/*
 Copyright 2019 New Vector Ltd
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
 
 http://www.apache.org/licenses/LICENSE-2.0
 
 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */

import Foundation

final class KeyBackupSetupPassphraseViewModel: KeyBackupSetupPassphraseViewModelType {
    
    // MARK: - Properties
    
    // MARK: Private
    
    private(set) var passphraseStrength: PasswordStrength = .tooGuessable
    private let passwordStrengthManager: PasswordStrengthManager
    private let keyBackup: MXKeyBackup
    private let coordinatorDelegateQueue: OperationQueue
    
    // MARK: Public
    
    var passphrase: String? {
        didSet {
            self.updatePassphraseStrength()
        }
    }
    
    var confirmPassphrase: String?
    
    var isPassphraseValid: Bool {
        return self.passphraseStrength == .veryUnguessable
    }
    
    var isConfirmPassphraseValid: Bool {
        guard self.isPassphraseValid, let confirmPassphrase = self.confirmPassphrase else {
            return false
        }
        return confirmPassphrase == passphrase
    }
    
    var isFormValid: Bool {
        return self.isPassphraseValid && self.isConfirmPassphraseValid
    }

    weak var viewDelegate: KeyBackupSetupPassphraseViewModelViewDelegate?
    weak var coordinatorDelegate: KeyBackupSetupPassphraseViewModelCoordinatorDelegate?
    
    // MARK: - Setup
    
    init(keyBackup: MXKeyBackup) {
        self.passwordStrengthManager = PasswordStrengthManager()
        self.keyBackup = keyBackup
        
        let coordinatorDelegateQueue = OperationQueue()
        coordinatorDelegateQueue.name = "KeyBackupSetupPassphraseViewModel.coordinatorDelegateQueue"
        coordinatorDelegateQueue.maxConcurrentOperationCount = 1
        self.coordinatorDelegateQueue = coordinatorDelegateQueue
    }
    
    // MARK: - Public
    
    func process(viewAction: KeyBackupSetupPassphraseViewAction) {
        switch viewAction {
        case .setupPassphrase:
            self.setupPassphrase()
        case .skip:
            self.pauseCoordinatorOperations()
            self.viewDelegate?.keyBackupSetupPassphraseViewModelShowSkipAlert(self)
        case.skipAlertContinue:
            self.resumeCoordinatorOperations()
        case.skipAlertSkip:
            self.cancelCoordinatorOperations()
            self.coordinatorDelegate?.keyBackupSetupPassphraseViewModelDidCancel(self)
        }
    }
    
    // MARK: - Private
    
    func setupPassphrase() {
        guard let passphrase = self.passphrase else {
            return
        }
        
        self.viewDelegate?.keyBackupSetupPassphraseViewModel(self, didUpdateViewState: .loading)
        
        self.keyBackup.prepareKeyBackupVersion(withPassword: passphrase, success: { [weak self] (megolmBackupCreationInfo) in
            guard let sself = self else {
                return
            }
            
            sself.viewDelegate?.keyBackupSetupPassphraseViewModel(sself, didUpdateViewState: .loaded)
            
            sself.coordinatorDelegateQueue.addOperation {
                DispatchQueue.main.async {
                    sself.coordinatorDelegate?.keyBackupSetupPassphraseViewModel(sself, didCompleteWithMegolmBackupCreationInfo: megolmBackupCreationInfo)
                }
            }
        }, failure: { [weak self] error in
            guard let sself = self else {
                return
            }            
            sself.viewDelegate?.keyBackupSetupPassphraseViewModel(sself, didUpdateViewState: .error(error))
        })
    }
    
    private func updatePassphraseStrength() {
        self.passphraseStrength = self.passwordStrength(for: self.passphrase)
    }
    
    private func passwordStrength(for password: String?) -> PasswordStrength {
        guard let password = password else {
            return .tooGuessable
        }
        return self.passwordStrengthManager.passwordStrength(for: password)
    }
    
    private func pauseCoordinatorOperations() {
        self.coordinatorDelegateQueue.isSuspended = true
    }
    
    private func resumeCoordinatorOperations() {
        self.coordinatorDelegateQueue.isSuspended = false
    }
    
    private func cancelCoordinatorOperations() {
        self.coordinatorDelegateQueue.cancelAllOperations()
    }
}