import XCTest
import Photos
@testable import NASBackup

@MainActor
final class BackupEngineTests: XCTestCase {

    private func makeAssets(count: Int) -> [PhotoAsset] {
        (0..<count).map { i in
            PhotoAsset(
                localIdentifier: "asset-\(i)",
                filename: "photo_\(i).jpg",
                creationDate: Date(),
                mediaType: .image,
                pixelWidth: 1024, pixelHeight: 768,
                duration: 0, isScreenshot: false, isRAW: false, isScreenRecording: false
            )
        }
    }

    private func makeConnection() -> NASConnection {
        NASConnection(host: "192.168.1.10", nasProtocol: .smb,
                      username: "user", password: "pass", remotePath: "/backup")
    }

    func test_backup_uploadsAllAssets() async throws {
        let mock = MockNASService()
        let photos = MockPhotoLibraryService(assets: makeAssets(count: 3))
        let engine = BackupEngine.testInstance(transfer: mock, photos: photos)

        let result = try await engine.run(connection: makeConnection(), filter: BackupFilter())

        XCTAssertEqual(result.uploadedCount, 3)
        XCTAssertEqual(result.failedCount, 0)
        XCTAssertEqual(mock.uploadCallCount, 3)
    }

    func test_backup_skipsExistingFiles_alwaysHardcoded() async throws {
        let mock = MockNASService()
        mock.fileExistsAnswer = true
        let photos = MockPhotoLibraryService(assets: makeAssets(count: 2))
        let engine = BackupEngine.testInstance(transfer: mock, photos: photos)

        let result = try await engine.run(connection: makeConnection(), filter: BackupFilter())

        XCTAssertEqual(result.skippedCount, 2)
        XCTAssertEqual(result.uploadedCount, 0)
    }

    func test_backup_handlesUploadFailure_gracefully() async throws {
        let mock = MockNASService()
        mock.shouldFail = true
        let photos = MockPhotoLibraryService(assets: makeAssets(count: 2))
        let engine = BackupEngine.testInstance(transfer: mock, photos: photos)

        let result = try await engine.run(connection: makeConnection(), filter: BackupFilter())

        XCTAssertEqual(result.failedCount, 2)
        XCTAssertEqual(result.uploadedCount, 0)
    }

    func test_backup_emitsProgressUpdates() async throws {
        let mock = MockNASService()
        let photos = MockPhotoLibraryService(assets: makeAssets(count: 5))
        let engine = BackupEngine.testInstance(transfer: mock, photos: photos)

        var progressEvents = 0
        let cancellable = engine.$job.sink { job in
            if case .running = job.status { progressEvents += 1 }
        }
        defer { cancellable.cancel() }

        _ = try await engine.run(connection: makeConnection(), filter: BackupFilter())

        XCTAssertGreaterThan(progressEvents, 0, "Expected progress events during backup")
    }

    func test_backup_canBePaused_andResumed() async throws {
        let mock = MockNASService()
        mock.uploadDelay = 0.05
        let photos = MockPhotoLibraryService(assets: makeAssets(count: 4))
        let engine = BackupEngine.testInstance(transfer: mock, photos: photos)

        let task = Task { try await engine.run(connection: makeConnection(), filter: BackupFilter()) }
        try await Task.sleep(nanoseconds: 70_000_000)
        engine.pause()
        let statusAfterPause = engine.job.status
        engine.resume()
        let result = try await task.value

        if case .paused = statusAfterPause { } else {
            XCTFail("Expected .paused status, got \(statusAfterPause)")
        }
        XCTAssertEqual(result.uploadedCount, 4)
    }
}

// MARK: - MockPhotoLibraryService

final class MockPhotoLibraryService: PhotoLibraryProtocol {
    var authorizationStatus: PHAuthorizationStatus { .authorized }
    private let assets: [PhotoAsset]

    init(assets: [PhotoAsset]) { self.assets = assets }

    func requestAuthorization() async -> PHAuthorizationStatus { .authorized }

    func fetchAssets(filter: BackupFilter) -> [PhotoAsset] { assets }

    func exportAsset(_ asset: PhotoAsset) async throws -> URL {
        let url = FileManager.default.temporaryDirectory.appendingPathComponent(asset.filename)
        try Data("mock-data".utf8).write(to: url)
        return url
    }
}