporary failure group error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/failure/permanent.rs

@@ -0,0 +1,126 @@
+pub mod bad_request;
+pub mod default;
+pub mod error;
+pub mod gone;
+pub mod not_found;
+pub mod proxy_request_refused;
+
+pub use bad_request::BadRequest;
+pub use default::Default;
+pub use error::Error;
+pub use gone::Gone;
+pub use not_found::NotFound;
+pub use proxy_request_refused::ProxyRequestRefused;
+
+const CODE: u8 = b'5';
+
+/// https://geminiprotocol.net/docs/protocol-specification.gmi#permanent-failure
+pub enum Permanent {
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-50
+    Default(Default),
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-51-not-found
+    NotFound(NotFound),
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-52-gone
+    Gone(Gone),
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-53-proxy-request-refused
+    ProxyRequestRefused(ProxyRequestRefused),
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-59-bad-request
+    BadRequest(BadRequest),
+}
+
+impl Permanent {
+    // Constructors
+
+    /// Create new `Self` from buffer include header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        match buffer.first() {
+            Some(b) => match *b {
+                CODE => match buffer.get(1) {
+                    Some(b) => match *b {
+                        b'0' => Ok(Self::Default(
+                            Default::from_utf8(buffer).map_err(Error::Default)?,
+                        )),
+                        b'1' => Ok(Self::NotFound(
+                            NotFound::from_utf8(buffer).map_err(Error::NotFound)?,
+                        )),
+                        b'2' => Ok(Self::Gone(Gone::from_utf8(buffer).map_err(Error::Gone)?)),
+                        b'3' => Ok(Self::ProxyRequestRefused(
+                            ProxyRequestRefused::from_utf8(buffer)
+                                .map_err(Error::ProxyRequestRefused)?,
+                        )),
+                        b'9' => Ok(Self::BadRequest(
+                            BadRequest::from_utf8(buffer).map_err(Error::BadRequest)?,
+                        )),
+                        b => Err(Error::SecondByte(b)),
+                    },
+                    None => Err(Error::UndefinedSecondByte),
+                },
+                b => Err(Error::FirstByte(b)),
+            },
+            None => Err(Error::UndefinedFirstByte),
+        }
+    }
+
+    // Getters
+
+    pub fn message(&self) -> Option<&str> {
+        match self {
+            Self::Default(default) => default.message(),
+            Self::NotFound(not_found) => not_found.message(),
+            Self::Gone(gone) => gone.message(),
+            Self::ProxyRequestRefused(proxy_request_refused) => proxy_request_refused.message(),
+            Self::BadRequest(bad_request) => bad_request.message(),
+        }
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return children `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        match self {
+            Self::Default(default) => default.message_or_default(),
+            Self::NotFound(not_found) => not_found.message_or_default(),
+            Self::Gone(gone) => gone.message_or_default(),
+            Self::ProxyRequestRefused(proxy_request_refused) => {
+                proxy_request_refused.message_or_default()
+            }
+            Self::BadRequest(bad_request) => bad_request.message_or_default(),
+        }
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        match self {
+            Self::Default(default) => default.as_str(),
+            Self::NotFound(not_found) => not_found.as_str(),
+            Self::Gone(gone) => gone.as_str(),
+            Self::ProxyRequestRefused(proxy_request_refused) => proxy_request_refused.as_str(),
+            Self::BadRequest(bad_request) => bad_request.as_str(),
+        }
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        match self {
+            Self::Default(default) => default.as_bytes(),
+            Self::NotFound(not_found) => not_found.as_bytes(),
+            Self::Gone(gone) => gone.as_bytes(),
+            Self::ProxyRequestRefused(proxy_request_refused) => proxy_request_refused.as_bytes(),
+            Self::BadRequest(bad_request) => bad_request.as_bytes(),
+        }
+    }
+}
+
+#[test]
+fn test() {
+    fn t(source: String, message: Option<&str>) {
+        let b = source.as_bytes();
+        let i = Permanent::from_utf8(b).unwrap();
+        assert_eq!(i.message(), message);
+        assert_eq!(i.as_str(), source);
+        assert_eq!(i.as_bytes(), b);
+    }
+    for code in [50, 51, 52, 53, 59] {
+        t(format!("{code} Message\r\n"), Some("Message"));
+        t(format!("{code}\r\n"), None);
+    }
+}

src/client/connection/response/failure/permanent/bad_request.rs

@@ -0,0 +1,78 @@
+pub mod error;
+pub use error::Error;
+
+/// [Bad Request](https://geminiprotocol.net/docs/protocol-specification.gmi#status-59-bad-request) error status code
+pub const CODE: &[u8] = b"59";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "Bad request";
+
+/// Hold header `String` for [Bad Request](https://geminiprotocol.net/docs/protocol-specification.gmi#status-59-bad-request) error status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct BadRequest(String);
+
+impl BadRequest {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let br = BadRequest::from_utf8("59 Message\r\n".as_bytes()).unwrap();
+    assert_eq!(br.message(), Some("Message"));
+    assert_eq!(br.message_or_default(), "Message");
+    assert_eq!(br.as_str(), "59 Message\r\n");
+    assert_eq!(br.as_bytes(), "59 Message\r\n".as_bytes());
+
+    let br = BadRequest::from_utf8("59\r\n".as_bytes()).unwrap();
+    assert_eq!(br.message(), None);
+    assert_eq!(br.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(br.as_str(), "59\r\n");
+    assert_eq!(br.as_bytes(), "59\r\n".as_bytes());
+
+    // err
+    assert!(BadRequest::from_utf8("13 Fail\r\n".as_bytes()).is_err());
+    assert!(BadRequest::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(BadRequest::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/failure/permanent/bad_request/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/failure/permanent/default.rs

@@ -0,0 +1,78 @@
+pub mod error;
+pub use error::Error;
+
+/// [Unspecified Permanent Error](https://geminiprotocol.net/docs/protocol-specification.gmi#status-50) status code
+pub const CODE: &[u8] = b"50";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "Permanent error";
+
+/// Hold header `String` for [Unspecified Permanent Error](https://geminiprotocol.net/docs/protocol-specification.gmi#status-50) status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct Default(String);
+
+impl Default {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let d = Default::from_utf8("50 Message\r\n".as_bytes()).unwrap();
+    assert_eq!(d.message(), Some("Message"));
+    assert_eq!(d.message_or_default(), "Message");
+    assert_eq!(d.as_str(), "50 Message\r\n");
+    assert_eq!(d.as_bytes(), "50 Message\r\n".as_bytes());
+
+    let d = Default::from_utf8("50\r\n".as_bytes()).unwrap();
+    assert_eq!(d.message(), None);
+    assert_eq!(d.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(d.as_str(), "50\r\n");
+    assert_eq!(d.as_bytes(), "50\r\n".as_bytes());
+
+    // err
+    assert!(Default::from_utf8("13 Fail\r\n".as_bytes()).is_err());
+    assert!(Default::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(Default::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/failure/permanent/default/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/failure/permanent/error.rs

@@ -0,0 +1,48 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    BadRequest(super::bad_request::Error),
+    Default(super::default::Error),
+    FirstByte(u8),
+    Gone(super::gone::Error),
+    NotFound(super::not_found::Error),
+    ProxyRequestRefused(super::proxy_request_refused::Error),
+    SecondByte(u8),
+    UndefinedFirstByte,
+    UndefinedSecondByte,
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::BadRequest(e) => {
+                write!(f, "BadRequest parse error: {e}")
+            }
+            Self::Default(e) => {
+                write!(f, "Default parse error: {e}")
+            }
+            Self::FirstByte(b) => {
+                write!(f, "Unexpected first byte: {b}")
+            }
+            Self::Gone(e) => {
+                write!(f, "Gone parse error: {e}")
+            }
+            Self::NotFound(e) => {
+                write!(f, "NotFound parse error: {e}")
+            }
+            Self::ProxyRequestRefused(e) => {
+                write!(f, "ProxyRequestRefused parse error: {e}")
+            }
+            Self::SecondByte(b) => {
+                write!(f, "Unexpected second byte: {b}")
+            }
+            Self::UndefinedFirstByte => {
+                write!(f, "Undefined first byte")
+            }
+            Self::UndefinedSecondByte => {
+                write!(f, "Undefined second byte")
+            }
+        }
+    }
+}

src/client/connection/response/failure/permanent/gone.rs

@@ -0,0 +1,78 @@
+pub mod error;
+pub use error::Error;
+
+/// [Server Gone Error](https://geminiprotocol.net/docs/protocol-specification.gmi#status-52-gone) status code
+pub const CODE: &[u8] = b"52";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "Resource gone";
+
+/// Hold header `String` for [Server Gone Error](https://geminiprotocol.net/docs/protocol-specification.gmi#status-52-gone) status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct Gone(String);
+
+impl Gone {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let g = Gone::from_utf8("52 Message\r\n".as_bytes()).unwrap();
+    assert_eq!(g.message(), Some("Message"));
+    assert_eq!(g.message_or_default(), "Message");
+    assert_eq!(g.as_str(), "52 Message\r\n");
+    assert_eq!(g.as_bytes(), "52 Message\r\n".as_bytes());
+
+    let g = Gone::from_utf8("52\r\n".as_bytes()).unwrap();
+    assert_eq!(g.message(), None);
+    assert_eq!(g.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(g.as_str(), "52\r\n");
+    assert_eq!(g.as_bytes(), "52\r\n".as_bytes());
+
+    // err
+    assert!(Gone::from_utf8("13 Fail\r\n".as_bytes()).is_err());
+    assert!(Gone::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(Gone::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/failure/permanent/gone/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/failure/permanent/not_found.rs

@@ -0,0 +1,78 @@
+pub mod error;
+pub use error::Error;
+
+/// [Not Found Permanent Error](https://geminiprotocol.net/docs/protocol-specification.gmi#status-51-not-found) status code
+pub const CODE: &[u8] = b"51";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "Not Found";
+
+/// Hold header `String` for [Not Found Permanent Error](https://geminiprotocol.net/docs/protocol-specification.gmi#status-51-not-found) status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct NotFound(String);
+
+impl NotFound {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let nf = NotFound::from_utf8("51 Message\r\n".as_bytes()).unwrap();
+    assert_eq!(nf.message(), Some("Message"));
+    assert_eq!(nf.message_or_default(), "Message");
+    assert_eq!(nf.as_str(), "51 Message\r\n");
+    assert_eq!(nf.as_bytes(), "51 Message\r\n".as_bytes());
+
+    let nf = NotFound::from_utf8("51\r\n".as_bytes()).unwrap();
+    assert_eq!(nf.message(), None);
+    assert_eq!(nf.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(nf.as_str(), "51\r\n");
+    assert_eq!(nf.as_bytes(), "51\r\n".as_bytes());
+
+    // err
+    assert!(NotFound::from_utf8("13 Fail\r\n".as_bytes()).is_err());
+    assert!(NotFound::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(NotFound::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/failure/permanent/not_found/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/failure/permanent/proxy_request_refused.rs

@@ -0,0 +1,78 @@
+pub mod error;
+pub use error::Error;
+
+/// [Proxy Request Refused](https://geminiprotocol.net/docs/protocol-specification.gmi#status-53-proxy-request-refused) permanent error status code
+pub const CODE: &[u8] = b"53";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "Proxy request refused";
+
+/// Hold header `String` for [Proxy Request Refused](https://geminiprotocol.net/docs/protocol-specification.gmi#status-53-proxy-request-refused) permanent error status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct ProxyRequestRefused(String);
+
+impl ProxyRequestRefused {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let prf = ProxyRequestRefused::from_utf8("53 Message\r\n".as_bytes()).unwrap();
+    assert_eq!(prf.message(), Some("Message"));
+    assert_eq!(prf.message_or_default(), "Message");
+    assert_eq!(prf.as_str(), "53 Message\r\n");
+    assert_eq!(prf.as_bytes(), "53 Message\r\n".as_bytes());
+
+    let prf = ProxyRequestRefused::from_utf8("53\r\n".as_bytes()).unwrap();
+    assert_eq!(prf.message(), None);
+    assert_eq!(prf.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(prf.as_str(), "53\r\n");
+    assert_eq!(prf.as_bytes(), "53\r\n".as_bytes());
+
+    // err
+    assert!(ProxyRequestRefused::from_utf8("13 Fail\r\n".as_bytes()).is_err());
+    assert!(ProxyRequestRefused::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(ProxyRequestRefused::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/failure/permanent/proxy_request_refused/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/failure/temporary.rs

@@ -0,0 +1,126 @@
+pub mod cgi_error;
+pub mod default;
+pub mod error;
+pub mod proxy_error;
+pub mod server_unavailable;
+pub mod slow_down;
+
+pub use cgi_error::CgiError;
+pub use default::Default;
+pub use error::Error;
+pub use proxy_error::ProxyError;
+pub use server_unavailable::ServerUnavailable;
+pub use slow_down::SlowDown;
+
+const CODE: u8 = b'4';
+
+/// https://geminiprotocol.net/docs/protocol-specification.gmi#temporary-failure
+pub enum Temporary {
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-40
+    Default(Default),
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-41-server-unavailable
+    ServerUnavailable(ServerUnavailable),
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-42-cgi-error
+    CgiError(CgiError),
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-43-proxy-error
+    ProxyError(ProxyError),
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-44-slow-down
+    SlowDown(SlowDown),
+}
+
+impl Temporary {
+    // Constructors
+
+    /// Create new `Self` from buffer include header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        match buffer.first() {
+            Some(b) => match *b {
+                CODE => match buffer.get(1) {
+                    Some(b) => match *b {
+                        b'0' => Ok(Self::Default(
+                            Default::from_utf8(buffer).map_err(Error::Default)?,
+                        )),
+                        b'1' => Ok(Self::ServerUnavailable(
+                            ServerUnavailable::from_utf8(buffer)
+                                .map_err(Error::ServerUnavailable)?,
+                        )),
+                        b'2' => Ok(Self::CgiError(
+                            CgiError::from_utf8(buffer).map_err(Error::CgiError)?,
+                        )),
+                        b'3' => Ok(Self::ProxyError(
+                            ProxyError::from_utf8(buffer).map_err(Error::ProxyError)?,
+                        )),
+                        b'4' => Ok(Self::SlowDown(
+                            SlowDown::from_utf8(buffer).map_err(Error::SlowDown)?,
+                        )),
+                        b => Err(Error::SecondByte(b)),
+                    },
+                    None => Err(Error::UndefinedSecondByte),
+                },
+                b => Err(Error::FirstByte(b)),
+            },
+            None => Err(Error::UndefinedFirstByte),
+        }
+    }
+
+    // Getters
+
+    pub fn message(&self) -> Option<&str> {
+        match self {
+            Self::Default(default) => default.message(),
+            Self::ServerUnavailable(server_unavailable) => server_unavailable.message(),
+            Self::CgiError(cgi_error) => cgi_error.message(),
+            Self::ProxyError(proxy_error) => proxy_error.message(),
+            Self::SlowDown(slow_down) => slow_down.message(),
+        }
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return children `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        match self {
+            Self::Default(default) => default.message_or_default(),
+            Self::ServerUnavailable(server_unavailable) => server_unavailable.message_or_default(),
+            Self::CgiError(cgi_error) => cgi_error.message_or_default(),
+            Self::ProxyError(proxy_error) => proxy_error.message_or_default(),
+            Self::SlowDown(slow_down) => slow_down.message_or_default(),
+        }
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        match self {
+            Self::Default(default) => default.as_str(),
+            Self::ServerUnavailable(server_unavailable) => server_unavailable.as_str(),
+            Self::CgiError(cgi_error) => cgi_error.as_str(),
+            Self::ProxyError(proxy_error) => proxy_error.as_str(),
+            Self::SlowDown(slow_down) => slow_down.as_str(),
+        }
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        match self {
+            Self::Default(default) => default.as_bytes(),
+            Self::ServerUnavailable(server_unavailable) => server_unavailable.as_bytes(),
+            Self::CgiError(cgi_error) => cgi_error.as_bytes(),
+            Self::ProxyError(proxy_error) => proxy_error.as_bytes(),
+            Self::SlowDown(slow_down) => slow_down.as_bytes(),
+        }
+    }
+}
+
+#[test]
+fn test() {
+    fn t(source: String, message: Option<&str>) {
+        let b = source.as_bytes();
+        let i = Temporary::from_utf8(b).unwrap();
+        assert_eq!(i.message(), message);
+        assert_eq!(i.as_str(), source);
+        assert_eq!(i.as_bytes(), b);
+    }
+    for code in [40, 41, 42, 43, 44] {
+        t(format!("{code} Message\r\n"), Some("Message"));
+        t(format!("{code}\r\n"), None);
+    }
+}

src/client/connection/response/failure/temporary/cgi_error.rs

@@ -0,0 +1,78 @@
+pub mod error;
+pub use error::Error;
+
+/// [CGI Error](https://geminiprotocol.net/docs/protocol-specification.gmi#status-42-cgi-error) status code
+pub const CODE: &[u8] = b"42";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "CGI Error";
+
+/// Hold header `String` for [CGI Error](https://geminiprotocol.net/docs/protocol-specification.gmi#status-42-cgi-error) status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct CgiError(String);
+
+impl CgiError {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let ce = CgiError::from_utf8("42 Message\r\n".as_bytes()).unwrap();
+    assert_eq!(ce.message(), Some("Message"));
+    assert_eq!(ce.message_or_default(), "Message");
+    assert_eq!(ce.as_str(), "42 Message\r\n");
+    assert_eq!(ce.as_bytes(), "42 Message\r\n".as_bytes());
+
+    let ce = CgiError::from_utf8("42\r\n".as_bytes()).unwrap();
+    assert_eq!(ce.message(), None);
+    assert_eq!(ce.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(ce.as_str(), "42\r\n");
+    assert_eq!(ce.as_bytes(), "42\r\n".as_bytes());
+
+    // err
+    assert!(CgiError::from_utf8("13 Fail\r\n".as_bytes()).is_err());
+    assert!(CgiError::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(CgiError::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/failure/temporary/cgi_error/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/failure/temporary/default.rs

@@ -0,0 +1,78 @@
+pub mod error;
+pub use error::Error;
+
+/// [Unspecified Temporary Error](https://geminiprotocol.net/docs/protocol-specification.gmi#status-40) status code
+pub const CODE: &[u8] = b"40";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "Temporary error";
+
+/// Hold header `String` for [Unspecified Temporary Error](https://geminiprotocol.net/docs/protocol-specification.gmi#status-40) status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct Default(String);
+
+impl Default {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let d = Default::from_utf8("40 Message\r\n".as_bytes()).unwrap();
+    assert_eq!(d.message(), Some("Message"));
+    assert_eq!(d.message_or_default(), "Message");
+    assert_eq!(d.as_str(), "40 Message\r\n");
+    assert_eq!(d.as_bytes(), "40 Message\r\n".as_bytes());
+
+    let d = Default::from_utf8("40\r\n".as_bytes()).unwrap();
+    assert_eq!(d.message(), None);
+    assert_eq!(d.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(d.as_str(), "40\r\n");
+    assert_eq!(d.as_bytes(), "40\r\n".as_bytes());
+
+    // err
+    assert!(Default::from_utf8("13 Fail\r\n".as_bytes()).is_err());
+    assert!(Default::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(Default::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/failure/temporary/default/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/failure/temporary/error.rs

@@ -0,0 +1,48 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    CgiError(super::cgi_error::Error),
+    Default(super::default::Error),
+    FirstByte(u8),
+    ProxyError(super::proxy_error::Error),
+    SecondByte(u8),
+    ServerUnavailable(super::server_unavailable::Error),
+    SlowDown(super::slow_down::Error),
+    UndefinedFirstByte,
+    UndefinedSecondByte,
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::CgiError(e) => {
+                write!(f, "CgiError parse error: {e}")
+            }
+            Self::Default(e) => {
+                write!(f, "Default parse error: {e}")
+            }
+            Self::FirstByte(b) => {
+                write!(f, "Unexpected first byte: {b}")
+            }
+            Self::ProxyError(e) => {
+                write!(f, "ProxyError parse error: {e}")
+            }
+            Self::SecondByte(b) => {
+                write!(f, "Unexpected second byte: {b}")
+            }
+            Self::ServerUnavailable(e) => {
+                write!(f, "ServerUnavailable parse error: {e}")
+            }
+            Self::SlowDown(e) => {
+                write!(f, "SlowDown parse error: {e}")
+            }
+            Self::UndefinedFirstByte => {
+                write!(f, "Undefined first byte")
+            }
+            Self::UndefinedSecondByte => {
+                write!(f, "Undefined second byte")
+            }
+        }
+    }
+}

src/client/connection/response/failure/temporary/proxy_error.rs

@@ -0,0 +1,78 @@
+pub mod error;
+pub use error::Error;
+
+/// [Proxy Error](https://geminiprotocol.net/docs/protocol-specification.gmi#status-43-proxy-error) status code
+pub const CODE: &[u8] = b"43";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "Proxy error";
+
+/// Hold header `String` for [Proxy Error](https://geminiprotocol.net/docs/protocol-specification.gmi#status-43-proxy-error) status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct ProxyError(String);
+
+impl ProxyError {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let pe = ProxyError::from_utf8("43 Message\r\n".as_bytes()).unwrap();
+    assert_eq!(pe.message(), Some("Message"));
+    assert_eq!(pe.message_or_default(), "Message");
+    assert_eq!(pe.as_str(), "43 Message\r\n");
+    assert_eq!(pe.as_bytes(), "43 Message\r\n".as_bytes());
+
+    let pe = ProxyError::from_utf8("43\r\n".as_bytes()).unwrap();
+    assert_eq!(pe.message(), None);
+    assert_eq!(pe.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(pe.as_str(), "43\r\n");
+    assert_eq!(pe.as_bytes(), "43\r\n".as_bytes());
+
+    // err
+    assert!(ProxyError::from_utf8("13 Fail\r\n".as_bytes()).is_err());
+    assert!(ProxyError::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(ProxyError::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/failure/temporary/proxy_error/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/failure/temporary/server_unavailable.rs

@@ -0,0 +1,81 @@
+pub mod error;
+pub use error::Error;
+
+/// [Server Unavailable](https://geminiprotocol.net/docs/protocol-specification.gmi#status-41-server-unavailable)
+/// temporary error status code
+pub const CODE: &[u8] = b"41";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "Server unavailable";
+
+/// Hold header `String` for [Server Unavailable](https://geminiprotocol.net/docs/protocol-specification.gmi#status-41-server-unavailable)
+/// temporary error status code
+///
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct ServerUnavailable(String);
+
+impl ServerUnavailable {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let su = ServerUnavailable::from_utf8("41 Message\r\n".as_bytes()).unwrap();
+    assert_eq!(su.message(), Some("Message"));
+    assert_eq!(su.message_or_default(), "Message");
+    assert_eq!(su.as_str(), "41 Message\r\n");
+    assert_eq!(su.as_bytes(), "41 Message\r\n".as_bytes());
+
+    let su = ServerUnavailable::from_utf8("41\r\n".as_bytes()).unwrap();
+    assert_eq!(su.message(), None);
+    assert_eq!(su.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(su.as_str(), "41\r\n");
+    assert_eq!(su.as_bytes(), "41\r\n".as_bytes());
+
+    // err
+    assert!(ServerUnavailable::from_utf8("13 Fail\r\n".as_bytes()).is_err());
+    assert!(ServerUnavailable::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(ServerUnavailable::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/failure/temporary/server_unavailable/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/failure/temporary/slow_down.rs

@@ -0,0 +1,81 @@
+pub mod error;
+pub use error::Error;
+
+/// [Slow Down](https://geminiprotocol.net/docs/protocol-specification.gmi#status-44-slow-down)
+/// temporary error status code
+pub const CODE: &[u8] = b"44";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "Slow down";
+
+/// Hold header `String` for [Unspecified Temporary Error](https://geminiprotocol.net/docs/protocol-specification.gmi#status-44-slow-down)
+/// temporary error status code
+///
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct SlowDown(String);
+
+impl SlowDown {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let sd = SlowDown::from_utf8("44 Message\r\n".as_bytes()).unwrap();
+    assert_eq!(sd.message(), Some("Message"));
+    assert_eq!(sd.message_or_default(), "Message");
+    assert_eq!(sd.as_str(), "44 Message\r\n");
+    assert_eq!(sd.as_bytes(), "44 Message\r\n".as_bytes());
+
+    let sd = SlowDown::from_utf8("44\r\n".as_bytes()).unwrap();
+    assert_eq!(sd.message(), None);
+    assert_eq!(sd.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(sd.as_str(), "44\r\n");
+    assert_eq!(sd.as_bytes(), "44\r\n".as_bytes());
+
+    // err
+    assert!(SlowDown::from_utf8("13 Fail\r\n".as_bytes()).is_err());
+    assert!(SlowDown::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(SlowDown::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/failure/temporary/slow_down/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/input.rs

@@ -0,0 +1,92 @@
+pub mod default;
+pub mod error;
+pub mod sensitive;
+
+pub use default::Default;
+pub use error::Error;
+pub use sensitive::Sensitive;
+
+const CODE: u8 = b'1';
+
+/// [Input expected](https://geminiprotocol.net/docs/protocol-specification.gmi#input-expected)
+pub enum Input {
+    Default(Default),
+    Sensitive(Sensitive),
+}
+
+impl Input {
+    // Constructors
+
+    /// Create new `Self` from buffer include header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        match buffer.first() {
+            Some(b) => match *b {
+                CODE => match buffer.get(1) {
+                    Some(b) => match *b {
+                        b'0' => Ok(Self::Default(
+                            Default::from_utf8(buffer).map_err(Error::Default)?,
+                        )),
+                        b'1' => Ok(Self::Sensitive(
+                            Sensitive::from_utf8(buffer).map_err(Error::Sensitive)?,
+                        )),
+                        b => Err(Error::SecondByte(b)),
+                    },
+                    None => Err(Error::UndefinedSecondByte),
+                },
+                b => Err(Error::FirstByte(b)),
+            },
+            None => Err(Error::UndefinedFirstByte),
+        }
+    }
+
+    // Getters
+
+    pub fn message(&self) -> Option<&str> {
+        match self {
+            Self::Default(default) => default.message(),
+            Self::Sensitive(sensitive) => sensitive.message(),
+        }
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return children `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        match self {
+            Self::Default(default) => default.message_or_default(),
+            Self::Sensitive(sensitive) => sensitive.message_or_default(),
+        }
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        match self {
+            Self::Default(default) => default.as_str(),
+            Self::Sensitive(sensitive) => sensitive.as_str(),
+        }
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        match self {
+            Self::Default(default) => default.as_bytes(),
+            Self::Sensitive(sensitive) => sensitive.as_bytes(),
+        }
+    }
+}
+
+#[test]
+fn test() {
+    fn t(source: &str, message: Option<&str>) {
+        let b = source.as_bytes();
+        let i = Input::from_utf8(b).unwrap();
+        assert_eq!(i.message(), message);
+        assert_eq!(i.as_str(), source);
+        assert_eq!(i.as_bytes(), b);
+    }
+    // 10
+    t("10 Default\r\n", Some("Default"));
+    t("10\r\n", None);
+    // 11
+    t("11 Sensitive\r\n", Some("Sensitive"));
+    t("11\r\n", None);
+}

src/client/connection/response/input/default.rs

@@ -0,0 +1,78 @@
+pub mod error;
+pub use error::Error;
+
+/// [Input Expected](https://geminiprotocol.net/docs/protocol-specification.gmi#status-10) status code
+pub const CODE: &[u8] = b"10";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "Input expected";
+
+/// Hold header `String` for [Input Expected](https://geminiprotocol.net/docs/protocol-specification.gmi#status-10) status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct Default(String);
+
+impl Default {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let d = Default::from_utf8("10 Default\r\n".as_bytes()).unwrap();
+    assert_eq!(d.message(), Some("Default"));
+    assert_eq!(d.message_or_default(), "Default");
+    assert_eq!(d.as_str(), "10 Default\r\n");
+    assert_eq!(d.as_bytes(), "10 Default\r\n".as_bytes());
+
+    let d = Default::from_utf8("10\r\n".as_bytes()).unwrap();
+    assert_eq!(d.message(), None);
+    assert_eq!(d.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(d.as_str(), "10\r\n");
+    assert_eq!(d.as_bytes(), "10\r\n".as_bytes());
+
+    // err
+    assert!(Default::from_utf8("13 Fail\r\n".as_bytes()).is_err());
+    assert!(Default::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(Default::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/input/default/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/input/error.rs

@@ -0,0 +1,36 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Default(super::default::Error),
+    FirstByte(u8),
+    SecondByte(u8),
+    Sensitive(super::sensitive::Error),
+    UndefinedFirstByte,
+    UndefinedSecondByte,
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Default(e) => {
+                write!(f, "Default parse error: {e}")
+            }
+            Self::FirstByte(b) => {
+                write!(f, "Unexpected first byte: {b}")
+            }
+            Self::SecondByte(b) => {
+                write!(f, "Unexpected second byte: {b}")
+            }
+            Self::Sensitive(e) => {
+                write!(f, "Sensitive parse error: {e}")
+            }
+            Self::UndefinedFirstByte => {
+                write!(f, "Undefined first byte")
+            }
+            Self::UndefinedSecondByte => {
+                write!(f, "Undefined second byte")
+            }
+        }
+    }
+}

src/client/connection/response/input/sensitive.rs

@@ -0,0 +1,78 @@
+pub mod error;
+pub use error::Error;
+
+/// [Sensitive Input](https://geminiprotocol.net/docs/protocol-specification.gmi#status-11-sensitive-input) status code
+pub const CODE: &[u8] = b"11";
+
+/// Default message if the optional value was not provided by the server
+/// * useful to skip match cases in external applications,
+///   by using `super::message_or_default` method.
+pub const DEFAULT_MESSAGE: &str = "Sensitive input expected";
+
+/// Hold header `String` for [Sensitive Input](https://geminiprotocol.net/docs/protocol-specification.gmi#status-11-sensitive-input) status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct Sensitive(String);
+
+impl Sensitive {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get optional message for `Self`
+    /// * return `None` if the message is empty
+    pub fn message(&self) -> Option<&str> {
+        self.0.get(2..).map(|s| s.trim()).filter(|x| !x.is_empty())
+    }
+
+    /// Get optional message for `Self`
+    /// * if the optional message not provided by the server, return `DEFAULT_MESSAGE`
+    pub fn message_or_default(&self) -> &str {
+        self.message().unwrap_or(DEFAULT_MESSAGE)
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+}
+
+#[test]
+fn test() {
+    // ok
+    let s = Sensitive::from_utf8("11 Sensitive\r\n".as_bytes()).unwrap();
+    assert_eq!(s.message(), Some("Sensitive"));
+    assert_eq!(s.message_or_default(), "Sensitive");
+    assert_eq!(s.as_str(), "11 Sensitive\r\n");
+    assert_eq!(s.as_bytes(), "11 Sensitive\r\n".as_bytes());
+
+    let s = Sensitive::from_utf8("11\r\n".as_bytes()).unwrap();
+    assert_eq!(s.message(), None);
+    assert_eq!(s.message_or_default(), DEFAULT_MESSAGE);
+    assert_eq!(s.as_str(), "11\r\n");
+    assert_eq!(s.as_bytes(), "11\r\n".as_bytes());
+
+    // err
+    assert!(Sensitive::from_utf8("13 Fail\r\n".as_bytes()).is_err());
+    assert!(Sensitive::from_utf8("Fail\r\n".as_bytes()).is_err());
+    assert!(Sensitive::from_utf8("Fail".as_bytes()).is_err());
+}

src/client/connection/response/input/sensitive/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/redirect.rs

@@ -0,0 +1,185 @@
+pub mod error;
+pub mod permanent;
+pub mod temporary;
+
+pub use error::{Error, UriError};
+pub use permanent::Permanent;
+pub use temporary::Temporary;
+
+// Local dependencies
+
+use glib::{Uri, UriFlags};
+
+const CODE: u8 = b'3';
+
+/// [Redirection](https://geminiprotocol.net/docs/protocol-specification.gmi#redirection) statuses
+pub enum Redirect {
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-30-temporary-redirection
+    Temporary(Temporary),
+    /// https://geminiprotocol.net/docs/protocol-specification.gmi#status-31-permanent-redirection
+    Permanent(Permanent),
+}
+
+impl Redirect {
+    // Constructors
+
+    /// Create new `Self` from buffer include header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        match buffer.first() {
+            Some(b) => match *b {
+                CODE => match buffer.get(1) {
+                    Some(b) => match *b {
+                        b'0' => Ok(Self::Temporary(
+                            Temporary::from_utf8(buffer).map_err(Error::Temporary)?,
+                        )),
+                        b'1' => Ok(Self::Permanent(
+                            Permanent::from_utf8(buffer).map_err(Error::Permanent)?,
+                        )),
+                        b => Err(Error::SecondByte(b)),
+                    },
+                    None => Err(Error::UndefinedSecondByte),
+                },
+                b => Err(Error::FirstByte(b)),
+            },
+            None => Err(Error::UndefinedFirstByte),
+        }
+    }
+
+    // Getters
+
+    pub fn target(&self) -> Result<&str, Error> {
+        match self {
+            Self::Temporary(temporary) => temporary.target().map_err(Error::Temporary),
+            Self::Permanent(permanent) => permanent.target().map_err(Error::Permanent),
+        }
+    }
+
+    pub fn as_str(&self) -> &str {
+        match self {
+            Self::Temporary(temporary) => temporary.as_str(),
+            Self::Permanent(permanent) => permanent.as_str(),
+        }
+    }
+
+    pub fn as_bytes(&self) -> &[u8] {
+        match self {
+            Self::Temporary(temporary) => temporary.as_bytes(),
+            Self::Permanent(permanent) => permanent.as_bytes(),
+        }
+    }
+
+    pub fn uri(&self, base: &Uri) -> Result<Uri, Error> {
+        match self {
+            Self::Temporary(temporary) => temporary.uri(base).map_err(Error::Temporary),
+            Self::Permanent(permanent) => permanent.uri(base).map_err(Error::Permanent),
+        }
+    }
+}
+
+// Tools
+
+/// Resolve [specification-compatible](https://geminiprotocol.net/docs/protocol-specification.gmi#redirection),
+/// absolute [Uri](https://docs.gtk.org/glib/struct.Uri.html) for `target` using `base`
+/// * fragment implementation uncompleted @TODO
+fn uri(target: &str, base: &Uri) -> Result<Uri, UriError> {
+    match Uri::build(
+        UriFlags::NONE,
+        base.scheme().as_str(),
+        None, // unexpected
+        base.host().as_deref(),
+        base.port(),
+        base.path().as_str(),
+        // > If a server sends a redirection in response to a request with a query string,
+        // > the client MUST NOT apply the query string to the new location
+        None,
+        // > A server SHOULD NOT include fragments in redirections,
+        // > but if one is given, and a client already has a fragment it could apply (from the original URI),
+        // > it is up to the client which fragment to apply.
+        None, // @TODO
+    )
+    .parse_relative(
+        &{
+            // URI started with double slash yet not supported by Glib function
+            // https://datatracker.ietf.org/doc/html/rfc3986#section-4.2
+            let t = target;
+            match t.strip_prefix("//") {
+                Some(p) => {
+                    let postfix = p.trim_start_matches(":");
+                    format!(
+                        "{}://{}",
+                        base.scheme(),
+                        if postfix.is_empty() {
+                            match base.host() {
+                                Some(h) => format!("{h}/"),
+                                None => return Err(UriError::BaseHost),
+                            }
+                        } else {
+                            postfix.to_string()
+                        }
+                    )
+                }
+                None => t.to_string(),
+            }
+        },
+        UriFlags::NONE,
+    ) {
+        Ok(absolute) => Ok(absolute),
+        Err(e) => Err(UriError::ParseRelative(e)),
+    }
+}
+
+#[test]
+fn test() {
+    /// Test common assertion rules
+    fn t(base: &Uri, source: &str, target: &str) {
+        let b = source.as_bytes();
+        let r = Redirect::from_utf8(b).unwrap();
+        assert!(r.uri(base).is_ok_and(|u| u.to_string() == target));
+        assert_eq!(r.as_str(), source);
+        assert_eq!(r.as_bytes(), b);
+    }
+    // common base
+    let base = Uri::build(
+        UriFlags::NONE,
+        "gemini",
+        None,
+        Some("geminiprotocol.net"),
+        -1,
+        "/path/",
+        Some("query"),
+        Some("fragment"),
+    );
+    // codes test
+    t(
+        &base,
+        "30 gemini://geminiprotocol.net/path\r\n",
+        "gemini://geminiprotocol.net/path",
+    );
+    t(
+        &base,
+        "31 gemini://geminiprotocol.net/path\r\n",
+        "gemini://geminiprotocol.net/path",
+    );
+    // relative test
+    t(
+        &base,
+        "31 path\r\n",
+        "gemini://geminiprotocol.net/path/path",
+    );
+    t(
+        &base,
+        "31 //geminiprotocol.net\r\n",
+        "gemini://geminiprotocol.net",
+    );
+    t(
+        &base,
+        "31 //geminiprotocol.net/path\r\n",
+        "gemini://geminiprotocol.net/path",
+    );
+    t(&base, "31 /path\r\n", "gemini://geminiprotocol.net/path");
+    t(&base, "31 //:\r\n", "gemini://geminiprotocol.net/");
+    t(&base, "31 //\r\n", "gemini://geminiprotocol.net/");
+    t(&base, "31 /\r\n", "gemini://geminiprotocol.net/");
+    t(&base, "31 ../\r\n", "gemini://geminiprotocol.net/");
+    t(&base, "31 ..\r\n", "gemini://geminiprotocol.net/");
+}

src/client/connection/response/redirect/error.rs

@@ -0,0 +1,56 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    FirstByte(u8),
+    Permanent(super::permanent::Error),
+    SecondByte(u8),
+    Temporary(super::temporary::Error),
+    UndefinedFirstByte,
+    UndefinedSecondByte,
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::FirstByte(b) => {
+                write!(f, "Unexpected first byte: {b}")
+            }
+            Self::Permanent(e) => {
+                write!(f, "Permanent parse error: {e}")
+            }
+            Self::SecondByte(b) => {
+                write!(f, "Unexpected second byte: {b}")
+            }
+            Self::Temporary(e) => {
+                write!(f, "Temporary parse error: {e}")
+            }
+            Self::UndefinedFirstByte => {
+                write!(f, "Undefined first byte")
+            }
+            Self::UndefinedSecondByte => {
+                write!(f, "Undefined second byte")
+            }
+        }
+    }
+}
+
+/// Handle `super::uri` method
+#[derive(Debug)]
+pub enum UriError {
+    BaseHost,
+    ParseRelative(glib::Error),
+}
+
+impl Display for UriError {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::BaseHost => {
+                write!(f, "URI base host required")
+            }
+            Self::ParseRelative(e) => {
+                write!(f, "URI parse relative error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/redirect/permanent.rs

@@ -0,0 +1,82 @@
+pub mod error;
+pub use error::Error;
+
+// Local dependencies
+
+use glib::Uri;
+
+/// [Permanent Redirection](https://geminiprotocol.net/docs/protocol-specification.gmi#status-31-permanent-redirection) status code
+pub const CODE: &[u8] = b"31";
+
+/// Hold header `String` for [Permanent Redirection](https://geminiprotocol.net/docs/protocol-specification.gmi#status-31-permanent-redirection) status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct Permanent(String);
+
+impl Permanent {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get raw target for `Self`
+    /// * return `Err` if the required target is empty
+    pub fn target(&self) -> Result<&str, Error> {
+        self.0
+            .get(2..)
+            .map(|s| s.trim())
+            .filter(|x| !x.is_empty())
+            .ok_or(Error::TargetEmpty)
+    }
+
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+
+    pub fn uri(&self, base: &Uri) -> Result<Uri, Error> {
+        super::uri(self.target()?, base).map_err(Error::Uri)
+    }
+}
+
+#[test]
+fn test() {
+    const BUFFER: &str = "31 gemini://geminiprotocol.net/path\r\n";
+    let bytes = BUFFER.as_bytes();
+    let base = Uri::build(
+        glib::UriFlags::NONE,
+        "gemini",
+        None,
+        Some("geminiprotocol.net"),
+        -1,
+        "/path/",
+        Some("query"),
+        Some("fragment"),
+    );
+    let permanent = Permanent::from_utf8(bytes).unwrap();
+    assert_eq!(permanent.as_str(), BUFFER);
+    assert_eq!(permanent.as_bytes(), bytes);
+    assert!(permanent.target().is_ok());
+    assert!(
+        permanent
+            .uri(&base)
+            .is_ok_and(|u| u.to_string() == "gemini://geminiprotocol.net/path")
+    );
+    assert!(Permanent::from_utf8("32 gemini://geminiprotocol.net/path\r\n".as_bytes()).is_err());
+}

src/client/connection/response/redirect/permanent/error.rs

@@ -0,0 +1,32 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    TargetEmpty,
+    Uri(super::super::UriError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::TargetEmpty => {
+                write!(f, "Expected target is empty")
+            }
+            Self::Uri(e) => {
+                write!(f, "URI parse error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/redirect/temporary.rs

@@ -0,0 +1,82 @@
+pub mod error;
+pub use error::Error;
+
+// Local dependencies
+
+use glib::Uri;
+
+/// [Temporary Redirection](https://geminiprotocol.net/docs/protocol-specification.gmi#status-30-temporary-redirection) status code
+pub const CODE: &[u8] = b"30";
+
+/// Hold header `String` for [Temporary Redirection](https://geminiprotocol.net/docs/protocol-specification.gmi#status-30-temporary-redirection) status code
+/// * this response type does not contain body data
+/// * the header member is closed to require valid construction
+pub struct Temporary(String);
+
+impl Temporary {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Get raw target for `Self`
+    /// * return `Err` if the required target is empty
+    pub fn target(&self) -> Result<&str, Error> {
+        self.0
+            .get(2..)
+            .map(|s| s.trim())
+            .filter(|x| !x.is_empty())
+            .ok_or(Error::TargetEmpty)
+    }
+
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+
+    pub fn uri(&self, base: &Uri) -> Result<Uri, Error> {
+        super::uri(self.target()?, base).map_err(Error::Uri)
+    }
+}
+
+#[test]
+fn test() {
+    const BUFFER: &str = "30 gemini://geminiprotocol.net/path\r\n";
+    let bytes = BUFFER.as_bytes();
+    let base = Uri::build(
+        glib::UriFlags::NONE,
+        "gemini",
+        None,
+        Some("geminiprotocol.net"),
+        -1,
+        "/path/",
+        Some("query"),
+        Some("fragment"),
+    );
+    let temporary = Temporary::from_utf8(BUFFER.as_bytes()).unwrap();
+    assert_eq!(temporary.as_str(), BUFFER);
+    assert_eq!(temporary.as_bytes(), bytes);
+    assert!(temporary.target().is_ok());
+    assert!(
+        temporary
+            .uri(&base)
+            .is_ok_and(|u| u.to_string() == "gemini://geminiprotocol.net/path")
+    );
+    assert!(Temporary::from_utf8("32 gemini://geminiprotocol.net/path\r\n".as_bytes()).is_err())
+}

src/client/connection/response/redirect/temporary/error.rs

@@ -0,0 +1,32 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(crate::client::connection::response::HeaderBytesError),
+    TargetEmpty,
+    Uri(super::super::UriError),
+    Utf8Error(std::str::Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::TargetEmpty => {
+                write!(f, "Expected target is empty")
+            }
+            Self::Uri(e) => {
+                write!(f, "URI parse error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 decode error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/success.rs

@@ -0,0 +1,76 @@
+pub mod default;
+pub mod error;
+
+pub use default::Default;
+pub use error::Error;
+
+const CODE: u8 = b'2';
+
+pub enum Success {
+    Default(Default),
+    // reserved for 2* codes
+}
+
+impl Success {
+    // Constructors
+
+    /// Parse new `Self` from buffer bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if buffer.first().is_none_or(|b| *b != CODE) {
+            return Err(Error::Code);
+        }
+        match Default::from_utf8(buffer) {
+            Ok(default) => Ok(Self::Default(default)),
+            Err(e) => Err(Error::Default(e)),
+        }
+    }
+
+    // Getters
+
+    /// Get header bytes for `Self` type
+    pub fn as_header_bytes(&self) -> &[u8] {
+        match self {
+            Self::Default(default) => default.header.as_bytes(),
+        }
+    }
+
+    /// Get header string for `Self` type
+    pub fn as_header_str(&self) -> &str {
+        match self {
+            Self::Default(default) => default.header.as_str(),
+        }
+    }
+
+    /// Get parsed MIME for `Self` type
+    ///
+    /// * high-level method, useful to skip extra match case constructions;
+    /// * at this moment, Gemini protocol has only one status code in this scope,\
+    ///   this method would be deprecated in future, use on your own risk!
+    pub fn mime(&self) -> Result<String, Error> {
+        match self {
+            Self::Default(default) => default
+                .header
+                .mime()
+                .map_err(|e| Error::Default(default::Error::Header(e))),
+        }
+    }
+}
+
+#[test]
+fn test() {
+    let r = "20 text/gemini; charset=utf-8; lang=en\r\n";
+    let b = r.as_bytes();
+    let s = Success::from_utf8(b).unwrap();
+
+    match s {
+        Success::Default(ref d) => {
+            assert_eq!(d.header.mime().unwrap(), "text/gemini");
+            assert!(d.content.is_empty())
+        }
+    }
+    assert_eq!(s.as_header_bytes(), b);
+    assert_eq!(s.as_header_str(), r);
+    assert_eq!(s.mime().unwrap(), "text/gemini");
+
+    assert!(Success::from_utf8("40 text/gemini; charset=utf-8; lang=en\r\n".as_bytes()).is_err())
+}

src/client/connection/response/success/default.rs

@@ -0,0 +1,51 @@
+pub mod error;
+pub mod header;
+
+pub use error::Error;
+pub use header::Header;
+
+/// [Success](https://geminiprotocol.net/docs/protocol-specification.gmi#success) status code
+pub const CODE: &[u8] = b"20";
+
+/// Holder for [Success](https://geminiprotocol.net/docs/protocol-specification.gmi#success) status code
+/// * this response type MAY contain body data
+/// * the header has closed members to require valid construction
+pub struct Default {
+    /// Formatted header holder with additional API
+    pub header: Header,
+    /// Default success response MAY include body data
+    /// * if the `Request` constructed with `Mode::HeaderOnly` flag,\
+    ///   this value wants to be processed manually, using external application logic (specific for content-type)
+    pub content: Vec<u8>,
+}
+
+impl Default {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(CODE) {
+            return Err(Error::Code);
+        }
+        let header = Header::from_utf8(buffer).map_err(Error::Header)?;
+        Ok(Self {
+            content: buffer
+                .get(header.as_bytes().len()..)
+                .filter(|s| !s.is_empty())
+                .map_or(Vec::new(), |v| v.to_vec()),
+            header,
+        })
+    }
+}
+
+#[test]
+fn test() {
+    let d = Default::from_utf8("20 text/gemini; charset=utf-8; lang=en\r\n".as_bytes()).unwrap();
+    assert_eq!(d.header.mime().unwrap(), "text/gemini");
+    assert!(d.content.is_empty());
+
+    let d =
+        Default::from_utf8("20 text/gemini; charset=utf-8; lang=en\r\ndata".as_bytes()).unwrap();
+    assert_eq!(d.header.mime().unwrap(), "text/gemini");
+    assert_eq!(d.content.len(), 4);
+}

src/client/connection/response/success/default/error.rs

@@ -0,0 +1,20 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Header(super::header::Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/success/default/header.rs

@@ -0,0 +1,60 @@
+pub mod error;
+pub use error::Error;
+
+pub struct Header(String);
+
+impl Header {
+    // Constructors
+
+    /// Parse `Self` from buffer contains header bytes
+    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
+        if !buffer.starts_with(super::CODE) {
+            return Err(Error::Code);
+        }
+        Ok(Self(
+            std::str::from_utf8(
+                crate::client::connection::response::header_bytes(buffer).map_err(Error::Header)?,
+            )
+            .map_err(Error::Utf8Error)?
+            .to_string(),
+        ))
+    }
+
+    // Getters
+
+    /// Parse content type for `Self`
+    pub fn mime(&self) -> Result<String, Error> {
+        glib::Regex::split_simple(
+            r"^\d{2}\s([^\/]+\/[^\s;]+)",
+            &self.0,
+            glib::RegexCompileFlags::DEFAULT,
+            glib::RegexMatchFlags::DEFAULT,
+        )
+        .get(1)
+        .map(|s| s.trim())
+        .filter(|s| !s.is_empty())
+        .map_or(Err(Error::Mime), |s| Ok(s.to_lowercase()))
+    }
+
+    /// Get header bytes of `Self`
+    pub fn as_bytes(&self) -> &[u8] {
+        self.0.as_bytes()
+    }
+
+    /// Get header string of `Self`
+    pub fn as_str(&self) -> &str {
+        self.0.as_str()
+    }
+}
+
+#[test]
+fn test() {
+    let s = "20 text/gemini; charset=utf-8; lang=en\r\n";
+    let b = s.as_bytes();
+    let h = Header::from_utf8(b).unwrap();
+    assert_eq!(h.mime().unwrap(), "text/gemini");
+    assert_eq!(h.as_bytes(), b);
+    assert_eq!(h.as_str(), s);
+
+    assert!(Header::from_utf8("21 text/gemini; charset=utf-8; lang=en\r\n".as_bytes()).is_err());
+}

src/client/connection/response/success/default/header/error.rs

@@ -0,0 +1,31 @@
+use std::{
+    fmt::{Display, Formatter, Result},
+    str::Utf8Error,
+};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Mime,
+    Header(crate::client::connection::response::HeaderBytesError),
+    Utf8Error(Utf8Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Mime => {
+                write!(f, "Unexpected content type")
+            }
+            Self::Header(e) => {
+                write!(f, "Header error: {e}")
+            }
+            Self::Utf8Error(e) => {
+                write!(f, "UTF-8 error: {e}")
+            }
+        }
+    }
+}

src/client/connection/response/success/error.rs

@@ -0,0 +1,20 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Code,
+    Default(super::default::Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Code => {
+                write!(f, "Unexpected status code")
+            }
+            Self::Default(e) => {
+                write!(f, "Header error: {e}")
+            }
+        }
+    }
+}

src/client/error.rs

@@ -1,8 +1,31 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
 pub enum Error {
-    Close,
-    Connect,
-    Input,
-    Output,
-    Response,
-    BufferOverflow,
+    Connect(gio::NetworkAddress, glib::Error),
+    Connection(gio::SocketConnection, crate::client::connection::Error),
+    NetworkAddress(crate::client::connection::request::Error),
+    Request(
+        crate::client::connection::Connection,
+        crate::client::connection::Error,
+    ),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Connect(_, e) => {
+                write!(f, "Connect error: {e}")
+            }
+            Self::Connection(_, e) => {
+                write!(f, "Connection init error: {e}")
+            }
+            Self::NetworkAddress(e) => {
+                write!(f, "Network address error: {e}")
+            }
+            Self::Request(_, e) => {
+                write!(f, "Connection error: {e}")
+            }
+        }
+    }
 }

src/client/response.rs

@@ -1,42 +0,0 @@
-pub mod body;
-pub mod error;
-pub mod header;
-
-pub use body::Body;
-pub use error::Error;
-pub use header::Header;
-
-pub struct Response {
-    header: Header,
-    body: Body,
-}
-
-impl Response {
-    /// Create new `client::Response`
-    pub fn new(header: Header, body: Body) -> Self {
-        Self { header, body }
-    }
-
-    /// Create new `client::Response` from UTF-8 buffer
-    pub fn from_utf8(buffer: &[u8]) -> Result<Self, Error> {
-        let header = match Header::from_response(buffer) {
-            Ok(result) => result,
-            Err(_) => return Err(Error::Header),
-        };
-
-        let body = match Body::from_response(buffer) {
-            Ok(result) => result,
-            Err(_) => return Err(Error::Body),
-        };
-
-        Ok(Self::new(header, body))
-    }
-
-    pub fn header(&self) -> &Header {
-        &self.header
-    }
-
-    pub fn body(&self) -> &Body {
-        &self.body
-    }
-}

src/client/response/body.rs

@@ -1,46 +0,0 @@
-pub mod error;
-pub use error::Error;
-
-use glib::GString;
-
-pub struct Body {
-    buffer: Vec<u8>,
-}
-
-impl Body {
-    /// Construct from response buffer
-    pub fn from_response(response: &[u8] /* @TODO */) -> Result<Self, Error> {
-        let start = Self::start(response)?;
-
-        let buffer = match response.get(start..) {
-            Some(result) => result,
-            None => return Err(Error::Buffer),
-        };
-
-        Ok(Self {
-            buffer: Vec::from(buffer),
-        })
-    }
-
-    // Getters
-    pub fn buffer(&self) -> &Vec<u8> {
-        &self.buffer
-    }
-
-    pub fn to_gstring(&self) -> Result<GString, Error> {
-        match GString::from_utf8(self.buffer.to_vec()) {
-            Ok(result) => Ok(result),
-            Err(_) => Err(Error::Decode),
-        }
-    }
-
-    // Tools
-    fn start(buffer: &[u8]) -> Result<usize, Error> {
-        for (offset, &byte) in buffer.iter().enumerate() {
-            if byte == b'\n' {
-                return Ok(offset + 1);
-            }
-        }
-        Err(Error::Format)
-    }
-}

src/client/response/body/error.rs

@@ -1,6 +0,0 @@
-pub enum Error {
-    Buffer,
-    Decode,
-    Format,
-    Status,
-}

src/client/response/error.rs

@@ -1,4 +0,0 @@
-pub enum Error {
-    Header,
-    Body,
-}

src/client/response/header.rs

@@ -1,70 +0,0 @@
-pub mod error;
-pub mod meta;
-pub mod mime;
-pub mod status;
-
-pub use error::Error;
-pub use meta::Meta;
-pub use mime::Mime;
-pub use status::Status;
-
-pub struct Header {
-    status: Status,
-    meta: Option<Meta>,
-    mime: Option<Mime>,
-    // @TODO
-    // charset: Option<Charset>,
-    // language: Option<Language>,
-}
-
-impl Header {
-    /// Construct from response buffer
-    /// https://geminiprotocol.net/docs/gemtext-specification.gmi#media-type-parameters
-    pub fn from_response(response: &[u8] /* @TODO */) -> Result<Self, Error> {
-        let end = Self::end(response)?;
-
-        let buffer = match response.get(..end) {
-            Some(result) => result,
-            None => return Err(Error::Buffer),
-        };
-
-        let meta = match Meta::from_header(buffer) {
-            Ok(result) => Some(result),
-            Err(_) => None,
-        };
-
-        let mime = mime::from_header(buffer); // optional
-                                              // let charset = charset::from_header(buffer); @TODO
-                                              // let language = language::from_header(buffer); @TODO
-
-        let status = match status::from_header(buffer) {
-            Ok(result) => result,
-            Err(_) => return Err(Error::Status),
-        };
-
-        Ok(Self { status, meta, mime })
-    }
-
-    // Getters
-    pub fn status(&self) -> &Status {
-        &self.status
-    }
-
-    pub fn mime(&self) -> &Option<Mime> {
-        &self.mime
-    }
-
-    pub fn meta(&self) -> &Option<Meta> {
-        &self.meta
-    }
-
-    // Tools
-    fn end(buffer: &[u8]) -> Result<usize, Error> {
-        for (offset, &byte) in buffer.iter().enumerate() {
-            if byte == b'\r' {
-                return Ok(offset);
-            }
-        }
-        Err(Error::Format)
-    }
-}

src/client/response/header/charset.rs

@@ -1 +0,0 @@
-// @TODO

src/client/response/header/error.rs

@@ -1,5 +0,0 @@
-pub enum Error {
-    Buffer,
-    Format,
-    Status,
-}

src/client/response/header/language.rs

@@ -1 +0,0 @@
-// @TODO

src/client/response/header/meta.rs

@@ -1,26 +0,0 @@
-pub mod error;
-pub use error::Error;
-
-use glib::GString;
-
-pub struct Meta {
-    buffer: Vec<u8>,
-}
-
-impl Meta {
-    pub fn from_header(buffer: &[u8] /* @TODO */) -> Result<Self, Error> {
-        let buffer = match buffer.get(2..) {
-            Some(bytes) => bytes.to_vec(),
-            None => return Err(Error::Undefined),
-        };
-
-        Ok(Self { buffer })
-    }
-
-    pub fn to_gstring(&self) -> Result<GString, Error> {
-        match GString::from_utf8(self.buffer.clone()) {
-            Ok(result) => Ok(result),
-            Err(_) => Err(Error::Undefined),
-        }
-    }
-}

src/client/response/header/meta/error.rs

@@ -1,4 +0,0 @@
-pub enum Error {
-    Decode,
-    Undefined,
-}

src/client/response/header/mime.rs

@@ -1,62 +0,0 @@
-use glib::{GString, Uri};
-use std::path::Path;
-
-pub enum Mime {
-    TextGemini,
-    TextPlain,
-    ImagePng,
-    ImageGif,
-    ImageJpeg,
-    ImageWebp,
-} // @TODO
-
-pub fn from_header(buffer: &[u8] /* @TODO */) -> Option<Mime> {
-    from_string(&match GString::from_utf8(buffer.to_vec()) {
-        Ok(result) => result,
-        Err(_) => return None, // @TODO error handler?
-    })
-}
-
-pub fn from_path(path: &Path) -> Option<Mime> {
-    match path.extension().and_then(|extension| extension.to_str()) {
-        Some("gmi") | Some("gemini") => Some(Mime::TextGemini),
-        Some("txt") => Some(Mime::TextPlain),
-        Some("png") => Some(Mime::ImagePng),
-        Some("gif") => Some(Mime::ImageGif),
-        Some("jpeg") | Some("jpg") => Some(Mime::ImageJpeg),
-        Some("webp") => Some(Mime::ImageWebp),
-        _ => None,
-    }
-}
-
-pub fn from_string(value: &str) -> Option<Mime> {
-    if value.contains("text/gemini") {
-        return Some(Mime::TextGemini);
-    }
-
-    if value.contains("text/plain") {
-        return Some(Mime::TextPlain);
-    }
-
-    if value.contains("image/gif") {
-        return Some(Mime::ImageGif);
-    }
-
-    if value.contains("image/jpeg") {
-        return Some(Mime::ImageJpeg);
-    }
-
-    if value.contains("image/webp") {
-        return Some(Mime::ImageWebp);
-    }
-
-    if value.contains("image/png") {
-        return Some(Mime::ImagePng);
-    }
-
-    None
-}
-
-pub fn from_uri(uri: &Uri) -> Option<Mime> {
-    from_path(Path::new(&uri.to_string()))
-}

src/client/response/header/status.rs

@@ -1,31 +0,0 @@
-pub mod error;
-pub use error::Error;
-
-use glib::GString;
-
-/// https://geminiprotocol.net/docs/protocol-specification.gmi#status-codes
-pub enum Status {
-    Input,
-    SensitiveInput,
-    Success,
-    Redirect,
-} // @TODO
-
-pub fn from_header(buffer: &[u8] /* @TODO */) -> Result<Status, Error> {
-    match buffer.get(0..2) {
-        Some(bytes) => match GString::from_utf8(bytes.to_vec()) {
-            Ok(string) => from_string(string.as_str()),
-            Err(_) => Err(Error::Decode),
-        },
-        None => Err(Error::Undefined),
-    }
-}
-
-pub fn from_string(code: &str) -> Result<Status, Error> {
-    match code {
-        "10" => Ok(Status::Input),
-        "11" => Ok(Status::SensitiveInput),
-        "20" => Ok(Status::Success),
-        _ => Err(Error::Undefined),
-    }
-}

src/client/response/header/status/error.rs

@@ -1,4 +0,0 @@
-pub enum Error {
-    Undefined,
-    Decode,
-}

src/client/socket.rs

@@ -1,23 +0,0 @@
-use gio::{prelude::SocketClientExt, SocketClient, SocketProtocol, TlsCertificateFlags};
-
-pub struct Socket {
-    gobject: SocketClient,
-}
-
-impl Socket {
-    /// Create new `gio::SocketClient` preset for Gemini Protocol
-    pub fn new() -> Self {
-        let gobject = SocketClient::new();
-
-        gobject.set_protocol(SocketProtocol::Tcp);
-        gobject.set_tls_validation_flags(TlsCertificateFlags::INSECURE);
-        gobject.set_tls(true);
-
-        Self { gobject }
-    }
-
-    /// Return ref to `gio::SocketClient` GObject
-    pub fn gobject(&self) -> &SocketClient {
-        self.gobject.as_ref()
-    }
-}

src/gio.rs

@@ -0,0 +1,3 @@
+pub mod file_output_stream;
+pub mod memory_input_stream;
+pub mod network_address;

src/gio/file_output_stream.rs

@@ -0,0 +1,69 @@
+pub mod error;
+pub mod size;
+
+pub use error::Error;
+pub use size::Size;
+
+use gio::{
+    Cancellable, FileOutputStream, IOStream,
+    prelude::{IOStreamExt, InputStreamExt, OutputStreamExtManual},
+};
+use glib::{Bytes, Priority, object::IsA};
+
+/// Asynchronously move all bytes from [IOStream](https://docs.gtk.org/gio/class.IOStream.html)
+/// to [FileOutputStream](https://docs.gtk.org/gio/class.FileOutputStream.html)
+/// * require `IOStream` reference to keep `Connection` active in async thread
+pub fn from_stream_async(
+    io_stream: impl IsA<IOStream>,
+    file_output_stream: FileOutputStream,
+    cancellable: Cancellable,
+    priority: Priority,
+    mut size: Size,
+    (on_chunk, on_complete): (
+        impl Fn(Bytes, usize) + 'static, // on_chunk
+        impl FnOnce(Result<(FileOutputStream, usize), Error>) + 'static, // on_complete
+    ),
+) {
+    io_stream.input_stream().read_bytes_async(
+        size.chunk,
+        priority,
+        Some(&cancellable.clone()),
+        move |result| match result {
+            Ok(bytes) => {
+                size.total += bytes.len();
+                on_chunk(bytes.clone(), size.total);
+
+                if let Some(limit) = size.limit
+                    && size.total > limit
+                {
+                    return on_complete(Err(Error::BytesTotal(size.total, limit)));
+                }
+
+                if bytes.is_empty() {
+                    return on_complete(Ok((file_output_stream, size.total)));
+                }
+
+                // Make sure **all bytes** sent to the destination
+                // > A partial write is performed with the size of a message block, which is 16kB
+                // > https://docs.openssl.org/3.0/man3/SSL_write/#notes
+                file_output_stream.clone().write_all_async(
+                    bytes,
+                    priority,
+                    Some(&cancellable.clone()),
+                    move |result| match result {
+                        Ok(_) => from_stream_async(
+                            io_stream,
+                            file_output_stream,
+                            cancellable,
+                            priority,
+                            size,
+                            (on_chunk, on_complete),
+                        ),
+                        Err((b, e)) => on_complete(Err(Error::OutputStream(b, e))),
+                    },
+                )
+            }
+            Err(e) => on_complete(Err(Error::InputStream(e))),
+        },
+    )
+}

src/gio/file_output_stream/error.rs

@@ -0,0 +1,24 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    BytesTotal(usize, usize),
+    InputStream(glib::Error),
+    OutputStream(glib::Bytes, glib::Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::BytesTotal(total, limit) => {
+                write!(f, "Bytes total limit reached: {total} / {limit}")
+            }
+            Self::InputStream(e) => {
+                write!(f, "Input stream error: {e}")
+            }
+            Self::OutputStream(_, e) => {
+                write!(f, "Output stream error: {e}")
+            }
+        }
+    }
+}

src/gio/file_output_stream/size.rs

@@ -0,0 +1,17 @@
+/// Mutable bytes count
+pub struct Size {
+    pub chunk: usize,
+    /// `None` for unlimited
+    pub limit: Option<usize>,
+    pub total: usize,
+}
+
+impl Default for Size {
+    fn default() -> Self {
+        Self {
+            chunk: 0x10000, // 64KB
+            limit: None,
+            total: 0,
+        }
+    }
+}

src/gio/memory_input_stream.rs

@@ -0,0 +1,95 @@
+pub mod error;
+pub mod size;
+
+pub use error::Error;
+pub use size::Size;
+
+use gio::{
+    Cancellable, IOStream, MemoryInputStream,
+    prelude::{IOStreamExt, InputStreamExt, MemoryInputStreamExt},
+};
+use glib::{Priority, object::IsA};
+
+/// Asynchronously create new [MemoryInputStream](https://docs.gtk.org/gio/class.MemoryInputStream.html)
+/// from [IOStream](https://docs.gtk.org/gio/class.IOStream.html)
+///
+/// **Useful for**
+/// * safe read (of memory overflow) to dynamically allocated buffer, where final size of target data unknown
+/// * calculate bytes processed on chunk load
+pub fn from_stream_async(
+    io_stream: impl IsA<IOStream>,
+    priority: Priority,
+    cancelable: Cancellable,
+    size: Size,
+    (on_chunk, on_complete): (
+        impl Fn(usize, usize) + 'static,
+        impl FnOnce(Result<(MemoryInputStream, usize), Error>) + 'static,
+    ),
+) {
+    for_memory_input_stream_async(
+        MemoryInputStream::new(),
+        io_stream,
+        priority,
+        cancelable,
+        size,
+        (on_chunk, on_complete),
+    );
+}
+
+/// Asynchronously move all bytes from [IOStream](https://docs.gtk.org/gio/class.IOStream.html)
+/// to [MemoryInputStream](https://docs.gtk.org/gio/class.MemoryInputStream.html)
+/// * require `IOStream` reference to keep `Connection` active in async thread
+pub fn for_memory_input_stream_async(
+    memory_input_stream: MemoryInputStream,
+    io_stream: impl IsA<IOStream>,
+    priority: Priority,
+    cancellable: Cancellable,
+    mut size: Size,
+    (on_chunk, on_complete): (
+        impl Fn(usize, usize) + 'static,
+        impl FnOnce(Result<(MemoryInputStream, usize), Error>) + 'static,
+    ),
+) {
+    io_stream.input_stream().read_bytes_async(
+        size.chunk,
+        priority,
+        Some(&cancellable.clone()),
+        move |result| match result {
+            Ok(bytes) => {
+                let len = bytes.len(); // calculate once
+
+                // is end of stream
+                if len == 0 {
+                    return on_complete(Ok((memory_input_stream, size.total)));
+                }
+
+                // callback chunk function
+                size.total += len;
+                on_chunk(len, size.total);
+
+                // push bytes into the memory pool
+                memory_input_stream.add_bytes(&bytes);
+
+                // prevent memory overflow
+                if size.total > size.limit {
+                    return on_complete(Err(Error::BytesTotal(
+                        memory_input_stream,
+                        size.total,
+                        size.limit,
+                    )));
+                }
+
+                // handle next chunk..
+                for_memory_input_stream_async(
+                    memory_input_stream,
+                    io_stream,
+                    priority,
+                    cancellable,
+                    size,
+                    (on_chunk, on_complete),
+                )
+            }
+            Err(e) => on_complete(Err(Error::InputStream(memory_input_stream, e))),
+        },
+    )
+}

src/gio/memory_input_stream/error.rs

@@ -0,0 +1,20 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    BytesTotal(gio::MemoryInputStream, usize, usize),
+    InputStream(gio::MemoryInputStream, glib::Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::BytesTotal(_, total, limit) => {
+                write!(f, "Bytes total limit reached: {total} / {limit}")
+            }
+            Self::InputStream(_, e) => {
+                write!(f, "Input stream error: {e}")
+            }
+        }
+    }
+}

src/gio/memory_input_stream/size.rs

@@ -0,0 +1,16 @@
+/// Mutable bytes count
+pub struct Size {
+    pub chunk: usize,
+    pub limit: usize,
+    pub total: usize,
+}
+
+impl Default for Size {
+    fn default() -> Self {
+        Self {
+            chunk: 0x10000, // 64KB
+            limit: 0xfffff, // 1 MB
+            total: 0,
+        }
+    }
+}

src/gio/network_address.rs

@@ -0,0 +1,24 @@
+pub mod error;
+pub use error::Error;
+
+use gio::NetworkAddress;
+use glib::Uri;
+
+/// Create new valid [NetworkAddress](https://docs.gtk.org/gio/class.NetworkAddress.html) from [Uri](https://docs.gtk.org/glib/struct.Uri.html)
+///
+/// Useful as:
+/// * shared [SocketConnectable](https://docs.gtk.org/gio/iface.SocketConnectable.html) interface
+/// * [SNI](https://geminiprotocol.net/docs/protocol-specification.gmi#server-name-indication) record for TLS connections
+pub fn from_uri(uri: &Uri, default_port: u16) -> Result<NetworkAddress, Error> {
+    Ok(NetworkAddress::new(
+        &match uri.host() {
+            Some(host) => host,
+            None => return Err(Error::Host(uri.to_string())),
+        },
+        if uri.port().is_positive() {
+            uri.port() as u16
+        } else {
+            default_port
+        },
+    ))
+}

src/gio/network_address/error.rs

@@ -0,0 +1,16 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Host(String),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Host(url) => {
+                write!(f, "Host required for {url}")
+            }
+        }
+    }
+}

src/lib.rs

@@ -1 +1,18 @@
 pub mod client;
+pub mod gio;
+
+// Main API
+
+pub use client::Client;
+
+// Global defaults
+
+pub const DEFAULT_PORT: u16 = 1965;
+
+// Debug
+
+pub const VERSION: &str = env!("CARGO_PKG_VERSION");
+
+pub const VERSION_MINOR: &str = env!("CARGO_PKG_VERSION_MINOR");
+pub const VERSION_MAJOR: &str = env!("CARGO_PKG_VERSION_MAJOR");
+pub const VERSION_PATCH: &str = env!("CARGO_PKG_VERSION_PATCH");