feat: improve inevitable communication between frontend & backend

src/main.rs

@@ -1,5 +1,3 @@
-use std::process::exit;
-
 use clap::{Parser, Subcommand};
 
 mod scrape;

src/player.rs

@@ -1,10 +1,12 @@
-use std::{collections::VecDeque, sync::Arc, time::Duration};
+use std::{collections::VecDeque, sync::Arc};
 
 use reqwest::Client;
-use rodio::{source::SineWave, Decoder, OutputStream, OutputStreamHandle, Sink, Source};
+use rodio::{Decoder, OutputStream, Sink};
 use tokio::{
-    sync::RwLock,
-    task, time::sleep,
+    select, sync::{
+        mpsc::{self, Receiver},
+        RwLock,
+    }, task
 };
 
 /// The amount of songs to buffer up.
@@ -12,6 +14,11 @@ const BUFFER_SIZE: usize = 5;
 
 use crate::tracks::Track;
 
+/// Handles communication between the frontend & audio player.
+pub enum Messages {
+    Skip,
+}
+
 /// Main struct responsible for queuing up tracks.
 ///
 /// Internally tracks are stored in an [Arc],
@@ -21,9 +28,6 @@ pub struct Queue {
     tracks: Arc<RwLock<VecDeque<Track>>>,
 }
 
-unsafe impl Send for Queue {}
-unsafe impl Sync for Queue {}
-
 impl Queue {
     pub async fn new() -> Self {
         Self {
@@ -57,28 +61,48 @@ impl Queue {
         Ok(track)
     }
 
-    pub async fn play(self, sink: Sink) -> eyre::Result<()> {
-        let client = Client::builder().build()?;
+    /// This is the main "audio server".
+    /// 
+    /// `rx` is used to communicate with it, for example when to
+    /// skip tracks or pause.
+    pub async fn play(
+        self,
+        sink: Sink,
+        client: Client,
+        mut rx: Receiver<Messages>
+    ) -> eyre::Result<()> {
         let sink = Arc::new(sink);
 
         loop {
+            let clone = sink.clone();
+            let msg = select! {
+                Some(x) = rx.recv() => x,
+
+                // This future will finish only at the end of the current track.
+                Ok(()) = task::spawn_blocking(move || clone.sleep_until_end()) => Messages::Skip,
+            };
+
+            match msg {
+                Messages::Skip => {
                     sink.stop();
 
                     let track = self.next(&client).await?;
                     sink.append(Decoder::new(track.data)?);
-
-            let sink = sink.clone();
-            task::spawn_blocking(move || sink.sleep_until_end()).await?;
+                }
+            }
         }
     }
 }
 
 pub async fn play() -> eyre::Result<()> {
     let queue = Queue::new().await;
-    let (stream, handle) = OutputStream::try_default()?;
+    let (tx, rx) = mpsc::channel(8);
+    let (_stream, handle) = OutputStream::try_default()?;
     let sink = Sink::try_new(&handle)?;
+    let client = Client::builder().build()?;
 
-    let audio = task::spawn(queue.clone().play(sink));
+    let audio = task::spawn(queue.clone().play(sink, client.clone(), rx));
+    tx.send(Messages::Skip).await?; // This is responsible for the initial track being played.
 
     crossterm::terminal::enable_raw_mode()?;
 
@@ -88,6 +112,8 @@ pub async fn play() -> eyre::Result<()> {
                 crossterm::event::KeyCode::Char(x) => {
                     if x == 'q' {
                         break 'a;
+                    } else if x == 's' {
+                        tx.send(Messages::Skip).await?;
                     }
                 }
                 _ => (),