Implement local song project store

Sources/MusicAssistantCore/Persistence/ProjectStore.swift

@@ -1,6 +1,81 @@
-public protocol ProjectStore: Sendable {
-    associatedtype Project
+import Foundation
 
-    func save(_ project: Project) async throws
+public protocol ProjectStore: Sendable {
+    func create(_ project: SongProject) async throws
+    func save(_ project: SongProject) async throws
+    func open(id: String) async throws -> SongProject
     func loadProjectIDs() async throws -> [String]
 }
+
+public actor LocalSongProjectStore: ProjectStore {
+    private let directoryURL: URL
+    private let encoder: JSONEncoder
+    private let decoder: JSONDecoder
+
+    public init(directoryURL: URL) {
+        self.directoryURL = directoryURL
+        self.encoder = JSONEncoder()
+        self.decoder = JSONDecoder()
+        encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
+    }
+
+    public func create(_ project: SongProject) async throws {
+        try ensureDirectoryExists()
+        let url = projectURL(for: project.id)
+        guard !FileManager.default.fileExists(atPath: url.path) else {
+            throw LocalSongProjectStoreError.projectAlreadyExists(project.id)
+        }
+        try saveEncoded(project, to: url)
+    }
+
+    public func save(_ project: SongProject) async throws {
+        try ensureDirectoryExists()
+        try saveEncoded(project, to: projectURL(for: project.id))
+    }
+
+    public func open(id: String) async throws -> SongProject {
+        let url = projectURL(for: id)
+        guard FileManager.default.fileExists(atPath: url.path) else {
+            throw LocalSongProjectStoreError.projectNotFound(id)
+        }
+        let data = try Data(contentsOf: url)
+        return try decoder.decode(SongProject.self, from: data)
+    }
+
+    public func loadProjectIDs() async throws -> [String] {
+        try ensureDirectoryExists()
+        let fileURLs = try FileManager.default.contentsOfDirectory(
+            at: directoryURL,
+            includingPropertiesForKeys: nil
+        )
+        return fileURLs
+            .filter { $0.pathExtension == Self.fileExtension }
+            .map { $0.deletingPathExtension().lastPathComponent }
+            .sorted()
+    }
+
+    private func ensureDirectoryExists() throws {
+        try FileManager.default.createDirectory(
+            at: directoryURL,
+            withIntermediateDirectories: true
+        )
+    }
+
+    private func saveEncoded(_ project: SongProject, to url: URL) throws {
+        let data = try encoder.encode(project)
+        try data.write(to: url, options: [.atomic])
+    }
+
+    private func projectURL(for id: String) -> URL {
+        directoryURL
+            .appendingPathComponent(id)
+            .appendingPathExtension(Self.fileExtension)
+    }
+
+    private static let fileExtension = "json"
+}
+
+public enum LocalSongProjectStoreError: Error, Equatable, Sendable {
+    case projectAlreadyExists(String)
+    case projectNotFound(String)
+}

Tests/MusicAssistantCoreTests/LocalSongProjectStoreTests.swift

@@ -0,0 +1,75 @@
+import Foundation
+import MusicAssistantCore
+import XCTest
+
+final class LocalSongProjectStoreTests: XCTestCase {
+    private var temporaryDirectoryURL: URL!
+
+    override func setUpWithError() throws {
+        temporaryDirectoryURL = FileManager.default.temporaryDirectory
+            .appendingPathComponent("music-assistant-store-tests")
+            .appendingPathComponent(UUID().uuidString)
+    }
+
+    override func tearDownWithError() throws {
+        if let temporaryDirectoryURL {
+            try? FileManager.default.removeItem(at: temporaryDirectoryURL)
+        }
+        temporaryDirectoryURL = nil
+    }
+
+    func testCreatesOpensSavesAndListsSongProjectsLocally() async throws {
+        let store = LocalSongProjectStore(directoryURL: temporaryDirectoryURL)
+        var project = SongProject(
+            id: "local-project",
+            title: "Local Project",
+            idea: "Persist this song locally",
+            genres: [GenreStyle(id: "pop", name: "Pop")]
+        )
+
+        try await store.create(project)
+
+        let createdProjectIDs = try await store.loadProjectIDs()
+        let openedProject = try await store.open(id: project.id)
+
+        XCTAssertEqual(createdProjectIDs, ["local-project"])
+        XCTAssertEqual(openedProject, project)
+
+        project.title = "Updated Local Project"
+        project.setBPMManually(100)
+        try await store.save(project)
+
+        let updatedProject = try await store.open(id: project.id)
+
+        XCTAssertEqual(updatedProject, project)
+    }
+
+    func testCreateDoesNotOverwriteExistingProject() async throws {
+        let store = LocalSongProjectStore(directoryURL: temporaryDirectoryURL)
+        let project = SongProject(
+            id: "duplicate-project",
+            title: "Duplicate",
+            idea: "Do not overwrite"
+        )
+
+        try await store.create(project)
+
+        do {
+            try await store.create(project)
+            XCTFail("Expected duplicate project creation to fail.")
+        } catch let error as LocalSongProjectStoreError {
+            XCTAssertEqual(error, .projectAlreadyExists(project.id))
+        }
+    }
+
+    func testOpenMissingProjectThrowsNotFound() async throws {
+        let store = LocalSongProjectStore(directoryURL: temporaryDirectoryURL)
+
+        do {
+            _ = try await store.open(id: "missing")
+            XCTFail("Expected missing project open to fail.")
+        } catch let error as LocalSongProjectStoreError {
+            XCTAssertEqual(error, .projectNotFound("missing"))
+        }
+    }
+}

docs/TASKS.md

@@ -32,7 +32,7 @@ requirement is missing and blocks implementation, record it in
 
 ## Phase 2 --- Project Persistence & Versions
 
--   [ ] Create new/open/save song projects locally.
+-   [x] Create new/open/save song projects locally.
 -   [ ] Implement project list.
 -   [ ] Implement immutable or snapshot-based version history.
 -   [ ] Restore a previous version without destroying later versions.