feat(*): subsonic client with avfoundation playback and apple music ui

Packages/AmphlifyKit/Sources/Playback/PlaybackModel.swift

@@ -0,0 +1,88 @@
+import Domain
+import Foundation
+
+public struct QueueItem: Identifiable, Hashable, Codable, Sendable {
+    public let id: UUID
+    public let track: Track
+
+    public init(id: UUID = UUID(), track: Track) {
+        self.id = id
+        self.track = track
+    }
+}
+
+public enum RepeatMode: String, Codable, Sendable, CaseIterable {
+    case off, all, one
+}
+
+public enum PlaybackCommand: Codable, Sendable {
+    case play
+    case pause
+    case togglePlayPause
+    case seek(to: TimeInterval)
+    case next
+    case previous
+    case setQueue(tracks: [Track], startIndex: Int, shuffled: Bool)
+    case insertNext([Track])
+    case insertLast([Track])
+    case jump(to: QueueItem.ID)
+    case move(item: QueueItem.ID, after: QueueItem.ID?)
+    case remove(QueueItem.ID)
+    case clearUpcoming
+    case setShuffle(Bool)
+    case setRepeat(RepeatMode)
+}
+
+public struct PlaybackAnchor: Hashable, Sendable {
+    public var position: TimeInterval
+    public var instant: ContinuousClock.Instant
+    public var rate: Double
+
+    public init(position: TimeInterval, instant: ContinuousClock.Instant, rate: Double) {
+        self.position = position
+        self.instant = instant
+        self.rate = rate
+    }
+
+    public func position(at now: ContinuousClock.Instant) -> TimeInterval {
+        let elapsed = now - instant
+        let seconds = Double(elapsed.components.seconds) + Double(elapsed.components.attoseconds) / 1e18
+        return position + seconds * rate
+    }
+}
+
+public enum PlaybackStatus: String, Sendable {
+    case stopped, paused, playing
+}
+
+public struct PlaybackState: Hashable, Sendable {
+    public var history: [QueueItem] = []
+    public var current: QueueItem?
+    public var upcoming: [QueueItem] = []
+    public var status: PlaybackStatus = .stopped
+    public var anchor = PlaybackAnchor(position: 0, instant: .now, rate: 0)
+    public var isShuffled = false
+    public var repeatMode: RepeatMode = .off
+
+    public init() {}
+}
+
+public enum OutputEvent: Sendable {
+    case finished(QueueItem.ID)
+    case failed(QueueItem.ID)
+    case anchor(QueueItem.ID, position: TimeInterval, rate: Double)
+}
+
+public protocol OutputEngine: Sendable {
+    var events: AsyncStream<OutputEvent> { get }
+    func load(_ item: QueueItem, at position: TimeInterval) async
+    func prepare(_ item: QueueItem?) async
+    func play() async
+    func pause() async
+    func seek(to position: TimeInterval) async
+    func stop() async
+}
+
+public extension OutputEngine {
+    func prepare(_: QueueItem?) async {}
+}