Keep playing random tracks after the playlist ends

backend/src/library.rs

@@ -1,5 +1,6 @@
 use crate::{Backend, BackendState, Player, Result};
 use gio::prelude::*;
+use glib::clone;
 use log::warn;
 use musicus_database::Database;
 use std::path::PathBuf;
@@ -41,10 +42,16 @@ impl Backend {
         let mut db_path = path.clone();
         db_path.push("musicus.db");
 
-        let database = Database::new(db_path.to_str().unwrap())?;
-        self.database.replace(Some(Rc::new(database)));
+        let database = Rc::new(Database::new(db_path.to_str().unwrap())?);
+        self.database.replace(Some(Rc::clone(&database)));
 
         let player = Player::new(path);
+
+        // Keep adding random tracks in case the playlist ends.
+        player.set_generate_next_track_cb(clone!(@weak database => @default-panic, move || {
+            database.random_track().unwrap()
+        }));
+
         self.player.replace(Some(player));
 
         self.set_state(BackendState::Ready);

backend/src/player.rs

@@ -17,6 +17,7 @@ pub struct Player {
     current_track: Cell<Option<usize>>,
     playing: Cell<bool>,
     duration: Cell<u64>,
+    generate_next_track_cb: RefCell<Option<Box<dyn Fn() -> Track>>>,
     playlist_cbs: RefCell<Vec<Box<dyn Fn(Vec<Track>)>>>,
     track_cbs: RefCell<Vec<Box<dyn Fn(usize)>>>,
     duration_cbs: RefCell<Vec<Box<dyn Fn(u64)>>>,
@@ -44,6 +45,7 @@ impl Player {
             current_track: Cell::new(None),
             playing: Cell::new(false),
             duration: Cell::new(0),
+            generate_next_track_cb: RefCell::new(None),
             playlist_cbs: RefCell::new(Vec::new()),
             track_cbs: RefCell::new(Vec::new()),
             duration_cbs: RefCell::new(Vec::new()),
@@ -144,6 +146,10 @@ impl Player {
         result
     }
 
+    pub fn set_generate_next_track_cb<F: Fn() -> Track + 'static>(&self, cb: F) {
+        self.generate_next_track_cb.replace(Some(Box::new(cb)));
+    }
+
     pub fn add_playlist_cb<F: Fn(Vec<Track>) + 'static>(&self, cb: F) {
         self.playlist_cbs.borrow_mut().push(Box::new(cb));
     }
@@ -270,7 +276,9 @@ impl Player {
     }
 
     pub fn has_next(&self) -> bool {
-        if let Some(current_track) = self.current_track.get() {
+        if self.generate_next_track_cb.borrow().is_some() {
+            true
+        } else if let Some(current_track) = self.current_track.get() {
             let playlist = self.playlist.borrow();
             current_track + 1 < playlist.len()
         } else {
@@ -285,9 +293,11 @@ impl Player {
             ))
         })?;
 
-        let playlist = self.playlist.borrow();
-
-        if current_track + 1 < playlist.len() {
+        if current_track + 1 < self.playlist.borrow().len() {
+            current_track += 1;
+        } else if let Some(cb) = &*self.generate_next_track_cb.borrow() {
+            let new_track = cb();
+            self.add_item(new_track)?;
             current_track += 1;
         } else {
             return Err(Error::Other(String::from("No existing next track.")));

database/src/medium.rs

@@ -49,7 +49,7 @@ struct MediumRow {
 }
 
 /// Table data for a [`Track`].
-#[derive(Insertable, Queryable, Debug, Clone)]
+#[derive(Insertable, Queryable, QueryableByName, Debug, Clone)]
 #[table_name = "tracks"]
 struct TrackRow {
     pub id: String,
@@ -224,6 +224,17 @@ impl Database {
         Ok(tracks)
     }
 
+    /// Get a random track from the database.
+    pub fn random_track(&self) -> Result<Track> {
+        let row = diesel::sql_query("SELECT * FROM tracks ORDER BY RANDOM() LIMIT 1")
+            .load::<TrackRow>(&self.connection)?
+            .into_iter()
+            .next()
+            .ok_or(Error::Other("Failed to generate random track"))?;
+
+        self.get_track_from_row(row)
+    }
+
     /// Retrieve all available information on a medium from related tables.
     fn get_medium_data(&self, row: MediumRow) -> Result<Medium> {
         let track_rows = tracks::table