import CoreServices
import PromiseKit
import SessionUIKit

final class ShareVC : UINavigationController, ShareViewDelegate, AppModeManagerDelegate {
    private var areVersionMigrationsComplete = false
    public static var attachmentPrepPromise: Promise<[SignalAttachment]>?
    
    // MARK: Error
    enum ShareViewControllerError: Error {
        case assertionError(description: String)
        case unsupportedMedia
        case notRegistered
        case obsoleteShare
    }
    
    // MARK: Lifecycle
    override func loadView() {
        super.loadView()

        // This should be the first thing we do.
        let appContext = ShareAppExtensionContext(rootViewController: self)
        SetCurrentAppContext(appContext)

        AppModeManager.configure(delegate: self)

        Logger.info("")

        _ = AppVersion.sharedInstance()

        Cryptography.seedRandom()

        // We don't need to use DeviceSleepManager in the SAE.

        // We don't need to use applySignalAppearence in the SAE.

        if CurrentAppContext().isRunningTests {
            // TODO: Do we need to implement isRunningTests in the SAE context?
            return
        }

        AppSetup.setupEnvironment(appSpecificSingletonBlock: {
            SSKEnvironment.shared.notificationsManager = NoopNotificationsManager()
        }, migrationCompletion: { [weak self] in
            AssertIsOnMainThread()

            guard let strongSelf = self else { return }

            // performUpdateCheck must be invoked after Environment has been initialized because
            // upgrade process may depend on Environment.
            strongSelf.versionMigrationsDidComplete()
        })

        // We don't need to use "screen protection" in the SAE.

        NotificationCenter.default.addObserver(self,
                                               selector: #selector(storageIsReady),
                                               name: .StorageIsReady,
                                               object: nil)
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(applicationDidEnterBackground),
                                               name: .OWSApplicationDidEnterBackground,
                                               object: nil)
    }

    @objc
    func versionMigrationsDidComplete() {
        AssertIsOnMainThread()

        Logger.debug("")

        areVersionMigrationsComplete = true

        checkIsAppReady()
    }

    @objc
    func storageIsReady() {
        AssertIsOnMainThread()

        Logger.debug("")

        checkIsAppReady()
    }

    @objc
    func checkIsAppReady() {
        AssertIsOnMainThread()

        // App isn't ready until storage is ready AND all version migrations are complete.
        guard areVersionMigrationsComplete else {
            return
        }
        guard OWSStorage.isStorageReady() else {
            return
        }
        guard !AppReadiness.isAppReady() else {
            // Only mark the app as ready once.
            return
        }

        SignalUtilitiesKit.Configuration.performMainSetup()

        Logger.debug("")

        // Note that this does much more than set a flag;
        // it will also run all deferred blocks.
        AppReadiness.setAppIsReady()

        // We don't need to use messageFetcherJob in the SAE.

        // We don't need to use SyncPushTokensJob in the SAE.

        // We don't need to use DeviceSleepManager in the SAE.

        AppVersion.sharedInstance().saeLaunchDidComplete()

        showLockScreenOrMainContent()

        // We don't need to use OWSMessageReceiver in the SAE.
        // We don't need to use OWSBatchMessageProcessor in the SAE.

        // We don't need to use OWSOrphanDataCleaner in the SAE.

        // We don't need to fetch the local profile in the SAE

        OWSReadReceiptManager.shared().prepareCachedValues()
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        AppReadiness.runNowOrWhenAppDidBecomeReady { [weak self] in
            AssertIsOnMainThread()
            guard let strongSelf = self else { return }
            strongSelf.showLockScreenOrMainContent()
        }
    }

    @objc
    public func applicationDidEnterBackground() {
        AssertIsOnMainThread()

        Logger.info("")

        if OWSScreenLock.shared.isScreenLockEnabled() {

            self.dismiss(animated: false) { [weak self] in
                AssertIsOnMainThread()
                guard let strongSelf = self else { return }
                strongSelf.extensionContext!.completeRequest(returningItems: [], completionHandler: nil)
            }
        }
    }

    deinit {
        NotificationCenter.default.removeObserver(self)

        // Share extensions reside in a process that may be reused between usages.
        // That isn't safe; the codebase is full of statics (e.g. singletons) which
        // we can't easily clean up.
        ExitShareExtension()
    }

    // MARK: App Mode
    public func getCurrentAppMode() -> AppMode {
        guard let window = self.view.window else { return .light }
        let userInterfaceStyle = window.traitCollection.userInterfaceStyle
        let isLightMode = (userInterfaceStyle == .light || userInterfaceStyle == .unspecified)
        return isLightMode ? .light : .dark
    }

    public func setCurrentAppMode(to appMode: AppMode) {
        return // Not applicable to share extensions
    }
    
    // MARK: Updating
    private func showLockScreenOrMainContent() {
        if OWSScreenLock.shared.isScreenLockEnabled() {
            showLockScreen()
        } else {
            showMainContent()
        }
    }
    
    private func showLockScreen() {
        let screenLockVC = SAEScreenLockViewController(shareViewDelegate: self)
        setViewControllers([ screenLockVC ], animated: false)
    }
    
    private func showMainContent() {
        let threadPickerVC = ThreadPickerVC()
        threadPickerVC.shareVC = self
        setViewControllers([ threadPickerVC ], animated: false)
        let promise = buildAttachments()
        ModalActivityIndicatorViewController.present(fromViewController: self, canCancel: false, message: NSLocalizedString("vc_share_loading_message", comment: "")) { activityIndicator in
            promise.done { _ in
                activityIndicator.dismiss { }
            }.catch { _ in
                activityIndicator.dismiss { }
            }
        }
        ShareVC.attachmentPrepPromise = promise
    }
    
    func shareViewWasUnlocked() {
        showMainContent()
    }
    
    func shareViewWasCompleted() {
        extensionContext!.completeRequest(returningItems: [], completionHandler: nil)
    }
    
    func shareViewWasCancelled() {
        extensionContext!.completeRequest(returningItems: [], completionHandler: nil)
    }
    
    func shareViewFailed(error: Error) {
        let alert = UIAlertController(title: "Session", message: error.localizedDescription, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: NSLocalizedString("OK", comment: ""), style: .default, handler: { _ in
            self.extensionContext!.cancelRequest(withError: error)
        }))
        present(alert, animated: true, completion: nil)
    }
    
    // MARK: Attachment Prep
    private class func itemMatchesSpecificUtiType(itemProvider: NSItemProvider, utiType: String) -> Bool {
        // URLs, contacts and other special items have to be detected separately.
        // Many shares (e.g. pdfs) will register many UTI types and/or conform to kUTTypeData.
        guard itemProvider.registeredTypeIdentifiers.count == 1 else {
            return false
        }
        guard let firstUtiType = itemProvider.registeredTypeIdentifiers.first else {
            return false
        }
        return firstUtiType == utiType
    }

    private class func isVisualMediaItem(itemProvider: NSItemProvider) -> Bool {
        return (itemProvider.hasItemConformingToTypeIdentifier(kUTTypeImage as String) ||
            itemProvider.hasItemConformingToTypeIdentifier(kUTTypeMovie as String))
    }

    private class func isUrlItem(itemProvider: NSItemProvider) -> Bool {
        return itemMatchesSpecificUtiType(itemProvider: itemProvider,
                                          utiType: kUTTypeURL as String)
    }

    private class func isContactItem(itemProvider: NSItemProvider) -> Bool {
        return itemMatchesSpecificUtiType(itemProvider: itemProvider,
                                          utiType: kUTTypeContact as String)
    }

    private class func utiType(itemProvider: NSItemProvider) -> String? {
        Logger.info("utiTypeForItem: \(itemProvider.registeredTypeIdentifiers)")

        if isUrlItem(itemProvider: itemProvider) {
            return kUTTypeURL as String
        } else if isContactItem(itemProvider: itemProvider) {
            return kUTTypeContact as String
        }

        // Use the first UTI that conforms to "data".
        let matchingUtiType = itemProvider.registeredTypeIdentifiers.first { (utiType: String) -> Bool in
            UTTypeConformsTo(utiType as CFString, kUTTypeData)
        }
        return matchingUtiType
    }

    private class func createDataSource(utiType: String, url: URL, customFileName: String?) -> DataSource? {
        if utiType == (kUTTypeURL as String) {
            // Share URLs as oversize text messages whose text content is the URL.
            //
            // NOTE: SharingThreadPickerViewController will try to unpack them
            //       and send them as normal text messages if possible.
            let urlString = url.absoluteString
            return DataSourceValue.dataSource(withOversizeText: urlString)
        } else if UTTypeConformsTo(utiType as CFString, kUTTypeText) {
            // Share text as oversize text messages.
            //
            // NOTE: SharingThreadPickerViewController will try to unpack them
            //       and send them as normal text messages if possible.
            return DataSourcePath.dataSource(with: url,
                                             shouldDeleteOnDeallocation: false)
        } else {
            guard let dataSource = DataSourcePath.dataSource(with: url,
                                                             shouldDeleteOnDeallocation: false) else {
                return nil
            }

            if let customFileName = customFileName {
                dataSource.sourceFilename = customFileName
            } else {
                // Ignore the filename for URLs.
                dataSource.sourceFilename = url.lastPathComponent
            }
            return dataSource
        }
    }

    private class func preferredItemProviders(inputItem: NSExtensionItem) -> [NSItemProvider]? {
        guard let attachments = inputItem.attachments else {
            return nil
        }

        var visualMediaItemProviders = [NSItemProvider]()
        var hasNonVisualMedia = false
        for attachment in attachments {
            if isVisualMediaItem(itemProvider: attachment) {
                visualMediaItemProviders.append(attachment)
            } else {
                hasNonVisualMedia = true
            }
        }
        // Only allow multiple-attachment sends if all attachments
        // are visual media.
        if visualMediaItemProviders.count > 0 && !hasNonVisualMedia {
            return visualMediaItemProviders
        }

        // A single inputItem can have multiple attachments, e.g. sharing from Firefox gives
        // one url attachment and another text attachment, where the the url would be https://some-news.com/articles/123-cat-stuck-in-tree
        // and the text attachment would be something like "Breaking news - cat stuck in tree"
        //
        // FIXME: For now, we prefer the URL provider and discard the text provider, since it's more useful to share the URL than the caption
        // but we *should* include both. This will be a bigger change though since our share extension is currently heavily predicated
        // on one itemProvider per share.

        // Prefer a URL provider if available
        if let preferredAttachment = attachments.first(where: { (attachment: Any) -> Bool in
            guard let itemProvider = attachment as? NSItemProvider else {
                return false
            }
            return isUrlItem(itemProvider: itemProvider)
        }) {
            return [preferredAttachment]
        }

        // else return whatever is available
        if let itemProvider = inputItem.attachments?.first {
            return [itemProvider]
        } else {
            owsFailDebug("Missing attachment.")
        }
        return []
    }

    private func selectItemProviders() -> Promise<[NSItemProvider]> {
        guard let inputItems = self.extensionContext?.inputItems else {
            let error = ShareViewControllerError.assertionError(description: "no input item")
            return Promise(error: error)
        }

        for inputItemRaw in inputItems {
            guard let inputItem = inputItemRaw as? NSExtensionItem else {
                Logger.error("invalid inputItem \(inputItemRaw)")
                continue
            }
            if let itemProviders = ShareVC.preferredItemProviders(inputItem: inputItem) {
                return Promise.value(itemProviders)
            }
        }
        let error = ShareViewControllerError.assertionError(description: "no input item")
        return Promise(error: error)
    }

    private
    struct LoadedItem {
        let itemProvider: NSItemProvider
        let itemUrl: URL
        let utiType: String

        var customFileName: String?
        var isConvertibleToTextMessage = false
        var isConvertibleToContactShare = false

        init(itemProvider: NSItemProvider,
             itemUrl: URL,
             utiType: String,
             customFileName: String? = nil,
             isConvertibleToTextMessage: Bool = false,
             isConvertibleToContactShare: Bool = false) {
            self.itemProvider = itemProvider
            self.itemUrl = itemUrl
            self.utiType = utiType
            self.customFileName = customFileName
            self.isConvertibleToTextMessage = isConvertibleToTextMessage
            self.isConvertibleToContactShare = isConvertibleToContactShare
        }
    }
    
    private func loadItemProvider(itemProvider: NSItemProvider) -> Promise<LoadedItem> {
        Logger.info("attachment: \(itemProvider)")

        // We need to be very careful about which UTI type we use.
        //
        // * In the case of "textual" shares (e.g. web URLs and text snippets), we want to
        //   coerce the UTI type to kUTTypeURL or kUTTypeText.
        // * We want to treat shared files as file attachments.  Therefore we do not
        //   want to treat file URLs like web URLs.
        // * UTIs aren't very descriptive (there are far more MIME types than UTI types)
        //   so in the case of file attachments we try to refine the attachment type
        //   using the file extension.
        guard let srcUtiType = ShareVC.utiType(itemProvider: itemProvider) else {
            let error = ShareViewControllerError.unsupportedMedia
            return Promise(error: error)
        }
        Logger.debug("matched utiType: \(srcUtiType)")

        let (promise, resolver) = Promise<LoadedItem>.pending()

        let loadCompletion: NSItemProvider.CompletionHandler = { [weak self]
            (value, error) in

            guard let _ = self else { return }
            guard error == nil else {
                resolver.reject(error!)
                return
            }

            guard let value = value else {
                let missingProviderError = ShareViewControllerError.assertionError(description: "missing item provider")
                resolver.reject(missingProviderError)
                return
            }

            Logger.info("value type: \(type(of: value))")

            if let data = value as? Data {
                let customFileName = "Contact.vcf"

                let customFileExtension = MIMETypeUtil.fileExtension(forUTIType: srcUtiType)
                guard let tempFilePath = OWSFileSystem.writeData(toTemporaryFile: data, fileExtension: customFileExtension) else {
                    let writeError = ShareViewControllerError.assertionError(description: "Error writing item data: \(String(describing: error))")
                    resolver.reject(writeError)
                    return
                }
                let fileUrl = URL(fileURLWithPath: tempFilePath)
                resolver.fulfill(LoadedItem(itemProvider: itemProvider,
                                            itemUrl: fileUrl,
                                            utiType: srcUtiType,
                                            customFileName: customFileName,
                                            isConvertibleToContactShare: false))
            } else if let string = value as? String {
                Logger.debug("string provider: \(string)")
                guard let data = string.filterStringForDisplay().data(using: String.Encoding.utf8) else {
                    let writeError = ShareViewControllerError.assertionError(description: "Error writing item data: \(String(describing: error))")
                    resolver.reject(writeError)
                    return
                }
                guard let tempFilePath = OWSFileSystem.writeData(toTemporaryFile: data, fileExtension: "txt") else {
                    let writeError = ShareViewControllerError.assertionError(description: "Error writing item data: \(String(describing: error))")
                    resolver.reject(writeError)
                    return
                }

                let fileUrl = URL(fileURLWithPath: tempFilePath)

                let isConvertibleToTextMessage = !itemProvider.registeredTypeIdentifiers.contains(kUTTypeFileURL as String)

                if UTTypeConformsTo(srcUtiType as CFString, kUTTypeText) {
                    resolver.fulfill(LoadedItem(itemProvider: itemProvider,
                                                itemUrl: fileUrl,
                                                utiType: srcUtiType,
                                                isConvertibleToTextMessage: isConvertibleToTextMessage))
                } else {
                    resolver.fulfill(LoadedItem(itemProvider: itemProvider,
                                                itemUrl: fileUrl,
                                                utiType: kUTTypeText as String,
                                                isConvertibleToTextMessage: isConvertibleToTextMessage))
                }
            } else if let url = value as? URL {
                // If the share itself is a URL (e.g. a link from Safari), try to send this as a text message.
                let isConvertibleToTextMessage = (itemProvider.registeredTypeIdentifiers.contains(kUTTypeURL as String) &&
                    !itemProvider.registeredTypeIdentifiers.contains(kUTTypeFileURL as String))
                if isConvertibleToTextMessage {
                    resolver.fulfill(LoadedItem(itemProvider: itemProvider,
                                                itemUrl: url,
                                                utiType: kUTTypeURL as String,
                                                isConvertibleToTextMessage: isConvertibleToTextMessage))
                } else {
                    resolver.fulfill(LoadedItem(itemProvider: itemProvider,
                                                itemUrl: url,
                                                utiType: srcUtiType,
                                                isConvertibleToTextMessage: isConvertibleToTextMessage))
                }
            } else if let image = value as? UIImage {
                if let data = image.pngData() {
                    let tempFilePath = OWSFileSystem.temporaryFilePath(withFileExtension: "png")
                    do {
                        let url = NSURL.fileURL(withPath: tempFilePath)
                        try data.write(to: url)
                        resolver.fulfill(LoadedItem(itemProvider: itemProvider, itemUrl: url,
                                                    utiType: srcUtiType))
                    } catch {
                        resolver.reject(ShareViewControllerError.assertionError(description: "couldn't write UIImage: \(String(describing: error))"))
                    }
                } else {
                    resolver.reject(ShareViewControllerError.assertionError(description: "couldn't convert UIImage to PNG: \(String(describing: error))"))
                }
            } else {
                // It's unavoidable that we may sometimes receives data types that we
                // don't know how to handle.
                let unexpectedTypeError = ShareViewControllerError.assertionError(description: "unexpected value: \(String(describing: value))")
                resolver.reject(unexpectedTypeError)
            }
        }

        itemProvider.loadItem(forTypeIdentifier: srcUtiType, options: nil, completionHandler: loadCompletion)

        return promise
    }
    
    private func buildAttachment(forLoadedItem loadedItem: LoadedItem) -> Promise<SignalAttachment> {
        let itemProvider = loadedItem.itemProvider
        let itemUrl = loadedItem.itemUrl
        let utiType = loadedItem.utiType

        var url = itemUrl
        do {
            if isVideoNeedingRelocation(itemProvider: itemProvider, itemUrl: itemUrl) {
                url = try SignalAttachment.copyToVideoTempDir(url: itemUrl)
            }
        } catch {
            let error = ShareViewControllerError.assertionError(description: "Could not copy video")
            return Promise(error: error)
        }

        Logger.debug("building DataSource with url: \(url), utiType: \(utiType)")

        guard let dataSource = ShareVC.createDataSource(utiType: utiType, url: url, customFileName: loadedItem.customFileName) else {
            let error = ShareViewControllerError.assertionError(description: "Unable to read attachment data")
            return Promise(error: error)
        }

        // start with base utiType, but it might be something generic like "image"
        var specificUTIType = utiType
        if utiType == (kUTTypeURL as String) {
            // Use kUTTypeURL for URLs.
        } else if UTTypeConformsTo(utiType as CFString, kUTTypeText) {
            // Use kUTTypeText for text.
        } else if url.pathExtension.count > 0 {
            // Determine a more specific utiType based on file extension
            if let typeExtension = MIMETypeUtil.utiType(forFileExtension: url.pathExtension) {
                Logger.debug("utiType based on extension: \(typeExtension)")
                specificUTIType = typeExtension
            }
        }

        guard !SignalAttachment.isInvalidVideo(dataSource: dataSource, dataUTI: specificUTIType) else {
            // This can happen, e.g. when sharing a quicktime-video from iCloud drive.
            let (promise, _) = SignalAttachment.compressVideoAsMp4(dataSource: dataSource, dataUTI: specificUTIType)
            return promise
        }

        let attachment = SignalAttachment.attachment(dataSource: dataSource, dataUTI: specificUTIType, imageQuality: .medium)
        if loadedItem.isConvertibleToContactShare {
            Logger.info("isConvertibleToContactShare")
            attachment.isConvertibleToContactShare = true
        } else if loadedItem.isConvertibleToTextMessage {
            Logger.info("isConvertibleToTextMessage")
            attachment.isConvertibleToTextMessage = true
        }
        return Promise.value(attachment)
    }

    private func buildAttachments() -> Promise<[SignalAttachment]> {
        return selectItemProviders().then {  [weak self] (itemProviders) -> Promise<[SignalAttachment]> in
            guard let strongSelf = self else {
                let error = ShareViewControllerError.assertionError(description: "expired")
                return Promise(error: error)
            }

            var loadPromises = [Promise<SignalAttachment>]()

            for itemProvider in itemProviders.prefix(SignalAttachment.maxAttachmentsAllowed) {
                let loadPromise = strongSelf.loadItemProvider(itemProvider: itemProvider)
                    .then({ (loadedItem) -> Promise<SignalAttachment> in
                        return strongSelf.buildAttachment(forLoadedItem: loadedItem)
                    })

                loadPromises.append(loadPromise)
            }
            return when(fulfilled: loadPromises)
        }.map { (signalAttachments) -> [SignalAttachment] in
            guard signalAttachments.count > 0 else {
                let error = ShareViewControllerError.assertionError(description: "no valid attachments")
                throw error
            }
            return signalAttachments
        }
    }

    // Some host apps (e.g. iOS Photos.app) sometimes auto-converts some video formats (e.g. com.apple.quicktime-movie)
    // into mp4s as part of the NSItemProvider `loadItem` API. (Some files the Photo's app doesn't auto-convert)
    //
    // However, when using this url to the converted item, AVFoundation operations such as generating a
    // preview image and playing the url in the AVMoviePlayer fails with an unhelpful error: "The operation could not be completed"
    //
    // We can work around this by first copying the media into our container.
    //
    // I don't understand why this is, and I haven't found any relevant documentation in the NSItemProvider
    // or AVFoundation docs.
    //
    // Notes:
    //
    // These operations succeed when sending a video which initially existed on disk as an mp4.
    // (e.g. Alice sends a video to Bob through the main app, which ensures it's an mp4. Bob saves it, then re-shares it)
    //
    // I *did* verify that the size and SHA256 sum of the original url matches that of the copied url. So there
    // is no difference between the contents of the file, yet one works one doesn't.
    // Perhaps the AVFoundation APIs require some extra file system permssion we don't have in the
    // passed through URL.
    private func isVideoNeedingRelocation(itemProvider: NSItemProvider, itemUrl: URL) -> Bool {
        let pathExtension = itemUrl.pathExtension
        guard pathExtension.count > 0 else {
            Logger.verbose("item URL has no file extension: \(itemUrl).")
            return false
        }
        guard let utiTypeForURL = MIMETypeUtil.utiType(forFileExtension: pathExtension) else {
            Logger.verbose("item has unknown UTI type: \(itemUrl).")
            return false
        }
        Logger.verbose("utiTypeForURL: \(utiTypeForURL)")
        guard utiTypeForURL == kUTTypeMPEG4 as String else {
            // Either it's not a video or it was a video which was not auto-converted to mp4.
            // Not affected by the issue.
            return false
        }

        // If video file already existed on disk as an mp4, then the host app didn't need to
        // apply any conversion, so no need to relocate the app.
        return !itemProvider.registeredTypeIdentifiers.contains(kUTTypeMPEG4 as String)
    }
}