librespot/playback/src/player.rs

use futures::sync::oneshot;
use futures::{future, Future};
use futures::sync::mpsc::{UnboundedReceiver, UnboundedSender, unbounded};
use std;
use std::borrow::Cow;
use std::io::{Read, Seek, SeekFrom, Result};
use std::mem;
use std::sync::mpsc::{RecvError, TryRecvError, RecvTimeoutError};
use std::thread;
use std::time::Duration;

use config::{Bitrate, PlayerConfig};
use core::session::Session;
use core::spotify_id::SpotifyId;

use audio_backend::Sink;
use audio::{AudioFile, AudioDecrypt};
use audio::{VorbisDecoder, VorbisPacket};
use metadata::{FileFormat, Track, Metadata};
use mixer::AudioFilter;

pub struct Player {
    commands: Option<std::sync::mpsc::Sender<PlayerCommand>>,
    thread_handle: Option<thread::JoinHandle<()>>,
}

struct PlayerInternal {
    session: Session,
    config: PlayerConfig,
    commands: std::sync::mpsc::Receiver<PlayerCommand>,

    state: PlayerState,
    sink: Box<Sink>,
    sink_running: bool,
    audio_filter: Option<Box<AudioFilter + Send>>,
    event_sender: UnboundedSender<PlayerEvent>,
}

enum PlayerCommand {
    Load(SpotifyId, bool, u32, oneshot::Sender<()>),
    Play,
    Pause,
    Stop,
    Seek(u32),
}

#[derive(Debug, Clone)]
pub enum PlayerEvent {
    Started {
        track_id: SpotifyId,
    },

    Changed {
        old_track_id: SpotifyId,
        new_track_id: SpotifyId,
    },

    Stopped {
        track_id: SpotifyId,
    }
}

type PlayerEventChannel = UnboundedReceiver<PlayerEvent>;
impl Player {
    pub fn new<F>(config: PlayerConfig, session: Session,
                  audio_filter: Option<Box<AudioFilter + Send>>,
                  sink_builder: F) -> (Player, PlayerEventChannel)
        where F: FnOnce() -> Box<Sink> + Send + 'static
    {
        let (cmd_tx, cmd_rx) = std::sync::mpsc::channel();
        let (event_sender, event_receiver) = unbounded();

        let handle = thread::spawn(move || {
            debug!("new Player[{}]", session.session_id());

            let internal = PlayerInternal {
                session: session,
                config: config,
                commands: cmd_rx,

                state: PlayerState::Stopped,
                sink: sink_builder(),
                sink_running: false,
                audio_filter: audio_filter,
                event_sender: event_sender,
            };

            internal.run();
        });

        (Player { commands: Some(cmd_tx), thread_handle: Some(handle) },
         event_receiver)
    }

    fn command(&self, cmd: PlayerCommand) {
        self.commands.as_ref().unwrap().send(cmd).unwrap();
    }

    pub fn load(&self, track: SpotifyId, start_playing: bool, position_ms: u32)
        -> oneshot::Receiver<()>
    {
        let (tx, rx) = oneshot::channel();
        self.command(PlayerCommand::Load(track, start_playing, position_ms, tx));

        rx
    }

    pub fn play(&self) {
        self.command(PlayerCommand::Play)
    }

    pub fn pause(&self) {
        self.command(PlayerCommand::Pause)
    }

    pub fn stop(&self) {
        self.command(PlayerCommand::Stop)
    }

    pub fn seek(&self, position_ms: u32) {
        self.command(PlayerCommand::Seek(position_ms));
    }
}

impl Drop for Player {
    fn drop(&mut self) {
        debug!("Shutting down player thread ...");
        self.commands = None;
        if let Some(handle) = self.thread_handle.take() {
            match handle.join() {
                Ok(_) => (),
                Err(_) => error!("Player thread panicked!")
            }
        }
    }
}

type Decoder = VorbisDecoder<Subfile<AudioDecrypt<AudioFile>>>;
enum PlayerState {
    Stopped,
    Paused {
        track_id: SpotifyId,
        decoder: Decoder,
        end_of_track: oneshot::Sender<()>,
    },
    Playing {
        track_id: SpotifyId,
        decoder: Decoder,
        end_of_track: oneshot::Sender<()>,
    },
    EndOfTrack { track_id: SpotifyId },
    Invalid,
}

impl PlayerState {
    fn is_playing(&self) -> bool {
        use self::PlayerState::*;
        match *self {
            Stopped | EndOfTrack { .. } | Paused { .. } => false,
            Playing { .. } => true,
            Invalid => panic!("invalid state"),
        }
    }

    fn decoder(&mut self) -> Option<&mut Decoder> {
        use self::PlayerState::*;
        match *self {
            Stopped | EndOfTrack { .. } => None,
            Paused { ref mut decoder, .. } |
            Playing { ref mut decoder, .. } => Some(decoder),
            Invalid => panic!("invalid state"),
        }
    }

    fn send_end_of_track(self) {
        use self::PlayerState::*;
        match self {
            Paused { end_of_track, .. } |
            Playing { end_of_track, .. } => {
                let _ = end_of_track.send(());
            },
            _ => ()
        }
    }

    fn playing_to_end_of_track(&mut self) {
        use self::PlayerState::*;
        match *self {
            Paused { track_id, .. } |
            Playing { track_id, .. } => {
                let old_state = mem::replace(self, EndOfTrack { track_id });
                old_state.send_end_of_track();
            },
            _ => panic!("Called playing_to_end_of_track in non-playing state.")
        }
    }

    fn paused_to_playing(&mut self) {
        use self::PlayerState::*;
        match ::std::mem::replace(self, Invalid) {
            Paused { decoder, end_of_track, track_id } => {
                *self = Playing {
                    decoder: decoder,
                    end_of_track: end_of_track,
                    track_id: track_id,
                };
            }
            _ => panic!("invalid state"),
        }
    }

    fn playing_to_paused(&mut self) {
        use self::PlayerState::*;
        match ::std::mem::replace(self, Invalid) {
            Playing { decoder, end_of_track, track_id } => {
                *self = Paused {
                    decoder: decoder,
                    end_of_track: end_of_track,
                    track_id: track_id,
                };
            }
            _ => panic!("invalid state"),
        }
    }
}

impl PlayerInternal {
    fn run(mut self) {
        loop {
            let cmd = if self.state.is_playing() {
                if self.sink_running
                {
                    match self.commands.try_recv() {
                        Ok(cmd) => Some(cmd),
                        Err(TryRecvError::Empty) => None,
                        Err(TryRecvError::Disconnected) => return,
                    }
                }
                else
                {
                    match self.commands.recv_timeout(Duration::from_secs(5)) {
                        Ok(cmd) => Some(cmd),
                        Err(RecvTimeoutError::Timeout) => None,
                        Err(RecvTimeoutError::Disconnected) => return,
                    }
                }
            } else {
                match self.commands.recv() {
                    Ok(cmd) => Some(cmd),
                    Err(RecvError) => return,
                }
            };

            if let Some(cmd) = cmd {
                self.handle_command(cmd);
            }

            if self.state.is_playing() && ! self.sink_running {
                self.start_sink();
            }

            if self.sink_running {
                let packet = if let PlayerState::Playing { ref mut decoder, .. } = self.state {
                    Some(decoder.next_packet().expect("Vorbis error"))
                } else {
                    None
                };

                if let Some(packet) = packet {
                    self.handle_packet(packet);
                }
            }
        }
    }

    fn start_sink(&mut self) {
        match self.sink.start() {
            Ok(()) => self.sink_running = true,
            Err(err) => error!("Could not start audio: {}", err),
        }
    }

    fn stop_sink_if_running(&mut self) {
        if self.sink_running {
            self.stop_sink();
        }
    }

    fn stop_sink(&mut self) {
        self.sink.stop().unwrap();
        self.sink_running = false;
    }

    fn handle_packet(&mut self, packet: Option<VorbisPacket>) {
        match packet {
            Some(mut packet) => {
                if let Some(ref editor) = self.audio_filter {
                    editor.modify_stream(&mut packet.data_mut())
                };

                if let Err(err) = self.sink.write(&packet.data()) {
                    error!("Could not write audio: {}", err);
                    self.stop_sink();
                }
            }

            None => {
                self.stop_sink();
                self.state.playing_to_end_of_track();
            }
        }
    }

    fn handle_command(&mut self, cmd: PlayerCommand) {
        debug!("command={:?}", cmd);
        match cmd {
            PlayerCommand::Load(track_id, play, position, end_of_track) => {
                if self.state.is_playing() {
                    self.stop_sink_if_running();
                }

                match self.load_track(track_id, position as i64) {
                    Some(decoder) => {
                        if play {
                            match self.state {
                                PlayerState::Playing { track_id: old_track_id, ..}
                                | PlayerState::EndOfTrack { track_id: old_track_id, .. } =>
                                    self.send_event(PlayerEvent::Changed {
                                        old_track_id: old_track_id,
                                        new_track_id: track_id
                                    }),
                                _ => self.send_event(PlayerEvent::Started { track_id }),
                            }

                            self.start_sink();

                            self.state = PlayerState::Playing {
                                track_id: track_id,
                                decoder: decoder,
                                end_of_track: end_of_track,
                            };
                        } else {
                            self.state = PlayerState::Paused {
                                track_id: track_id,
                                decoder: decoder,
                                end_of_track: end_of_track,
                            };
                            match self.state {
                                PlayerState::Playing { track_id: old_track_id, ..}
                                | PlayerState::EndOfTrack { track_id: old_track_id, .. } =>
                                    self.send_event(PlayerEvent::Changed {
                                        old_track_id: old_track_id,
                                        new_track_id: track_id
                                    }),
                                _ => (),
                            }
                            self.send_event(PlayerEvent::Stopped { track_id });
                        }
                    }

                    None => {
                        let _ = end_of_track.send(());
                    }
                }
            }

            PlayerCommand::Seek(position) => {
                if let Some(decoder) = self.state.decoder() {
                    match decoder.seek(position as i64) {
                        Ok(_) => (),
                        Err(err) => error!("Vorbis error: {:?}", err),
                    }
                } else {
                    warn!("Player::seek called from invalid state");
                }
            }

            PlayerCommand::Play => {
                if let PlayerState::Paused { track_id, .. } = self.state {
                    self.state.paused_to_playing();

                    self.send_event(PlayerEvent::Started { track_id });
                    self.start_sink();
                } else {
                    warn!("Player::play called from invalid state");
                }
            }

            PlayerCommand::Pause => {
                if let PlayerState::Playing { track_id, .. } = self.state {
                    self.state.playing_to_paused();

                    self.stop_sink_if_running();
                    self.send_event(PlayerEvent::Stopped { track_id });
                } else {
                    warn!("Player::pause called from invalid state");
                }
            }

            PlayerCommand::Stop => {
                match self.state {
                    PlayerState::Playing { track_id, .. }
                    | PlayerState::Paused { track_id, .. }
                    | PlayerState::EndOfTrack { track_id } => {
                        self.stop_sink_if_running();
                        self.send_event(PlayerEvent::Stopped { track_id });
                        self.state = PlayerState::Stopped;
                    },
                    PlayerState::Stopped => {
                        warn!("Player::stop called from invalid state");
                    }
                    PlayerState::Invalid => panic!("invalid state"),
                }
            }
        }
    }

    fn send_event(&mut self, event: PlayerEvent) {
        let _ = self.event_sender.unbounded_send(event.clone());
    }

    fn find_available_alternative<'a>(&self, track: &'a Track) -> Option<Cow<'a, Track>> {
        if track.available {
            Some(Cow::Borrowed(track))
        } else {
            let alternatives = track.alternatives
                .iter()
                .map(|alt_id| {
                    Track::get(&self.session, *alt_id)
                });
            let alternatives = future::join_all(alternatives).wait().unwrap();

            alternatives.into_iter().find(|alt| alt.available).map(Cow::Owned)
        }
    }

    fn load_track(&self, track_id: SpotifyId, position: i64) -> Option<Decoder> {
        let track = Track::get(&self.session, track_id).wait().unwrap();

        info!("Loading track \"{}\"", track.name);

        let track = match self.find_available_alternative(&track) {
            Some(track) => track,
            None => {
                warn!("Track \"{}\" is not available", track.name);
                return None;
            }
        };

        let format = match self.config.bitrate {
            Bitrate::Bitrate96 => FileFormat::OGG_VORBIS_96,
            Bitrate::Bitrate160 => FileFormat::OGG_VORBIS_160,
            Bitrate::Bitrate320 => FileFormat::OGG_VORBIS_320,
        };

        let file_id = match track.files.get(&format) {
            Some(&file_id) => file_id,
            None => {
                warn!("Track \"{}\" is not available in format {:?}", track.name, format);
                return None;
            }
        };

        let key = self.session.audio_key().request(track.id, file_id).wait().unwrap();

        let encrypted_file = AudioFile::open(&self.session, file_id).wait().unwrap();
        let audio_file = Subfile::new(AudioDecrypt::new(key, encrypted_file), 0xa7);

        let mut decoder = VorbisDecoder::new(audio_file).unwrap();

        match decoder.seek(position) {
            Ok(_) => (),
            Err(err) => error!("Vorbis error: {:?}", err),
        }

        info!("Track \"{}\" loaded", track.name);

        Some(decoder)
    }
}

impl Drop for PlayerInternal {
    fn drop(&mut self) {
        debug!("drop Player[{}]", self.session.session_id());
    }
}

impl ::std::fmt::Debug for PlayerCommand {
    fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
        match *self {
            PlayerCommand::Load(track, play, position, _) => {
                f.debug_tuple("Load")
                 .field(&track)
                 .field(&play)
                 .field(&position)
                 .finish()
            }
            PlayerCommand::Play => {
                f.debug_tuple("Play").finish()
            }
            PlayerCommand::Pause => {
                f.debug_tuple("Pause").finish()
            }
            PlayerCommand::Stop => {
                f.debug_tuple("Stop").finish()
            }
            PlayerCommand::Seek(position) => {
                f.debug_tuple("Seek")
                 .field(&position)
                 .finish()
            }
        }
    }
}

struct Subfile<T: Read + Seek> {
    stream: T,
    offset: u64,
}

impl<T: Read + Seek> Subfile<T> {
    pub fn new(mut stream: T, offset: u64) -> Subfile<T> {
        stream.seek(SeekFrom::Start(offset)).unwrap();
        Subfile {
            stream: stream,
            offset: offset,
        }
    }
}

impl<T: Read + Seek> Read for Subfile<T> {
    fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
        self.stream.read(buf)
    }
}

impl<T: Read + Seek> Seek for Subfile<T> {
    fn seek(&mut self, mut pos: SeekFrom) -> Result<u64> {
        pos = match pos {
            SeekFrom::Start(offset) => SeekFrom::Start(offset + self.offset),
            x => x,
        };

        let newpos = try!(self.stream.seek(pos));
        if newpos > self.offset {
            Ok(newpos - self.offset)
        } else {
            Ok(0)
        }
    }
}