iOS: export/import stem playlists and sound settings

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

ios/Stemify/Core/Backup.swift

@@ -0,0 +1,84 @@
+import Foundation
+import SwiftUI
+import UniformTypeIdentifiers
+
+/// What an export file holds: stem playlists (with each song's mix) and the non-secret sound settings.
+/// Plex and stem server tokens and URLs are never included.
+struct StemifyExport: Codable {
+    static let format = "stemify-export"
+    static let version = 1
+
+    struct Prefs: Codable {
+        var stemQuality: String?
+        var keepStemMix: Bool?
+        var karaokeVocals: Int?
+        var karaokeSoftDb: Int?
+        var playbackSpeed: Double?
+        var downloadsWifiOnly: Bool?
+    }
+
+    var format = StemifyExport.format
+    var version = StemifyExport.version
+    var exported = Date()
+    var playlists: [StemPlaylist]
+    var prefs: Prefs
+
+    @MainActor
+    static func capture(_ lists: StemPlaylists, _ s: Settings) -> StemifyExport {
+        StemifyExport(playlists: lists.lists, prefs: Prefs(
+            stemQuality: s.stemQuality.rawValue, keepStemMix: s.keepStemMix, karaokeVocals: s.karaokeVocals,
+            karaokeSoftDb: s.karaokeSoftDb, playbackSpeed: s.playbackSpeed, downloadsWifiOnly: s.downloadsWifiOnly))
+    }
+
+    func encoded() throws -> Data {
+        let e = JSONEncoder()
+        e.outputFormatting = [.prettyPrinted, .sortedKeys]
+        e.dateEncodingStrategy = .iso8601
+        return try e.encode(self)
+    }
+
+    static func decode(_ data: Data) throws -> StemifyExport {
+        let d = JSONDecoder()
+        d.dateDecodingStrategy = .iso8601
+        let x = try d.decode(StemifyExport.self, from: data)
+        guard x.format == Self.format else { throw BackupError.notAnExport }
+        guard x.version <= Self.version else { throw BackupError.newerVersion }
+        return x
+    }
+
+    @MainActor
+    func apply(to s: Settings) {
+        if let v = prefs.stemQuality.flatMap(StemQuality.init(rawValue:)) { s.stemQuality = v }
+        if let v = prefs.keepStemMix { s.keepStemMix = v }
+        if let v = prefs.karaokeVocals { s.karaokeVocals = v }
+        if let v = prefs.karaokeSoftDb { s.karaokeSoftDb = v }
+        if let v = prefs.playbackSpeed { s.playbackSpeed = v }
+        if let v = prefs.downloadsWifiOnly { s.downloadsWifiOnly = v }
+    }
+}
+
+enum BackupError: LocalizedError {
+    case notAnExport, newerVersion
+    var errorDescription: String? {
+        switch self {
+        case .notAnExport: "That file isn't a Stemify export."
+        case .newerVersion: "That export is from a newer version of Stemify."
+        }
+    }
+}
+
+/// Where an export goes and comes from. The Files sheet covers local storage and iCloud Drive;
+/// a direct iCloud (ubiquity container / CloudKit) backend would be another conformer.
+protocol BackupDestination {
+    func write(_ data: Data, name: String) async throws
+    func read() async throws -> Data
+}
+
+/// The export as a document for fileExporter, which also reaches iCloud Drive through Files.
+struct ExportDocument: FileDocument {
+    static var readableContentTypes: [UTType] { [.json] }
+    var data: Data
+    init(data: Data = Data()) { self.data = data }
+    init(configuration: ReadConfiguration) throws { data = configuration.file.regularFileContents ?? Data() }
+    func fileWrapper(configuration: WriteConfiguration) throws -> FileWrapper { FileWrapper(regularFileWithContents: data) }
+}

ios/Stemify/Playback/StemPlaylists.swift

@@ -70,6 +70,24 @@ final class StemPlaylists {
         return MixPresets.current(allStems, mix)?.label ?? "Custom Mix"
     }
 
+    /// Brings in playlists from an export: new ids are added, ids already here are replaced when the
+    /// import was updated more recently. Returns how many lists were added or replaced.
+    @discardableResult
+    func merge(_ incoming: [StemPlaylist]) -> Int {
+        var n = 0
+        for pl in incoming {
+            if let i = lists.firstIndex(where: { $0.id == pl.id }) {
+                guard pl.updated > lists[i].updated else { continue }
+                lists[i] = pl
+            } else {
+                lists.append(pl)
+            }
+            n += 1
+        }
+        if n > 0 { save() }
+        return n
+    }
+
     private func edit(_ id: String, _ change: (inout StemPlaylist) -> Void) {
         guard let i = lists.firstIndex(where: { $0.id == id }) else { return }
         change(&lists[i])

ios/Stemify/UI/Screens/SettingsScreens.swift

@@ -1,4 +1,5 @@
 import SwiftUI
+import UniformTypeIdentifiers
 
 /// A Settings.app row that pushes [route]: icon, title, grey value, chevron.
 private struct NavCell: View {
@@ -147,6 +148,11 @@ struct SettingsScreen: View {
                 NavCell(title: "Cache & Downloads", value: gb(g.cache.usage.cachedBytes), icon: "externaldrive.fill", iconBg: 0x8E8E93, route: .Storage)
                 ToggleCell(title: "Download on Wi-Fi Only", icon: "arrow.down.circle.fill", iconBg: 0x30B0C7, isOn: $s.downloadsWifiOnly)
             } header: { Header(text: "Storage") }
+            Section {
+                BackupCells()
+            } header: { Header(text: "Backup") } footer: {
+                Footer(text: "Stem playlists, their mixes and sound settings. Tokens and server addresses are left out. Save to iCloud Drive from the Files sheet.")
+            }
             Section {
                 NavCell(title: "Appearance", value: s.theme.label, icon: "paintbrush.fill", iconBg: 0x007AFF, route: .Appearance)
             } header: { Header(text: "Display") } footer: {
@@ -159,6 +165,42 @@ struct SettingsScreen: View {
     }
 }
 
+struct BackupCells: View {
+    private var g: AppGraph { .shared }
+    @State private var doc = ExportDocument()
+    @State private var exporting = false
+    @State private var importing = false
+    @State private var message: String?
+    @Environment(\.palette) private var p
+
+    var body: some View {
+        Button {
+            do { doc = ExportDocument(data: try StemifyExport.capture(g.stemPlaylists, g.settings).encoded()); exporting = true }
+            catch { message = error.localizedDescription }
+        } label: { ValueCell(title: "Export", value: "\(g.stemPlaylists.lists.count) playlists", icon: "square.and.arrow.up", iconBg: 0x007AFF) }
+            .themedRow()
+        Button { importing = true } label: { ValueCell(title: "Import", value: nil, icon: "square.and.arrow.down", iconBg: 0x34C759) }
+            .themedRow()
+            .fileExporter(isPresented: $exporting, document: doc, contentType: .json, defaultFilename: "Stemify \(Date().formatted(.iso8601.year().month().day()))") { r in
+                if case .failure(let e) = r { message = e.localizedDescription }
+            }
+            .fileImporter(isPresented: $importing, allowedContentTypes: [.json]) { r in
+                do {
+                    let url = try r.get()
+                    let scoped = url.startAccessingSecurityScopedResource()
+                    defer { if scoped { url.stopAccessingSecurityScopedResource() } }
+                    let x = try StemifyExport.decode(Data(contentsOf: url))
+                    let n = g.stemPlaylists.merge(x.playlists)
+                    x.apply(to: g.settings)
+                    message = "Imported \(n) playlist\(n == 1 ? "" : "s") and your sound settings."
+                } catch { message = error.localizedDescription }
+            }
+            .alert("Backup", isPresented: Binding(get: { message != nil }, set: { if !$0 { message = nil } })) {
+                Button("OK", role: .cancel) {}
+            } message: { Text(message ?? "") }
+    }
+}
+
 // ---- plex -----------------------------------------------------------------------------------
 
 struct PlexAccountScreen: View {