// File created from ScreenTemplate
// $ createScreen.sh KeyVerification/Common/ScanConfirmation KeyVerificationScanConfirmation
/*
 Copyright 2020 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 KeyVerificationScanConfirmationViewModel: KeyVerificationScanConfirmationViewModelType {
    
    // MARK: - Properties
    
    // MARK: Private

    private let session: MXSession
    private let transaction: MXQRCodeTransaction
    private let codeScanning: KeyVerificationScanning
    private let verificationKind: KeyVerificationKind
    
    private var isScanning: Bool {
        if case .scannedOtherQRCode = self.codeScanning {
            return true
        }
        return false
    }
    
    // MARK: Public

    weak var viewDelegate: KeyVerificationScanConfirmationViewModelViewDelegate?
    weak var coordinatorDelegate: KeyVerificationScanConfirmationViewModelCoordinatorDelegate?
    
    // MARK: - Setup
    
    init(session: MXSession,
         transaction: MXQRCodeTransaction,
         codeScanning: KeyVerificationScanning,
         verificationKind: KeyVerificationKind) {
        self.session = session
        self.transaction = transaction
        self.codeScanning = codeScanning
        self.verificationKind = verificationKind
    }
    
    // MARK: - Public
    
    func process(viewAction: KeyVerificationScanConfirmationViewAction) {
        switch viewAction {
        case .loadData:
            self.loadData()
        case .acknowledgeOtherScannedMyCode(let otherHasScannedMyCode):
            self.transaction.otherUserScannedMyQrCode(otherHasScannedMyCode)
            if otherHasScannedMyCode == false {                self.coordinatorDelegate?.keyVerificationScanConfirmationViewModelDidCancel(self)
            } else {
                self.update(viewState: .loading)
            }
        case .cancel:
            self.cancel()
        }
    }
    
    // MARK: - Private
    
    private func loadData() {
        let otherUserId = self.transaction.otherUserId
        let otherUser = self.session.user(withUserId: otherUserId)
        let otherDisplayName = otherUser?.displayname ?? otherUserId
        
        let viewData = KeyVerificationScanConfirmationViewData(isScanning: self.isScanning, verificationKind: self.verificationKind, otherDisplayName: otherDisplayName)
        self.update(viewState: .loaded(viewData))
        
        self.registerTransactionDidStateChangeNotification()
        
        if case .scannedOtherQRCode(let qrCodeData) = self.codeScanning {
            self.transaction.userHasScannedOtherQrCodeData(qrCodeData)
        }
    }
    
    private func update(viewState: KeyVerificationScanConfirmationViewState) {
        self.viewDelegate?.keyVerificationScanConfirmationViewModel(self, didUpdateViewState: viewState)
    }
    
    private func cancel() {
        self.transaction.cancel(with: MXTransactionCancelCode.user())
        self.coordinatorDelegate?.keyVerificationScanConfirmationViewModelDidCancel(self)
    }
    
    // MARK: - MXKeyVerificationTransactionDidChange
    
    private func registerTransactionDidStateChangeNotification() {
        NotificationCenter.default.addObserver(self, selector: #selector(transactionDidStateChange(notification:)), name: .MXKeyVerificationTransactionDidChange, object: self.transaction)
    }
    
    private func unregisterTransactionDidStateChangeNotification() {
        NotificationCenter.default.removeObserver(self, name: .MXKeyVerificationTransactionDidChange, object: nil)
    }
    
    @objc private func transactionDidStateChange(notification: Notification) {
        guard let transaction = notification.object as? MXQRCodeTransaction else {
            return
        }

        switch transaction.state {
        case .verified:
            self.unregisterTransactionDidStateChangeNotification()
            self.coordinatorDelegate?.keyVerificationScanConfirmationViewModelDidComplete(self)
        case .cancelled:
            guard let reason = transaction.reasonCancelCode else {
                return
            }
            self.unregisterTransactionDidStateChangeNotification()
            self.update(viewState: .cancelled(reason))
        case .cancelledByMe:
            guard let reason = transaction.reasonCancelCode else {
                return
            }
            self.unregisterTransactionDidStateChangeNotification()
            self.update(viewState: .cancelledByMe(reason))
        default:
            break
        }
    }
}