//
//  KeymanTextView.swift
//  KeymanEngine
//
//  Created by Gabriel Wong on 2017-10-06.
//  Copyright © 2017 SIL International. All rights reserved.
//

import AudioToolbox
import UIKit

public class KeymanTextView: UITextView, UITextViewDelegate, UIInputViewAudioFeedback, KeymanWebViewDelegate {
  // viewController should be set to main view controller to enable keyboard picker.
  public var viewController: UIViewController?

  // Sets Keyman custom font (if any) to KeymanTextView instance on keyboard change event
  public var shouldSetCustomFontOnKeyboardChange = true
  public var isInputClickSoundEnabled = true

  private var delegateProxy: KeymanTextViewDelegateProxy!
  private var shouldUpdateKMText = false

  // MARK: - Object Admin
  deinit {
    NotificationCenter.default.removeObserver(self)
    delegate = nil
  }

  public convenience init() {
    self.init(frame: CGRect.zero)
  }

  public convenience init(frame: CGRect) {
    self.init(frame: frame, textContainer: nil)
  }

  public override init(frame: CGRect, textContainer: NSTextContainer?) {
    super.init(frame: frame, textContainer: textContainer)
    performCommonInit()
  }

  public required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
    performCommonInit()
  }

  private func performCommonInit() {
    delegateProxy = KeymanTextViewDelegateProxy(self)
    delegate = delegateProxy

    if #available(iOS 9.0, *) {
      inputAssistantItem.leadingBarButtonGroups = []
      inputAssistantItem.trailingBarButtonGroups = []
    }

    Manager.shared // Preload webview keyboard
    NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardChanged),
                                           name: .keymanKeyboardChanged, object: nil)
  }

  // MARK: - Class Overrides
  public override var inputView: UIView? {
    get {
      Manager.shared.webDelegate = self
      return Manager.inputView()
    }

    set(inputView) {
      super.inputView = inputView
    }
  }

  // Prevent the delegate being set to anything but the delegateProxy
  public override weak var delegate: UITextViewDelegate? {
    get {
      return super.delegate
    }

    set(delegate) {
      // Allow clearing of delegate
      guard let delegate = delegate else {
        super.delegate = nil
        return
      }

      if delegate !== delegateProxy {
        Manager.shared.kmLog(
          "Trying to set KeymanTextView's delegate directly. Use setKeymanDelegate() instead.",
          checkDebugPrinting: true)
      }
      super.delegate = delegateProxy
    }
  }

  // MARK: - Public Methods

  // Use this KeymanTextViewDelegate instead of the normal UITextViewDelegate.
  //   - All of the normal UITextViewDelegate methods are supported.
  public func setKeymanDelegate(_ keymanDelegate: KeymanTextViewDelegate?) {
    delegateProxy.keymanDelegate = keymanDelegate
    Manager.shared.kmLog(
      "KeymanTextView: \(self.debugDescription) keymanDelegate set to: \(keymanDelegate.debugDescription)",
      checkDebugPrinting: true)
  }

  // Dismisses the keyboard if this textview is the first responder.
  //   - Use this instead of [resignFirstResponder] as it also resigns the Keyman keyboard's responders.
  @objc public func dismissKeyboard() {
    Manager.shared.kmLog(
      "KeymanTextView: \(self.debugDescription) Dismissing keyboard. Was first responder:\(isFirstResponder)",
      checkDebugPrinting: true)
    resignFirstResponder()
    Manager.inputView().endEditing(true)
  }

  public override var text: String! {
    get {
      return super.text ?? ""
    }

    set(text) {
      if let text = text {
        super.text = text
      } else {
        super.text = ""
      }

      Manager.setText(self.text)
      Manager.setSelectionRange(selectedRange, manually: false)
    }
  }

  // MARK: - KMWebViewDelegate
  @objc public func updatedFragment(_ fragment: String) {
    if fragment.contains("insertText") {
      processInsertText(fragment)
    } else if fragment.contains("hideKeyboard") {
      dismissKeyboard()
    } else if fragment.contains("menuKeyUp") {
      if let viewController = viewController {
        Manager.shared.showKeyboardPicker(in: viewController, shouldAddKeyboard: false)
      } else {
        Manager.shared.switchToNextKeyboard()
      }
    }
  }

  private func processInsertText(_ fragment: String) {
    if Manager.shared.isSubKeysMenuVisible {
      return
    }

    if isInputClickSoundEnabled {
      AudioServicesPlaySystemSound(0x450)

      // Disable input click sound for 0.1 second to ensure it plays for single key stroke.
      isInputClickSoundEnabled = false
      perform(#selector(self.enableInputClickSound), with: nil, afterDelay: 0.1)
    }

    let dnRange = fragment.range(of: "+dn=")!
    let sRange = fragment.range(of: "+s=")!

    let dn = Int(fragment[dnRange.upperBound..<sRange.lowerBound])!
    let s = fragment[sRange.upperBound...]

    let hexStrings: [String]
    if !s.isEmpty {
      hexStrings = s.components(separatedBy: ",")
    } else {
      hexStrings = []
    }

    let codeUnits = hexStrings.map { hexString -> UInt16 in
      let scanner = Scanner(string: hexString)
      var codeUnit: UInt32 = 0
      scanner.scanHexInt32(&codeUnit)
      return UInt16(codeUnit)
    }

    let text = String(utf16CodeUnits: codeUnits, count: codeUnits.count)

    let textRange = selectedTextRange!
    let selRange = NSRange(location: offset(from: beginningOfDocument, to: textRange.start),
                           length: offset(from: textRange.start, to: textRange.end))

    if dn <= 0 {
      if selRange.length == 0 {
        insertText(text)
      } else {
        self.text = (self.text! as NSString).replacingCharacters(in: selRange, with: text)
      }
    } else {
      if s.isEmpty {
        for _ in 0..<dn {
          deleteBackward()
        }
      } else {
        if selRange.length == 0 {
          for _ in 0..<dn {
            deleteBackward()
          }
          insertText(text)
        } else {
          self.text = (self.text! as NSString).replacingCharacters(in: selRange, with: text)
        }
      }
    }

    // Workaround for iOS 7 UITextView scroll bug
    // TODO check if fixed
    perform(#selector(self.scroll(toShowSelection:)), with: self, afterDelay: 0.1)
    // Smaller delays are unreliable.
  }

  // MARK: - UITextViewDelegate Hooks
  public override var selectedTextRange: UITextRange? {
    didSet {
      Manager.setSelectionRange(selectedRange, manually: false)
    }
  }

  public func textViewDidChangeSelection(_ textView: UITextView) {
    // Workaround for iOS 7 UITextView scroll bug
    scroll(toCarret: textView)
    scrollRangeToVisible(textView.selectedRange)
  }

  public func textViewShouldBeginEditing(_ textView: UITextView) -> Bool {
    let leftToRightMark = "\u{200e}"
    let rightToLeftMark = "\u{200f}" // or "\u{202e}"
    let keyboardID = Manager.shared.keyboardID!
    let languageID = Manager.shared.languageID!
    let textWD = baseWritingDirection(for: beginningOfDocument, in: .forward)

    if Manager.shared.isRTLKeyboard(withID: keyboardID, languageID: languageID) {
      if textWD != .rightToLeft {
        if text.hasPrefix(leftToRightMark) {
          text = String(text.utf16.dropFirst())
        }

        if text.isEmpty || !text.hasPrefix(rightToLeftMark) {
          text = "\(rightToLeftMark)\(text!)"
        }
        makeTextWritingDirectionRightToLeft(nil)
      }
    } else {
      if textWD != .leftToRight {
        if textWD != .leftToRight {
          if text.hasPrefix(rightToLeftMark) {
            text = String(text.utf16.dropFirst())
          }

          if text.isEmpty || !text.hasPrefix(leftToRightMark) {
            text = "\(leftToRightMark)\(text!)"
          }
          makeTextWritingDirectionLeftToRight(nil)
        }
      }
    }

    return true
  }

  public func textViewDidBeginEditing(_ textView: UITextView) {
    Manager.shared.webDelegate = self

    let keyboardID = Manager.shared.keyboardID!
    let languageID = Manager.shared.languageID!
    let fontName = Manager.shared.fontNameForKeyboard(withID: keyboardID, languageID: languageID)
    let fontSize = font?.pointSize ?? UIFont.systemFontSize
    if let fontName = fontName {
      font = UIFont(name: fontName, size: fontSize)
    } else {
      font = UIFont.systemFont(ofSize: fontSize)
    }

    Manager.shared.kmLog("TextView setFont: \(String(describing: font?.familyName))",
      checkDebugPrinting: true)

    // copy this textView's text to the webview
    Manager.setText(text)
    Manager.setSelectionRange(selectedRange, manually: false)
    Manager.shared.kmLog(
      "KeymanTextView: \(self.debugDescription) Became first responder. Value: \(text.debugDescription)",
      checkDebugPrinting: true)
  }

  public func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange,
                       replacementText text: String) -> Bool {
    // Enable text update to catch copy/paste operations
    shouldUpdateKMText = true
    return true
  }

  public func textViewDidChange(_ textView: UITextView) {
    if shouldUpdateKMText {
      // Catches copy/paste operations
      Manager.setText(textView.text)
      Manager.setSelectionRange(textView.selectedRange, manually: false)
      shouldUpdateKMText = false
    }
  }

  public func textViewShouldEndEditing(_ textView: UITextView) -> Bool {
    if textView == self {
      resignFirstResponder()
    }
    return true
  }

  // MARK: - Keyman notifications
  @objc func keyboardChanged(_ notification: Notification) {
    if !shouldSetCustomFontOnKeyboardChange {
      return
    }

    let kbInfo = notification.userInfo?[kKeymanKeyboardInfoKey] as? [AnyHashable: Any]
    let keyboardID = kbInfo?[kKeymanKeyboardIdKey] as? String
    let languageID = kbInfo?[kKeymanLanguageIdKey] as? String
    let fontName = Manager.shared.fontNameForKeyboard(withID: keyboardID!, languageID: languageID!)
    let fontSize = font?.pointSize ?? UIFont.systemFontSize
    if let fontName = fontName {
      font = UIFont(name: fontName, size: fontSize)
    } else {
      font = UIFont.systemFont(ofSize: fontSize)
    }

    if isFirstResponder {
      resignFirstResponder()
      becomeFirstResponder()
    }

    Manager.shared.kmLog("TextView setFont: \(String(describing: font?.familyName))",
      checkDebugPrinting: true)
  }

  // MARK: iOS 7 TextView Scroll bug fix
  func scroll(toCarret textView: UITextView) {
    guard let range = textView.selectedTextRange else {
      return
    }
    var caretRect = textView.caretRect(for: range.end)
    caretRect.size.height += textView.textContainerInset.bottom
    textView.scrollRectToVisible(caretRect, animated: false)
  }

  @objc func scroll(toShowSelection textView: UITextView) {
    if textView.selectedRange.location < textView.text.count {
      return
    }

    var bottomOffset = CGPoint(x: 0, y: textView.contentSize.height - textView.bounds.size.height)
    if bottomOffset.y < 0 {
      bottomOffset.y = 0
    }
    textView.setContentOffset(bottomOffset, animated: true)
  }

  // MARK: - Private Methods
  @objc func enableInputClickSound() {
    isInputClickSoundEnabled = true
  }
}