Minor Dispatcher cleanup

src/dispatching/dispatcher.rs

@@ -1,13 +1,3 @@
-use crate::{
-    dispatching::{
-        stop_token::StopToken,
-        update_listeners::{self, UpdateListener},
-        DispatcherHandler, UpdateWithCx,
-    },
-    error_handlers::{ErrorHandler, LoggingErrorHandler},
-};
-use core::panic;
-use futures::{stream::FuturesUnordered, Future, StreamExt};
 use std::{
     fmt::Debug,
     sync::{
@@ -16,6 +6,17 @@ use std::{
     },
     time::Duration,
 };
+
+use crate::{
+    dispatching::{
+        stop_token::StopToken,
+        update_listeners::{self, UpdateListener},
+        DispatcherHandler, UpdateWithCx,
+    },
+    error_handlers::{ErrorHandler, LoggingErrorHandler},
+};
+
+use futures::{stream::FuturesUnordered, Future, StreamExt};
 use teloxide_core::{
     requests::Requester,
     types::{
@@ -81,15 +82,12 @@ where
             my_chat_members_queue: None,
             chat_members_queue: None,
             running_handlers: FuturesUnordered::new(),
-            shutdown_state: Arc::new(AtomicShutdownState {
-                inner: AtomicU8::new(ShutdownState::IsntRunning as _),
-            }),
-            shutdown_notify_back: Arc::new(Notify::new()),
+            shutdown_state: <_>::default(),
+            shutdown_notify_back: <_>::default(),
         }
     }
 
     #[must_use]
-    #[allow(clippy::unnecessary_wraps)]
     fn new_tx<H, Upd>(&mut self, h: H) -> Tx<R, Upd>
     where
         H: DispatcherHandler<R, Upd> + Send + 'static,
@@ -97,10 +95,7 @@ where
         R: Send + 'static,
     {
         let (tx, rx) = mpsc::unbounded_channel();
-        let join_handle = tokio::spawn(async move {
-            let fut = h.handle(rx);
-            fut.await;
-        });
+        let join_handle = tokio::spawn(h.handle(rx));
 
         self.running_handlers.push(join_handle);
 
@@ -251,7 +246,8 @@ where
     /// errors produced by this listener).
     ///
     /// Please note that after shutting down (either because of [`shutdown`],
-    /// [ctrlc signal], or `update_listener` returning `None`)
+    /// [ctrlc signal], or `update_listener` returning `None`) all handlers will
+    /// be gone. As such, to restart listening you need to re-add handlers.
     ///
     /// [`shutdown`]; ShutdownToken::shutdown
     /// [ctrlc signal]: Dispatcher::setup_ctrlc_handler
@@ -260,11 +256,11 @@ where
         R: Requester + Clone,
         <R as Requester>::GetUpdatesFaultTolerant: Send,
     {
-        self.dispatch_with_listener(
-            update_listeners::polling_default(self.requester.clone()).await,
-            LoggingErrorHandler::with_custom_text("An error from the update listener"),
-        )
-        .await;
+        let listener = update_listeners::polling_default(self.requester.clone()).await;
+        let error_handler =
+            LoggingErrorHandler::with_custom_text("An error from the update listener");
+
+        self.dispatch_with_listener(listener, error_handler).await;
     }
 
     /// Starts your bot with custom `update_listener` and
@@ -288,22 +284,14 @@ where
     {
         use ShutdownState::*;
 
-        const MIN_SHUTDOWN_CHECK_TIMEOUT: Duration = Duration::from_secs(1);
-
-        // FIXME: replace this by just Duration::ZERO once 1.53 will be released
-        const DZERO: Duration = Duration::from_secs(0);
-
-        let shutdown_check_timeout = update_listener.timeout_hint().unwrap_or(DZERO);
-
-        // FIXME: replace this by just saturating_add once 1.53 will be released
-        let shutdown_check_timeout = shutdown_check_timeout
-            .checked_add(MIN_SHUTDOWN_CHECK_TIMEOUT)
-            .unwrap_or(shutdown_check_timeout);
-
+        let shutdown_check_timeout = shutdown_check_timeout_for(&update_listener);
         let mut stop_token = Some(update_listener.stop_token());
 
-        if let Err(_) = self.shutdown_state.compare_exchange(IsntRunning, Running) {
-            panic!("Dispatching is already running");
+        if let Err(actual) = self.shutdown_state.compare_exchange(IsntRunning, Running) {
+            unreachable!(
+                "Dispatching is already running: expected `IsntRunning` state, found `{:?}`",
+                actual
+            );
         }
 
         {
@@ -327,23 +315,7 @@ where
             }
         }
 
-        // Drop all senders, so handlers can stop
-        self.messages_queue.take();
-        self.edited_messages_queue.take();
-        self.channel_posts_queue.take();
-        self.edited_channel_posts_queue.take();
-        self.inline_queries_queue.take();
-        self.chosen_inline_results_queue.take();
-        self.callback_queries_queue.take();
-        self.shipping_queries_queue.take();
-        self.pre_checkout_queries_queue.take();
-        self.polls_queue.take();
-        self.poll_answers_queue.take();
-        self.my_chat_members_queue.take();
-        self.chat_members_queue.take();
-
-        // Wait untill all handlers process all updates
-        self.running_handlers.by_ref().for_each(|_| async {}).await;
+        self.wait_for_handlers().await;
 
         if let ShuttingDown = self.shutdown_state.load() {
             // Stopped because of a `shutdown` call.
@@ -462,8 +434,32 @@ where
             }
         }
     }
+
+    async fn wait_for_handlers(&mut self) {
+        log::debug!("Waiting for handlers to finish");
+
+        // Drop all senders, so handlers can stop
+        self.messages_queue.take();
+        self.edited_messages_queue.take();
+        self.channel_posts_queue.take();
+        self.edited_channel_posts_queue.take();
+        self.inline_queries_queue.take();
+        self.chosen_inline_results_queue.take();
+        self.callback_queries_queue.take();
+        self.shipping_queries_queue.take();
+        self.pre_checkout_queries_queue.take();
+        self.polls_queue.take();
+        self.poll_answers_queue.take();
+        self.my_chat_members_queue.take();
+        self.chat_members_queue.take();
+
+        // Wait untill all handlers finish
+        self.running_handlers.by_ref().for_each(|_| async {}).await;
+    }
 }
 
+/// A token which can be used to shutdown dispatcher.
+#[derive(Clone)]
 pub struct ShutdownToken {
     shutdown_state: Arc<AtomicShutdownState>,
     shutdown_notify_back: Arc<Notify>,
@@ -481,6 +477,7 @@ impl ShutdownToken {
     }
 }
 
+/// Error occured while trying to shutdown dispatcher.
 #[derive(Debug)]
 pub enum ShutdownError {
     IsntRunning,
@@ -511,7 +508,14 @@ impl AtomicShutdownState {
     }
 }
 
+impl Default for AtomicShutdownState {
+    fn default() -> Self {
+        Self { inner: AtomicU8::new(ShutdownState::IsntRunning as _) }
+    }
+}
+
 #[repr(u8)]
+#[derive(Debug)]
 enum ShutdownState {
     Running,
     ShuttingDown,
@@ -533,6 +537,18 @@ impl ShutdownState {
     }
 }
 
+fn shutdown_check_timeout_for<E>(update_listener: &impl UpdateListener<E>) -> Duration {
+    const MIN_SHUTDOWN_CHECK_TIMEOUT: Duration = Duration::from_secs(1);
+
+    // FIXME: replace this by just Duration::ZERO once 1.53 will be released
+    const DZERO: Duration = Duration::from_secs(0);
+
+    let shutdown_check_timeout = update_listener.timeout_hint().unwrap_or(DZERO);
+
+    // FIXME: replace this by just saturating_add once 1.53 will be released
+    shutdown_check_timeout.checked_add(MIN_SHUTDOWN_CHECK_TIMEOUT).unwrap_or(shutdown_check_timeout)
+}
+
 fn shutdown_inner(shutdown_state: &AtomicShutdownState) -> Result<(), ShutdownError> {
     use ShutdownState::*;