implement gemini redirection handler

src/app/browser/window/tab/item/page/client/request.rs

@@ -14,17 +14,20 @@ use gtk::{
 pub enum Request {
     Gemini {
         feature: Feature,
-        referrer: Vec<Self>,
+        referrer: Option<Box<Self>>,
+        uri: Uri,
+    },
+    Titan {
+        referrer: Option<Box<Self>>,
         uri: Uri,
     },
-    Titan(Uri),
 }
 
 impl Request {
     // Constructors
 
     /// Create new `Self` from featured string
-    pub fn parse(query: &str, referrer: Option<Vec<Self>>) -> Result<Self, Error> {
+    pub fn parse(query: &str, referrer: Option<Box<Self>>) -> Result<Self, Error> {
         let (feature, request) = Feature::parse(query);
 
         match Uri::parse(request, UriFlags::NONE) {
@@ -37,15 +40,15 @@ impl Request {
     pub fn from_uri(
         uri: Uri,
         feature: Option<Feature>,
-        referrer: Option<Vec<Self>>,
+        referrer: Option<Box<Self>>,
     ) -> Result<Self, Error> {
         match uri.scheme().as_str() {
             "gemini" => Ok(Self::Gemini {
                 feature: feature.unwrap_or_default(),
-                referrer: referrer.unwrap_or_default(),
+                referrer,
                 uri,
             }),
-            "titan" => Ok(Self::Titan(uri)),
+            "titan" => Ok(Self::Titan { referrer, uri }),
             _ => Err(Error::Unsupported),
         }
     }
@@ -65,7 +68,10 @@ impl Request {
                 referrer,
                 uri,
             } => gemini::send(client, feature, uri, referrer, cancellable, callback),
-            Self::Titan(_) => todo!(),
+            Self::Titan {
+                referrer: _,
+                uri: _,
+            } => todo!(),
         }
     }
 
@@ -79,7 +85,19 @@ impl Request {
                 referrer: _,
                 uri,
             }
-            | Self::Titan(uri) => uri,
+            | Self::Titan { referrer: _, uri } => uri,
         }
     }
+
+    /// Recursively count referrers of `Self`
+    /// * useful to apply redirection rules by protocol driver selected
+    pub fn referrers(&self) -> usize {
+        let count = match self {
+            Request::Gemini { referrer, .. } => referrer,
+            Request::Titan { referrer, .. } => referrer,
+        }
+        .as_ref()
+        .map_or(0, |request| request.referrers());
+        1 + count
+    }
 }