import CryptoKit
import Foundation
import XCTest
import VelodyDomain
import VelodyNetworking
import VelodyPersistence
@testable import VelodySync

final class RemoteLibrarySyncServiceTests: XCTestCase {
    func testSuccessfulSyncPersistsRemoteTracks() async throws {
        let store = InMemoryRemoteLibraryStore()
        let downloadStateStore = InMemoryRemoteTrackDownloadStateStore()
        let service = RemoteLibrarySyncService(
            repository: DefaultRemoteLibraryRepository(
                apiClient: MockVelodyAPIClient(
                    remoteLibraryResponse: RemoteLibraryResponseDTO(
                        tracks: [
                            RemoteTrackDTO(
                                trackId: "track-123",
                                title: "Remote Title",
                                artist: "Remote Artist",
                                durationSeconds: 245,
                                sha256: String(repeating: "a", count: 64),
                                assetId: "asset-456",
                                createdAt: "2026-05-29T08:00:00.000Z",
                                updatedAt: "2026-05-29T08:05:00.000Z"
                            ),
                        ]
                    )
                ),
                store: store
            ),
            downloadStateStore: downloadStateStore,
            audioFileStore: InMemoryOfflineAudioFileStore()
        )

        let tracks = try await service.syncRemoteLibrary(deviceId: "device-123")
        let cachedTracks = try await service.loadCachedRemoteTracks()
        let downloadStates = try await service.loadDownloadStates()

        XCTAssertEqual(tracks.count, 1)
        XCTAssertEqual(cachedTracks, tracks)
        XCTAssertEqual(cachedTracks.first?.trackId, "track-123")
        XCTAssertEqual(downloadStates.first?.downloadStatus, .notDownloaded)
    }

    func testEmptyResponseClearsCachedRemoteLibrary() async throws {
        let store = InMemoryRemoteLibraryStore(
            tracks: [
                RemoteTrack(
                    trackId: "track-123",
                    title: "Old",
                    artist: "Artist",
                    durationSeconds: 100,
                    sha256: String(repeating: "b", count: 64),
                    assetId: "asset-123",
                    createdAt: "2026-05-29T08:00:00.000Z",
                    updatedAt: "2026-05-29T08:05:00.000Z"
                ),
            ]
        )
        let downloadStateStore = InMemoryRemoteTrackDownloadStateStore(
            states: [
                RemoteTrackDownloadState(
                    remoteTrackId: "track-123",
                    assetId: "asset-123",
                    downloadStatus: .downloaded
                ),
            ]
        )
        let service = RemoteLibrarySyncService(
            repository: DefaultRemoteLibraryRepository(
                apiClient: MockVelodyAPIClient(
                    remoteLibraryResponse: RemoteLibraryResponseDTO(tracks: [])
                ),
                store: store
            ),
            downloadStateStore: downloadStateStore,
            audioFileStore: InMemoryOfflineAudioFileStore()
        )

        let tracks = try await service.syncRemoteLibrary(deviceId: "device-123")
        let cachedTracks = try await service.loadCachedRemoteTracks()
        let downloadStates = try await service.loadDownloadStates()

        XCTAssertEqual(tracks, [])
        XCTAssertEqual(cachedTracks, [])
        XCTAssertEqual(downloadStates.count, 1)
    }

    func testNetworkFailureLeavesCachedRemoteLibraryIntact() async throws {
        let cachedTrack = RemoteTrack(
            trackId: "track-123",
            title: "Cached",
            artist: "Artist",
            durationSeconds: 100,
            sha256: String(repeating: "c", count: 64),
            assetId: "asset-123",
            createdAt: "2026-05-29T08:00:00.000Z",
            updatedAt: "2026-05-29T08:05:00.000Z"
        )
        let store = InMemoryRemoteLibraryStore(tracks: [cachedTrack])
        let downloadStateStore = InMemoryRemoteTrackDownloadStateStore()
        let service = RemoteLibrarySyncService(
            repository: DefaultRemoteLibraryRepository(
                apiClient: MockVelodyAPIClient(
                    remoteLibraryError: VelodyAPIError.requestFailed("Offline")
                ),
                store: store
            ),
            downloadStateStore: downloadStateStore,
            audioFileStore: InMemoryOfflineAudioFileStore()
        )

        await XCTAssertThrowsErrorAsync {
            _ = try await service.syncRemoteLibrary(deviceId: "device-123")
        }

        let cachedTracks = try await service.loadCachedRemoteTracks()
        XCTAssertEqual(cachedTracks, [cachedTrack])
    }

    func testDownloadTrackPersistsDownloadedStateAndFile() async throws {
        let downloadStateStore = InMemoryRemoteTrackDownloadStateStore()
        let audioFileStore = InMemoryOfflineAudioFileStore()
        let service = RemoteLibrarySyncService(
            repository: DefaultRemoteLibraryRepository(
                apiClient: MockVelodyAPIClient(
                    remoteLibraryResponse: RemoteLibraryResponseDTO(tracks: []),
                    audioAssetData: sampleMp3Data(seed: "download-success")
                ),
                store: InMemoryRemoteLibraryStore()
            ),
            downloadStateStore: downloadStateStore,
            audioFileStore: audioFileStore
        )
        let track = RemoteTrack(
            trackId: "track-123",
            title: "Remote Title",
            artist: "Remote Artist",
            durationSeconds: 245,
            sha256: sha256Hex(sampleMp3Data(seed: "download-success")),
            assetId: "asset-456",
            createdAt: "2026-05-29T08:00:00.000Z",
            updatedAt: "2026-05-29T08:05:00.000Z"
        )

        let state = try await service.downloadTrack(track, deviceId: "device-123")
        let storedStates = try await service.loadDownloadStates()
        let fileExists = await audioFileStore.fileExists(at: state.localFilePath)

        XCTAssertEqual(state.downloadStatus, .downloaded)
        XCTAssertEqual(state.assetId, "asset-456")
        XCTAssertFalse(state.localFilePath.isEmpty)
        XCTAssertEqual(storedStates.first?.downloadStatus, .downloaded)
        XCTAssertTrue(fileExists)
    }

    func testDownloadTrackPersistsFailureState() async throws {
        let service = RemoteLibrarySyncService(
            repository: DefaultRemoteLibraryRepository(
                apiClient: MockVelodyAPIClient(
                    remoteLibraryResponse: RemoteLibraryResponseDTO(tracks: []),
                    downloadError: VelodyAPIError.server(statusCode: 404, message: "Missing")
                ),
                store: InMemoryRemoteLibraryStore()
            ),
            downloadStateStore: InMemoryRemoteTrackDownloadStateStore(),
            audioFileStore: InMemoryOfflineAudioFileStore()
        )
        let track = RemoteTrack(
            trackId: "track-123",
            title: "Remote Title",
            artist: "Remote Artist",
            durationSeconds: 245,
            sha256: sha256Hex(sampleMp3Data(seed: "download-failure")),
            assetId: "asset-456",
            createdAt: "2026-05-29T08:00:00.000Z",
            updatedAt: "2026-05-29T08:05:00.000Z"
        )

        await XCTAssertThrowsErrorAsync {
            _ = try await service.downloadTrack(track, deviceId: "device-123")
        }

        let storedStates = try await service.loadDownloadStates()
        XCTAssertEqual(storedStates.first?.downloadStatus, .failed)
        XCTAssertEqual(storedStates.first?.remoteTrackId, "track-123")
    }

    func testLoadDownloadStatesRepairsStaleLocalFilePathAfterStoreRecreation() async throws {
        let fileManager = FileManager.default
        let tempDirectory = fileManager.temporaryDirectory.appendingPathComponent(
            UUID().uuidString,
            isDirectory: true
        )
        let firstAudioDirectory = tempDirectory.appendingPathComponent("audio-v1", isDirectory: true)
        let secondAudioDirectory = tempDirectory.appendingPathComponent("audio-v2", isDirectory: true)
        let stateFileURL = tempDirectory.appendingPathComponent("remote-download-states.json")
        let audioData = sampleMp3Data(seed: "relaunch-repair")
        let track = RemoteTrack(
            trackId: "track-123",
            title: "1 Mai 2026",
            artist: "Remote Artist",
            durationSeconds: 245,
            sha256: sha256Hex(audioData),
            assetId: "asset-456",
            createdAt: "2026-05-29T08:00:00.000Z",
            updatedAt: "2026-05-29T08:05:00.000Z"
        )

        defer {
            try? fileManager.removeItem(at: tempDirectory)
        }

        let firstService = RemoteLibrarySyncService(
            repository: DefaultRemoteLibraryRepository(
                apiClient: MockVelodyAPIClient(
                    remoteLibraryResponse: RemoteLibraryResponseDTO(tracks: []),
                    audioAssetData: audioData
                ),
                store: InMemoryRemoteLibraryStore()
            ),
            downloadStateStore: try FileRemoteTrackDownloadStateStore(fileURL: stateFileURL),
            audioFileStore: try FileOfflineAudioFileStore(baseDirectoryURL: firstAudioDirectory)
        )

        let originalState = try await firstService.downloadTrack(track, deviceId: "device-123")
        let originalFileURL = URL(fileURLWithPath: originalState.localFilePath)
        let recreatedStoreFileURL = secondAudioDirectory.appendingPathComponent("asset-456.mp3")
        try fileManager.createDirectory(at: secondAudioDirectory, withIntermediateDirectories: true)
        try fileManager.moveItem(at: originalFileURL, to: recreatedStoreFileURL)

        let relaunchedAudioStore = try FileOfflineAudioFileStore(baseDirectoryURL: secondAudioDirectory)
        let relaunchedService = RemoteLibrarySyncService(
            repository: DefaultRemoteLibraryRepository(
                apiClient: MockVelodyAPIClient(remoteLibraryResponse: RemoteLibraryResponseDTO(tracks: [])),
                store: InMemoryRemoteLibraryStore()
            ),
            downloadStateStore: try FileRemoteTrackDownloadStateStore(fileURL: stateFileURL),
            audioFileStore: relaunchedAudioStore
        )

        let restoredStates = try await relaunchedService.loadDownloadStates()
        let restoredState = try XCTUnwrap(restoredStates.first)
        let restoredBytes = try await relaunchedAudioStore.readAudioFile(at: restoredState.localFilePath)
        let persistedRestoredState = try await FileRemoteTrackDownloadStateStore(fileURL: stateFileURL)
            .loadDownloadStates()
            .first

        XCTAssertEqual(restoredState.downloadStatus, .downloaded)
        XCTAssertEqual(restoredState.localFilePath, recreatedStoreFileURL.standardizedFileURL.path)
        XCTAssertEqual(persistedRestoredState?.localFilePath, recreatedStoreFileURL.standardizedFileURL.path)
        XCTAssertTrue(fileManager.fileExists(atPath: restoredState.localFilePath))
        XCTAssertEqual(restoredBytes, audioData)
    }
}

private struct MockVelodyAPIClient: VelodyAPIClient {
    let remoteLibraryResponse: RemoteLibraryResponseDTO?
    let remoteLibraryError: VelodyAPIError?
    let audioAssetData: Data?
    let downloadError: VelodyAPIError?

    init(
        remoteLibraryResponse: RemoteLibraryResponseDTO? = nil,
        remoteLibraryError: VelodyAPIError? = nil,
        audioAssetData: Data? = nil,
        downloadError: VelodyAPIError? = nil
    ) {
        self.remoteLibraryResponse = remoteLibraryResponse
        self.remoteLibraryError = remoteLibraryError
        self.audioAssetData = audioAssetData
        self.downloadError = downloadError
    }

    func registerDevice(
        _ payload: DeviceRegistrationPayload
    ) async throws -> DeviceRegistrationResponse {
        _ = payload
        return DeviceRegistrationResponse(
            deviceId: UUID().uuidString,
            bootstrapToken: UUID().uuidString,
            serverTime: "2026-05-29T08:00:00.000Z"
        )
    }

    func sendHeartbeat(
        _ payload: DeviceHeartbeatPayload
    ) async throws -> DeviceHeartbeatResponse {
        _ = payload
        return DeviceHeartbeatResponse(
            ok: true,
            serverTime: "2026-05-29T08:00:00.000Z"
        )
    }

    func fetchSyncBootstrap() async throws -> SyncBootstrapResponse {
        SyncBootstrapResponse(
            nextCursor: SyncCursor(value: "0"),
            tracks: [],
            events: [],
            deletedTrackIds: [],
            serverTime: "2026-05-29T08:00:00.000Z"
        )
    }

    func fetchRemoteLibrary(
        deviceId: String
    ) async throws -> RemoteLibraryResponseDTO {
        _ = deviceId

        if let remoteLibraryError {
            throw remoteLibraryError
        }

        return remoteLibraryResponse ?? RemoteLibraryResponseDTO(tracks: [])
    }

    func downloadAudioAsset(
        assetId: String,
        deviceId: String
    ) async throws -> Data {
        _ = assetId
        _ = deviceId

        if let downloadError {
            throw downloadError
        }

        return audioAssetData ?? Data()
    }

    func prepareUpload(
        _ payload: UploadPrepareRequest
    ) async throws -> UploadPrepareResponse {
        _ = payload
        return UploadPrepareResponse(status: .uploadRequired, uploadId: UUID().uuidString, nextOffset: 0)
    }

    func fetchUploadStatus(
        uploadId: String
    ) async throws -> UploadSessionStatusResponse {
        UploadSessionStatusResponse(
            uploadId: uploadId,
            status: .completed,
            receivedBytes: "0",
            expectedSizeBytes: "0",
            nextOffset: "0"
        )
    }

    func uploadFile(
        uploadId: String,
        fileURL: URL,
        mimeType: String
    ) async throws -> UploadSessionStatusResponse {
        _ = fileURL
        _ = mimeType
        return UploadSessionStatusResponse(
            uploadId: uploadId,
            status: .completed,
            receivedBytes: "0",
            expectedSizeBytes: "0",
            nextOffset: "0"
        )
    }

    func finalizeUpload(
        uploadId: String,
        payload: UploadFinalizeRequest
    ) async throws -> UploadFinalizeResponse {
        _ = uploadId
        _ = payload
        return UploadFinalizeResponse(
            trackId: UUID().uuidString,
            assetId: UUID().uuidString
        )
    }
}

private func sampleMp3Data(seed: String) -> Data {
    Data([
        0x49, 0x44, 0x33, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x21,
    ] + Array(seed.utf8))
}

private func sha256Hex(_ data: Data) -> String {
    SHA256.hash(data: data).map { String(format: "%02x", $0) }.joined()
}

private func XCTAssertThrowsErrorAsync(
    _ expression: @escaping () async throws -> Void,
    file: StaticString = #filePath,
    line: UInt = #line
) async {
    do {
        try await expression()
        XCTFail("Expected expression to throw an error.", file: file, line: line)
    } catch {
        XCTAssertTrue(true)
    }
}