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//! A song instance within one publisher generation; independent of the RTP clock.
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use crate::{
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    music::{Catalog, Error, FRAME_MS, Track},
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    playback::Due,
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};
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use serde::Serialize;
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#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
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#[serde(rename_all = "camelCase")]
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pub struct NowPlaying {
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    pub revision: u32,
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    pub track_index: u32,
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    pub track_count: u32,
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    pub track: Option<Track>,
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}
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/// Published state describes the most recent frame returned by
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/// [`Playback::due`](crate::playback::Playback::due).
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/// Use the same immutable catalog for construction and subsequent updates.
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#[derive(Debug)]
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pub struct Snapshot {
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    pub now_playing: NowPlaying,
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    pub position_ms: u32,
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    pub duration_ms: u32,
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}
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impl Snapshot {
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    pub fn new(catalog: &Catalog) -> Self {
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        let first = &catalog.songs()[0];
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        Self {
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            now_playing: NowPlaying {
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                revision: 0,
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                track_index: 0,
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                track_count: catalog.songs().len() as u32,
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                track: first.metadata.clone(),
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            },
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            position_ms: 0,
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            duration_ms: first.frames.get() * FRAME_MS,
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        }
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    }
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    /// Records a due frame and reports whether its playback revision changed.
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    pub fn record(&mut self, catalog: &Catalog, due: Due) -> Result<bool, Error> {
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        let song = catalog
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            .songs()
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            .get(due.track_index as usize)
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            .ok_or(Error::TrackCount)?;
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        if due.index >= song.frames.get() {
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            return Err(Error::FrameCount);
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        }
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        let changed = due.revision != self.now_playing.revision;
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        if changed {
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            self.now_playing = NowPlaying {
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                revision: due.revision,
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                track_index: due.track_index,
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                track_count: catalog.songs().len() as u32,
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                track: song.metadata.clone(),
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            };
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        }
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        self.position_ms = due.index * FRAME_MS;
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        self.duration_ms = song.frames.get() * FRAME_MS;
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        Ok(changed)
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    }
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}
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#[derive(Debug, Serialize)]
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#[serde(rename_all = "camelCase")]
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pub struct Message<'a> {
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    pub event: &'static str,
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    pub now_playing: &'a NowPlaying,
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}