//! A [`MediaPlayer`] over the old [`PlayerBackend`] trait.
//!
//! Two purposes.
//!
//! **Migration.** Engines not yet ported — ExoPlayer, the webview element, the
//! null backend — keep working while `PlayerController` moves onto the new
//! contract (DR-245). Without this the port would have to land all four engines
//! at once.
//!
//! **Evidence.** It reproduces exactly what every caller used to do: `load`,
//! then `play`, then `seek` for a start position. Running the conformance suite
//! against it therefore shows the old path failing the cases the new one passes,
//! on the same engine and the same media — which is the difference between
//! asserting that a design was wrong and demonstrating it.
//!
//! It is deliberately a faithful reproduction, not a fixed-up one. Making it
//! pass would defeat the point.
//!
//! TRACES: UR-081 | DR-245

#![allow(dead_code)] // Consumed when PlayerController is ported (DR-245).

use std::time::Duration;

use super::backend::{PlayerBackend, PlayerError};
use super::media_player::{Capabilities, MediaPlayer, OpenRequest, Phase, PlaybackSnapshot};
use super::state::PlayerState;

pub struct LegacyPlayer<B: PlayerBackend> {
    inner: B,
    /// The old trait has no notion of "opening", so this is the best the wrapper
    /// can do: it knows an item was handed over, not whether the engine is ready
    /// for one. That gap is the whole problem.
    has_item: bool,
}

impl<B: PlayerBackend> LegacyPlayer<B> {
    pub fn new(inner: B) -> Self {
        Self {
            inner,
            has_item: false,
        }
    }

    pub fn inner_mut(&mut self) -> &mut B {
        &mut self.inner
    }
}

impl<B: PlayerBackend + Send> MediaPlayer for LegacyPlayer<B> {
    /// Load, play, then seek — the sequence every caller used to write.
    ///
    /// The seek is issued immediately, because a caller has no way to know when
    /// the engine becomes ready. On an engine whose load is asynchronous it
    /// fails and is discarded, and playback begins at zero: DR-241, reproduced.
    fn open(&mut self, req: OpenRequest) -> Result<(), PlayerError> {
        self.inner.load(&req.media)?;
        self.has_item = true;
        if req.autoplay {
            self.inner.play()?;
        }
        if !req.start.is_zero() {
            // Faithfully ignoring the failure, exactly as the old callers did.
            let _ = self.inner.seek(req.start.as_secs_f64());
        }
        Ok(())
    }

    fn play(&mut self) -> Result<(), PlayerError> {
        self.inner.play()
    }

    fn pause(&mut self) -> Result<(), PlayerError> {
        self.inner.pause()
    }

    fn close(&mut self) -> Result<(), PlayerError> {
        self.has_item = false;
        self.inner.stop()
    }

    fn seek(&mut self, to: Duration) -> Result<(), PlayerError> {
        self.inner.seek(to.as_secs_f64())
    }

    fn set_volume(&mut self, volume: f32) -> Result<(), PlayerError> {
        self.inner.set_volume(volume)
    }

    /// The old trait has no mute. Folding it into volume would lose the user's
    /// level, so this reports unsupported rather than pretending.
    fn set_muted(&mut self, _muted: bool) -> Result<(), PlayerError> {
        Err(PlayerError {
            message: "mute is not supported by this backend".to_string(),
        })
    }

    fn set_rate(&mut self, _rate: f64) -> Result<(), PlayerError> {
        Err(PlayerError {
            message: "playback rate is not supported by this backend".to_string(),
        })
    }

    fn select_audio_track(&mut self, index: Option<i32>) -> Result<(), PlayerError> {
        self.inner.set_audio_track(index.unwrap_or(-1))
    }

    fn select_subtitle_track(&mut self, index: Option<i32>) -> Result<(), PlayerError> {
        self.inner.set_subtitle_track(index)
    }

    fn snapshot(&self) -> PlaybackSnapshot {
        let phase = match self.inner.state() {
            _ if !self.has_item => Phase::Idle,
            PlayerState::Playing { .. } => Phase::Playing,
            PlayerState::Paused { .. } => Phase::Paused,
            PlayerState::Idle => Phase::Idle,
            PlayerState::Error { error, .. } => Phase::Failed(error),
            // `Loading` is the closest the old trait comes to an opening state,
            // but it is set once the engine has accepted the item rather than
            // while it is still accepting it — which is precisely the window it
            // cannot describe.
            PlayerState::Loading { .. } | PlayerState::Seeking { .. } => Phase::Ready,
        };
        PlaybackSnapshot {
            phase,
            position: Duration::from_secs_f64(self.inner.position().max(0.0)),
            duration: self.inner.duration().map(Duration::from_secs_f64),
            seekable: true,
            volume: self.inner.volume(),
            muted: false,
            rate: 1.0,
            audio_track: None,
            subtitle_track: None,
        }
    }

    fn capabilities(&self) -> Capabilities {
        Capabilities {
            video: false,
            audio_settings: true,
            subtitle_switching: true,
            audio_track_switching: true,
        }
    }
}