//
//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
//

import Foundation
import SignalServiceKit
import CloudKit

@objc public class OWSBackupAPI: NSObject {
    @objc
    public class func recordIdForTest() -> String {
        return "test-\(NSUUID().uuidString)"
    }

//    @objc
//    public class func recordNameForTest(value: TSAttachmentStream) -> String {
//        guard let uniqueId = value.uniqueId else {
//            owsFail("Database entity missing uniqueId.")
//            return "unknown"
//        }
//        return "attachment-stream-\(uniqueId)"
//    }

    @objc
    public class func saveTestFileToCloud(fileUrl: URL,
                                          success: @escaping (String) -> Swift.Void,
                                          failure: @escaping (Error) -> Swift.Void) {
        saveFileToCloud(fileUrl: fileUrl,
                        recordName: NSUUID().uuidString,
                        recordType: "test",
                        success: success,
                        failure: failure)
    }

    // "Ephemeral" files are specific to this backup export and will always need to
    // be saved.  For example, a complete image of the database is exported each time.
    // We wouldn't want to overwrite previous images until the entire backup export is
    // complete.
    @objc
    public class func saveEphemeralDatabaseFileToCloud(fileUrl: URL,
                                            success: @escaping (String) -> Swift.Void,
                                            failure: @escaping (Error) -> Swift.Void) {
        saveFileToCloud(fileUrl: fileUrl,
                        recordName: NSUUID().uuidString,
                        recordType: "ephemeralFile",
                        success: success,
                        failure: failure)
    }

    // "Persistent" files may be shared between backup export; they should only be saved
    // once.  For example, attachment files should only be uploaded once.  Subsequent
    //
    @objc
    public class func savePersistentFileOnceToCloud(fileId: String,
                                                  fileUrlBlock: @escaping (Swift.Void) -> URL?,
                                            success: @escaping (String) -> Swift.Void,
                                            failure: @escaping (Error) -> Swift.Void) {
        saveFileOnceToCloud(recordName: "persistentFile-\(fileId)",
                        recordType: "persistentFile",
                        fileUrlBlock: fileUrlBlock,
                        success: success,
                        failure: failure)
    }

    // TODO:
    static let manifestRecordName = "manifest_"
    static let manifestRecordType = "manifest"
    static let payloadKey = "payload"

    @objc
    public class func upsertAttachmentToCloud(fileUrl: URL,
                                                success: @escaping (String) -> Swift.Void,
                                                failure: @escaping (Error) -> Swift.Void) {
        // We want to use a well-known record id and type for manifest files.
        upsertFileToCloud(fileUrl: fileUrl,
                          recordName: manifestRecordName,
                          recordType: manifestRecordType,
                          success: success,
                          failure: failure)
    }

    @objc
    public class func upsertManifestFileToCloud(fileUrl: URL,
                                                success: @escaping (String) -> Swift.Void,
                                                failure: @escaping (Error) -> Swift.Void) {
        // We want to use a well-known record id and type for manifest files.
        upsertFileToCloud(fileUrl: fileUrl,
                          recordName: manifestRecordName,
                          recordType: manifestRecordType,
                          success: success,
                          failure: failure)
    }

    @objc
    public class func saveFileToCloud(fileUrl: URL,
                                      recordName: String,
                                      recordType: String,
                                      success: @escaping (String) -> Swift.Void,
                                      failure: @escaping (Error) -> Swift.Void) {
        let recordID = CKRecordID(recordName: recordName)
        let record = CKRecord(recordType: recordType, recordID: recordID)
        let asset = CKAsset(fileURL: fileUrl)
        record[payloadKey] = asset

        saveRecordToCloud(record: record,
                          success: success,
                          failure: failure)
    }

    @objc
    public class func saveRecordToCloud(record: CKRecord,
                                        success: @escaping (String) -> Swift.Void,
                                        failure: @escaping (Error) -> Swift.Void) {

        let myContainer = CKContainer.default()
        let privateDatabase = myContainer.privateCloudDatabase
        privateDatabase.save(record) {
            (record, error) in

            if let error = error {
                Logger.error("\(self.logTag) error saving record: \(error)")
                failure(error)
            } else {
                guard let recordName = record?.recordID.recordName else {
                    Logger.error("\(self.logTag) error retrieving saved record's name.")
                    failure(OWSErrorWithCodeDescription(.exportBackupError,
                                                        NSLocalizedString("BACKUP_EXPORT_ERROR_SAVE_FILE_TO_CLOUD_FAILED",
                                                                          comment: "Error indicating the a backup export failed to save a file to the cloud.")))
                    return
                }
                Logger.info("\(self.logTag) saved record.")
                success(recordName)
            }
        }
    }

    @objc
    public class func upsertFileToCloud(fileUrl: URL,
                                        recordName: String,
                                        recordType: String,
                                        success: @escaping (String) -> Swift.Void,
                                        failure: @escaping (Error) -> Swift.Void) {
        let recordId = CKRecordID(recordName: recordName)
        let fetchOperation = CKFetchRecordsOperation(recordIDs: [recordId ])
        fetchOperation.perRecordCompletionBlock = { (record, recordId, error) in
            if let error = error {
                if let ckerror = error as? CKError {
                    if ckerror.code == .unknownItem {
                        // No record found to update, saving new record.
                        saveFileToCloud(fileUrl: fileUrl,
                                        recordName: recordName,
                                        recordType: recordType,
                                        success: success,
                                        failure: failure)
                        return
                    }
                    Logger.error("\(self.logTag) error fetching record: \(error) \(ckerror.code).")
                } else {
                    Logger.error("\(self.logTag) error fetching record: \(error).")
                }
                failure(error)
                return
            }
            guard let record = record else {
                Logger.error("\(self.logTag) error missing record.")
                Logger.flush()
                failure(OWSErrorWithCodeDescription(.exportBackupError,
                                                    NSLocalizedString("BACKUP_EXPORT_ERROR_SAVE_FILE_TO_CLOUD_FAILED",
                                                                      comment: "Error indicating the a backup export failed to save a file to the cloud.")))
                return
            }
            Logger.verbose("\(self.logTag) updating record.")
            let asset = CKAsset(fileURL: fileUrl)
            record[payloadKey] = asset
            saveRecordToCloud(record: record,
                              success: success,
                              failure: failure)
        }
        let myContainer = CKContainer.default()
        let privateDatabase = myContainer.privateCloudDatabase
        privateDatabase.add(fetchOperation)
    }

    @objc
    public class func saveFileOnceToCloud(recordName: String,
                                        recordType: String,
                                        fileUrlBlock: @escaping (Swift.Void) -> URL?,
                                        success: @escaping (String) -> Swift.Void,
                                        failure: @escaping (Error) -> Swift.Void) {
        let recordId = CKRecordID(recordName: recordName)
        let fetchOperation = CKFetchRecordsOperation(recordIDs: [recordId ])
        fetchOperation.perRecordCompletionBlock = { (record, recordId, error) in
            if let error = error {
                if let ckerror = error as? CKError {
                    if ckerror.code == .unknownItem {
                        // No record found to update, saving new record.

                        guard let fileUrl = fileUrlBlock() else {
                            Logger.error("\(self.logTag) error preparing file for upload: \(error).")
                            return
                        }

                        saveFileToCloud(fileUrl: fileUrl,
                                        recordName: recordName,
                                        recordType: recordType,
                                        success: success,
                                        failure: failure)
                        return
                    }
                    Logger.error("\(self.logTag) error fetching record: \(error) \(ckerror.code).")
                } else {
                    Logger.error("\(self.logTag) error fetching record: \(error).")
                }
                failure(error)
                return
            }
            Logger.info("\(self.logTag) record already exists; skipping save.")
            success(recordName)
        }
        let myContainer = CKContainer.default()
        let privateDatabase = myContainer.privateCloudDatabase
        privateDatabase.add(fetchOperation)
    }

    @objc
    public class func checkCloudKitAccess(completion: @escaping (Bool) -> Swift.Void) {
        CKContainer.default().accountStatus(completionHandler: { (accountStatus, error) in
            DispatchQueue.main.async {
                switch accountStatus {
                case .couldNotDetermine:
                    Logger.error("\(self.logTag) could not determine CloudKit account status:\(String(describing: error)).")
                    OWSAlerts.showErrorAlert(withMessage: NSLocalizedString("CLOUDKIT_STATUS_COULD_NOT_DETERMINE", comment: "Error indicating that the app could not determine that user's CloudKit account status"))
                    completion(false)
                case .noAccount:
                    Logger.error("\(self.logTag) no CloudKit account.")
                    OWSAlerts.showErrorAlert(withMessage: NSLocalizedString("CLOUDKIT_STATUS_NO_ACCOUNT", comment: "Error indicating that user does not have an iCloud account."))
                    completion(false)
                case .restricted:
                    Logger.error("\(self.logTag) restricted CloudKit account.")
                    OWSAlerts.showErrorAlert(withMessage: NSLocalizedString("CLOUDKIT_STATUS_RESTRICTED", comment: "Error indicating that the app was prevented from accessing the user's CloudKit account."))
                    completion(false)
                case .available:
                    completion(true)
                }
            }
        })
    }
}