import Combine
import Foundation
import Path
import AppleAPI
import Version
import LegibleError
import os.log

/// Downloads and installs Xcodes
extension AppState {
    
    // check to see if we should auto install for the user
    public func autoInstallIfNeeded() {
        guard let storageValue = UserDefaults.standard.object(forKey: "autoInstallation") as? Int, let autoInstallType = AutoInstallationType(rawValue: storageValue) else { return }
        
        if autoInstallType == .none { return }
        
        // get newest xcode version
        guard let newestXcode = allXcodes.first, newestXcode.installState == .notInstalled else {
            Logger.appState.info("User has latest Xcode already installed")
            return
        }
        
        if autoInstallType == .newestBeta {
            Logger.appState.info("Auto installing newest Xcode Beta")
            // install it, as user doesn't have it installed and it's either latest beta or latest release
            checkMinVersionAndInstall(id: newestXcode.id)
        } else if autoInstallType == .newestVersion && newestXcode.version.isNotPrerelease {
            Logger.appState.info("Auto installing newest Xcode")
            checkMinVersionAndInstall(id: newestXcode.id)
        } else {
            Logger.appState.info("No new Xcodes version found to auto install")
        }
    }
    
    public func install(_ installationType: InstallationType, downloader: Downloader) -> AnyPublisher<Void, Error> {
        install(installationType, downloader: downloader, attemptNumber: 0)
            .map { _ in Void() }
            .eraseToAnyPublisher()
    }
    
    private func install(_ installationType: InstallationType, downloader: Downloader, attemptNumber: Int) -> AnyPublisher<InstalledXcode, Error> {
        
        Logger.appState.info("Using \(downloader) downloader")
        
        return validateSession()
            .flatMap { _ in
                self.getXcodeArchive(installationType, downloader: downloader)
            }
            .flatMap { xcode, url -> AnyPublisher<InstalledXcode, Swift.Error> in
                self.installArchivedXcode(xcode, at: url)
            }
            .catch { error -> AnyPublisher<InstalledXcode, Swift.Error> in
                switch error {
                case InstallationError.damagedXIP(let damagedXIPURL):
                    guard attemptNumber < 1 else { return Fail(error: error).eraseToAnyPublisher() }

                    switch installationType {
                    case .version:
                        // If the XIP was just downloaded, remove it and try to recover.
                        do {
                            Logger.appState.error("\(error.legibleLocalizedDescription)")
                            Logger.appState.info("Removing damaged XIP and re-attempting installation.")
                            try Current.files.removeItem(at: damagedXIPURL)
                            return self.install(installationType, downloader: downloader, attemptNumber: attemptNumber + 1)
                                .eraseToAnyPublisher()
                        } catch {
                            return Fail(error: error)
                                .eraseToAnyPublisher()
                        }
                    }
                default:
                    return Fail(error: error)
                        .eraseToAnyPublisher()
                }
            }
            .handleEvents(receiveOutput: { installedXcode in
                DispatchQueue.main.async {
                    guard let index = self.allXcodes.firstIndex(where: { $0.version.isEquivalent(to: installedXcode.version) }) else { return }
                    self.allXcodes[index].installState = .installed(installedXcode.path)
                }
            })
            .eraseToAnyPublisher()
    }
    
    private func getXcodeArchive(_ installationType: InstallationType, downloader: Downloader) -> AnyPublisher<(AvailableXcode, URL), Error> {
        switch installationType {
        case .version(let availableXcode):
            if let installedXcode = Current.files.installedXcodes(Path.installDirectory).first(where: { $0.version.isEquivalent(to: availableXcode.version) }) {
                return Fail(error: InstallationError.versionAlreadyInstalled(installedXcode))
                    .eraseToAnyPublisher()
            }
            
            return downloadXcode(availableXcode: availableXcode, downloader: downloader)
        }
    }

    private func downloadXcode(availableXcode: AvailableXcode, downloader: Downloader) -> AnyPublisher<(AvailableXcode, URL), Error> {
            self.downloadOrUseExistingArchive(for: availableXcode, downloader: downloader, progressChanged: { [unowned self] progress in
                DispatchQueue.main.async {
                    self.setInstallationStep(of: availableXcode.version, to: .downloading(progress: progress))
                }
            })
            .map { return (availableXcode, $0) }
            .eraseToAnyPublisher()
    }
    
    public func downloadOrUseExistingArchive(for availableXcode: AvailableXcode, downloader: Downloader, progressChanged: @escaping (Progress) -> Void) -> AnyPublisher<URL, Error> {
        // Check to see if the archive is in the expected path in case it was downloaded but failed to install
        let expectedArchivePath = Path.xcodesApplicationSupport/"Xcode-\(availableXcode.version).\(availableXcode.filename.suffix(fromLast: "."))"
        // aria2 downloads directly to the destination (instead of into /tmp first) so we need to make sure that the download isn't incomplete
        let aria2DownloadMetadataPath = expectedArchivePath.parent/(expectedArchivePath.basename() + ".aria2")
        var aria2DownloadIsIncomplete = false
        if case .aria2 = downloader, aria2DownloadMetadataPath.exists {
            aria2DownloadIsIncomplete = true
        }
        if Current.files.fileExistsAtPath(expectedArchivePath.string), aria2DownloadIsIncomplete == false {
            Logger.appState.info("Found existing archive that will be used for installation at \(expectedArchivePath).")
            return Just(expectedArchivePath.url)
                .setFailureType(to: Error.self)
                .eraseToAnyPublisher()
        }
        else {
            let destination = Path.xcodesApplicationSupport/"Xcode-\(availableXcode.version).\(availableXcode.filename.suffix(fromLast: "."))"
            switch downloader {
            case .aria2:
                let aria2Path = Path(url: Bundle.main.url(forAuxiliaryExecutable: "aria2c")!)!
                return downloadXcodeWithAria2(
                    availableXcode,
                    to: destination,
                    aria2Path: aria2Path,
                    progressChanged: progressChanged
                )
            case .urlSession:
                return downloadXcodeWithURLSession(
                    availableXcode,
                    to: destination,
                    progressChanged: progressChanged
                )
            }
        }
    }
    
    public func downloadXcodeWithAria2(_ availableXcode: AvailableXcode, to destination: Path, aria2Path: Path, progressChanged: @escaping (Progress) -> Void) -> AnyPublisher<URL, Error> {
        let cookies = AppleAPI.Current.network.session.configuration.httpCookieStorage?.cookies(for: availableXcode.url) ?? []
    
        let (progress, publisher) = Current.shell.downloadWithAria2(
            aria2Path, 
            availableXcode.url,
            destination,
            cookies
        )
        progressChanged(progress)
        return publisher
            .map { _ in destination.url }
            .eraseToAnyPublisher()
    }

    public func downloadXcodeWithURLSession(_ availableXcode: AvailableXcode, to destination: Path, progressChanged: @escaping (Progress) -> Void) -> AnyPublisher<URL, Error> {
        let resumeDataPath = Path.xcodesApplicationSupport/"Xcode-\(availableXcode.version).resumedata"
        let persistedResumeData = Current.files.contents(atPath: resumeDataPath.string)
        
        return attemptResumableTask(maximumRetryCount: 3) { resumeData -> AnyPublisher<URL, Error> in
            let (progress, publisher) = Current.network.downloadTask(with: availableXcode.url,
                                                                   to: destination.url,
                                                                   resumingWith: resumeData ?? persistedResumeData)
            progressChanged(progress)
            return publisher
                .map { $0.saveLocation }
                .eraseToAnyPublisher()
        }
        .handleEvents(receiveCompletion: { completion in
            self.persistOrCleanUpResumeData(at: resumeDataPath, for: completion)
        })
        .eraseToAnyPublisher()
    }

    public func installArchivedXcode(_ availableXcode: AvailableXcode, at archiveURL: URL) -> AnyPublisher<InstalledXcode, Error> {
        do {
            let destinationURL = Path.installDirectory.join("Xcode-\(availableXcode.version.descriptionWithoutBuildMetadata).app").url
            switch archiveURL.pathExtension {
            case "xip":
                return unarchiveAndMoveXIP(availableXcode: availableXcode, at: archiveURL, to: destinationURL)
                    .tryMap { xcodeURL throws -> InstalledXcode in
                        guard 
                            let path = Path(url: xcodeURL),
                            Current.files.fileExists(atPath: path.string),
                            let installedXcode = InstalledXcode(path: path)
                        else { throw InstallationError.failedToMoveXcodeToApplications }
                        return installedXcode
                    }
                    .flatMap { installedXcode -> AnyPublisher<InstalledXcode, Error> in
                        do {
                            self.setInstallationStep(of: availableXcode.version, to: .trashingArchive)
                            try Current.files.trashItem(at: archiveURL)
                            self.setInstallationStep(of: availableXcode.version, to: .checkingSecurity)
                            
                            return self.verifySecurityAssessment(of: installedXcode)
                                .combineLatest(self.verifySigningCertificate(of: installedXcode.path.url))
                                .map { _ in installedXcode }
                                .eraseToAnyPublisher()
                        } catch {
                            return Fail(error: error)
                                .eraseToAnyPublisher()
                        }
                    }
                    .flatMap { installedXcode -> AnyPublisher<InstalledXcode, Error> in
                        self.setInstallationStep(of: availableXcode.version, to: .finishing)

                        return self.performPostInstallSteps(for: installedXcode)
                            .map { installedXcode }
                            // Show post-install errors but don't fail because of them
                            .handleEvents(receiveCompletion: { [unowned self] completion in
                                if case let .failure(error) = completion {
                                    self.error = error
                                    self.presentedAlert = .generic(title: localizeString("Alert.InstallArchive.Error.Title"), message: error.legibleLocalizedDescription)
                                }
                            })
                            .catch { _ in
                                Just(installedXcode)
                                    .setFailureType(to: Error.self)
                                    .eraseToAnyPublisher()
                            }
                            .eraseToAnyPublisher()
                    }
                    .eraseToAnyPublisher()
            case "dmg":
                throw InstallationError.unsupportedFileFormat(extension: "dmg")
            default:
                throw InstallationError.unsupportedFileFormat(extension: archiveURL.pathExtension)
            }
        } catch {
            return Fail(error: error)
                .eraseToAnyPublisher()
        }
    }

    func unarchiveAndMoveXIP(availableXcode: AvailableXcode, at source: URL, to destination: URL) -> AnyPublisher<URL, Swift.Error> {
        self.setInstallationStep(of: availableXcode.version, to: .unarchiving)
        
        return unxipOrUnxipExperiment(source)
            .catch { error -> AnyPublisher<ProcessOutput, Swift.Error> in
                if let executionError = error as? ProcessExecutionError {
                   if executionError.standardError.contains("damaged and can’t be expanded") {
                    return Fail(error: InstallationError.damagedXIP(url: source))
                        .eraseToAnyPublisher()
                   } else if executionError.standardError.contains("can’t be expanded because the selected volume doesn’t have enough free space.") {
                    return Fail(error: InstallationError.notEnoughFreeSpaceToExpandArchive(archivePath: Path(url: source)!,
                                                                                           version: availableXcode.version))
                        .eraseToAnyPublisher()
                   }
                }
                return Fail(error: error)
                    .eraseToAnyPublisher()
            }
        .tryMap { output -> URL in
            self.setInstallationStep(of: availableXcode.version, to: .moving(destination: destination.path))

            let xcodeURL = source.deletingLastPathComponent().appendingPathComponent("Xcode.app")
            let xcodeBetaURL = source.deletingLastPathComponent().appendingPathComponent("Xcode-beta.app")
            if Current.files.fileExists(atPath: xcodeURL.path) {
                try Current.files.moveItem(at: xcodeURL, to: destination)
            }
            else if Current.files.fileExists(atPath: xcodeBetaURL.path) {
                try Current.files.moveItem(at: xcodeBetaURL, to: destination)
            }

            return destination
        }
        .handleEvents(receiveCancel: {
            if Current.files.fileExists(atPath: source.path) {
                try? Current.files.removeItem(source)
            }
            if Current.files.fileExists(atPath: destination.path) {
                try? Current.files.removeItem(destination)
            }
        })
        .eraseToAnyPublisher()
    }
    
    func unxipOrUnxipExperiment(_ source: URL) -> AnyPublisher<ProcessOutput, Error> {
        if unxipExperiment {
            // All hard work done by https://github.com/saagarjha/unxip
            // Compiled to binary with `swiftc -parse-as-library -O unxip.swift`
            return Current.shell.unxipExperiment(source)
        } else {
            return Current.shell.unxip(source)
        }
    }

    public func verifySecurityAssessment(of xcode: InstalledXcode) -> AnyPublisher<Void, Error> {
        return Current.shell.spctlAssess(xcode.path.url)
            .catch { (error: Swift.Error) -> AnyPublisher<ProcessOutput, Error> in
                var output = ""
                if let executionError = error as? ProcessExecutionError {
                    output = [executionError.standardOutput, executionError.standardError].joined(separator: "\n")
                }
                return Fail(error: InstallationError.failedSecurityAssessment(xcode: xcode, output: output))
                    .eraseToAnyPublisher()
            }
            .map { _ in Void() }
            .eraseToAnyPublisher()
    }

    func verifySigningCertificate(of url: URL) -> AnyPublisher<Void, Error> {
        return Current.shell.codesignVerify(url)
            .catch { error -> AnyPublisher<ProcessOutput, Error> in
                var output = ""
                if let executionError = error as? ProcessExecutionError {
                    output = [executionError.standardOutput, executionError.standardError].joined(separator: "\n")
                }
                return Fail(error: InstallationError.codesignVerifyFailed(output: output))
                    .eraseToAnyPublisher()
            }
            .map { output -> CertificateInfo in
                // codesign prints to stderr
                return self.parseCertificateInfo(output.err)
            }
            .tryMap { cert in
                guard
                    cert.teamIdentifier == XcodeTeamIdentifier,
                    cert.authority == XcodeCertificateAuthority
                else { throw InstallationError.unexpectedCodeSigningIdentity(identifier: cert.teamIdentifier, certificateAuthority: cert.authority) }
                
                return Void()
            }
            .eraseToAnyPublisher()
    }

    public struct CertificateInfo {
        public var authority: [String]
        public var teamIdentifier: String
        public var bundleIdentifier: String
    }

    public func parseCertificateInfo(_ rawInfo: String) -> CertificateInfo {
        var info = CertificateInfo(authority: [], teamIdentifier: "", bundleIdentifier: "")

        for part in rawInfo.trimmingCharacters(in: .whitespacesAndNewlines).components(separatedBy: .newlines) {
            if part.hasPrefix("Authority") {
                info.authority.append(part.components(separatedBy: "=")[1])
            }
            if part.hasPrefix("TeamIdentifier") {
                info.teamIdentifier = part.components(separatedBy: "=")[1]
            }
            if part.hasPrefix("Identifier") {
                info.bundleIdentifier = part.components(separatedBy: "=")[1]
            }
        }

        return info
    }
    
    // MARK: - Post-Install
    
    /// Attemps to install the helper once, then performs all post-install steps
    public func performPostInstallSteps(for xcode: InstalledXcode) {
        performPostInstallSteps(for: xcode)
            .sink(
                receiveCompletion: { completion in
                    if case let .failure(error) = completion {
                        self.error = error
                        self.presentedAlert = .generic(title: localizeString("Alert.PostInstall.Title"), message: error.legibleLocalizedDescription)
                    }
                }, 
                receiveValue: {}
            )
            .store(in: &cancellables)
    }
    
    /// Attemps to install the helper once, then performs all post-install steps
    public func performPostInstallSteps(for xcode: InstalledXcode) -> AnyPublisher<Void, Error> {
        let postInstallPublisher: AnyPublisher<Void, Error> =
            Deferred { [unowned self] in
                self.installHelperIfNecessary()
            }
            .flatMap { [unowned self] in
                self.enableDeveloperMode()
            }
            .flatMap { [unowned self] in
                self.approveLicense(for: xcode)
            }
            .flatMap { [unowned self] in
                self.installComponents(for: xcode)
            }
            .mapError { [unowned self] error in
                Logger.appState.error("Performing post-install steps failed: \(error.legibleLocalizedDescription)")
                return InstallationError.postInstallStepsNotPerformed(version: xcode.version, helperInstallState: self.helperInstallState)
            }
            .eraseToAnyPublisher()

        guard helperInstallState == .installed else {
            // If the helper isn't installed yet then we need to prepare the user for the install prompt,
            // and then actually perform the installation,
            // and the post-install steps need to wait until that is complete.
            // This subject, which completes upon isPreparingUserForActionRequiringHelper being invoked, is used to achieve that.
            // This is not the most straightforward code I've ever written...
            let helperInstallConsentSubject = PassthroughSubject<Void, Error>()

            // Need to dispatch this to avoid duplicate alerts, 
            // the second of which will crash when force-unwrapping isPreparingUserForActionRequiringHelper 
            DispatchQueue.main.async {
                self.isPreparingUserForActionRequiringHelper = { [unowned self] userConsented in
                    if userConsented {
                        helperInstallConsentSubject.send()
                    } else {
                        Logger.appState.info("User did not consent to installing helper during post-install steps.")

                        helperInstallConsentSubject.send(
                            completion: .failure(
                                InstallationError.postInstallStepsNotPerformed(version: xcode.version, helperInstallState: self.helperInstallState)
                            )
                        )
                    }
                }
                self.presentedAlert = .privilegedHelper
            }

            return helperInstallConsentSubject
                .flatMap { 
                    postInstallPublisher 
                }
                .eraseToAnyPublisher()
        }
        
        return postInstallPublisher
    }

    private func enableDeveloperMode() -> AnyPublisher<Void, Error> {
        Current.helper.devToolsSecurityEnable()
            .flatMap {
                Current.helper.addStaffToDevelopersGroup()
            }
            .eraseToAnyPublisher()
    }

    private func approveLicense(for xcode: InstalledXcode) -> AnyPublisher<Void, Error> {
        Current.helper.acceptXcodeLicense(xcode.path.string)
            .eraseToAnyPublisher()
    }

    private func installComponents(for xcode: InstalledXcode) -> AnyPublisher<Void, Swift.Error> {
        Current.helper.runFirstLaunch(xcode.path.string)
            .flatMap {
                Current.shell.getUserCacheDir().map { $0.out }
                    .combineLatest(
                        Current.shell.buildVersion().map { $0.out },
                        Current.shell.xcodeBuildVersion(xcode).map { $0.out }
                    )
            }
            .flatMap { cacheDirectory, macOSBuildVersion, toolsVersion in
                Current.shell.touchInstallCheck(cacheDirectory, macOSBuildVersion, toolsVersion)
            }
            .map { _ in Void() }
            .eraseToAnyPublisher()
    }
    
    // MARK: - 
    
    func setInstallationStep(of version: Version, to step: InstallationStep) {
        DispatchQueue.main.async {
            guard let index = self.allXcodes.firstIndex(where: { $0.version.isEquivalent(to: version) }) else { return }
            self.allXcodes[index].installState = .installing(step)
            
            let xcode = self.allXcodes[index]
            Current.notificationManager.scheduleNotification(title: xcode.id.appleDescription, body: step.description, category: .normal)
        }
    }
}

extension AppState {
    func persistOrCleanUpResumeData<T>(at path: Path, for completion: Subscribers.Completion<T>) {
        switch completion {
        case .finished:
            try? Current.files.removeItem(at: path.url)
        case .failure(let error):
            guard let resumeData = (error as NSError).userInfo[NSURLSessionDownloadTaskResumeData] as? Data else { return }
            Current.files.createFile(atPath: path.string, contents: resumeData)
        }
    }
}

public enum InstallationError: LocalizedError, Equatable {
    case damagedXIP(url: URL)
    case notEnoughFreeSpaceToExpandArchive(archivePath: Path, version: Version)
    case failedToMoveXcodeToApplications
    case failedSecurityAssessment(xcode: InstalledXcode, output: String)
    case codesignVerifyFailed(output: String)
    case unexpectedCodeSigningIdentity(identifier: String, certificateAuthority: [String])
    case unsupportedFileFormat(extension: String)
    case missingSudoerPassword
    case unavailableVersion(Version)
    case noNonPrereleaseVersionAvailable
    case noPrereleaseVersionAvailable
    case missingUsernameOrPassword
    case versionAlreadyInstalled(InstalledXcode)
    case invalidVersion(String)
    case versionNotInstalled(Version)
    case postInstallStepsNotPerformed(version: Version, helperInstallState: HelperInstallState)

    public var errorDescription: String? {
        switch self {
        case .damagedXIP(let url):
            return String(format: localizeString("InstallationError.DamagedXIP"), url.lastPathComponent)
        case let .notEnoughFreeSpaceToExpandArchive(archivePath, version):
            return String(format: localizeString("InstallationError.NotEnoughFreeSpaceToExpandArchive"), archivePath.basename(), version.appleDescription)
        case .failedToMoveXcodeToApplications:
            return String(format: localizeString("InstallationError.FailedToMoveXcodeToApplications"), Path.installDirectory.string)
        case .failedSecurityAssessment(let xcode, let output):
            return String(format: localizeString("InstallationError.FailedSecurityAssessment"), String(xcode.version), output, xcode.path.string)
        case .codesignVerifyFailed(let output):
            return String(format: localizeString("InstallationError.CodesignVerifyFailed"), output)
        case .unexpectedCodeSigningIdentity(let identity, let certificateAuthority):
            return String(format: localizeString("InstallationError.UnexpectedCodeSigningIdentity"), identity, certificateAuthority, XcodeTeamIdentifier, XcodeCertificateAuthority)
        case .unsupportedFileFormat(let fileExtension):
            return String(format: localizeString("InstallationError.UnsupportedFileFormat"), fileExtension)
        case .missingSudoerPassword:
            return localizeString("InstallationError.MissingSudoerPassword")
        case let .unavailableVersion(version):
            return String(format: localizeString("InstallationError.UnavailableVersion"), version.appleDescription)
        case .noNonPrereleaseVersionAvailable:
            return localizeString("InstallationError.NoNonPrereleaseVersionAvailable")
        case .noPrereleaseVersionAvailable:
            return localizeString("InstallationError.NoPrereleaseVersionAvailable")
        case .missingUsernameOrPassword:
            return localizeString("InstallationError.MissingUsernameOrPassword")
        case let .versionAlreadyInstalled(installedXcode):
            return String(format: localizeString("InstallationError.VersionAlreadyInstalled"), installedXcode.version.appleDescription, installedXcode.path.string)
        case let .invalidVersion(version):
            return String(format: localizeString("InstallationError.InvalidVersion"), version)
        case let .versionNotInstalled(version):
            return String(format: localizeString("InstallationError.VersionNotInstalled"), version.appleDescription)
        case let .postInstallStepsNotPerformed(version, helperInstallState):
            switch helperInstallState {
            case .installed:
                return String(format: localizeString("InstallationError.PostInstallStepsNotPerformed.Installed"), version.appleDescription)
            case .notInstalled, .unknown:
                return String(format: localizeString("InstallationError.PostInstallStepsNotPerformed.NotInstalled"), version.appleDescription)
            }
        }
    }
}

public enum InstallationType {
    case version(AvailableXcode)
}

public enum AutoInstallationType: Int, Identifiable {
    case none = 0
    case newestVersion
    case newestBeta
    
    public var id: Self { self }
    
    public var isAutoInstalling: Bool {
        get {
            return self != .none
        }
        set {
            self = newValue ? .newestVersion : .none
        }
    }
    public var isAutoInstallingBeta: Bool {
        get {
            return self == .newestBeta
        }
        set {
            self = newValue ? .newestBeta : (isAutoInstalling ? .newestVersion : .none)
        }
    }
}

let XcodeTeamIdentifier = "59GAB85EFG"
let XcodeCertificateAuthority = ["Software Signing", "Apple Code Signing Certification Authority", "Apple Root CA"]