BrowserPrompts.swift

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

import Foundation
import WebKit
import Shared

@objc protocol JSPromptAlertControllerDelegate: AnyObject {
  func promptAlertControllerDidDismiss(_ alertController: JSPromptAlertController)
}

/// A simple version of UIAlertController that attaches a delegate to the viewDidDisappear method
/// to allow forwarding the event. The reason this is needed for prompts from Javascript is we
/// need to invoke the completionHandler passed to us from the WKWebView delegate or else
/// a runtime exception is thrown.
class JSPromptAlertController: UIAlertController {

  var info: JSAlertInfo?
  var showsCancel: Bool = false

  convenience init(title: String?, message: String?, preferredStyle: UIAlertController.Style = .alert, info: JSAlertInfo, showCancel: Bool = true) {
    self.init(title: title, message: message, preferredStyle: preferredStyle)
    self.info = info
    self.showsCancel = showCancel
  }

  override func viewDidLoad() {
    super.viewDidLoad()
    if let handler = info?.suppressHandler {
      self.addAction(
        UIAlertAction(
          title: Strings.suppressAlertsActionTitle, style: .default,
          handler: { _ in
            handler(true)
          }))
    }
    if showsCancel {
      self.addAction(
        UIAlertAction(
          title: Strings.cancelButtonTitle, style: .cancel,
          handler: { _ in
            self.info?.cancel()
          }))
    }
  }

  weak var delegate: JSPromptAlertControllerDelegate?

  override func viewDidDisappear(_ animated: Bool) {
    super.viewDidDisappear(animated)
    delegate?.promptAlertControllerDidDismiss(self)
  }
}

/**
 *  An JSAlertInfo is used to store information about an alert we want to show either immediately or later.
 *  Since alerts are generated by web pages and have no upper limit it would be unwise to allocate a
 *  UIAlertController instance for each generated prompt which could potentially be queued in the background.
 *  Instead, the JSAlertInfo structure retains the relevant data needed for the prompt along with a copy
 *  of the provided completionHandler to let us generate the UIAlertController when needed.
 */
protocol JSAlertInfo {
  typealias SuppressHandler = (Bool) -> Void
  func alertController() -> JSPromptAlertController
  func cancel()
  var suppressHandler: SuppressHandler? { get set }
}

struct MessageAlert: JSAlertInfo {
  let message: String
  let frame: WKFrameInfo
  let completionHandler: () -> Void
  var suppressHandler: SuppressHandler?

  func alertController() -> JSPromptAlertController {
    let alertController = JSPromptAlertController(
      title: titleForJavaScriptPanelInitiatedByFrame(frame),
      message: message,
      info: self,
      showCancel: false)
    alertController.addAction(
      UIAlertAction(title: Strings.OKString, style: .default) { _ in
        self.completionHandler()
      })
    return alertController
  }

  func cancel() {
    completionHandler()
  }
}

struct ConfirmPanelAlert: JSAlertInfo {
  let message: String
  let frame: WKFrameInfo
  let completionHandler: (Bool) -> Void
  var suppressHandler: SuppressHandler?

  func alertController() -> JSPromptAlertController {
    // Show JavaScript confirm dialogs.
    let alertController = JSPromptAlertController(
      title: titleForJavaScriptPanelInitiatedByFrame(frame),
      message: message,
      info: self)
    alertController.addAction(
      UIAlertAction(title: Strings.OKString, style: .default) { _ in
        self.completionHandler(true)
      })
    return alertController
  }

  func cancel() {
    completionHandler(false)
  }
}

struct TextInputAlert: JSAlertInfo {
  let message: String
  let frame: WKFrameInfo
  let completionHandler: (String?) -> Void
  let defaultText: String?
  var suppressHandler: SuppressHandler?

  func alertController() -> JSPromptAlertController {
    let alertController = JSPromptAlertController(
      title: titleForJavaScriptPanelInitiatedByFrame(frame),
      message: message,
      info: self)
    var input: UITextField!
    alertController.addTextField(configurationHandler: { (textField: UITextField) in
      input = textField
      input.text = self.defaultText
    })
    alertController.addAction(
      UIAlertAction(title: Strings.OKString, style: .default) { _ in
        self.completionHandler(input.text)
      })
    return alertController
  }

  func cancel() {
    completionHandler(nil)
  }
}

/// Show a title for a JavaScript Panel (alert) based on the WKFrameInfo. On iOS9 we will use the new securityOrigin
/// and on iOS 8 we will fall back to the request URL. If the request URL is nil, which happens for JavaScript pages,
/// we fall back to "JavaScript" as a title.
private func titleForJavaScriptPanelInitiatedByFrame(_ frame: WKFrameInfo) -> String {
  var title = "\(frame.securityOrigin.`protocol`)://\(frame.securityOrigin.host)"
  if frame.securityOrigin.port != 0 {
    title += ":\(frame.securityOrigin.port)"
  }
  return title
}