diff --git a/src/ban.rs b/src/ban.rs
new file mode 100644
index 0000000..937e471
--- /dev/null
+++ b/src/ban.rs
@@ -0,0 +1,45 @@
+use chrono::{DateTime, Local};
+use librqbit::dht::Id20;
+use std::{collections::HashMap, time::Duration};
+
+pub struct Ban {
+    index: HashMap<Id20, DateTime<Local>>,
+    timeout: u64,
+}
+
+impl Ban {
+    pub fn init(timeout: u64, capacity: usize) -> Self {
+        Self {
+            index: HashMap::with_capacity(capacity),
+            timeout,
+        }
+    }
+
+    pub fn has(&self, key: &Id20) -> bool {
+        self.index.contains_key(key)
+    }
+
+    pub fn total(&self) -> usize {
+        self.index.len()
+    }
+
+    pub fn update(&mut self, time: DateTime<Local>) {
+        self.index.retain(|i, &mut expires| {
+            if time > expires {
+                log::debug!(
+                    "remove ban for `{}` by the timeout expiration ({expires})",
+                    i.as_string()
+                );
+                false
+            } else {
+                true
+            }
+        })
+    }
+
+    pub fn add(&mut self, key: Id20) -> DateTime<Local> {
+        let t = Local::now() + Duration::from_secs(self.index.len() as u64 * self.timeout);
+        assert!(self.index.insert(key, t).is_none());
+        t
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index c419e72..556ad7f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,19 +1,16 @@
 mod api;
+mod ban;
 mod config;
 mod preload;
 
 use anyhow::Result;
-use chrono::DateTime;
+use ban::Ban;
 use config::Config;
 use librqbit::{
     AddTorrent, AddTorrentOptions, AddTorrentResponse, ConnectionOptions, SessionOptions,
 };
 use preload::Preload;
-use std::{
-    collections::{HashMap, HashSet},
-    num::NonZero,
-    time::Duration,
-};
+use std::{collections::HashSet, num::NonZero, time::Duration};
 use url::Url;
 
 #[tokio::main]
@@ -59,23 +56,12 @@ async fn main() -> Result<()> {
         },
     )
     .await?;
-    let mut ban: HashMap<librqbit::dht::Id20, DateTime<Local>> =
-        HashMap::with_capacity(config.index_capacity);
+    let mut ban = Ban::init(config.timeout, config.index_capacity);
     log::info!("crawler started at {time_init}");
     loop {
         let time_queue = Local::now();
         log::debug!("queue crawl begin at {time_queue}...");
-        ban.retain(|i, &mut expires| {
-            if time_queue > expires {
-                log::debug!(
-                    "remove ban for `{}` by the timeout expiration ({expires})",
-                    i.as_string()
-                );
-                false
-            } else {
-                true
-            }
-        });
+        ban.update(time_queue);
         for source in &config.infohash {
             log::debug!("index source `{source}`...");
             // grab latest info-hashes from this source
@@ -99,7 +85,7 @@ async fn main() -> Result<()> {
                     log::debug!("torrent `{h}` exists, skip.");
                     continue;
                 }
-                if ban.contains_key(&i) {
+                if ban.has(&i) {
                     log::debug!("torrent `{h}` is temporary banned, skip for this queue.");
                     continue;
                 }
@@ -194,15 +180,13 @@ async fn main() -> Result<()> {
                             )
                             .await
                             {
-                                let t = Local::now()
-                                    + Duration::from_secs(ban.len() as u64 * config.timeout);
-                                log::debug!(
-                                    "skip awaiting the completion of preload `{h}` data (`{e}`), ban until {t}."
-                                );
-                                assert!(ban.insert(i, t).is_none());
                                 session
                                     .delete(librqbit::api::TorrentIdOrHash::Id(id), false)
                                     .await?; // * do not collect billions of slow torrents in the session pool
+                                log::debug!(
+                                    "skip awaiting the completion of preload `{h}` data (`{e}`), ban until {}.",
+                                    ban.add(i)
+                                );
                                 continue;
                             }
                             log::debug!("torrent `{h}` preload completed.");
@@ -219,21 +203,15 @@ async fn main() -> Result<()> {
                             log::debug!("torrent `{h}` resolved.")
                         }
                         Ok(_) => panic!(),
-                        Err(e) => {
-                            let t = Local::now()
-                                + Duration::from_secs(ban.len() as u64 * config.timeout);
-                            log::debug!("failed to resolve torrent `{h}`: `{e}`, ban until {t}.");
-                            assert!(ban.insert(i, t).is_none())
-                        }
+                        Err(e) => log::debug!(
+                            "failed to resolve torrent `{h}`: `{e}`, ban until {}.",
+                            ban.add(i)
+                        ),
                     },
-                    Err(e) => {
-                        let t =
-                            Local::now() + Duration::from_secs(ban.len() as u64 * config.timeout);
-                        log::debug!(
-                            "skip awaiting the completion of adding torrent `{h}` data (`{e}`), ban until {t}."
-                        );
-                        assert!(ban.insert(i, t).is_none())
-                    }
+                    Err(e) => log::debug!(
+                        "skip awaiting the completion of adding torrent `{h}` data (`{e}`), ban until {}.",
+                        ban.add(i)
+                    ),
                 }
             }
         }
@@ -245,7 +223,7 @@ async fn main() -> Result<()> {
             Local::now()
                 .signed_duration_since(time_init)
                 .as_seconds_f32(),
-            ban.len(),
+            ban.total(),
             config.sleep
         );
         std::thread::sleep(Duration::from_secs(config.sleep))