// Copyright © 2022 Rangeproof Pty Ltd. All rights reserved.

import Foundation
import Combine
import GRDB
import CallKit
import UserNotifications
import BackgroundTasks
import SessionMessagingKit
import SignalUtilitiesKit
import SessionUtilitiesKit

public final class NotificationServiceExtension: UNNotificationServiceExtension {
    private let dependencies: Dependencies = Dependencies()
    private var didPerformSetup = false
    private var contentHandler: ((UNNotificationContent) -> Void)?
    private var request: UNNotificationRequest?
    private var hasCompleted: Atomic<Bool> = Atomic(false)

    public static let isFromRemoteKey = "remote"                                                                   // stringlint:disable
    public static let threadIdKey = "Signal.AppNotificationsUserInfoKey.threadId"                                  // stringlint:disable
    public static let threadVariantRaw = "Signal.AppNotificationsUserInfoKey.threadVariantRaw"                     // stringlint:disable
    public static let threadNotificationCounter = "Session.AppNotificationsUserInfoKey.threadNotificationCounter"  // stringlint:disable
    private static let callPreOfferLargeNotificationSupressionDuration: TimeInterval = 30

    // MARK: Did receive a remote push notification request
    
    override public func didReceive(_ request: UNNotificationRequest, withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void) {
        self.contentHandler = contentHandler
        self.request = request
        
        // It's technically possible for 'completeSilently' to be called twice due to the NSE timeout so
        self.hasCompleted.mutate { $0 = false }
        
        // Abort if the main app is running
        guard !(UserDefaults.sharedLokiProject?[.isMainAppActive]).defaulting(to: false) else {
            Log.info("didReceive called while main app running.")
            return self.completeSilenty(handledNotification: false, isMainAppAndActive: true)
        }
        
        guard let notificationContent = request.content.mutableCopy() as? UNMutableNotificationContent else {
            Log.info("didReceive called with no content.")
            return self.completeSilenty(handledNotification: false)
        }
        
        Log.info("didReceive called.")
        
        /// Create the context if we don't have it (needed before _any_ interaction with the database)
        if !Singleton.hasAppContext {
            Singleton.setup(appContext: NotificationServiceExtensionContext())
        }
        
        // Perform main setup
        Storage.resumeDatabaseAccess(using: dependencies)
        DispatchQueue.main.sync {
            self.setUpIfNecessary() { [weak self] in
                self?.handleNotification(notificationContent, isPerformingResetup: false)
            }
        }
    }
    
    private func handleNotification(_ notificationContent: UNMutableNotificationContent, isPerformingResetup: Bool) {
        let (maybeData, metadata, result) = PushNotificationAPI.processNotification(
            notificationContent: notificationContent,
            using: dependencies
        )
        
        guard metadata.accountId == getUserHexEncodedPublicKey(using: dependencies) else {
            guard !isPerformingResetup else {
                Log.error("Received notification for an accountId that isn't the current user, resetup failed.")
                return self.completeSilenty(handledNotification: false)
            }
            
            Log.warn("Received notification for an accountId that isn't the current user, attempting to resetup.")
            return self.forceResetup(notificationContent)
        }
        
        guard
            (result == .success || result == .legacySuccess),
            let data: Data = maybeData
        else {
            switch result {
                // If we got an explicit failure, or we got a success but no content then show
                // the fallback notification
                case .success, .legacySuccess, .failure, .legacyFailure:
                    return self.handleFailure(for: notificationContent, error: .processing(result))
                    
                // Just log if the notification was too long (a ~2k message should be able to fit so
                // these will most commonly be call or config messages)
                case .successTooLong:
                    Log.info("Received too long notification for namespace: \(metadata.namespace), dataLength: \(metadata.dataLength).")
                    return self.completeSilenty(handledNotification: false)
                    
                case .legacyForceSilent:
                    Log.info("Ignoring non-group legacy notification.")
                    return self.completeSilenty(handledNotification: false)
                    
                case .failureNoContent:
                    Log.warn("Failed due to missing notification content.")
                    return self.completeSilenty(handledNotification: false)
            }
        }
        
        let isCallOngoing: Bool = (UserDefaults.sharedLokiProject?[.isCallOngoing])
            .defaulting(to: false)
        
        // HACK: It is important to use write synchronously here to avoid a race condition
        // where the completeSilenty() is called before the local notification request
        // is added to notification center
        dependencies.storage.write { [weak self, dependencies] db in
            do {
                guard let processedMessage: ProcessedMessage = try Message.processRawReceivedMessageAsNotification(db, data: data, metadata: metadata, using: dependencies) else {
                    throw NotificationError.messageProcessing
                }
                
                switch processedMessage {
                    /// Custom handle config messages (as they don't get handled by the normal `MessageReceiver.handle` call
                    case .config(let publicKey, let namespace, let serverHash, let serverTimestampMs, let data):
                        try LibSession.handleConfigMessages(
                            db,
                            messages: [
                                ConfigMessageReceiveJob.Details.MessageInfo(
                                    namespace: namespace,
                                    serverHash: serverHash,
                                    serverTimestampMs: serverTimestampMs,
                                    data: data
                                )
                            ],
                            publicKey: publicKey,
                            using: dependencies
                        )
                        
                    /// Due to the way the `CallMessage` works we need to custom handle it's behaviour within the notification
                    /// extension, for all other message types we want to just use the standard `MessageReceiver.handle` call
                    case .standard(let threadId, let threadVariant, _, let messageInfo) where messageInfo.message is CallMessage:
                        guard let callMessage = messageInfo.message as? CallMessage else {
                            throw NotificationError.ignorableMessage
                        }
                        
                        // Throw if the message is outdated and shouldn't be processed
                        try MessageReceiver.throwIfMessageOutdated(
                            db,
                            message: messageInfo.message,
                            threadId: threadId,
                            threadVariant: threadVariant,
                            using: dependencies
                        )
                        
                        try MessageReceiver.handleCallMessage(
                            db,
                            threadId: threadId,
                            threadVariant: threadVariant,
                            message: callMessage,
                            using: dependencies
                        )
                        
                        guard case .preOffer = callMessage.kind else {
                            throw NotificationError.ignorableMessage
                        }
                        
                        switch (db[.areCallsEnabled], isCallOngoing) {
                            case (false, _):
                                if
                                    let sender: String = callMessage.sender,
                                    let interaction: Interaction = try MessageReceiver.insertCallInfoMessage(
                                        db,
                                        for: callMessage,
                                        state: .permissionDenied,
                                        using: dependencies
                                    )
                                {
                                    let thread: SessionThread = try SessionThread
                                        .fetchOrCreate(
                                            db,
                                            id: sender,
                                            variant: .contact,
                                            shouldBeVisible: nil
                                        )

                                    // Notify the user if the call message wasn't already read
                                    if !interaction.wasRead {
                                        SessionEnvironment.shared?.notificationsManager.wrappedValue?
                                            .notifyUser(
                                                db,
                                                forIncomingCall: interaction,
                                                in: thread,
                                                applicationState: .background
                                            )
                                    }
                                }
                                
                            case (true, true):
                                try MessageReceiver.handleIncomingCallOfferInBusyState(
                                    db,
                                    message: callMessage
                                )
                                
                            case (true, false):
                                try MessageReceiver.insertCallInfoMessage(db, for: callMessage, using: dependencies)
                                
                                // Perform any required post-handling logic
                                try MessageReceiver.postHandleMessage(
                                    db,
                                    threadId: threadId,
                                    threadVariant: threadVariant,
                                    message: messageInfo.message
                                )
                                
                                return self?.handleSuccessForIncomingCall(db, for: callMessage)
                        }
                        
                        // Perform any required post-handling logic
                        try MessageReceiver.postHandleMessage(
                            db,
                            threadId: threadId,
                            threadVariant: threadVariant,
                            message: messageInfo.message
                        )
                        
                    case .standard(let threadId, let threadVariant, let proto, let messageInfo):
                        try MessageReceiver.handle(
                            db,
                            threadId: threadId,
                            threadVariant: threadVariant,
                            message: messageInfo.message,
                            serverExpirationTimestamp: messageInfo.serverExpirationTimestamp,
                            associatedWithProto: proto,
                            using: dependencies
                        )
                }
                
                db.afterNextTransaction(
                    onCommit: { _ in self?.completeSilenty(handledNotification: true) },
                    onRollback: { _ in self?.completeSilenty(handledNotification: false) }
                )
            }
            catch {
                // If an error occurred we want to rollback the transaction (by throwing) and then handle
                // the error outside of the database
                let handleError = {
                    switch error {
                        case MessageReceiverError.noGroupKeyPair:
                            Log.warn("Failed due to having no legacy group decryption keys.")
                            self?.completeSilenty(handledNotification: false)
                            
                        case MessageReceiverError.outdatedMessage:
                            Log.info("Ignoring notification for already seen message.")
                            self?.completeSilenty(handledNotification: false)
                            
                        case NotificationError.ignorableMessage:
                            Log.info("Ignoring message which requires no notification.")
                            self?.completeSilenty(handledNotification: false)
                            
                        case MessageReceiverError.duplicateMessage, MessageReceiverError.duplicateControlMessage,
                            MessageReceiverError.duplicateMessageNewSnode:
                            Log.info("Ignoring duplicate message (probably received it just before going to the background).")
                            self?.completeSilenty(handledNotification: false)
                            
                        case NotificationError.messageProcessing:
                            self?.handleFailure(for: notificationContent, error: .messageProcessing)
                            
                        case let msgError as MessageReceiverError:
                            self?.handleFailure(for: notificationContent, error: .messageHandling(msgError))
                            
                        default: self?.handleFailure(for: notificationContent, error: .other(error))
                    }
                }
                
                db.afterNextTransaction(
                    onCommit: { _ in  handleError() },
                    onRollback: { _ in handleError() }
                )
                throw error
            }
        }
    }

    // MARK: Setup

    private func setUpIfNecessary(completion: @escaping () -> Void) {
        Log.assertOnMainThread()

        // The NSE will often re-use the same process, so if we're
        // already set up we want to do nothing; we're already ready
        // to process new messages.
        guard !didPerformSetup else { return completion() }

        Log.info("Performing setup.")
        didPerformSetup = true

        _ = AppVersion.shared

        AppSetup.setupEnvironment(
            retrySetupIfDatabaseInvalid: true,
            appSpecificBlock: {
                Log.setup(with: Logger(
                    primaryPrefix: "NotificationServiceExtension",                                               // stringlint:disable
                    level: .info,
                    customDirectory: "\(FileManager.default.appSharedDataDirectoryPath)/Logs/NotificationExtension", // stringlint:disable
                    forceNSLog: true
                ))
                
                SessionEnvironment.shared?.notificationsManager.mutate {
                    $0 = NSENotificationPresenter()
                }
                
                // Setup LibSession
                LibSession.addLogger()
            },
            migrationsCompletion: { [weak self] result, needsConfigSync in
                switch result {
                    case .failure(let error):
                        Log.error("Failed to complete migrations: \(error).")
                        self?.completeSilenty(handledNotification: false)
                        
                    case .success:
                        // We should never receive a non-voip notification on an app that doesn't support
                        // app extensions since we have to inform the service we wanted these, so in theory
                        // this path should never occur. However, the service does have our push token
                        // so it is possible that could change in the future. If it does, do nothing
                        // and don't disturb the user. Messages will be processed when they open the app.
                        guard Storage.shared[.isReadyForAppExtensions] else {
                            Log.error("Not ready for extensions.")
                            self?.completeSilenty(handledNotification: false)
                            return
                        }
                        
                        DispatchQueue.main.async {
                            self?.versionMigrationsDidComplete(needsConfigSync: needsConfigSync, completion: completion)
                        }
                }
            },
            using: dependencies
        )
    }
    
    private func versionMigrationsDidComplete(needsConfigSync: Bool, completion: @escaping () -> Void) {
        Log.assertOnMainThread()

        // If we need a config sync then trigger it now
        if needsConfigSync {
            Storage.shared.write { db in
                ConfigurationSyncJob.enqueue(db, publicKey: getUserHexEncodedPublicKey(db))
            }
        }

        // App isn't ready until storage is ready AND all version migrations are complete.
        guard Storage.shared.isValid else {
            Log.error("Storage invalid.")
            return self.completeSilenty(handledNotification: false)
        }
        
        // If the app wasn't ready then mark it as ready now
        if !Singleton.appReadiness.isAppReady {
            // Note that this does much more than set a flag; it will also run all deferred blocks.
            Singleton.appReadiness.setAppReady()
        }
        
        completion()
    }
    
    /// It's possible for the NotificationExtension to still have some kind of cached data from the old database after it's been deleted
    /// when a new account is created shortly after, this results in weird errors when receiving PNs for the new account
    ///
    /// In order to avoid this situation we check to see whether the received PN is targetting the current user and, if not, we call this
    /// method to force a resetup of the notification extension
    ///
    /// **Note:** We need to reconfigure the database here because if the database was deleted it's possible for the NotificationExtension
    /// to somehow still have some form of access to the old one
    private func forceResetup(_ notificationContent: UNMutableNotificationContent) {
        Storage.reconfigureDatabase()
        LibSession.clearMemoryState(using: dependencies)
        dependencies.caches.mutate(cache: .general) { $0.clearCachedUserPublicKey() }
        
        self.setUpIfNecessary() { [weak self, dependencies] in
            // If we had already done a setup then `libSession` won't have been re-setup so
            // we need to do so now (this ensures it has the correct user keys as well)
            Storage.shared.read { db in
                LibSession.loadState(
                    db,
                    userPublicKey: getUserHexEncodedPublicKey(db),
                    ed25519SecretKey: Identity.fetchUserEd25519KeyPair(db)?.secretKey,
                    using: dependencies
                )
            }
            
            self?.handleNotification(notificationContent, isPerformingResetup: true)
        }
    }
    
    // MARK: Handle completion
    
    override public func serviceExtensionTimeWillExpire() {
        // Called just before the extension will be terminated by the system.
        // Use this as an opportunity to deliver your "best attempt" at modified content, otherwise the original push payload will be used.
        Log.warn("Execution time expired.")
        completeSilenty(handledNotification: false)
    }
    
    private func completeSilenty(handledNotification: Bool, isMainAppAndActive: Bool = false) {
        // Ensure we only run this once
        guard
            hasCompleted.mutate({ hasCompleted in
                let wasCompleted: Bool = hasCompleted
                hasCompleted = true
                return wasCompleted
            }) == false
        else { return }
        
        let silentContent: UNMutableNotificationContent = UNMutableNotificationContent()
        silentContent.badge = Storage.shared
            .read { db in try Interaction.fetchUnreadCount(db) }
            .map { NSNumber(value: $0) }
            .defaulting(to: NSNumber(value: 0))
        
        Log.info(handledNotification ? "Completed after handling notification." : "Completed silently.")
        if !isMainAppAndActive {
            Storage.suspendDatabaseAccess(using: dependencies)
        }
        Log.flush()
        
        self.contentHandler!(silentContent)
    }
    
    private func handleSuccessForIncomingCall(_ db: Database, for callMessage: CallMessage) {
        if #available(iOSApplicationExtension 14.5, *), Preferences.isCallKitSupported {
            guard let caller: String = callMessage.sender, let timestamp = callMessage.sentTimestamp else { return }
            
            let reportCall: () -> () = { [weak self] in
                let payload: JSON = [
                    "uuid": callMessage.uuid,   // stringlint:disable
                    "caller": caller,           // stringlint:disable
                    "timestamp": timestamp      // stringlint:disable
                ]
                
                CXProvider.reportNewIncomingVoIPPushPayload(payload) { error in
                    if let error = error {
                        Log.error("Failed to notify main app of call message: \(error).")
                        Storage.shared.read { db in
                            self?.handleFailureForVoIP(db, for: callMessage)
                        }
                    }
                    else {
                        Log.info("Successfully notified main app of call message.")
                        UserDefaults.sharedLokiProject?[.lastCallPreOffer] = Date()
                        self?.completeSilenty(handledNotification: true)
                    }
                }
            }
            
            db.afterNextTransaction(
                onCommit: { _ in reportCall() },
                onRollback: { _ in reportCall() }
            )
        }
        else {
            self.handleFailureForVoIP(db, for: callMessage)
        }
    }
    
    private func handleFailureForVoIP(_ db: Database, for callMessage: CallMessage) {
        let notificationContent = UNMutableNotificationContent()
        notificationContent.userInfo = [ NotificationServiceExtension.isFromRemoteKey : true ]
        notificationContent.title = "Session"
        notificationContent.badge = (try? Interaction.fetchUnreadCount(db))
            .map { NSNumber(value: $0) }
            .defaulting(to: NSNumber(value: 0))
        
        if let sender: String = callMessage.sender {
            let senderDisplayName: String = Profile.displayName(db, id: sender, threadVariant: .contact)
            notificationContent.body = "\(senderDisplayName) is calling..."
        }
        else {
            notificationContent.body = "Incoming call..."
        }
        
        let identifier = self.request?.identifier ?? UUID().uuidString
        let request = UNNotificationRequest(identifier: identifier, content: notificationContent, trigger: nil)
        let semaphore = DispatchSemaphore(value: 0)
        
        UNUserNotificationCenter.current().add(request) { error in
            if let error = error {
                Log.error("Failed to add notification request due to error: \(error).")
            }
            semaphore.signal()
        }
        semaphore.wait()
        Log.info("Add remote notification request.")
        
        db.afterNextTransaction(
            onCommit: { [weak self] _ in self?.completeSilenty(handledNotification: true) },
            onRollback: { [weak self] _ in self?.completeSilenty(handledNotification: false) }
        )
    }

    private func handleFailure(for content: UNMutableNotificationContent, error: NotificationError) {
        Log.error("Show generic failure message due to error: \(error).")
        Storage.suspendDatabaseAccess(using: dependencies)
        Log.flush()
        
        content.title = "Session"
        content.body = "APN_Message".localized()
        let userInfo: [String: Any] = [ NotificationServiceExtension.isFromRemoteKey: true ]
        content.userInfo = userInfo
        contentHandler!(content)
        hasCompleted.mutate { $0 = true }
    }
}