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import type { DeviceStart } from '@/shared/contracts/signaling.ts';
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import { newerRevision, sameNowPlaying } from '@/shared/contracts/track.ts';
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import type { NowPlaying, Track } from '@/shared/contracts/track.ts';
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import type { Publisher } from './room-state.ts';
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import { demand } from './rpc.ts';
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function sameTrack(a: Track | null | undefined, b: Track | null | undefined): boolean {
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  return a?.title === b?.title && a?.artist === b?.artist && a?.durationMs === b?.durationMs;
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}
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export function startupMetadata(input: DeviceStart) {
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  if (input.nowPlaying && input.track !== undefined) {
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    demand(
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      sameTrack(input.track, input.nowPlaying.track),
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      400,
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      'Initial song metadata must agree.',
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    );
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  }
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  return {
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    track: (input.nowPlaying ? input.nowPlaying.track : input.track) ?? undefined,
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    nowPlaying: input.nowPlaying,
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  };
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}
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export function checkStartupMetadata(
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  existing: Publisher,
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  input: ReturnType<typeof startupMetadata>,
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): void {
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  const initialTrack = existing.initialNowPlaying
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    ? existing.initialNowPlaying.track
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    : existing.track;
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  demand(
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    sameTrack(initialTrack, input.track),
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    409,
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    'Startup track information cannot change within a device boot.',
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  );
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  demand(
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    existing.initialNowPlaying
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      ? !!input.nowPlaying && sameNowPlaying(existing.initialNowPlaying, input.nowPlaying)
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      : !input.nowPlaying,
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    409,
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    'Startup playlist information cannot change within a device boot.',
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  );
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}
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/** Reject conflicts, ignore delayed revisions, and retain the accepted immutable value. */
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export function heartbeatMetadata(previous: NowPlaying | undefined, next: NowPlaying): NowPlaying {
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  demand(
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    !previous || previous.trackCount === next.trackCount,
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    409,
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    'Playlist size cannot change within a device boot.',
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  );
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  if (previous?.revision === next.revision) {
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    demand(sameNowPlaying(previous, next), 409, 'A playback revision cannot describe two songs.');
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  }
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  return !previous || newerRevision(next.revision, previous.revision) ? next : previous;
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}