iOS 1.0.4: per-song saved mixes, karaoke mode with synced lyrics

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ios/Stemify/Playback/Lyrics.swift

@@ -0,0 +1,86 @@
+import Foundation
+
+struct LyricLine: Hashable {
+    let ms: Int64
+    let text: String
+}
+
+struct Lyrics {
+    var lines: [LyricLine] = []
+    /// False for plain lyrics, which have no timings (every [ms] is 0).
+    var synced = false
+    var instrumental = false
+}
+
+/// Lyrics from LRCLIB (lrclib.net), synced when it has them. Hits are cached on disk by track,
+/// misses only until the app restarts.
+actor LyricsSource {
+    static let shared = LyricsSource()
+
+    private struct Record: Codable {
+        var syncedLyrics: String?
+        var plainLyrics: String?
+        var instrumental: Bool?
+        var duration: Double?
+    }
+
+    private let dir: URL
+    private var misses: Set<String> = []
+
+    private init() {
+        dir = FileManager.default.urls(for: .cachesDirectory, in: .userDomainMask)[0].appendingPathComponent("lyrics", isDirectory: true)
+        try? FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
+    }
+
+    /// Nil when LRCLIB has nothing for this song or couldn't be reached.
+    func lyrics(_ t: Track) async -> Lyrics? {
+        let file = dir.appendingPathComponent(t.ratingKey.replacingOccurrences(of: "/", with: "_") + ".json")
+        if let data = try? Data(contentsOf: file), let r = try? JSONDecoder().decode(Record.self, from: data) { return Self.parse(r) }
+        if misses.contains(t.ratingKey) { return nil }
+        let secs = Double(t.durationMs) / 1000
+        var rec = await get("get", ["track_name": t.title, "artist_name": t.artist, "album_name": t.album, "duration": String(Int(secs.rounded()))])
+            .flatMap { try? JSONDecoder().decode(Record.self, from: $0) }
+        if rec == nil, let data = await get("search", ["track_name": t.title, "artist_name": t.artist]),
+           let found = try? JSONDecoder().decode([Record].self, from: data) {
+            // Closest length first, so a live or extended version doesn't win.
+            let close = found.filter { abs(($0.duration ?? 0) - secs) < 8 || secs <= 0 }
+            rec = close.first { $0.syncedLyrics?.isEmpty == false } ?? close.first { $0.plainLyrics?.isEmpty == false } ?? close.first
+        }
+        guard let rec else {
+            misses.insert(t.ratingKey)
+            return nil
+        }
+        if let data = try? JSONEncoder().encode(rec) { try? data.write(to: file, options: .atomic) }
+        return Self.parse(rec)
+    }
+
+    private func get(_ path: String, _ query: [String: String]) async -> Data? {
+        var c = URLComponents(string: "https://lrclib.net/api/\(path)")!
+        c.queryItems = query.map { URLQueryItem(name: $0.key, value: $0.value) }
+        var req = URLRequest(url: c.url!, timeoutInterval: 10)
+        req.setValue("Stemify iOS (https://git.iamchrisama.com/cdnutter/stemify)", forHTTPHeaderField: "User-Agent")
+        guard let (data, resp) = try? await URLSession.shared.data(for: req), (resp as? HTTPURLResponse)?.statusCode == 200 else { return nil }
+        return data
+    }
+
+    private static let stamp = #/\[(\d+):(\d+(?:\.\d+)?)\]/#
+
+    /// LRC: each line starts with one or more [mm:ss.xx] stamps.
+    private static func parse(_ r: Record) -> Lyrics {
+        if let lrc = r.syncedLyrics, !lrc.isEmpty {
+            var lines: [LyricLine] = []
+            for raw in lrc.split(separator: "\n", omittingEmptySubsequences: false) {
+                let stamps = raw.matches(of: stamp)
+                guard let last = stamps.last else { continue }
+                let text = raw[last.range.upperBound...].trimmingCharacters(in: .whitespaces)
+                for m in stamps {
+                    let ms = (Int64(m.output.1) ?? 0) * 60_000 + Int64((Double(m.output.2) ?? 0) * 1000)
+                    lines.append(LyricLine(ms: ms, text: text))
+                }
+            }
+            return Lyrics(lines: lines.sorted { $0.ms < $1.ms }, synced: true)
+        }
+        let plain = (r.plainLyrics ?? "").split(separator: "\n", omittingEmptySubsequences: false).map { LyricLine(ms: 0, text: String($0)) }
+        return Lyrics(lines: plain.count > 1 || plain.first?.text.isEmpty == false ? plain : [], instrumental: r.instrumental == true)
+    }
+}

ios/Stemify/Playback/PlaybackManager.swift

@@ -106,6 +106,7 @@ final class PlaybackManager: StemEngineListener, @unchecked Sendable {
     @ObservationIgnored private let eq: EqController
     @ObservationIgnored private(set) var engine: StemEngine!
     @ObservationIgnored private let queueFile: URL
+    @ObservationIgnored private let songMixFile: URL
 
     private(set) var queue: [QueueItem] = []
     private(set) var index = -1
@@ -121,6 +122,11 @@ final class PlaybackManager: StemEngineListener, @unchecked Sendable {
     private(set) var waveform: Waveform?
     private(set) var durationMs: Int64 = 0
     private(set) var message: AppMessage?
+    /// Mixes saved for single songs (by rating key), put back whenever that song starts.
+    private(set) var songMixes: [String: [String: StemSetting]] = [:]
+    /// Karaoke mode: vocals out on every song, lyrics on Now Playing.
+    private(set) var karaoke = false
+    @ObservationIgnored private var preKaraokeMix: [String: StemSetting]?
 
     @ObservationIgnored private var listeners: [UUID: () -> Void] = [:]
     @ObservationIgnored private var messageListeners: [UUID: (String) -> Void] = [:]
@@ -148,6 +154,8 @@ final class PlaybackManager: StemEngineListener, @unchecked Sendable {
         self.cache = cache
         self.eq = eq
         queueFile = dir.appendingPathComponent("queue.json")
+        songMixFile = dir.appendingPathComponent("song-mixes.json")
+        songMixes = (try? JSONDecoder().decode([String: [String: StemSetting]].self, from: Data(contentsOf: songMixFile))) ?? [:]
         master = settings.masterVolume
         engine = StemEngine(listener: self)
         eq.onParams = { [weak self] p in self?.engine.eqParams = p }
@@ -405,6 +413,42 @@ final class PlaybackManager: StemEngineListener, @unchecked Sendable {
         pushMix()
     }
 
+    /// The mix a song starts with: karaoke if that's on, else the song's saved mix, else cleared (or kept, per settings).
+    private func startMix(_ t: Track) -> [String: StemSetting] {
+        if karaoke { return Self.karaokeMix }
+        return songMixes[t.ratingKey] ?? (settings.keepStemMix ? mix : [:])
+    }
+
+    private static let karaokeMix = ["vocals": StemSetting(muted: true)]
+
+    /// Turning it off puts back the song's saved mix, or the one from before, unless the mix was changed meanwhile.
+    func setKaraoke(_ on: Bool) {
+        guard on != karaoke else { return }
+        karaoke = on
+        if on {
+            preKaraokeMix = mix
+            applyMix(Self.karaokeMix)
+        } else {
+            if MixPresets.normalized(mix) == Self.karaokeMix { applyMix(songMix ?? preKaraokeMix ?? [:]) }
+            preKaraokeMix = nil
+            changed()
+        }
+    }
+
+    var songMix: [String: StemSetting]? { current.flatMap { songMixes[$0.track.ratingKey] } }
+
+    func saveSongMix() { setSongMix(MixPresets.normalized(mix)) }
+    func forgetSongMix() { setSongMix(nil) }
+
+    private func setSongMix(_ m: [String: StemSetting]?) {
+        guard let key = current?.track.ratingKey else { return }
+        songMixes[key] = m
+        let all = songMixes, file = songMixFile
+        DispatchQueue.global(qos: .utility).async {
+            if let data = try? JSONEncoder().encode(all) { try? data.write(to: file, options: .atomic) }
+        }
+    }
+
     private func editMix(_ name: String, _ f: (inout StemSetting) -> Void) {
         var s = mix[name] ?? StemSetting()
         f(&s)
@@ -462,7 +506,7 @@ final class PlaybackManager: StemEngineListener, @unchecked Sendable {
         if play && !activateSession() { return }
         playWhenReady = play
         buffering = true
-        if !settings.keepStemMix { mix = [:] }
+        mix = startMix(item.track)
         changed()
         save()
         loadTask = Task { @MainActor [weak self] in
@@ -635,7 +679,7 @@ final class PlaybackManager: StemEngineListener, @unchecked Sendable {
         guard let item = current else { return }
         durationMs = item.track.durationMs
         waveform = nil
-        if !settings.keepStemMix { mix = [:] }
+        mix = startMix(item.track)
         source = currentEntry != nil ? .Stems : .Original
         stemNames = Stems.sort(currentEntry?.stems.map(\.name) ?? ["mix"])
         pushMix()