safe-ios/Multisig/UI/Settings/OwnerKeyManagement/ImportOwnerKey/EnterKeyOrSeedPhraseViewController.swift

//
//  EnterKeyOrSeedPhraseViewController.swift
//  Multisig
//
//  Created by Andrey Scherbovich on 20.01.21.
//  Copyright © 2021 Gnosis Ltd. All rights reserved.
//

import UIKit

class EnterKeyOrSeedPhraseViewController: UIViewController {

    var completion: () -> Void = {}

    @IBOutlet private weak var descriptionLabel: UILabel!
    @IBOutlet private weak var textView: UITextView!
    @IBOutlet private weak var placeholderLabel: UILabel!
    @IBOutlet private weak var errorLabel: UILabel!
    @IBOutlet private weak var scrollView: UIScrollView!

    private var nextButton: UIBarButtonItem!
    private var secureButton: UIBarButtonItem!

    private var keyboardBehavior: KeyboardAvoidingBehavior!

    private var enteredText: String = ""
    private var isSecure: Bool = true
    private var secureSymbol: Character = "⦁"

    private(set) var seedNode: HDNode?
    private(set) var privateKey: PrivateKey?


    override func viewDidLoad() {
        super.viewDidLoad()

        title = "Import Owner Key"

        keyboardBehavior = KeyboardAvoidingBehavior(scrollView: scrollView)

        nextButton = UIBarButtonItem(title: "Next", style: .done, target: self, action: #selector(didTapNextButton(_:)))
        secureButton = UIBarButtonItem(image: secureButtonImage, style: .plain, target: self, action: #selector(didTapSecureButton(_:)))

        navigationItem.rightBarButtonItems = [nextButton, secureButton]
        nextButton.isEnabled = false

        descriptionLabel.setStyle(.body)

        errorLabel.setStyle(.calloutError)
        errorLabel.isHidden = true

        textView.textContentType = .password
        textView.delegate = self
        textView.layer.borderWidth = 2
        textView.layer.borderColor = UIColor.labelTertiary.cgColor
        textView.layer.cornerRadius = 10
        textView.textContainerInset = UIEdgeInsets(top: 16, left: 12, bottom: 16, right: 12)
        textView.setStyle(.body)
        
        textView.becomeFirstResponder()

        placeholderLabel.setStyle(.bodyTertiary)
        placeholderLabel.text = "Enter private key or seed phrase"
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        keyboardBehavior.start()
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        Tracker.trackEvent(.ownerEnterSeed)
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        keyboardBehavior.stop()
    }

    @objc private func didTapSecureButton(_ sender: Any) {
        isSecure = !isSecure
        secureButton.image = secureButtonImage
        textView.text = isSecure ? secured(enteredText) : enteredText
        updateTextDependentViews(with: enteredText)
    }

    var secureButtonImage: UIImage? {
        isSecure ? UIImage(named: "ico-text-secure") : UIImage(named: "ico-text-insecure")
    }

    @objc private func didTapNextButton(_ sender: Any) {
        let phrase = enteredText.trimmingCharacters(in: .whitespacesAndNewlines)
        if isPotentiallyValidSeedPhrase(phrase) {
            nextButton.isEnabled = false
            guard let seedData = BIP39.seedFromMmemonics(phrase),
                let rootNode = HDNode(seed: seedData)?.derive(path: HDNode.defaultPathMetamaskPrefix,
                                                              derivePrivateKey: true) else {
                nextButton.isEnabled = true
                setError(GSError.WrongSeedPhrase())
                return
            }
            nextButton.isEnabled = true
            self.seedNode = rootNode
            self.completion()
        } else if isValidPK(phrase),
                  // we need to use Data(ethHex:) here in case if some software
                  // exported private key without a leading 0
                  let privateKey = try? PrivateKey(data: Data(ethHex: phrase)) {

            self.privateKey = privateKey
            self.completion()
        }
    }

    private func updateTextDependentViews(with text: String) {
        placeholderLabel.isHidden = !text.isEmpty
        setError(nil)

        let phrase = text.trimmingCharacters(in: .whitespacesAndNewlines)
        nextButton.isEnabled = isPotentiallyValidSeedPhrase(phrase) || isValidPK(phrase)
    }

    private func isPotentiallyValidSeedPhrase(_ phrase: String) -> Bool {
        [12, 15, 18, 21, 24].contains(phrase.split(separator: " ").count)
    }

    private func isValidPK(_ pk: String) -> Bool {
        if let data = Data(exactlyHex: pk),
           data.count == 32,
           data != Data(hex: "0x0000000000000000000000000000000000000000000000000000000000000000") {
            return true
        }
        return false
    }

    private func setError(_ error: Error?) {
        errorLabel.text = error?.localizedDescription
        errorLabel.isHidden = error == nil
        textView.layer.borderColor = error == nil ? UIColor.labelTertiary.cgColor : UIColor.error.cgColor
    }

    private func secured(_ text: String) -> String {
        text.map { _ in String(secureSymbol) }.joined()
    }
}

extension EnterKeyOrSeedPhraseViewController: UITextViewDelegate {
    func textViewDidBeginEditing(_ textView: UITextView) {
        keyboardBehavior.activeTextView = textView
    }

    func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
        let oldText = enteredText
        let newText = (oldText as NSString).replacingCharacters(in: range, with: text)
        enteredText = newText
        updateTextDependentViews(with: newText)
        if isSecure {
            textView.text = secured(newText)
            return false
        }
        return true
    }

    func textViewDidChange(_ textView: UITextView) {
        // after entering the text via password autofill, the text view shows the text in clear.
        // This secures text in that case.
        if isSecure && !textView.text.isEmpty && !textView.text.allSatisfy({ $0 == secureSymbol }) {
            textView.text = secured(textView.text)
        }
    }
}