//
//  NCNetworkingProcessUpload.swift
//  Nextcloud
//
//  Created by Marino Faggiana on 25/06/2020.
//  Copyright © 2020 Marino Faggiana. All rights reserved.
//
//  Author Marino Faggiana <marino.faggiana@nextcloud.com>
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program.  If not, see <http://www.gnu.org/licenses/>.
//

import UIKit
import NextcloudKit
import Photos
import JGProgressHUD
import RealmSwift

class NCNetworkingProcessUpload: NSObject {
    public static let shared: NCNetworkingProcessUpload = {
        let instance = NCNetworkingProcessUpload()
        return instance
    }()

    private let appDelegate = UIApplication.shared.delegate as! AppDelegate
    private var notificationToken: NotificationToken?
    private var timerProcess: Timer?
    private var pauseProcess: Bool = false

    func observeTableMetadata() {
        let realm = try! Realm()
        let results = realm.objects(tableMetadata.self).filter("session != '' || sessionError != ''")
        notificationToken = results.observe { [weak self] (changes: RealmCollectionChange) in
            switch changes {
            case .initial:
                print("Initial")
            case .update(_, let deletions, let insertions, let modifications):
                if (deletions.count > 0 || insertions.count > 0 || modifications.count > 0) {
                    self?.invalidateObserveTableMetadata()
                    self?.start(completition: { items in
                        print("[LOG] PROCESS-UPLOAD-OBSERVE \(items)")
                        DispatchQueue.main.async {
                            self?.observeTableMetadata()
                        }
                    })
                }
            case .error(let error):
                NKCommon.shared.writeLog("[ERROR] Could not write to TableMetadata: \(error)")
            }
        }
    }

    func invalidateObserveTableMetadata() {
        notificationToken?.invalidate()
        notificationToken = nil
    }

    func startTimer() {
        DispatchQueue.main.async {
            self.timerProcess?.invalidate()
            self.timerProcess = Timer.scheduledTimer(timeInterval: 5, target: self, selector: #selector(self.processTimer), userInfo: nil, repeats: true)
        }
    }

    func stopTimer() {
        DispatchQueue.main.async {
            self.timerProcess?.invalidate()
        }
    }

    @objc private func processTimer() {
        start { items in
            print("[LOG] PROCESS-UPLOAD-TIMER \(items)")
        }
    }

    func start(completition: @escaping (_ items: Int) -> Void) {

        if appDelegate.account.isEmpty || pauseProcess {
            return completition(0)
        } else {
            pauseProcess = true
        }

        let applicationState = UIApplication.shared.applicationState
        let queue = DispatchQueue.global()
        var maxConcurrentOperationUpload = 10
        let viewController = appDelegate.window?.rootViewController
        let hud = JGProgressHUD()

        queue.async {

            let metadatasUpload = NCManageDatabase.shared.getMetadatas(predicate: NSPredicate(format: "account == %@ AND (status == %d OR status == %d)", self.appDelegate.account, NCGlobal.shared.metadataStatusInUpload, NCGlobal.shared.metadataStatusUploading))
            let isWiFi = NCNetworking.shared.networkReachability == NKCommon.typeReachability.reachableEthernetOrWiFi
            var counterUpload: Int = 0
            let sessionSelectors = [NCGlobal.shared.selectorUploadFileNODelete, NCGlobal.shared.selectorUploadFile, NCGlobal.shared.selectorUploadAutoUpload, NCGlobal.shared.selectorUploadAutoUploadAll]

            counterUpload = metadatasUpload.count

            // Update Badge
            let counterBadge = NCManageDatabase.shared.getMetadatas(predicate: NSPredicate(format: "account == %@ AND (status == %d OR status == %d OR status == %d)", self.appDelegate.account, NCGlobal.shared.metadataStatusWaitUpload, NCGlobal.shared.metadataStatusInUpload, NCGlobal.shared.metadataStatusUploading))
            NotificationCenter.default.postOnMainThread(name: NCGlobal.shared.notificationCenterUpdateBadgeNumber, userInfo: ["counter":counterBadge.count])

            NCNetworking.shared.getOcIdInBackgroundSession(queue: queue, completion: { listOcId in

                for sessionSelector in sessionSelectors where counterUpload < maxConcurrentOperationUpload {

                    let limit = maxConcurrentOperationUpload - counterUpload
                    let metadatas = NCManageDatabase.shared.getAdvancedMetadatas(predicate: NSPredicate(format: "account == %@ AND sessionSelector == %@ AND status == %d", self.appDelegate.account, sessionSelector, NCGlobal.shared.metadataStatusWaitUpload), page: 1, limit: limit, sorted: "date", ascending: true)
                    if metadatas.count > 0 {
                        NKCommon.shared.writeLog("[INFO] PROCESS-UPLOAD find \(metadatas.count) items")
                    }

                    for metadata in metadatas where counterUpload < maxConcurrentOperationUpload {

                        // Is already in upload background? skipped
                        if listOcId.contains(metadata.ocId) {
                            NKCommon.shared.writeLog("[INFO] Process auto upload skipped file: \(metadata.serverUrl)/\(metadata.fileNameView), because is already in session.")
                            continue
                        }

                        // Chunk or E2EE ... only one ? skipped
                        if metadatasUpload.filter({ $0.chunk || $0.e2eEncrypted }).count > 0 {
                            continue
                        }

                        // Session Extension ? skipped
                        if metadata.session == NCNetworking.shared.sessionIdentifierBackgroundExtension {
                            continue
                        }

                        let semaphore = DispatchSemaphore(value: 0)
                        NCUtility.shared.extractFiles(from: metadata, viewController: viewController, hud: hud) { metadatas in
                            if metadatas.isEmpty {
                                NCManageDatabase.shared.deleteMetadata(predicate: NSPredicate(format: "ocId == %@", metadata.ocId))
                            }
                            for metadata in metadatas where counterUpload < maxConcurrentOperationUpload {

                                // NO WiFi
                                if !isWiFi && metadata.session == NCNetworking.shared.sessionIdentifierBackgroundWWan {
                                    continue
                                }

                                // NO E2EE, CHUCK in background
                                let isDirectoryE2EE = NCUtility.shared.isDirectoryE2EE(metadata: metadata)
                                if applicationState != .active && (isDirectoryE2EE || metadata.chunk) {
                                    continue
                                }

                                if let metadata = NCManageDatabase.shared.setMetadataStatus(ocId: metadata.ocId, status: NCGlobal.shared.metadataStatusInUpload) {
                                    NCNetworking.shared.upload(metadata: metadata)
                                    if isDirectoryE2EE || metadata.chunk {
                                        maxConcurrentOperationUpload = 1
                                    }
                                    counterUpload += 1
                                }
                            }
                            semaphore.signal()
                        }
                        semaphore.wait()
                    }
                }

                // No upload available ? --> Retry Upload in Error
                if counterUpload == 0 {
                    let metadatas = NCManageDatabase.shared.getMetadatas(predicate: NSPredicate(format: "account == %@ AND status == %d", self.appDelegate.account, NCGlobal.shared.metadataStatusUploadError))
                    for metadata in metadatas {
                        NCManageDatabase.shared.setMetadataSession(ocId: metadata.ocId, session: NCNetworking.shared.sessionIdentifierBackground, sessionError: "", sessionTaskIdentifier: 0, status: NCGlobal.shared.metadataStatusWaitUpload)
                    }

                    // verify delete Asset Local Identifiers in auto upload (DELETE Photos album)
                    if applicationState == .active && metadatas.isEmpty && !self.appDelegate.isPasscodePresented() {
                        self.deleteAssetLocalIdentifiers {
                            self.pauseProcess = false
                        }
                    } else {
                        self.pauseProcess = false
                    }
                } else {
                    self.pauseProcess = false
                }

                completition(counterUpload)
            })
        }
    }

    private func deleteAssetLocalIdentifiers(completition: @escaping () -> Void) {

        let metadatasSessionUpload = NCManageDatabase.shared.getMetadatas(predicate: NSPredicate(format: "account == %@ AND session CONTAINS[cd] %@", appDelegate.account, "upload"))
        if !metadatasSessionUpload.isEmpty { return completition() }

        let localIdentifiers = NCManageDatabase.shared.getAssetLocalIdentifiersUploaded(account: appDelegate.account)
        if localIdentifiers.isEmpty { return completition() }

        let assets = PHAsset.fetchAssets(withLocalIdentifiers: localIdentifiers, options: nil)

        PHPhotoLibrary.shared().performChanges({
            PHAssetChangeRequest.deleteAssets(assets as NSFastEnumeration)
        }, completionHandler: { _, _ in
            NCManageDatabase.shared.clearAssetLocalIdentifiers(localIdentifiers, account: self.appDelegate.account)
            completition()
        })
    }

    // MARK: -

    func createProcessUploads(metadatas: [tableMetadata], verifyAlreadyExists: Bool = false, completion: @escaping (_ items: Int) -> Void) {

        var metadatasForUpload: [tableMetadata] = []
        for metadata in metadatas {
            if verifyAlreadyExists {
                if NCManageDatabase.shared.getMetadata(predicate: NSPredicate(format: "account == %@ && serverUrl == %@ && fileName == %@ && session != ''", metadata.account, metadata.serverUrl, metadata.fileName)) != nil {
                    continue
                }
            }
            metadatasForUpload.append(metadata)
        }
        NCManageDatabase.shared.addMetadatas(metadatasForUpload)
        completion(metadatasForUpload.count)
    }

    // MARK: -

    func verifyUploadZombie() {

        var session: URLSession?

        // remove leaning upload share extension
        let metadatasUploadShareExtension = NCManageDatabase.shared.getMetadatas(predicate: NSPredicate(format: "session == %@ AND sessionSelector == %@", NKCommon.shared.sessionIdentifierUpload, NCGlobal.shared.selectorUploadFileShareExtension))
        for metadata in metadatasUploadShareExtension {
            let path = CCUtility.getDirectoryProviderStorageOcId(metadata.ocId)!
            NCManageDatabase.shared.deleteMetadata(predicate: NSPredicate(format: "ocId == %@", metadata.ocId))
            NCManageDatabase.shared.deleteChunks(account: metadata.account, ocId: metadata.ocId)
            NCUtilityFileSystem.shared.deleteFile(filePath: path)
        }

        // verify metadataStatusInUpload (BACKGROUND)
        let metadatasInUploadBackground = NCManageDatabase.shared.getMetadatas(
            predicate: NSPredicate(
                format: "(session == %@ OR session == %@ OR session == %@) AND status == %d AND sessionTaskIdentifier == 0",
                NCNetworking.shared.sessionIdentifierBackground,
                NCNetworking.shared.sessionIdentifierBackgroundExtension,
                NCNetworking.shared.sessionIdentifierBackgroundWWan,
                NCGlobal.shared.metadataStatusInUpload))
        for metadata in metadatasInUploadBackground {
            DispatchQueue.main.asyncAfter(deadline: .now() + 5) {
                if let metadata = NCManageDatabase.shared.getMetadata(predicate: NSPredicate(format: "ocId == %@ AND status == %d AND sessionTaskIdentifier == 0", metadata.ocId, NCGlobal.shared.metadataStatusInUpload)) {
                    NCManageDatabase.shared.setMetadataSession(ocId: metadata.ocId, session: NCNetworking.shared.sessionIdentifierBackground, sessionError: "", sessionSelector: nil, sessionTaskIdentifier: 0, status: NCGlobal.shared.metadataStatusWaitUpload)
                }
            }
        }

        // metadataStatusUploading (BACKGROUND)
        let metadatasUploadingBackground = NCManageDatabase.shared.getMetadatas(predicate: NSPredicate(format: "(session == %@ OR session == %@ OR session == %@) AND status == %d", NCNetworking.shared.sessionIdentifierBackground, NCNetworking.shared.sessionIdentifierBackgroundWWan, NCNetworking.shared.sessionIdentifierBackgroundExtension, NCGlobal.shared.metadataStatusUploading))
        for metadata in metadatasUploadingBackground {

            if metadata.session == NCNetworking.shared.sessionIdentifierBackground {
                session = NCNetworking.shared.sessionManagerBackground
            } else if metadata.session == NCNetworking.shared.sessionIdentifierBackgroundWWan {
                session = NCNetworking.shared.sessionManagerBackgroundWWan
            }

            var taskUpload: URLSessionTask?

            session?.getAllTasks(completionHandler: { tasks in
                for task in tasks {
                    if task.taskIdentifier == metadata.sessionTaskIdentifier {
                        taskUpload = task
                    }
                }

                if taskUpload == nil {
                    if let metadata = NCManageDatabase.shared.getMetadata(predicate: NSPredicate(format: "ocId == %@ AND status == %d", metadata.ocId, NCGlobal.shared.metadataStatusUploading)) {
                        NCManageDatabase.shared.setMetadataSession(ocId: metadata.ocId, session: NCNetworking.shared.sessionIdentifierBackground, sessionError: "", sessionSelector: nil, sessionTaskIdentifier: 0, status: NCGlobal.shared.metadataStatusWaitUpload)
                    }
                }
            })
        }

        // metadataStatusUploading OR metadataStatusInUpload (FOREGROUND)
        let metadatasUploading = NCManageDatabase.shared.getMetadatas(predicate: NSPredicate(format: "session == %@ AND (status == %d OR status == %d)", NKCommon.shared.sessionIdentifierUpload, NCGlobal.shared.metadataStatusUploading, NCGlobal.shared.metadataStatusInUpload))
        for metadata in metadatasUploading {
            let fileNameLocalPath = CCUtility.getDirectoryProviderStorageOcId(metadata.ocId, fileNameView: metadata.fileNameView)!
            if NCNetworking.shared.uploadRequest[fileNameLocalPath] == nil {
                NCManageDatabase.shared.setMetadataSession(ocId: metadata.ocId, session: nil, sessionError: "", sessionSelector: nil, sessionTaskIdentifier: 0, status: NCGlobal.shared.metadataStatusWaitUpload)
            }
        }

        // download
        let metadatasDownload = NCManageDatabase.shared.getMetadatas(predicate: NSPredicate(format: "session == %@", NKCommon.shared.sessionIdentifierDownload))
        for metadata in metadatasDownload {
            NCManageDatabase.shared.setMetadataSession(ocId: metadata.ocId, session: "", sessionError: "", sessionSelector: "", sessionTaskIdentifier: 0, status: NCGlobal.shared.metadataStatusNormal)
        }
    }
}