Driver/Input: Migrate audio backend to Symphonia (#89)

This extensive PR rewrites the internal mixing logic of the driver to use symphonia for parsing and decoding audio data, and rubato to resample audio. Existing logic to decode DCA and Opus formats/data have been reworked as plugins for symphonia. The main benefit is that we no longer need to keep yt-dlp and ffmpeg processes alive, saving a lot of memory and CPU: all decoding can be done in Rust! In exchange, we now need to do a lot of the HTTP handling and resumption ourselves, but this is still a huge net positive.

`Input`s have been completely reworked such that all default (non-cached) sources are lazy by default, and are no longer covered by a special-case `Restartable`. These now span a gamut from a `Compose` (lazy), to a live source, to a fully `Parsed` source. As mixing is still sync, this includes adapters for `AsyncRead`/`AsyncSeek`, and HTTP streams.

`Track`s have been reworked so that they only contain initialisation state for each track. `TrackHandles` are only created once a `Track`/`Input` has been handed over to the driver, replacing `create_player` and related functions. `TrackHandle::action` now acts on a `View` of (im)mutable state, and can request seeks/readying via `Action`.

Per-track event handling has also been improved -- we can now determine and propagate the reason behind individual track errors due to the new backend. Some `TrackHandle` commands (seek etc.) benefit from this, and now use internal callbacks to signal completion.

Due to associated PRs on felixmcfelix/songbird from avid testers, this includes general clippy tweaks, API additions, and other repo-wide cleanup. Thanks go out to the below co-authors.

Co-authored-by: Gnome! <45660393+GnomedDev@users.noreply.github.com>
Co-authored-by: Alakh <36898190+alakhpc@users.noreply.github.com>

src/events/store.rs

@@ -1,7 +1,7 @@
 use super::*;
 use crate::{
     constants::*,
-    tracks::{PlayMode, TrackHandle, TrackState},
+    tracks::{ReadyState, TrackHandle, TrackState},
 };
 use std::{
     collections::{BinaryHeap, HashMap},
@@ -24,8 +24,9 @@ pub struct EventStore {
 
 impl EventStore {
     /// Creates a new event store to be used globally.
+    #[must_use]
     pub fn new() -> Self {
-        Default::default()
+        Self::default()
     }
 
     /// Creates a new event store to be used within a [`Track`].
@@ -34,6 +35,7 @@ impl EventStore {
     /// a track has been registered.
     ///
     /// [`Track`]: crate::tracks::Track
+    #[must_use]
     pub fn new_local() -> Self {
         EventStore {
             local_only: true,
@@ -53,21 +55,20 @@ impl EventStore {
             return;
         }
 
-        use Event::*;
         match evt.event {
-            Core(c) => {
+            Event::Core(c) => {
                 self.untimed
                     .entry(c.into())
                     .or_insert_with(Vec::new)
                     .push(evt);
             },
-            Track(t) => {
+            Event::Track(t) => {
                 self.untimed
                     .entry(t.into())
                     .or_insert_with(Vec::new)
                     .push(evt);
             },
-            Delayed(_) | Periodic(_, _) => {
+            Event::Delayed(_) | Event::Periodic(_, _) => {
                 self.timed.push(evt);
             },
             _ => {
@@ -105,15 +106,12 @@ impl EventStore {
 
     /// Processes all events due up to and including `now`.
     pub(crate) fn timed_event_ready(&self, now: Duration) -> bool {
-        self.timed
-            .peek()
-            .map(|evt| {
-                evt.fire_time
-                    .as_ref()
-                    .expect("Timed event must have a fire_time.")
-                    <= &now
-            })
-            .unwrap_or(false)
+        self.timed.peek().map_or(false, |evt| {
+            evt.fire_time
+                .as_ref()
+                .expect("Timed event must have a fire_time.")
+                <= &now
+        })
     }
 
     /// Processes all events attached to the given track event.
@@ -183,9 +181,9 @@ impl GlobalEvents {
 
     pub(crate) async fn tick(
         &mut self,
-        events: &mut Vec<EventStore>,
-        states: &mut Vec<TrackState>,
-        handles: &mut Vec<TrackHandle>,
+        events: &mut [EventStore],
+        states: &mut [TrackState],
+        handles: &mut [TrackHandle],
     ) {
         // Global timed events
         self.time += TIMESTEP_LENGTH;
@@ -199,7 +197,7 @@ impl GlobalEvents {
 
         // Local timed events
         for (i, state) in states.iter_mut().enumerate() {
-            if state.playing == PlayMode::Play {
+            if state.playing.is_playing() && state.ready == ReadyState::Playable {
                 state.step_frame();
 
                 let event_store = events
@@ -215,7 +213,7 @@ impl GlobalEvents {
             }
         }
 
-        for (evt, indices) in self.awaiting_tick.iter() {
+        for (evt, indices) in &self.awaiting_tick {
             let untimed = (*evt).into();
 
             if !indices.is_empty() {
@@ -223,7 +221,7 @@ impl GlobalEvents {
             }
 
             // Local untimed track events.
-            for &i in indices.iter() {
+            for &i in indices {
                 let event_store = events
                     .get_mut(i)
                     .expect("Missing store index for Tick (local untimed).");
@@ -261,12 +259,12 @@ impl GlobalEvents {
 
                 self.store
                     .process_untimed(self.time, untimed, EventContext::Track(&global_ctx[..]))
-                    .await
+                    .await;
             }
         }
 
         // Now drain vecs.
-        for (_evt, indices) in self.awaiting_tick.iter_mut() {
+        for indices in self.awaiting_tick.values_mut() {
             indices.clear();
         }
     }