import AppKit
import AppleAPI
import Combine
import Path
import LegibleError
import KeychainAccess
import Path
import Version
import os.log
import DockProgress
import XcodesKit
import LibFido2Swift

enum PreferenceKey: String {
    case installPath
    case localPath
    case unxipExperiment
    case createSymLinkOnSelect
    case onSelectActionType
    case showOpenInRosettaOption
    case autoInstallation
    case SUEnableAutomaticChecks
    case includePrereleaseVersions
    case downloader
    case dataSource
    case xcodeListCategory
    case allowedMajorVersions
    case hideSupportXcodes
    case xcodeListArchitectures

    func isManaged() -> Bool { UserDefaults.standard.objectIsForced(forKey: self.rawValue) }
}

class AppState: ObservableObject {
    private let client = AppleAPI.Client()
    internal let runtimeService = RuntimeService()
   
    // MARK: - Published Properties
    
    @Published var authenticationState: AuthenticationState = .unauthenticated
    @Published var availableXcodes: [AvailableXcode] = [] {
        willSet {
            if newValue.count > availableXcodes.count && availableXcodes.count != 0 {
                Current.notificationManager.scheduleNotification(title: localizeString("Notification.NewXcodeVersion.Title"), body: localizeString("Notification.NewXcodeVersion.Body"), category: .normal)
            }
            updateAllXcodes(
                availableXcodes: newValue, 
                installedXcodes: Current.files.installedXcodes(Path.installDirectory), 
                selectedXcodePath: selectedXcodePath
            )
        }
        didSet {
            autoInstallIfNeeded()
        }
    }
    @Published var allXcodes: [Xcode] = []
    @Published var selectedXcodePath: String? {
        willSet {
            updateAllXcodes(
                availableXcodes: availableXcodes,
                installedXcodes: Current.files.installedXcodes(Path.installDirectory),
                selectedXcodePath: newValue
            )
        }
    }
    @Published var updatePublisher: AnyCancellable?
    var isUpdating: Bool { updatePublisher != nil }
    @Published var presentedSheet: XcodesSheet? = nil
    @Published var isProcessingAuthRequest = false
    @Published var xcodeBeingConfirmedForUninstallation: Xcode?
    @Published var presentedAlert: XcodesAlert?
    @Published var presentedPreferenceAlert: XcodesPreferencesAlert?
    @Published var helperInstallState: HelperInstallState = .notInstalled
    /// Whether the user is being prepared for the helper installation alert with an explanation.
    /// This closure will be performed after the user chooses whether or not to proceed.
    @Published var isPreparingUserForActionRequiringHelper: ((Bool) -> Void)?

    // MARK: - Errors

    @Published var error: Error?
    @Published var authError: Error?
    
    // MARK: Advanced Preferences
    @Published var localPath = "" {
        didSet {
            Current.defaults.set(localPath, forKey: "localPath")
        }
    }
    
    var disableLocalPathChange: Bool { PreferenceKey.localPath.isManaged() }

    @Published var installPath = "" {
        didSet {
            Current.defaults.set(installPath, forKey: "installPath")
        }
    }

    var disableInstallPathChange: Bool { PreferenceKey.installPath.isManaged() }

    @Published var unxipExperiment = false {
        didSet {
            Current.defaults.set(unxipExperiment, forKey: "unxipExperiment")
        }
    }
    
    var disableUnxipExperiment: Bool { PreferenceKey.unxipExperiment.isManaged() }

    @Published var createSymLinkOnSelect = false {
        didSet {
            Current.defaults.set(createSymLinkOnSelect, forKey: "createSymLinkOnSelect")
        }
    }
    
    var createSymLinkOnSelectDisabled: Bool {
        return onSelectActionType == .rename || PreferenceKey.createSymLinkOnSelect.isManaged()
    }
    
    @Published var onSelectActionType = SelectedActionType.none {
        didSet {
            Current.defaults.set(onSelectActionType.rawValue, forKey: "onSelectActionType")
            
            if onSelectActionType == .rename {
                createSymLinkOnSelect = false
            }
        }
    }
    
    var onSelectActionTypeDisabled: Bool { PreferenceKey.onSelectActionType.isManaged() }

    @Published var showOpenInRosettaOption = false {
        didSet {
            Current.defaults.set(showOpenInRosettaOption, forKey: "showOpenInRosettaOption")
        }
    }
    
    @Published var terminateAfterLastWindowClosed = false {
        didSet {
            Current.defaults.set(terminateAfterLastWindowClosed, forKey: "terminateAfterLastWindowClosed")
        }
    }
    
    // MARK: - Runtimes
    
    @Published var downloadableRuntimes: [DownloadableRuntime] = []
    @Published var installedRuntimes: [CoreSimulatorImage] = []

    // MARK: - Publisher Cancellables
    
    var cancellables = Set<AnyCancellable>()
    private var installationPublishers: [XcodeID: AnyCancellable] = [:]
    internal var runtimePublishers: [String: Task<(), any Error>] = [:]
    private var selectPublisher: AnyCancellable?
    private var uninstallPublisher: AnyCancellable?
    private var autoInstallTimer: Timer?
    
    // MARK: - Dock Progress Tracking
    
    public static let totalProgressUnits = Int64(10)
    public static let unxipProgressWeight = Int64(1)
    var overallProgress = Progress()
    var unxipProgress = {
        let progress = Progress(totalUnitCount: totalProgressUnits)
        progress.kind = .file
        progress.fileOperationKind = .copying
        return progress
    }()
    
    // MARK: - 
    
    var dataSource: DataSource {
        Current.defaults.string(forKey: "dataSource").flatMap(DataSource.init(rawValue:)) ?? .default
    }

    var savedUsername: String? {
        Current.defaults.string(forKey: "username")
    }

    var hasSavedUsername: Bool {
        savedUsername != nil
    }
    
    var bottomStatusBarMessage: String {
        let formatter = DateFormatter()
        formatter.dateFormat = "dd/MM/yyyy"
        let finishDate = formatter.date(from: "11/06/2022")
        
        if Date().compare(finishDate!) == .orderedAscending {
            return String(format: localizeString("WWDC.Message"), "2022")
        }
        return ""
    }
    
    // MARK: - Init
    
    init() {
        guard !isTesting else { return }
        try? loadCachedAvailableXcodes()
        try? loadCacheDownloadableRuntimes()
        checkIfHelperIsInstalled()
        setupAutoInstallTimer()
        setupDefaults()
    }
    
    func setupDefaults() {
        localPath = Current.defaults.string(forKey: "localPath") ?? Path.defaultXcodesApplicationSupport.string
        unxipExperiment = Current.defaults.bool(forKey: "unxipExperiment") ?? false
        createSymLinkOnSelect = Current.defaults.bool(forKey: "createSymLinkOnSelect") ?? false
        onSelectActionType = SelectedActionType(rawValue: Current.defaults.string(forKey: "onSelectActionType") ?? "none") ?? .none
        installPath = Current.defaults.string(forKey: "installPath") ?? Path.defaultInstallDirectory.string
        showOpenInRosettaOption = Current.defaults.bool(forKey: "showOpenInRosettaOption") ?? false
        terminateAfterLastWindowClosed = Current.defaults.bool(forKey: "terminateAfterLastWindowClosed") ?? false
    }
    
    // MARK: Timer
    /// Runs a timer every 6 hours when app is open to check if it needs to auto install any xcodes
    func setupAutoInstallTimer() {
        guard let storageValue = Current.defaults.get(forKey: "autoInstallation") as? Int, let autoInstallType = AutoInstallationType(rawValue: storageValue) else { return }

        if autoInstallType == .none { return }
        
        autoInstallTimer = Timer.scheduledTimer(withTimeInterval: 60*60*6, repeats: true) { [weak self] _ in
            self?.updateIfNeeded()
        }
    }
    // MARK: - Authentication
    
    func validateADCSession(path: String) -> AnyPublisher<Void, Error> {
        return Current.network.dataTask(with: URLRequest.downloadADCAuth(path: path))
            .receive(on: DispatchQueue.main)
            .tryMap { result -> Void in
                let httpResponse = result.response as! HTTPURLResponse
                if httpResponse.statusCode == 401 {
                    throw AuthenticationError.notAuthorized
                }
            }
            .eraseToAnyPublisher()
    }
    
    func validateADCSession(path: String) async throws {
        let result = try await Current.network.dataTaskAsync(with: URLRequest.downloadADCAuth(path: path))
        let httpResponse = result.1 as! HTTPURLResponse
        if httpResponse.statusCode == 401 {
            throw AuthenticationError.notAuthorized
        }
    }
    
    func validateSession() -> AnyPublisher<Void, Error> {
        
        return Current.network.validateSession()
            .receive(on: DispatchQueue.main)
            .handleEvents(receiveCompletion: { completion in 
                if case .failure = completion {
                    // this is causing some awkwardness with showing an alert with the error and also popping up the sign in view
                    // self.authenticationState = .unauthenticated
                    // self.presentedSheet = .signIn
                }
            })
            .eraseToAnyPublisher()
    }
    
    func signInIfNeeded() -> AnyPublisher<Void, Error> {
        validateSession()
            .catch { (error) -> AnyPublisher<Void, Error> in
                guard
                    let username = self.savedUsername,
                    let password = try? Current.keychain.getString(username)
                else {
                    return Fail(error: error) 
                        .eraseToAnyPublisher()
                }

                return self.signIn(username: username, password: password)
                    .map { _ in Void() }
                    .eraseToAnyPublisher()
            }
            .eraseToAnyPublisher()
    }
    
    func signIn(username: String, password: String) {
        authError = nil
        signIn(username: username.lowercased(), password: password)
            .sink(
                receiveCompletion: { _ in },
                receiveValue: { _ in }
            )
            .store(in: &cancellables)
    }
    
    func signIn(username: String, password: String) -> AnyPublisher<AuthenticationState, Error> {
        try? Current.keychain.set(password, key: username)
        Current.defaults.set(username, forKey: "username")
        
        isProcessingAuthRequest = true
        return client.srpLogin(accountName: username, password: password)
            .receive(on: DispatchQueue.main)
            .handleEvents(
                receiveOutput: { authenticationState in 
                    self.authenticationState = authenticationState
                },
                receiveCompletion: { completion in
                    self.handleAuthenticationFlowCompletion(completion)
                    self.isProcessingAuthRequest = false
                }
            )
            .eraseToAnyPublisher()
    }
    
    func handleTwoFactorOption(_ option: TwoFactorOption, authOptions: AuthOptionsResponse, serviceKey: String, sessionID: String, scnt: String) {
        let sessionData = AppleSessionData(serviceKey: serviceKey, sessionID: sessionID, scnt: scnt)

        if option == .securityKey, fido2DeviceIsPresent() && !fido2DeviceNeedsPin() {
            createAndSubmitSecurityKeyAssertationWithPinCode(nil, sessionData: sessionData, authOptions: authOptions)
        } else {
            self.presentedSheet = .twoFactor(.init(
                option: option,
                authOptions: authOptions,
                sessionData: sessionData
            ))
        }
    }

    func requestSMS(to trustedPhoneNumber: AuthOptionsResponse.TrustedPhoneNumber, authOptions: AuthOptionsResponse, sessionData: AppleSessionData) {        
        isProcessingAuthRequest = true
        client.requestSMSSecurityCode(to: trustedPhoneNumber, authOptions: authOptions, sessionData: sessionData)
            .receive(on: DispatchQueue.main)
            .sink(
                receiveCompletion: { completion in
                    self.handleAuthenticationFlowCompletion(completion)
                    self.isProcessingAuthRequest = false
                }, 
                receiveValue: { authenticationState in 
                    self.authenticationState = authenticationState
                    if case let AuthenticationState.waitingForSecondFactor(option, authOptions, sessionData) = authenticationState {
                        self.handleTwoFactorOption(option, authOptions: authOptions, serviceKey: sessionData.serviceKey, sessionID: sessionData.sessionID, scnt: sessionData.scnt)
                    }
                }
            )
            .store(in: &cancellables)
    }
    
    func choosePhoneNumberForSMS(authOptions: AuthOptionsResponse, sessionData: AppleSessionData) {
        self.presentedSheet = .twoFactor(.init(
            option: .smsPendingChoice,
            authOptions: authOptions,
            sessionData: sessionData
        ))
    }
    
    func submitSecurityCode(_ code: SecurityCode, sessionData: AppleSessionData) {
        isProcessingAuthRequest = true
        client.submitSecurityCode(code, sessionData: sessionData)
            .receive(on: DispatchQueue.main)
            .sink(
                receiveCompletion: { completion in
                    self.handleAuthenticationFlowCompletion(completion)
                    self.isProcessingAuthRequest = false
                },
                receiveValue: { authenticationState in
                    self.authenticationState = authenticationState
                }
            )
            .store(in: &cancellables)
    }
    
    private lazy var fido2 = FIDO2()

    func createAndSubmitSecurityKeyAssertationWithPinCode(_ pinCode: String?, sessionData: AppleSessionData, authOptions: AuthOptionsResponse) {
        self.presentedSheet = .securityKeyTouchToConfirm
        
        guard let fsaChallenge = authOptions.fsaChallenge else {
            // This shouldn't happen
            // we shouldn't have called this method without setting the fsaChallenge
            // so this is an assertionFailure
            assertionFailure()
            self.authError = "Something went wrong. Please file a bug report"
            return
        }
        
        // The challenge is encoded in Base64URL encoding
        let challengeUrl = fsaChallenge.challenge
        let challenge = FIDO2.base64urlToBase64(base64url: challengeUrl)
        let origin = "https://idmsa.apple.com"
        let rpId = "apple.com"
        // Allowed creds is sent as a comma separated string
        let validCreds = fsaChallenge.allowedCredentials.split(separator: ",").map(String.init)

        Task {
            do {
                let response = try fido2.respondToChallenge(args: ChallengeArgs(rpId: rpId, validCredentials: validCreds, devPin: pinCode, challenge: challenge, origin: origin))
            
                Task { @MainActor in
                    self.isProcessingAuthRequest = true
                }
                
                let respData = try JSONEncoder().encode(response)
                client.submitChallenge(response: respData, sessionData: AppleSessionData(serviceKey: sessionData.serviceKey, sessionID: sessionData.sessionID, scnt: sessionData.scnt))
                    .receive(on: DispatchQueue.main)
                    .handleEvents(
                        receiveOutput: { authenticationState in
                            self.authenticationState = authenticationState
                        },
                        receiveCompletion: { completion in
                            self.handleAuthenticationFlowCompletion(completion)
                            self.isProcessingAuthRequest = false
                        }
                    ).sink(
                        receiveCompletion: { _ in },
                        receiveValue: { _ in }
                    ).store(in: &cancellables)
            } catch FIDO2Error.canceledByUser {
                // User cancelled the auth flow
                // we don't have to show an error
                // because the sheet will already be dismissed
            } catch {
                Task { @MainActor in
                    authError = error
                }
            }
        }
    }

    func fido2DeviceIsPresent() -> Bool {
        fido2.hasDeviceAttached()
    }

    func fido2DeviceNeedsPin() -> Bool {
        do {
            return try fido2.deviceHasPin()
        } catch {
            Task { @MainActor in
                authError = error
            }

            return true
        }
    }
    
    func cancelSecurityKeyAssertationRequest() {
        self.fido2.cancel()
    }
    
    private func handleAuthenticationFlowCompletion(_ completion: Subscribers.Completion<Error>) {
        switch completion {
        case let .failure(error):
            // remove saved username and any stored keychain password if authentication fails so it doesn't try again.
            clearLoginCredentials()
            Logger.appState.error("Authentication error: \(error.legibleDescription)")
            self.authError = error
        case .finished:
            switch self.authenticationState {
                case .authenticated, .unauthenticated, .notAppleDeveloper:
                self.presentedSheet = nil
            case let .waitingForSecondFactor(option, authOptions, sessionData):
                self.handleTwoFactorOption(option, authOptions: authOptions, serviceKey: sessionData.serviceKey, sessionID: sessionData.sessionID, scnt: sessionData.scnt)
            }
        }
    }
    
    func signOut() {
        clearLoginCredentials()
        AppleAPI.Current.network.session.configuration.httpCookieStorage?.removeCookies(since: .distantPast)
        authenticationState = .unauthenticated
    }
    
    // MARK: - Helper
    
    /// Install the privileged helper if it isn't already installed.
    ///
    /// The way this is done is a little roundabout, because it requires user interaction in an alert before installation should be attempted.
    /// The first time this method is invoked should be with `shouldPrepareUserForHelperInstallation` set to true.
    /// If the helper is already installed, then nothing will happen.
    /// If the helper is not already installed, the user will be prepared for installation and this method will return early.
    /// If they consent to installing the helper then this method will be invoked again with  `shouldPrepareUserForHelperInstallation` set to false.
    /// This will install the helper.
    ///
    /// - Parameter shouldPrepareUserForHelperInstallation: Whether the user should be presented with an alert preparing them for helper installation.
    func installHelperIfNecessary(shouldPrepareUserForHelperInstallation: Bool = true) {
        guard helperInstallState == .installed || shouldPrepareUserForHelperInstallation == false else {
            isPreparingUserForActionRequiringHelper = { [unowned self] userConsented in
                guard userConsented else { return }
                self.installHelperIfNecessary(shouldPrepareUserForHelperInstallation: false) 
            }
            presentedAlert = .privilegedHelper
            return
        }
        
        installHelperIfNecessary()
            .sink(
                receiveCompletion: { [unowned self] completion in
                    if case let .failure(error) = completion {
                        self.error = error
                        self.presentedAlert = .generic(title: localizeString("Alert.PrivilegedHelper.Error.Title"), message: error.legibleLocalizedDescription)
                    }
                }, 
                receiveValue: {}
            )
            .store(in: &cancellables)
    }
    
    func installHelperIfNecessary() -> AnyPublisher<Void, Error> {
        Result {
            if helperInstallState == .notInstalled {
                try Current.helper.install()
                checkIfHelperIsInstalled()
            }
        }
        .publisher
        .subscribe(on: DispatchQueue.main)
        .eraseToAnyPublisher()
    }
    
    private func checkIfHelperIsInstalled() {
        helperInstallState = .unknown

        Current.helper.checkIfLatestHelperIsInstalled()
            .receive(on: DispatchQueue.main)
            .sink(
                receiveValue: { installed in
                    self.helperInstallState = installed ? .installed : .notInstalled
                }
            )
            .store(in: &cancellables)
    }
    
    // MARK: - Install
    
    func checkMinVersionAndInstall(id: XcodeID) {
        guard let availableXcode = availableXcodes.first(where: { $0.xcodeID == id }) else { return }
        
        // Check to see if users macOS is supported
        if let requiredMacOSVersion = availableXcode.requiredMacOSVersion {
            if hasMinSupportedOS(requiredMacOSVersion: requiredMacOSVersion) {
                // prompt
                self.presentedAlert = .checkMinSupportedVersion(xcode: availableXcode, macOS: ProcessInfo.processInfo.operatingSystemVersion.versionString())
                return
            }
        }
        
        switch self.dataSource {
        case .apple:
            install(id: id)
        case .xcodeReleases:
            install(id: id)
        }
    }
    
    func hasMinSupportedOS(requiredMacOSVersion: String) -> Bool {
        let split = requiredMacOSVersion.components(separatedBy: ".").compactMap { Int($0) }
        let xcodeMinimumMacOSVersion = OperatingSystemVersion(majorVersion: split[safe: 0] ?? 0, minorVersion: split[safe: 1] ?? 0, patchVersion: split[safe: 2] ?? 0)
        
        return !ProcessInfo.processInfo.isOperatingSystemAtLeast(xcodeMinimumMacOSVersion)
    }
    
    func install(id: XcodeID) {
        guard let availableXcode = availableXcodes.first(where: { $0.xcodeID == id }) else { return }

        installationPublishers[id] = signInIfNeeded()
            .handleEvents(
                receiveSubscription: { [unowned self] _ in
                    self.setInstallationStep(of: availableXcode.version, to: .authenticating)
                }
            )
            .flatMap { [unowned self] in
                // signInIfNeeded might finish before the user actually authenticates if UI is involved. 
                // This publisher will wait for the @Published authentication state to change to authenticated or unauthenticated before finishing,
                // indicating that the user finished what they were doing in the UI.
                self.$authenticationState
                    .filter { state in
                        switch state {
                            case .authenticated, .unauthenticated, .notAppleDeveloper: return true
                        case .waitingForSecondFactor: return false
                        }
                    }
                    .prefix(1)
                    .tryMap { state in
                        if state == .unauthenticated {
                            throw AuthenticationError.invalidSession
                        }
                        if state == .notAppleDeveloper {
                            throw AuthenticationError.notDeveloperAppleId
                        }
                        return Void()
                    }
            }
            .flatMap {
                // This request would've already been made if the Apple data source were being used.
                // That's not the case for the Xcode Releases data source.
                // We need the cookies from its response in order to download Xcodes though,
                // so perform it here first just to be sure.
                Current.network.dataTask(with: URLRequest.downloads)
                    .map(\.data)
                    .decode(type: Downloads.self, decoder: configure(JSONDecoder()) {
                        $0.dateDecodingStrategy = .formatted(.downloadsDateModified)
                    })
                    .tryMap { downloads -> Void in
                        if downloads.hasError {
                            throw AuthenticationError.invalidResult(resultString: downloads.resultsString)
                        }
                       if downloads.downloads == nil {
                            throw AuthenticationError.invalidResult(resultString: localizeString("DownloadingError"))
                        }
                    }
                    .mapError { $0 as Error }
            }
            .flatMap { [unowned self] in
                self.install(.version(availableXcode), downloader: Downloader(rawValue: Current.defaults.string(forKey: "downloader") ?? "aria2") ?? .aria2)
            }
            .receive(on: DispatchQueue.main)
            .sink(
                receiveCompletion: { [unowned self] completion in 
                    self.installationPublishers[id] = nil
                    if case let .failure(error) = completion {
                        // Prevent setting the app state error if it is an invalid session, we will present the sign in view instead
                        if error as? AuthenticationError != .invalidSession {
                            self.error = error
                            self.presentedAlert = .generic(title: localizeString("Alert.Install.Error.Title"), message: error.legibleLocalizedDescription)
                        }
                        if let index = self.allXcodes.firstIndex(where: { $0.id == id }) { 
                            self.allXcodes[index].installState = .notInstalled
                        }
                    }
                },
                receiveValue: { _ in }
            )
    }
    
    /// Skips using the username/password to log in to Apple, and simply gets a Auth Cookie used in downloading
    /// As of Nov 2022 this was returning a 403 forbidden
    func installWithoutLogin(id: Xcode.ID) {
        guard let availableXcode = availableXcodes.first(where: { $0.xcodeID == id }) else { return }
        
        installationPublishers[id] = self.install(.version(availableXcode), downloader: Downloader(rawValue: Current.defaults.string(forKey: "downloader") ?? "aria2") ?? .aria2)
            .receive(on: DispatchQueue.main)
            .sink(
                receiveCompletion: { [unowned self] completion in
                    self.installationPublishers[id] = nil
                    if case let .failure(error) = completion {
                        // Prevent setting the app state error if it is an invalid session, we will present the sign in view instead
                        if error as? AuthenticationError != .invalidSession {
                            self.error = error
                            self.presentedAlert = .generic(title: localizeString("Alert.Install.Error.Title"), message: error.legibleLocalizedDescription)
                        }
                        if let index = self.allXcodes.firstIndex(where: { $0.id == id }) {
                            self.allXcodes[index].installState = .notInstalled
                        }
                    }
                },
                receiveValue: { _ in }
            )
    }
    
    func cancelInstall(id: Xcode.ID) {
        guard let availableXcode = availableXcodes.first(where: { $0.xcodeID == id }) else { return }

        // Cancel the publisher
        installationPublishers[id] = nil
        
        resetDockProgressTracking()
                
        // If the download is cancelled by the user, clean up the download files that aria2 creates.
        // This isn't done as part of the publisher with handleEvents(receiveCancel:) because it shouldn't happen when e.g. the app quits.
        let expectedArchivePath = Path.xcodesApplicationSupport/"Xcode-\(availableXcode.version).\(availableXcode.filename.suffix(fromLast: "."))"
        let aria2DownloadMetadataPath = expectedArchivePath.parent/(expectedArchivePath.basename() + ".aria2")
        try? Current.files.removeItem(at: expectedArchivePath.url)
        try? Current.files.removeItem(at: aria2DownloadMetadataPath.url)
        
        if let index = allXcodes.firstIndex(where: { $0.id == id }) { 
            allXcodes[index].installState = .notInstalled
        }
    }
    
    // MARK: - Uninstall
    func uninstall(xcode: Xcode) {
        guard
            let installedXcodePath = xcode.installedPath,
            uninstallPublisher == nil
        else { return }
        
        uninstallPublisher = uninstallXcode(path: installedXcodePath)
            .flatMap { [unowned self] _ in
                self.updateSelectedXcodePath()
            }
            .sink(
                receiveCompletion: { [unowned self] completion in
                    if case let .failure(error) = completion {
                        self.error = error
                        self.presentedAlert = .generic(title: localizeString("Alert.Uninstall.Error.Title"), message: error.legibleLocalizedDescription)
                    }
                    self.uninstallPublisher = nil
                },
                receiveValue: { _ in }
        )
    }
    
    func reveal(_ path: Path?) {
        // TODO: show error if not
        guard let path = path else { return }
        NSWorkspace.shared.activateFileViewerSelecting([path.url])
    }
    
    func reveal(path: String) {
        let url = URL(fileURLWithPath: path)
        NSWorkspace.shared.activateFileViewerSelecting([url])
    }

    /// Make an Xcode active, a.k.a select it, in the `xcode-select` sense.
    ///
    /// The underlying work is done by the privileged helper, so we need to make sure that it's installed first.
    /// The way this is done is a little roundabout, because it requires user interaction in an alert before the `selectPublisher` is subscribed to.
    /// The first time this method is invoked should be with `shouldPrepareUserForHelperInstallation` set to true.
    /// If the helper is already installed, the Xcode will be made active immediately.
    /// If the helper is not already installed, the user will be prepared for installation and this method will return early.
    /// If they consent to installing the helper then this method will be invoked again with  `shouldPrepareUserForHelperInstallation` set to false.
    /// This will install the helper and make the Xcode active.
    ///
    /// - Parameter xcode: The Xcode to make active.
    /// - Parameter shouldPrepareUserForHelperInstallation: Whether the user should be presented with an alert preparing them for helper installation before making the Xcode version active.
    func select(xcode: Xcode, shouldPrepareUserForHelperInstallation: Bool = true) {
        guard helperInstallState == .installed || shouldPrepareUserForHelperInstallation == false else {
            isPreparingUserForActionRequiringHelper = { [unowned self] userConsented in
                guard userConsented else { return }
                self.select(xcode: xcode, shouldPrepareUserForHelperInstallation: false)
            }
            presentedAlert = .privilegedHelper
            return
        }

        guard
            var installedXcodePath = xcode.installedPath,
            selectPublisher == nil
        else { return }
       
        if onSelectActionType == .rename {
            guard let newDestinationXcodePath = renameToXcode(xcode: xcode) else { return }
            installedXcodePath = newDestinationXcodePath
        }
        
        selectPublisher = installHelperIfNecessary()
            .flatMap {
                Current.helper.switchXcodePath(installedXcodePath.string)
            }
            .flatMap { [unowned self] _ in
                self.updateSelectedXcodePath()
            }
            .sink(
                receiveCompletion: { [unowned self] completion in
                    if case let .failure(error) = completion {
                        self.error = error
                        self.presentedAlert = .generic(title: localizeString("Alert.Select.Error.Title"), message: error.legibleLocalizedDescription)
                    } else {
                        if self.createSymLinkOnSelect {
                            createSymbolicLink(xcode: xcode)
                        }
                    }
                    self.selectPublisher = nil
                },
                receiveValue: { _ in }
            )
    }
    
    func open(xcode: Xcode, openInRosetta: Bool? = false) {
        switch xcode.installState {
        case let .installed(path):
            let config = NSWorkspace.OpenConfiguration.init()
            if (openInRosetta ?? false) {
                config.architecture = CPU_TYPE_X86_64
            }
            config.allowsRunningApplicationSubstitution = false
            NSWorkspace.shared.openApplication(at: path.url, configuration: config)
        default:
            Logger.appState.error("\(xcode.id.version) is not installed")
            return
        }
    }
    
    func copyPath(xcode: Xcode) {
        guard let installedXcodePath = xcode.installedPath else { return }
        
        NSPasteboard.general.declareTypes([.URL, .string], owner: nil)
        NSPasteboard.general.writeObjects([installedXcodePath.url as NSURL])
        NSPasteboard.general.setString(installedXcodePath.string, forType: .string)
    }

    func copyReleaseNote(from url: URL?) {
      guard let url = url else { return }
      NSPasteboard.general.declareTypes([.URL, .string], owner: nil)
      NSPasteboard.general.writeObjects([url as NSURL])
      NSPasteboard.general.setString(url.absoluteString, forType: .string)
    }
    
    func createSymbolicLink(xcode: Xcode, isBeta: Bool = false) {
        guard let installedXcodePath = xcode.installedPath else { return }
        
        let destinationPath: Path = Path.installDirectory/"Xcode\(isBeta ? "-Beta" : "").app"
        
        // does an Xcode.app file exist?
        if FileManager.default.fileExists(atPath: destinationPath.string) {
            do {
                // if it's not a symlink, error because we don't want to delete an actual xcode.app file
                let attributes: [FileAttributeKey : Any]? = try? FileManager.default.attributesOfItem(atPath: destinationPath.string)
                
                if attributes?[.type] as? FileAttributeType == FileAttributeType.typeSymbolicLink {
                    try FileManager.default.removeItem(atPath: destinationPath.string)
                    Logger.appState.info("Successfully deleted old symlink")
                } else {
                    self.presentedAlert = .generic(title: localizeString("Alert.SymLink.Title"), message: localizeString("Alert.SymLink.Message"))
                    return
                }
            } catch {
                self.presentedAlert = .generic(title: localizeString("Alert.SymLink.Title"), message: error.localizedDescription)
            }
        }
        
        do {
            try FileManager.default.createSymbolicLink(atPath: destinationPath.string, withDestinationPath: installedXcodePath.string)
            Logger.appState.info("Successfully created symbolic link with Xcode\(isBeta ? "-Beta": "").app")
        } catch {
            Logger.appState.error("Unable to create symbolic Link")
            self.error = error
            self.presentedAlert = .generic(title: localizeString("Alert.SymLink.Title"), message: error.legibleLocalizedDescription)
        }
    }
    
    func renameToXcode(xcode: Xcode) -> Path? {
        guard let installedXcodePath = xcode.installedPath else { return nil }
        
        let destinationPath: Path = Path.installDirectory/"Xcode.app"
        
        // rename any old named `Xcode.app` to the Xcodes versioned named files
        if FileManager.default.fileExists(atPath: destinationPath.string) {
            if let originalXcode = Current.files.installedXcode(destination: destinationPath) {
                let newName = "Xcode-\(originalXcode.version.descriptionWithoutBuildMetadata).app"
                Logger.appState.debug("Found Xcode.app - renaming back to \(newName)")
                do {
                    try destinationPath.rename(to: newName)
                } catch {
                    Logger.appState.error("Unable to create rename Xcode.app back to original")
                    self.error = error
                    // TODO UPDATE MY ERROR STRING
                    self.presentedAlert = .generic(title: localizeString("Alert.SymLink.Title"), message: error.legibleLocalizedDescription)
                }
            }
        }
        // rename passed in xcode to xcode.app
        Logger.appState.debug("Found Xcode.app - renaming back to Xcode.app")
        do {
            return try installedXcodePath.rename(to: "Xcode.app")
        } catch {
            Logger.appState.error("Unable to create rename Xcode.app back to original")
            self.error = error
            // TODO UPDATE MY ERROR STRING
            self.presentedAlert = .generic(title: localizeString("Alert.SymLink.Title"), message: error.legibleLocalizedDescription)
        }
        return nil
    }

    func updateAllXcodes(availableXcodes: [AvailableXcode], installedXcodes: [InstalledXcode], selectedXcodePath: String?) {
        var adjustedAvailableXcodes = availableXcodes
        
        // First, adjust all of the available Xcodes so that available and installed versions line up and the second part of this function works properly.
        if dataSource == .apple {
            for installedXcode in installedXcodes {
                // We can trust that build metadata identifiers are unique for each version of Xcode, so if we have it then it's all we need.
                // If build metadata matches exactly, replace the available version with the installed version.
                // This should handle Apple versions from /downloads/more which don't have build metadata identifiers. 
                if let index = adjustedAvailableXcodes.map(\.version).firstIndex(where: { $0.buildMetadataIdentifiers == installedXcode.version.buildMetadataIdentifiers }) {
                    adjustedAvailableXcodes[index].xcodeID = installedXcode.xcodeID
                }
                // If an installed version is the same as one that's listed online which doesn't have build metadata, replace it with the installed version
                // Not all prerelease Apple versions available online include build metadata
                else if let index = adjustedAvailableXcodes.firstIndex(where: { availableXcode in
                    availableXcode.version.isEquivalent(to: installedXcode.version) &&
                        availableXcode.version.buildMetadataIdentifiers.isEmpty
                }) {
                    adjustedAvailableXcodes[index].xcodeID = installedXcode.xcodeID
                }
            }
        }

        // Map all of the available versions into Xcode values that join available and installed Xcode data for display.
        var newAllXcodes = adjustedAvailableXcodes
            .filter { availableXcode in
                // If we don't have the build identifier, don't attempt to filter prerelease versions with identical build identifiers
                guard !availableXcode.version.buildMetadataIdentifiers.isEmpty else { return true }

                let availableXcodesWithIdenticalBuildIdentifiers = availableXcodes
                    .filter({ $0.version.buildMetadataIdentifiers == availableXcode.version.buildMetadataIdentifiers })
                
                // Include this version if there's only one with this build identifier
                return availableXcodesWithIdenticalBuildIdentifiers.count == 1 ||
                    // Or if there's more than one with this build identifier and this is the release version
                
                availableXcodesWithIdenticalBuildIdentifiers.count > 1 && (availableXcode.version.prereleaseIdentifiers.isEmpty || availableXcode.architectures?.count ?? 0 != 0)
            }
            .map { availableXcode -> Xcode in
                let installedXcode = installedXcodes.first(where: { installedXcode in
                    if availableXcode.architectures == nil {
                        return availableXcode.version.isEquivalent(to: installedXcode.version)
                    } else {
                        return availableXcode.xcodeID == installedXcode.xcodeID
                    }
                })

                let identicalBuilds: [XcodeID]
                let prereleaseAvailableXcodesWithIdenticalBuildIdentifiers = availableXcodes
                    .filter {
                        return $0.version.buildMetadataIdentifiers == availableXcode.version.buildMetadataIdentifiers &&
                            !$0.version.prereleaseIdentifiers.isEmpty &&
                            // If we don't have the build identifier, don't consider this as a potential identical build
                            !$0.version.buildMetadataIdentifiers.isEmpty
                    }
                // If this is the release version, add the identical builds to it
                if !prereleaseAvailableXcodesWithIdenticalBuildIdentifiers.isEmpty, availableXcode.version.prereleaseIdentifiers.isEmpty {
                    identicalBuilds = [availableXcode.xcodeID] + prereleaseAvailableXcodesWithIdenticalBuildIdentifiers.map(\.xcodeID)
                } else {
                    identicalBuilds = []
                }
                
                // If the existing install state is "installing", keep it 
                let existingXcodeInstallState = allXcodes.first { $0.id == availableXcode.xcodeID && $0.installState.installing }?.installState
                // Otherwise, determine it from whether there's an installed Xcode
                let defaultXcodeInstallState: XcodeInstallState = installedXcode.map { .installed($0.path) } ?? .notInstalled
                
                return Xcode(
                    version: availableXcode.version,
                    identicalBuilds: identicalBuilds,
                    installState: existingXcodeInstallState ?? defaultXcodeInstallState,
                    selected: installedXcode != nil && selectedXcodePath?.hasPrefix(installedXcode!.path.string) == true, 
                    icon: (installedXcode?.path.string).map(NSWorkspace.shared.icon(forFile:)),
                    requiredMacOSVersion: availableXcode.requiredMacOSVersion,
                    releaseNotesURL: availableXcode.releaseNotesURL,
                    releaseDate: availableXcode.releaseDate,
                    sdks: availableXcode.sdks,
                    compilers: availableXcode.compilers,
                    downloadFileSize: availableXcode.fileSize,
                    architectures: availableXcode.architectures
                )
            }
        
        // If an installed version isn't listed in the available versions, add the installed version
        // Xcode Releases should have all versions
        // Apple didn't used to keep all prerelease versions around but has started to recently
        for installedXcode in installedXcodes {
            if !newAllXcodes.contains(where: { xcode in xcode.version.isEquivalent(to: installedXcode.version) }) {
                newAllXcodes.append(
                    Xcode(
                        version: installedXcode.version, 
                        installState: .installed(installedXcode.path), 
                        selected: selectedXcodePath?.hasPrefix(installedXcode.path.string) == true, 
                        icon: NSWorkspace.shared.icon(forFile: installedXcode.path.string)
                    )
                )
            }
        }
        
        self.allXcodes = newAllXcodes.sorted { $0.version > $1.version }
    }

    
    // MARK: - Private
    
    private func uninstallXcode(path: Path) -> AnyPublisher<Void, Error> {
        return Deferred {
            Future { promise in
                do {
                    try Current.files.trashItem(at: path.url)
                    promise(.success(()))
                } catch {
                    promise(.failure(error))
                }
            }
        }
        .eraseToAnyPublisher()
    }

    /// removes saved username and credentials stored in keychain
    private func clearLoginCredentials() {
        if let username = savedUsername {
            try? Current.keychain.remove(username)
        }
        Current.defaults.removeObject(forKey: "username")

    }

    // MARK: - Nested Types

    struct AlertContent: Identifiable {
        var title: String
        var message: String
        var id: String { title + message }
    }
}

extension OperatingSystemVersion {
    func versionString() -> String {
        return String(majorVersion) + "." + String(minorVersion) + "." + String(patchVersion)
    }
}