Amphlify/Packages/AmphlifyKit/Tests/PlaybackTests/PlaybackSessionTests.swift

import Domain
import Foundation
@testable import Playback
import Testing

actor RecordingEngine: OutputEngine {
    nonisolated let events: AsyncStream<OutputEvent>
    nonisolated let continuation: AsyncStream<OutputEvent>.Continuation
    private(set) var loaded: [QueueItem.ID] = []
    private(set) var prepared: [QueueItem.ID?] = []

    init() {
        (events, continuation) = AsyncStream<OutputEvent>.makeStream()
    }

    func load(_ item: QueueItem, at _: TimeInterval) {
        loaded.append(item.id)
    }

    func prepare(_ item: QueueItem?) {
        prepared.append(item?.id)
    }

    func play() {}
    func pause() {}
    func seek(to _: TimeInterval) {}
    func stop() {}
}

final class FakeClock: @unchecked Sendable {
    private let lock = NSLock()
    private var instant = ContinuousClock.now

    var now: ContinuousClock.Instant {
        lock.withLock { instant }
    }

    func advance(_ seconds: Double) {
        lock.withLock { instant += .seconds(seconds) }
    }
}

private func tracks(_ count: Int) -> [Track] {
    let source = SourceID()
    return (0 ..< count).map {
        Track(
            id: EntityID(source: source, remote: "\($0)"),
            title: "Track \($0)",
            albumID: nil,
            albumTitle: "",
            artistID: nil,
            artistName: "",
            duration: 200
        )
    }
}

@Test func queueStartsAtIndexAndAnchorsPosition() async {
    let clock = FakeClock()
    let session = PlaybackSession(engine: RecordingEngine()) { clock.now }
    await session.send(.setQueue(tracks: tracks(5), startIndex: 2, shuffled: false))
    clock.advance(10)
    let state = await session.snapshot
    #expect(state.current?.track.title == "Track 2")
    #expect(state.history.count == 2 && state.upcoming.count == 2)
    #expect(state.status == .playing)
    #expect(abs(state.anchor.position(at: clock.now) - 10) < 0.001)
}

@Test func pauseFreezesAnchor() async {
    let clock = FakeClock()
    let session = PlaybackSession(engine: RecordingEngine()) { clock.now }
    await session.send(.setQueue(tracks: tracks(2), startIndex: 0, shuffled: false))
    clock.advance(30)
    await session.send(.pause)
    clock.advance(30)
    let state = await session.snapshot
    #expect(abs(state.anchor.position(at: clock.now) - 30) < 0.001)
}

@Test func previousRestartsAfterThresholdAndGoesBackBefore() async {
    let clock = FakeClock()
    let session = PlaybackSession(engine: RecordingEngine()) { clock.now }
    await session.send(.setQueue(tracks: tracks(3), startIndex: 1, shuffled: false))
    clock.advance(10)
    await session.send(.previous)
    #expect(await session.snapshot.current?.track.title == "Track 1")
    await session.send(.previous)
    #expect(await session.snapshot.current?.track.title == "Track 0")
}

@Test func queueEditsAddressItemsByID() async {
    let session = PlaybackSession(engine: RecordingEngine())
    await session.send(.setQueue(tracks: tracks(4), startIndex: 0, shuffled: false))
    let upcoming = await session.snapshot.upcoming
    await session.send(.move(item: upcoming[2].id, after: nil))
    await session.send(.remove(upcoming[0].id))
    #expect(await session.snapshot.upcoming.map(\.track.title) == ["Track 3", "Track 2"])
    await session.send(.jump(to: upcoming[1].id))
    let state = await session.snapshot
    #expect(state.current?.track.title == "Track 2" && state.upcoming.isEmpty)
}

@Test func finishedTrackAdvancesAndStopsAtEndWithoutRepeat() async throws {
    let engine = RecordingEngine()
    let session = PlaybackSession(engine: engine)
    let states = await session.states()
    await session.send(.setQueue(tracks: tracks(2), startIndex: 0, shuffled: false))
    for expected in [("Track 1", PlaybackStatus.playing), ("Track 0", .paused)] {
        let current = try #require(await session.snapshot.current)
        engine.continuation.yield(.finished(current.id))
        for await state in states where state.current?.id != current.id {
            #expect(state.current?.track.title == expected.0 && state.status == expected.1)
            break
        }
    }
}

@Test func unshuffleRestoresOriginalOrder() async {
    let session = PlaybackSession(engine: RecordingEngine())
    await session.send(.setQueue(tracks: tracks(8), startIndex: 0, shuffled: false))
    await session.send(.setShuffle(true))
    await session.send(.setShuffle(false))
    #expect(await session.snapshot.upcoming.map(\.track.title) == (1 ..< 8).map { "Track \($0)" })
}

@Test func prepareFollowsHeadOfUpcoming() async {
    let engine = RecordingEngine()
    let session = PlaybackSession(engine: engine)
    await session.send(.setQueue(tracks: tracks(3), startIndex: 0, shuffled: false))
    var state = await session.snapshot
    #expect(await engine.prepared == [state.upcoming[0].id])
    await session.send(.next)
    state = await session.snapshot
    #expect(await engine.prepared.last == state.upcoming[0].id)
    await session.send(.next)
    #expect(await engine.prepared.last == .some(nil))
}

@Test func anchorEventReanchorsCurrentAndIgnoresStaleID() async throws {
    let clock = FakeClock()
    let engine = RecordingEngine()
    let session = PlaybackSession(engine: engine) { clock.now }
    let states = await session.states()
    await session.send(.setQueue(tracks: tracks(2), startIndex: 0, shuffled: false))
    let current = try #require(await session.snapshot.current)
    engine.continuation.yield(.anchor(UUID(), position: 50, rate: 1))
    engine.continuation.yield(.anchor(current.id, position: 70, rate: 0))
    for await state in states where state.anchor.rate == 0 {
        #expect(state.status == .playing && state.current?.id == current.id)
        #expect(abs(state.anchor.position(at: clock.now) - 70) < 0.001)
        break
    }
}

@Test func failedTrackAdvancesToNext() async throws {
    let engine = RecordingEngine()
    let session = PlaybackSession(engine: engine)
    let states = await session.states()
    await session.send(.setQueue(tracks: tracks(2), startIndex: 0, shuffled: false))
    let current = try #require(await session.snapshot.current)
    engine.continuation.yield(.failed(current.id))
    for await state in states where state.current?.id != current.id {
        #expect(state.current?.track.title == "Track 1" && state.status == .playing)
        break
    }
}

@Test func everyTrackFailingStopsInsteadOfLooping() async throws {
    let engine = RecordingEngine()
    let session = PlaybackSession(engine: engine)
    let states = await session.states()
    await session.send(.setQueue(tracks: tracks(2), startIndex: 0, shuffled: false))
    await session.send(.setRepeat(.all))
    for _ in 0 ..< 3 {
        let current = try #require(await session.snapshot.current)
        engine.continuation.yield(.failed(current.id))
        for await state in states where state.current?.id != current.id || state.status == .paused {
            break
        }
    }
    let state = await session.snapshot
    #expect(state.status == .paused && state.anchor.rate == 0)
    #expect(await engine.loaded.count == 2)
}