/**
 * Copyright (c) 2014 The xterm.js authors. All rights reserved.
 * Copyright (c) 2012-2013, Christopher Jeffrey (MIT License)
 * @license MIT
 *
 * Originally forked from (with the author's permission):
 *   Fabrice Bellard's javascript vt100 for jslinux:
 *   http://bellard.org/jslinux/
 *   Copyright (c) 2011 Fabrice Bellard
 *   The original design remains. The terminal itself
 *   has been extended to include xterm CSI codes, among
 *   other features.
 *
 * Terminal Emulation References:
 *   http://vt100.net/
 *   http://invisible-island.net/xterm/ctlseqs/ctlseqs.txt
 *   http://invisible-island.net/xterm/ctlseqs/ctlseqs.html
 *   http://invisible-island.net/vttest/
 *   http://www.inwap.com/pdp10/ansicode.txt
 *   http://linux.die.net/man/4/console_codes
 *   http://linux.die.net/man/7/urxvt
 */

import { BufferSet } from './BufferSet';
import { Buffer, MAX_BUFFER_SIZE } from './Buffer';
import { CompositionHelper } from './CompositionHelper';
import { EventEmitter } from './EventEmitter';
import { Viewport } from './Viewport';
import { rightClickHandler, moveTextAreaUnderMouseCursor, pasteHandler, copyHandler } from './handlers/Clipboard';
import { CircularList } from './utils/CircularList';
import { C0 } from './EscapeSequences';
import { InputHandler } from './InputHandler';
import { Parser } from './Parser';
import { Renderer } from './renderer/Renderer';
import { Linkifier } from './Linkifier';
import { SelectionManager } from './SelectionManager';
import { CharMeasure } from './utils/CharMeasure';
import * as Browser from './utils/Browser';
import { MouseHelper } from './utils/MouseHelper';
import { CHARSETS } from './Charsets';
import { CustomKeyEventHandler, Charset, LinkMatcherHandler, LinkMatcherValidationCallback, CharData, LineData } from './Types';
import { ITerminal, IBrowser, ITerminalOptions, IInputHandlingTerminal, ILinkMatcherOptions, IViewport, ICompositionHelper, ITheme, ILinkifier } from './Interfaces';
import { BellSound } from './utils/Sounds';
import { DEFAULT_ANSI_COLORS } from './renderer/ColorManager';
import { IMouseZoneManager } from './input/Interfaces';
import { MouseZoneManager } from './input/MouseZoneManager';
import { initialize as initializeCharAtlas } from './renderer/CharAtlas';
import { IRenderer } from './renderer/Interfaces';

// Let it work inside Node.js for automated testing purposes.
const document = (typeof window !== 'undefined') ? window.document : null;

/**
 * The amount of write requests to queue before sending an XOFF signal to the
 * pty process. This number must be small in order for ^C and similar sequences
 * to be responsive.
 */
const WRITE_BUFFER_PAUSE_THRESHOLD = 5;

/**
 * The number of writes to perform in a single batch before allowing the
 * renderer to catch up with a 0ms setTimeout.
 */
const WRITE_BATCH_SIZE = 300;

const DEFAULT_OPTIONS: ITerminalOptions = {
  cols: 80,
  rows: 24,
  convertEol: false,
  termName: 'xterm',
  cursorBlink: false,
  cursorStyle: 'block',
  bellSound: BellSound,
  bellStyle: 'none',
  enableBold: true,
  fontFamily: 'courier-new, courier, monospace',
  fontSize: 15,
  lineHeight: 1.0,
  letterSpacing: 0,
  scrollback: 1000,
  screenKeys: false,
  debug: false,
  cancelEvents: false,
  disableStdin: false,
  useFlowControl: false,
  tabStopWidth: 8,
  theme: null
  // programFeatures: false,
  // focusKeys: false,
};

export class Terminal extends EventEmitter implements ITerminal, IInputHandlingTerminal {
  public textarea: HTMLTextAreaElement;
  public element: HTMLElement;

  /**
   * The HTMLElement that the terminal is created in, set by Terminal.open.
   */
  private parent: HTMLElement;
  private context: Window;
  private document: Document;
  private body: HTMLBodyElement;
  private viewportScrollArea: HTMLElement;
  private viewportElement: HTMLElement;
  private helperContainer: HTMLElement;
  private compositionView: HTMLElement;
  private charSizeStyleElement: HTMLStyleElement;
  private bellAudioElement: HTMLAudioElement;
  private visualBellTimer: number;

  public browser: IBrowser = <any>Browser;

  public options: ITerminalOptions;
  private colors: any;

  // TODO: This can be changed to an enum or boolean, 0 and 1 seem to be the only options
  public cursorState: number;
  public cursorHidden: boolean;
  public convertEol: boolean;

  private sendDataQueue: string;
  private customKeyEventHandler: CustomKeyEventHandler;

  // modes
  public applicationKeypad: boolean;
  public applicationCursor: boolean;
  public originMode: boolean;
  public insertMode: boolean;
  public wraparoundMode: boolean; // defaults: xterm - true, vt100 - false
  public bracketedPasteMode: boolean;

  // charset
  // The current charset
  public charset: Charset;
  public gcharset: number;
  public glevel: number;
  public charsets: Charset[];

  // mouse properties
  private decLocator: boolean; // This is unstable and never set
  public x10Mouse: boolean;
  public vt200Mouse: boolean;
  private vt300Mouse: boolean; // This is unstable and never set
  public normalMouse: boolean;
  public mouseEvents: boolean;
  public sendFocus: boolean;
  public utfMouse: boolean;
  public sgrMouse: boolean;
  public urxvtMouse: boolean;

  // misc
  private refreshStart: number;
  private refreshEnd: number;
  public savedCols: number;

  // stream
  private readable: boolean;
  private writable: boolean;

  public defAttr: number;
  public curAttr: number;

  public params: (string | number)[];
  public currentParam: string | number;
  public prefix: string;
  public postfix: string;

  // user input states
  public writeBuffer: string[];
  private writeInProgress: boolean;

  /**
   * Whether _xterm.js_ sent XOFF in order to catch up with the pty process.
   * This is a distinct state from writeStopped so that if the user requested
   * XOFF via ^S that it will not automatically resume when the writeBuffer goes
   * below threshold.
   */
  private xoffSentToCatchUp: boolean;

  /** Whether writing has been stopped as a result of XOFF */
  private writeStopped: boolean;

  // leftover surrogate high from previous write invocation
  private surrogate_high: string;

  // Store if user went browsing history in scrollback
  private userScrolling: boolean;

  private inputHandler: InputHandler;
  private parser: Parser;
  public renderer: IRenderer;
  public selectionManager: SelectionManager;
  public linkifier: ILinkifier;
  public buffers: BufferSet;
  public buffer: Buffer;
  public viewport: IViewport;
  private compositionHelper: ICompositionHelper;
  public charMeasure: CharMeasure;
  private _mouseZoneManager: IMouseZoneManager;
  public mouseHelper: MouseHelper;

  public cols: number;
  public rows: number;

  /**
   * Creates a new `Terminal` object.
   *
   * @param {object} options An object containing a set of options, the available options are:
   *   - `cursorBlink` (boolean): Whether the terminal cursor blinks
   *   - `cols` (number): The number of columns of the terminal (horizontal size)
   *   - `rows` (number): The number of rows of the terminal (vertical size)
   *
   * @public
   * @class Xterm Xterm
   * @alias module:xterm/src/xterm
   */
  constructor(
    options: ITerminalOptions = {}
  ) {
    super();
    this.options = options;
    this.setup();
  }

  private setup(): void {
    Object.keys(DEFAULT_OPTIONS).forEach((key) => {
      if (this.options[key] == null) {
        this.options[key] = DEFAULT_OPTIONS[key];
      }
      // TODO: We should move away from duplicate options on the Terminal object
      this[key] = this.options[key];
    });

    // this.context = options.context || window;
    // this.document = options.document || document;
    // TODO: WHy not document.body?
    this.parent = document ? document.body : null;

    this.cols = this.options.cols;
    this.rows = this.options.rows;

    if (this.options.handler) {
      this.on('data', this.options.handler);
    }

    this.cursorState = 0;
    this.cursorHidden = false;
    this.sendDataQueue = '';
    this.customKeyEventHandler = null;

    // modes
    this.applicationKeypad = false;
    this.applicationCursor = false;
    this.originMode = false;
    this.insertMode = false;
    this.wraparoundMode = true; // defaults: xterm - true, vt100 - false
    this.bracketedPasteMode = false;

    // charset
    this.charset = null;
    this.gcharset = null;
    this.glevel = 0;
    // TODO: Can this be just []?
    this.charsets = [null];

    this.readable = true;
    this.writable = true;

    this.defAttr = (0 << 18) | (257 << 9) | (256 << 0);
    this.curAttr = (0 << 18) | (257 << 9) | (256 << 0);

    this.params = [];
    this.currentParam = 0;
    this.prefix = '';
    this.postfix = '';

    // user input states
    this.writeBuffer = [];
    this.writeInProgress = false;

    this.xoffSentToCatchUp = false;
    this.writeStopped = false;
    this.surrogate_high = '';
    this.userScrolling = false;

    this.inputHandler = new InputHandler(this);
    this.parser = new Parser(this.inputHandler, this);
    // Reuse renderer if the Terminal is being recreated via a reset call.
    this.renderer = this.renderer || null;
    this.selectionManager = this.selectionManager || null;
    this.linkifier = this.linkifier || new Linkifier(this);
    this._mouseZoneManager = this._mouseZoneManager || null;

    // Create the terminal's buffers and set the current buffer
    this.buffers = new BufferSet(this);
    this.buffer = this.buffers.active;  // Convenience shortcut;
    this.buffers.on('activate', (buffer: Buffer) => {
      this.buffer = buffer;
    });

    // Ensure the selection manager has the correct buffer
    if (this.selectionManager) {
      this.selectionManager.setBuffer(this.buffer);
    }
  }

  /**
   * back_color_erase feature for xterm.
   */
  public eraseAttr(): number {
    // if (this.is('screen')) return this.defAttr;
    return (this.defAttr & ~0x1ff) | (this.curAttr & 0x1ff);
  }

  /**
   * Focus the terminal. Delegates focus handling to the terminal's DOM element.
   */
  public focus(): void {
    if (this.textarea) {
      this.textarea.focus();
    }
  }

  public get isFocused(): boolean {
    return document.activeElement === this.textarea;
  }

  /**
   * Retrieves an option's value from the terminal.
   * @param {string} key The option key.
   */
  public getOption(key: string): any {
    if (!(key in DEFAULT_OPTIONS)) {
      throw new Error('No option with key "' + key + '"');
    }

    if (typeof this.options[key] !== 'undefined') {
      return this.options[key];
    }

    return this[key];
  }

  /**
   * Sets an option on the terminal.
   * @param {string} key The option key.
   * @param {any} value The option value.
   */
  public setOption(key: string, value: any): void {
    if (!(key in DEFAULT_OPTIONS)) {
      throw new Error('No option with key "' + key + '"');
    }
    switch (key) {
      case 'bellStyle':
        if (!value) {
          value = 'none';
        }
        break;
      case 'cursorStyle':
        if (!value) {
          value = 'block';
        }
        break;
      case 'lineHeight':
        if (value < 1) {
          console.warn(`${key} cannot be less than 1, value: ${value}`);
          return;
        }
      case 'tabStopWidth':
        if (value < 1) {
          console.warn(`${key} cannot be less than 1, value: ${value}`);
          return;
        }
        break;
      case 'theme':
        // If open has been called we do not want to set options.theme as the
        // source of truth is owned by the renderer.
        if (this.renderer) {
          this._setTheme(<ITheme>value);
          return;
        }
        break;
      case 'scrollback':
        value = Math.min(value, MAX_BUFFER_SIZE);

        if (value < 0) {
          console.warn(`${key} cannot be less than 0, value: ${value}`);
          return;
        }
        if (this.options[key] !== value) {
          const newBufferLength = this.rows + value;
          if (this.buffer.lines.length > newBufferLength) {
            const amountToTrim = this.buffer.lines.length - newBufferLength;
            const needsRefresh = (this.buffer.ydisp - amountToTrim < 0);
            this.buffer.lines.trimStart(amountToTrim);
            this.buffer.ybase = Math.max(this.buffer.ybase - amountToTrim, 0);
            this.buffer.ydisp = Math.max(this.buffer.ydisp - amountToTrim, 0);
            if (needsRefresh) {
              this.refresh(0, this.rows - 1);
            }
          }
        }
        break;
    }
    this[key] = value;
    this.options[key] = value;
    switch (key) {
      case 'fontFamily':
      case 'fontSize':
        // When the font changes the size of the cells may change which requires a renderer clear
        this.renderer.clear();
        this.charMeasure.measure(this.options);
        break;
      case 'enableBold':
      case 'letterSpacing':
      case 'lineHeight':
        // When the font changes the size of the cells may change which requires a renderer clear
        this.renderer.clear();
        this.renderer.onResize(this.cols, this.rows, false);
        this.refresh(0, this.rows - 1);
        // this.charMeasure.measure(this.options);
      case 'scrollback':
        this.buffers.resize(this.cols, this.rows);
        this.viewport.syncScrollArea();
        break;
      case 'tabStopWidth': this.buffers.setupTabStops(); break;
      case 'bellSound':
      case 'bellStyle': this.syncBellSound(); break;
    }
    // Inform renderer of changes
    if (this.renderer) {
      this.renderer.onOptionsChanged();
    }
  }

  /**
   * Binds the desired focus behavior on a given terminal object.
   */
  private _onTextAreaFocus(): void {
    if (this.sendFocus) {
      this.send(C0.ESC + '[I');
    }
    this.element.classList.add('focus');
    this.showCursor();
    this.emit('focus');
  };

  /**
   * Blur the terminal, calling the blur function on the terminal's underlying
   * textarea.
   */
  public blur(): void {
    return this.textarea.blur();
  }

  /**
   * Binds the desired blur behavior on a given terminal object.
   */
  private _onTextAreaBlur(): void {
    this.refresh(this.buffer.y, this.buffer.y);
    if (this.sendFocus) {
      this.send(C0.ESC + '[O');
    }
    this.element.classList.remove('focus');
    this.emit('blur');
  }

  /**
   * Initialize default behavior
   */
  private initGlobal(): void {
    this.bindKeys();

    // Bind clipboard functionality
    on(this.element, 'copy', (event: ClipboardEvent) => {
      // If mouse events are active it means the selection manager is disabled and
      // copy should be handled by the host program.
      if (!this.hasSelection()) {
        return;
      }
      copyHandler(event, this, this.selectionManager);
    });
    const pasteHandlerWrapper = event => pasteHandler(event, this);
    on(this.textarea, 'paste', pasteHandlerWrapper);
    on(this.element, 'paste', pasteHandlerWrapper);

    // Handle right click context menus
    if (Browser.isFirefox) {
      // Firefox doesn't appear to fire the contextmenu event on right click
      on(this.element, 'mousedown', (event: MouseEvent) => {
        if (event.button === 2) {
          rightClickHandler(event, this.textarea, this.selectionManager);
        }
      });
    } else {
      on(this.element, 'contextmenu', (event: MouseEvent) => {
        rightClickHandler(event, this.textarea, this.selectionManager);
      });
    }

    // Move the textarea under the cursor when middle clicking on Linux to ensure
    // middle click to paste selection works. This only appears to work in Chrome
    // at the time is writing.
    if (Browser.isLinux) {
      // Use auxclick event over mousedown the latter doesn't seem to work. Note
      // that the regular click event doesn't fire for the middle mouse button.
      on(this.element, 'auxclick', (event: MouseEvent) => {
        if (event.button === 1) {
          moveTextAreaUnderMouseCursor(event, this.textarea);
        }
      });
    }
  }

  /**
   * Apply key handling to the terminal
   */
  private bindKeys(): void {
    const self = this;
    on(this.element, 'keydown', function (ev: KeyboardEvent): void {
      if (document.activeElement !== this) {
        return;
      }
      self._keyDown(ev);
    }, true);

    on(this.element, 'keypress', function (ev: KeyboardEvent): void {
      if (document.activeElement !== this) {
        return;
      }
      self._keyPress(ev);
    }, true);

    on(this.element, 'keyup', (ev: KeyboardEvent) => {
      if (!wasMondifierKeyOnlyEvent(ev)) {
        this.focus();
      }
    }, true);

    on(this.textarea, 'keydown', (ev: KeyboardEvent) => {
      this._keyDown(ev);
    }, true);

    on(this.textarea, 'keypress', (ev: KeyboardEvent) => {
      this._keyPress(ev);
      // Truncate the textarea's value, since it is not needed
      this.textarea.value = '';
    }, true);

    on(this.textarea, 'compositionstart', () => this.compositionHelper.compositionstart());
    on(this.textarea, 'compositionupdate', (e: CompositionEvent) => this.compositionHelper.compositionupdate(e));
    on(this.textarea, 'compositionend', () => this.compositionHelper.compositionend());
    this.on('refresh', () => this.compositionHelper.updateCompositionElements());
    this.on('refresh', (data) => this.queueLinkification(data.start, data.end));
  }

  /**
   * Opens the terminal within an element.
   *
   * @param {HTMLElement} parent The element to create the terminal within.
   */
  public open(parent: HTMLElement): void {
    let i = 0;
    let div;

    this.parent = parent || this.parent;

    if (!this.parent) {
      throw new Error('Terminal requires a parent element.');
    }

    // Grab global elements
    this.context = this.parent.ownerDocument.defaultView;
    this.document = this.parent.ownerDocument;
    this.body = <HTMLBodyElement>this.document.body;

    initializeCharAtlas(this.document);

    // Create main element container
    this.element = this.document.createElement('div');
    this.element.classList.add('terminal');
    this.element.classList.add('xterm');
    this.element.setAttribute('tabindex', '0');
    this.parent.appendChild(this.element);

    // Performance: Use a document fragment to build the terminal
    // viewport and helper elements detached from the DOM
    const fragment = document.createDocumentFragment();
    this.viewportElement = document.createElement('div');
    this.viewportElement.classList.add('xterm-viewport');
    fragment.appendChild(this.viewportElement);
    this.viewportScrollArea = document.createElement('div');
    this.viewportScrollArea.classList.add('xterm-scroll-area');
    this.viewportElement.appendChild(this.viewportScrollArea);

    this._mouseZoneManager = new MouseZoneManager(this);
    this.on('scroll', () => this._mouseZoneManager.clearAll());
    this.linkifier.attachToDom(this._mouseZoneManager);

    // Create the container that will hold helpers like the textarea for
    // capturing DOM Events. Then produce the helpers.
    this.helperContainer = document.createElement('div');
    this.helperContainer.classList.add('xterm-helpers');
    fragment.appendChild(this.helperContainer);

    this.textarea = document.createElement('textarea');
    this.textarea.classList.add('xterm-helper-textarea');
    this.textarea.setAttribute('autocorrect', 'off');
    this.textarea.setAttribute('autocapitalize', 'off');
    this.textarea.setAttribute('spellcheck', 'false');
    this.textarea.tabIndex = 0;
    this.textarea.addEventListener('focus', () => this._onTextAreaFocus());
    this.textarea.addEventListener('blur', () => this._onTextAreaBlur());
    this.helperContainer.appendChild(this.textarea);

    this.compositionView = document.createElement('div');
    this.compositionView.classList.add('composition-view');
    this.compositionHelper = new CompositionHelper(this.textarea, this.compositionView, this);
    this.helperContainer.appendChild(this.compositionView);

    this.charSizeStyleElement = document.createElement('style');
    this.helperContainer.appendChild(this.charSizeStyleElement);
    this.charMeasure = new CharMeasure(document, this.helperContainer);

    // Preload audio, this relied on helperContainer
    this.syncBellSound();

    // Performance: Add viewport and helper elements from the fragment
    this.element.appendChild(fragment);

    this.renderer = new Renderer(this, this.options.theme);
    this.options.theme = null;
    this.viewport = new Viewport(this, this.viewportElement, this.viewportScrollArea, this.charMeasure);
    this.viewport.onThemeChanged(this.renderer.colorManager.colors);

    this.on('cursormove', () => this.renderer.onCursorMove());
    this.on('resize', () => this.renderer.onResize(this.cols, this.rows, false));
    this.on('blur', () => this.renderer.onBlur());
    this.on('focus', () => this.renderer.onFocus());
    window.addEventListener('resize', () => this.renderer.onWindowResize(window.devicePixelRatio));
    this.charMeasure.on('charsizechanged', () => this.renderer.onResize(this.cols, this.rows, true));
    this.renderer.on('resize', (dimensions) => this.viewport.syncScrollArea());

    this.selectionManager = new SelectionManager(this, this.buffer, this.charMeasure);
    this.element.addEventListener('mousedown', (e: MouseEvent) => this.selectionManager.onMouseDown(e));
    this.selectionManager.on('refresh', data => this.renderer.onSelectionChanged(data.start, data.end));
    this.selectionManager.on('newselection', text => {
      // If there's a new selection, put it into the textarea, focus and select it
      // in order to register it as a selection on the OS. This event is fired
      // only on Linux to enable middle click to paste selection.
      this.textarea.value = text;
      this.textarea.focus();
      this.textarea.select();
    });
    this.on('scroll', () => {
      this.viewport.syncScrollArea();
      this.selectionManager.refresh();
    });
    this.viewportElement.addEventListener('scroll', () => this.selectionManager.refresh());

    this.mouseHelper = new MouseHelper(this.renderer);

    // Measure the character size
    this.charMeasure.measure(this.options);

    // Setup loop that draws to screen
    this.refresh(0, this.rows - 1);

    // Initialize global actions that need to be taken on the document.
    this.initGlobal();

    // Listen for mouse events and translate
    // them into terminal mouse protocols.
    this.bindMouse();

  }

  /**
   * Sets the theme on the renderer. The renderer must have been initialized.
   * @param theme The theme to ste.
   */
  private _setTheme(theme: ITheme): void {
    const colors = this.renderer.setTheme(theme);
    if (this.viewport) {
      this.viewport.onThemeChanged(colors);
    }
  }

  /**
   * Apply the provided addon on the `Terminal` class.
   * @param addon The addon to apply.
   */
  public static applyAddon(addon: any): void {
    addon.apply(Terminal);
  }

  /**
   * XTerm mouse events
   * http://invisible-island.net/xterm/ctlseqs/ctlseqs.html#Mouse%20Tracking
   * To better understand these
   * the xterm code is very helpful:
   * Relevant files:
   *   button.c, charproc.c, misc.c
   * Relevant functions in xterm/button.c:
   *   BtnCode, EmitButtonCode, EditorButton, SendMousePosition
   */
  public bindMouse(): void {
    const el = this.element;
    const self = this;
    let pressed = 32;

    // mouseup, mousedown, wheel
    // left click: ^[[M 3<^[[M#3<
    // wheel up: ^[[M`3>
    function sendButton(ev: MouseEvent | WheelEvent): void {
      let button;
      let pos;

      // get the xterm-style button
      button = getButton(ev);

      // get mouse coordinates
      pos = self.mouseHelper.getRawByteCoords(ev, self.element, self.charMeasure, self.options.lineHeight, self.cols, self.rows);
      if (!pos) return;

      sendEvent(button, pos);

      switch ((<any>ev).overrideType || ev.type) {
        case 'mousedown':
          pressed = button;
          break;
        case 'mouseup':
          // keep it at the left
          // button, just in case.
          pressed = 32;
          break;
        case 'wheel':
          // nothing. don't
          // interfere with
          // `pressed`.
          break;
      }
    }

    // motion example of a left click:
    // ^[[M 3<^[[M@4<^[[M@5<^[[M@6<^[[M@7<^[[M#7<
    function sendMove(ev: MouseEvent): void {
      let button = pressed;
      let pos = self.mouseHelper.getRawByteCoords(ev, self.element, self.charMeasure, self.options.lineHeight, self.cols, self.rows);
      if (!pos) return;

      // buttons marked as motions
      // are incremented by 32
      button += 32;

      sendEvent(button, pos);
    }

    // encode button and
    // position to characters
    function encode(data: number[], ch: number): void {
      if (!self.utfMouse) {
        if (ch === 255) {
          data.push(0);
          return;
        }
        if (ch > 127) ch = 127;
        data.push(ch);
      } else {
        if (ch === 2047) {
          data.push(0);
          return;
        }
        if (ch < 127) {
          data.push(ch);
        } else {
          if (ch > 2047) ch = 2047;
          data.push(0xC0 | (ch >> 6));
          data.push(0x80 | (ch & 0x3F));
        }
      }
    }

    // send a mouse event:
    // regular/utf8: ^[[M Cb Cx Cy
    // urxvt: ^[[ Cb ; Cx ; Cy M
    // sgr: ^[[ Cb ; Cx ; Cy M/m
    // vt300: ^[[ 24(1/3/5)~ [ Cx , Cy ] \r
    // locator: CSI P e ; P b ; P r ; P c ; P p & w
    function sendEvent(button: number, pos: {x: number, y: number}): void {
      // self.emit('mouse', {
      //   x: pos.x - 32,
      //   y: pos.x - 32,
      //   button: button
      // });

      if (self.vt300Mouse) {
        // NOTE: Unstable.
        // http://www.vt100.net/docs/vt3xx-gp/chapter15.html
        button &= 3;
        pos.x -= 32;
        pos.y -= 32;
        let data = C0.ESC + '[24';
        if (button === 0) data += '1';
        else if (button === 1) data += '3';
        else if (button === 2) data += '5';
        else if (button === 3) return;
        else data += '0';
        data += '~[' + pos.x + ',' + pos.y + ']\r';
        self.send(data);
        return;
      }

      if (self.decLocator) {
        // NOTE: Unstable.
        button &= 3;
        pos.x -= 32;
        pos.y -= 32;
        if (button === 0) button = 2;
        else if (button === 1) button = 4;
        else if (button === 2) button = 6;
        else if (button === 3) button = 3;
        self.send(C0.ESC + '['
                  + button
                  + ';'
                  + (button === 3 ? 4 : 0)
                  + ';'
                  + pos.y
                  + ';'
                  + pos.x
                  + ';'
                  // Not sure what page is meant to be
                  + (<any>pos).page || 0
                  + '&w');
        return;
      }

      if (self.urxvtMouse) {
        pos.x -= 32;
        pos.y -= 32;
        pos.x++;
        pos.y++;
        self.send(C0.ESC + '[' + button + ';' + pos.x + ';' + pos.y + 'M');
        return;
      }

      if (self.sgrMouse) {
        pos.x -= 32;
        pos.y -= 32;
        self.send(C0.ESC + '[<'
                  + (((button & 3) === 3 ? button & ~3 : button) - 32)
                  + ';'
                  + pos.x
                  + ';'
                  + pos.y
                  + ((button & 3) === 3 ? 'm' : 'M'));
        return;
      }

      let data: number[] = [];

      encode(data, button);
      encode(data, pos.x);
      encode(data, pos.y);

      self.send(C0.ESC + '[M' + String.fromCharCode.apply(String, data));
    }

    function getButton(ev: MouseEvent): number {
      let button;
      let shift;
      let meta;
      let ctrl;
      let mod;

      // two low bits:
      // 0 = left
      // 1 = middle
      // 2 = right
      // 3 = release
      // wheel up/down:
      // 1, and 2 - with 64 added
      switch ((<any>ev).overrideType || ev.type) {
        case 'mousedown':
          button = ev.button != null
            ? +ev.button
          : ev.which != null
            ? ev.which - 1
          : null;

          if (Browser.isMSIE) {
            button = button === 1 ? 0 : button === 4 ? 1 : button;
          }
          break;
        case 'mouseup':
          button = 3;
          break;
        case 'DOMMouseScroll':
          button = ev.detail < 0
            ? 64
          : 65;
          break;
        case 'wheel':
          button = (<WheelEvent>ev).wheelDeltaY > 0
            ? 64
          : 65;
          break;
      }

      // next three bits are the modifiers:
      // 4 = shift, 8 = meta, 16 = control
      shift = ev.shiftKey ? 4 : 0;
      meta = ev.metaKey ? 8 : 0;
      ctrl = ev.ctrlKey ? 16 : 0;
      mod = shift | meta | ctrl;

      // no mods
      if (self.vt200Mouse) {
        // ctrl only
        mod &= ctrl;
      } else if (!self.normalMouse) {
        mod = 0;
      }

      // increment to SP
      button = (32 + (mod << 2)) + button;

      return button;
    }

    on(el, 'mousedown', (ev: MouseEvent) => {

      // Prevent the focus on the textarea from getting lost
      // and make sure we get focused on mousedown
      ev.preventDefault();
      this.focus();

      // Don't send the mouse button to the pty if mouse events are disabled or
      // if the selection manager is having selection forced (ie. a modifier is
      // held).
      if (!this.mouseEvents || this.selectionManager.shouldForceSelection(ev)) {
        return;
      }

      // send the button
      sendButton(ev);

      // fix for odd bug
      // if (this.vt200Mouse && !this.normalMouse) {
      if (this.vt200Mouse) {
        (<any>ev).overrideType = 'mouseup';
        sendButton(ev);
        return this.cancel(ev);
      }

      // bind events
      if (this.normalMouse) on(this.document, 'mousemove', sendMove);

      // x10 compatibility mode can't send button releases
      if (!this.x10Mouse) {
        const handler = (ev: MouseEvent) => {
          sendButton(ev);
          // TODO: Seems dangerous calling this on document?
          if (this.normalMouse) off(this.document, 'mousemove', sendMove);
          off(this.document, 'mouseup', handler);
          return this.cancel(ev);
        };
        // TODO: Seems dangerous calling this on document?
        on(this.document, 'mouseup', handler);
      }

      return this.cancel(ev);
    });

    // if (this.normalMouse) {
    //  on(this.document, 'mousemove', sendMove);
    // }

    on(el, 'wheel', (ev: WheelEvent) => {
      if (!this.mouseEvents) return;
      if (this.x10Mouse || this.vt300Mouse || this.decLocator) return;
      sendButton(ev);
      ev.preventDefault();
    });

    // allow wheel scrolling in
    // the shell for example
    on(el, 'wheel', (ev: WheelEvent) => {
      if (this.mouseEvents) return;
      this.viewport.onWheel(ev);
      return this.cancel(ev);
    });

    on(el, 'touchstart', (ev: TouchEvent) => {
      if (this.mouseEvents) return;
      this.viewport.onTouchStart(ev);
      return this.cancel(ev);
    });

    on(el, 'touchmove', (ev: TouchEvent) => {
      if (this.mouseEvents) return;
      this.viewport.onTouchMove(ev);
      return this.cancel(ev);
    });
  }

  /**
   * Destroys the terminal.
   */
  public destroy(): void {
    super.destroy();
    this.readable = false;
    this.writable = false;
    this.handler = () => {};
    this.write = () => {};
    if (this.element && this.element.parentNode) {
      this.element.parentNode.removeChild(this.element);
    }
    // this.emit('close');
  }

  /**
   * Tells the renderer to refresh terminal content between two rows (inclusive) at the next
   * opportunity.
   * @param {number} start The row to start from (between 0 and this.rows - 1).
   * @param {number} end The row to end at (between start and this.rows - 1).
   */
  public refresh(start: number, end: number): void {
    if (this.renderer) {
      this.renderer.queueRefresh(start, end);
    }
  }

  /**
   * Queues linkification for the specified rows.
   * @param {number} start The row to start from (between 0 and this.rows - 1).
   * @param {number} end The row to end at (between start and this.rows - 1).
   */
  private queueLinkification(start: number, end: number): void {
    if (this.linkifier) {
      this.linkifier.linkifyRows(start, end);
    }
  }

  /**
   * Display the cursor element
   */
  public showCursor(): void {
    if (!this.cursorState) {
      this.cursorState = 1;
      this.refresh(this.buffer.y, this.buffer.y);
    }
  }

  /**
   * Scroll the terminal down 1 row, creating a blank line.
   * @param isWrapped Whether the new line is wrapped from the previous line.
   */
  public scroll(isWrapped?: boolean): void {
    const newLine = this.blankLine(undefined, isWrapped);
    const topRow = this.buffer.ybase + this.buffer.scrollTop;
    let bottomRow = this.buffer.ybase + this.buffer.scrollBottom;

    if (this.buffer.scrollTop === 0) {
      // Determine whether the buffer is going to be trimmed after insertion.
      const willBufferBeTrimmed = this.buffer.lines.length === this.buffer.lines.maxLength;

      // Insert the line using the fastest method
      if (bottomRow === this.buffer.lines.length - 1) {
        this.buffer.lines.push(newLine);
      } else {
        this.buffer.lines.splice(bottomRow + 1, 0, newLine);
      }

      // Only adjust ybase and ydisp when the buffer is not trimmed
      if (!willBufferBeTrimmed) {
        this.buffer.ybase++;
        // Only scroll the ydisp with ybase if the user has not scrolled up
        if (!this.userScrolling) {
          this.buffer.ydisp++;
        }
      } else {
        // When the buffer is full and the user has scrolled up, keep the text
        // stable unless ydisp is right at the top
        if (this.userScrolling) {
          this.buffer.ydisp = Math.max(this.buffer.ydisp - 1, 0);
        }
      }
    } else {
      // scrollTop is non-zero which means no line will be going to the
      // scrollback, instead we can just shift them in-place.
      const scrollRegionHeight = bottomRow - topRow + 1/*as it's zero-based*/;
      this.buffer.lines.shiftElements(topRow + 1, scrollRegionHeight - 1, -1);
      this.buffer.lines.set(bottomRow, newLine);
    }

    // Move the viewport to the bottom of the buffer unless the user is
    // scrolling.
    if (!this.userScrolling) {
      this.buffer.ydisp = this.buffer.ybase;
    }

    // Flag rows that need updating
    this.updateRange(this.buffer.scrollTop);
    this.updateRange(this.buffer.scrollBottom);

    /**
     * This event is emitted whenever the terminal is scrolled.
     * The one parameter passed is the new y display position.
     *
     * @event scroll
     */
    this.emit('scroll', this.buffer.ydisp);
  }

  /**
   * Scroll the display of the terminal
   * @param {number} disp The number of lines to scroll down (negative scroll up).
   * @param {boolean} suppressScrollEvent Don't emit the scroll event as scrollLines. This is used
   * to avoid unwanted events being handled by the viewport when the event was triggered from the
   * viewport originally.
   */
  public scrollLines(disp: number, suppressScrollEvent?: boolean): void {
    if (disp < 0) {
      if (this.buffer.ydisp === 0) {
        return;
      }
      this.userScrolling = true;
    } else if (disp + this.buffer.ydisp >= this.buffer.ybase) {
      this.userScrolling = false;
    }

    const oldYdisp = this.buffer.ydisp;
    this.buffer.ydisp = Math.max(Math.min(this.buffer.ydisp + disp, this.buffer.ybase), 0);

    // No change occurred, don't trigger scroll/refresh
    if (oldYdisp === this.buffer.ydisp) {
      return;
    }

    if (!suppressScrollEvent) {
      this.emit('scroll', this.buffer.ydisp);
    }

    this.refresh(0, this.rows - 1);
  }

  /**
   * Scroll the display of the terminal by a number of pages.
   * @param {number} pageCount The number of pages to scroll (negative scrolls up).
   */
  public scrollPages(pageCount: number): void {
    this.scrollLines(pageCount * (this.rows - 1));
  }

  /**
   * Scrolls the display of the terminal to the top.
   */
  public scrollToTop(): void {
    this.scrollLines(-this.buffer.ydisp);
  }

  /**
   * Scrolls the display of the terminal to the bottom.
   */
  public scrollToBottom(): void {
    this.scrollLines(this.buffer.ybase - this.buffer.ydisp);
  }

  /**
   * Writes text to the terminal.
   * @param {string} data The text to write to the terminal.
   */
  public write(data: string): void {
    this.writeBuffer.push(data);

    // Send XOFF to pause the pty process if the write buffer becomes too large so
    // xterm.js can catch up before more data is sent. This is necessary in order
    // to keep signals such as ^C responsive.
    if (this.options.useFlowControl && !this.xoffSentToCatchUp && this.writeBuffer.length >= WRITE_BUFFER_PAUSE_THRESHOLD) {
      // XOFF - stop pty pipe
      // XON will be triggered by emulator before processing data chunk
      this.send(C0.DC3);
      this.xoffSentToCatchUp = true;
    }

    if (!this.writeInProgress && this.writeBuffer.length > 0) {
      // Kick off a write which will write all data in sequence recursively
      this.writeInProgress = true;
      // Kick off an async innerWrite so more writes can come in while processing data
      setTimeout(() => {
        this.innerWrite();
      });
    }
  }

  private innerWrite(): void {
    const writeBatch = this.writeBuffer.splice(0, WRITE_BATCH_SIZE);
    while (writeBatch.length > 0) {
      const data = writeBatch.shift();

      // If XOFF was sent in order to catch up with the pty process, resume it if
      // the writeBuffer is empty to allow more data to come in.
      if (this.xoffSentToCatchUp && writeBatch.length === 0 && this.writeBuffer.length === 0) {
        this.send(C0.DC1);
        this.xoffSentToCatchUp = false;
      }

      this.refreshStart = this.buffer.y;
      this.refreshEnd = this.buffer.y;

      // HACK: Set the parser state based on it's state at the time of return.
      // This works around the bug #662 which saw the parser state reset in the
      // middle of parsing escape sequence in two chunks. For some reason the
      // state of the parser resets to 0 after exiting parser.parse. This change
      // just sets the state back based on the correct return statement.
      const state = this.parser.parse(data);
      this.parser.setState(state);

      this.updateRange(this.buffer.y);
      this.refresh(this.refreshStart, this.refreshEnd);
    }
    if (this.writeBuffer.length > 0) {
      // Allow renderer to catch up before processing the next batch
      setTimeout(() => this.innerWrite(), 0);
    } else {
      this.writeInProgress = false;
    }
  }

  /**
   * Writes text to the terminal, followed by a break line character (\n).
   * @param {string} data The text to write to the terminal.
   */
  public writeln(data: string): void {
    this.write(data + '\r\n');
  }

  /**
   * Attaches a custom key event handler which is run before keys are processed,
   * giving consumers of xterm.js ultimate control as to what keys should be
   * processed by the terminal and what keys should not.
   * @param customKeyEventHandler The custom KeyboardEvent handler to attach.
   * This is a function that takes a KeyboardEvent, allowing consumers to stop
   * propogation and/or prevent the default action. The function returns whether
   * the event should be processed by xterm.js.
   */
  public attachCustomKeyEventHandler(customKeyEventHandler: CustomKeyEventHandler): void {
    this.customKeyEventHandler = customKeyEventHandler;
  }

  /**
   * Attaches a http(s) link handler, forcing web links to behave differently to
   * regular <a> tags. This will trigger a refresh as links potentially need to be
   * reconstructed. Calling this with null will remove the handler.
   * @param handler The handler callback function.
   */
  public setHypertextLinkHandler(handler: LinkMatcherHandler): void {
    if (!this.linkifier) {
      throw new Error('Cannot attach a hypertext link handler before Terminal.open is called');
    }
    this.linkifier.setHypertextLinkHandler(handler);
    // Refresh to force links to refresh
    this.refresh(0, this.rows - 1);
  }

  /**
   * Attaches a validation callback for hypertext links. This is useful to use
   * validation logic or to do something with the link's element and url.
   * @param callback The callback to use, this can
   * be cleared with null.
   */
  public setHypertextValidationCallback(callback: LinkMatcherValidationCallback): void {
    if (!this.linkifier) {
      throw new Error('Cannot attach a hypertext validation callback before Terminal.open is called');
    }
    this.linkifier.setHypertextValidationCallback(callback);
    // // Refresh to force links to refresh
    this.refresh(0, this.rows - 1);
  }

  /**
   * Registers a link matcher, allowing custom link patterns to be matched and
   * handled.
   * @param regex The regular expression to search for, specifically
   * this searches the textContent of the rows. You will want to use \s to match
   * a space ' ' character for example.
   * @param handler The callback when the link is called.
   * @param options Options for the link matcher.
   * @return The ID of the new matcher, this can be used to deregister.
   */
  public registerLinkMatcher(regex: RegExp, handler: LinkMatcherHandler, options?: ILinkMatcherOptions): number {
    if (this.linkifier) {
      const matcherId = this.linkifier.registerLinkMatcher(regex, handler, options);
      this.refresh(0, this.rows - 1);
      return matcherId;
    }
    return 0;
  }

  /**
   * Deregisters a link matcher if it has been registered.
   * @param matcherId The link matcher's ID (returned after register)
   */
  public deregisterLinkMatcher(matcherId: number): void {
    if (this.linkifier) {
      if (this.linkifier.deregisterLinkMatcher(matcherId)) {
        this.refresh(0, this.rows - 1);
      }
    }
  }

  /**
   * Gets whether the terminal has an active selection.
   */
  public hasSelection(): boolean {
    return this.selectionManager ? this.selectionManager.hasSelection : false;
  }

  /**
   * Gets the terminal's current selection, this is useful for implementing copy
   * behavior outside of xterm.js.
   */
  public getSelection(): string {
    return this.selectionManager ? this.selectionManager.selectionText : '';
  }

  /**
   * Clears the current terminal selection.
   */
  public clearSelection(): void {
    if (this.selectionManager) {
      this.selectionManager.clearSelection();
    }
  }

  /**
   * Selects all text within the terminal.
   */
  public selectAll(): void {
    if (this.selectionManager) {
      this.selectionManager.selectAll();
    }
  }

  /**
   * Handle a keydown event
   * Key Resources:
   *   - https://developer.mozilla.org/en-US/docs/DOM/KeyboardEvent
   * @param {KeyboardEvent} ev The keydown event to be handled.
   */
  protected _keyDown(ev: KeyboardEvent): boolean {
    if (this.customKeyEventHandler && this.customKeyEventHandler(ev) === false) {
      return false;
    }

    if (!this.compositionHelper.keydown(ev)) {
      if (this.buffer.ybase !== this.buffer.ydisp) {
        this.scrollToBottom();
      }
      return false;
    }

    const result = this._evaluateKeyEscapeSequence(ev);

    if (result.key === C0.DC3) { // XOFF
      this.writeStopped = true;
    } else if (result.key === C0.DC1) { // XON
      this.writeStopped = false;
    }

    if (result.scrollLines) {
      this.scrollLines(result.scrollLines);
      return this.cancel(ev, true);
    }

    if (isThirdLevelShift(this.browser, ev)) {
      return true;
    }

    if (result.cancel) {
      // The event is canceled at the end already, is this necessary?
      this.cancel(ev, true);
    }

    if (!result.key) {
      return true;
    }

    this.emit('keydown', ev);
    this.emit('key', result.key, ev);
    this.showCursor();
    this.handler(result.key);

    return this.cancel(ev, true);
  }

  /**
   * Returns an object that determines how a KeyboardEvent should be handled. The key of the
   * returned value is the new key code to pass to the PTY.
   *
   * Reference: http://invisible-island.net/xterm/ctlseqs/ctlseqs.html
   * @param ev The keyboard event to be translated to key escape sequence.
   */
  protected _evaluateKeyEscapeSequence(ev: KeyboardEvent): {cancel: boolean, key: string, scrollLines: number} {
    const result: {cancel: boolean, key: string, scrollLines: number} = {
      // Whether to cancel event propogation (NOTE: this may not be needed since the event is
      // canceled at the end of keyDown
      cancel: false,
      // The new key even to emit
      key: undefined,
      // The number of characters to scroll, if this is defined it will cancel the event
      scrollLines: undefined
    };
    const modifiers = (ev.shiftKey ? 1 : 0) | (ev.altKey ? 2 : 0) | (ev.ctrlKey ? 4 : 0) | (ev.metaKey ? 8 : 0);
    switch (ev.keyCode) {
      case 0:
        if (ev.key === 'UIKeyInputUpArrow') {
          if (this.applicationCursor) {
            result.key = C0.ESC + 'OA';
          } else {
            result.key = C0.ESC + '[A';
          }
        }
        else if (ev.key === 'UIKeyInputLeftArrow') {
          if (this.applicationCursor) {
            result.key = C0.ESC + 'OD';
          } else {
            result.key = C0.ESC + '[D';
          }
        }
        else if (ev.key === 'UIKeyInputRightArrow') {
          if (this.applicationCursor) {
            result.key = C0.ESC + 'OC';
          } else {
            result.key = C0.ESC + '[C';
          }
        }
        else if (ev.key === 'UIKeyInputDownArrow') {
          if (this.applicationCursor) {
            result.key = C0.ESC + 'OB';
          } else {
            result.key = C0.ESC + '[B';
          }
        }
        break;
      case 8:
        // backspace
        if (ev.shiftKey) {
          result.key = C0.BS; // ^H
          break;
        }
        result.key = C0.DEL; // ^?
        break;
      case 9:
        // tab
        if (ev.shiftKey) {
          result.key = C0.ESC + '[Z';
          break;
        }
        result.key = C0.HT;
        result.cancel = true;
        break;
      case 13:
        // return/enter
        result.key = C0.CR;
        result.cancel = true;
        break;
      case 27:
        // escape
        result.key = C0.ESC;
        result.cancel = true;
        break;
      case 37:
        // left-arrow
        if (modifiers) {
          result.key = C0.ESC + '[1;' + (modifiers + 1) + 'D';
          // HACK: Make Alt + left-arrow behave like Ctrl + left-arrow: move one word backwards
          // http://unix.stackexchange.com/a/108106
          // macOS uses different escape sequences than linux
          if (result.key === C0.ESC + '[1;3D') {
            result.key = (this.browser.isMac) ? C0.ESC + 'b' : C0.ESC + '[1;5D';
          }
        } else if (this.applicationCursor) {
          result.key = C0.ESC + 'OD';
        } else {
          result.key = C0.ESC + '[D';
        }
        break;
      case 39:
        // right-arrow
        if (modifiers) {
          result.key = C0.ESC + '[1;' + (modifiers + 1) + 'C';
          // HACK: Make Alt + right-arrow behave like Ctrl + right-arrow: move one word forward
          // http://unix.stackexchange.com/a/108106
          // macOS uses different escape sequences than linux
          if (result.key === C0.ESC + '[1;3C') {
            result.key = (this.browser.isMac) ? C0.ESC + 'f' : C0.ESC + '[1;5C';
          }
        } else if (this.applicationCursor) {
          result.key = C0.ESC + 'OC';
        } else {
          result.key = C0.ESC + '[C';
        }
        break;
      case 38:
        // up-arrow
        if (modifiers) {
          result.key = C0.ESC + '[1;' + (modifiers + 1) + 'A';
          // HACK: Make Alt + up-arrow behave like Ctrl + up-arrow
          // http://unix.stackexchange.com/a/108106
          if (result.key === C0.ESC + '[1;3A') {
            result.key = C0.ESC + '[1;5A';
          }
        } else if (this.applicationCursor) {
          result.key = C0.ESC + 'OA';
        } else {
          result.key = C0.ESC + '[A';
        }
        break;
      case 40:
        // down-arrow
        if (modifiers) {
          result.key = C0.ESC + '[1;' + (modifiers + 1) + 'B';
          // HACK: Make Alt + down-arrow behave like Ctrl + down-arrow
          // http://unix.stackexchange.com/a/108106
          if (result.key === C0.ESC + '[1;3B') {
            result.key = C0.ESC + '[1;5B';
          }
        } else if (this.applicationCursor) {
          result.key = C0.ESC + 'OB';
        } else {
          result.key = C0.ESC + '[B';
        }
        break;
      case 45:
        // insert
        if (!ev.shiftKey && !ev.ctrlKey) {
          // <Ctrl> or <Shift> + <Insert> are used to
          // copy-paste on some systems.
          result.key = C0.ESC + '[2~';
        }
        break;
      case 46:
        // delete
        if (modifiers) {
          result.key = C0.ESC + '[3;' + (modifiers + 1) + '~';
        } else {
          result.key = C0.ESC + '[3~';
        }
        break;
      case 36:
        // home
        if (modifiers)
          result.key = C0.ESC + '[1;' + (modifiers + 1) + 'H';
        else if (this.applicationCursor)
          result.key = C0.ESC + 'OH';
        else
          result.key = C0.ESC + '[H';
        break;
      case 35:
        // end
        if (modifiers)
          result.key = C0.ESC + '[1;' + (modifiers + 1) + 'F';
        else if (this.applicationCursor)
          result.key = C0.ESC + 'OF';
        else
          result.key = C0.ESC + '[F';
        break;
      case 33:
        // page up
        if (ev.shiftKey) {
          result.scrollLines = -(this.rows - 1);
        } else {
          result.key = C0.ESC + '[5~';
        }
        break;
      case 34:
        // page down
        if (ev.shiftKey) {
          result.scrollLines = this.rows - 1;
        } else {
          result.key = C0.ESC + '[6~';
        }
        break;
      case 112:
        // F1-F12
        if (modifiers) {
          result.key = C0.ESC + '[1;' + (modifiers + 1) + 'P';
        } else {
          result.key = C0.ESC + 'OP';
        }
        break;
      case 113:
        if (modifiers) {
          result.key = C0.ESC + '[1;' + (modifiers + 1) + 'Q';
        } else {
          result.key = C0.ESC + 'OQ';
        }
        break;
      case 114:
        if (modifiers) {
          result.key = C0.ESC + '[1;' + (modifiers + 1) + 'R';
        } else {
          result.key = C0.ESC + 'OR';
        }
        break;
      case 115:
        if (modifiers) {
          result.key = C0.ESC + '[1;' + (modifiers + 1) + 'S';
        } else {
          result.key = C0.ESC + 'OS';
        }
        break;
      case 116:
        if (modifiers) {
          result.key = C0.ESC + '[15;' + (modifiers + 1) + '~';
        } else {
          result.key = C0.ESC + '[15~';
        }
        break;
      case 117:
        if (modifiers) {
          result.key = C0.ESC + '[17;' + (modifiers + 1) + '~';
        } else {
          result.key = C0.ESC + '[17~';
        }
        break;
      case 118:
        if (modifiers) {
          result.key = C0.ESC + '[18;' + (modifiers + 1) + '~';
        } else {
          result.key = C0.ESC + '[18~';
        }
        break;
      case 119:
        if (modifiers) {
          result.key = C0.ESC + '[19;' + (modifiers + 1) + '~';
        } else {
          result.key = C0.ESC + '[19~';
        }
        break;
      case 120:
        if (modifiers) {
          result.key = C0.ESC + '[20;' + (modifiers + 1) + '~';
        } else {
          result.key = C0.ESC + '[20~';
        }
        break;
      case 121:
        if (modifiers) {
          result.key = C0.ESC + '[21;' + (modifiers + 1) + '~';
        } else {
          result.key = C0.ESC + '[21~';
        }
        break;
      case 122:
        if (modifiers) {
          result.key = C0.ESC + '[23;' + (modifiers + 1) + '~';
        } else {
          result.key = C0.ESC + '[23~';
        }
        break;
      case 123:
        if (modifiers) {
          result.key = C0.ESC + '[24;' + (modifiers + 1) + '~';
        } else {
          result.key = C0.ESC + '[24~';
        }
        break;
      default:
        // a-z and space
        if (ev.ctrlKey && !ev.shiftKey && !ev.altKey && !ev.metaKey) {
          if (ev.keyCode >= 65 && ev.keyCode <= 90) {
            result.key = String.fromCharCode(ev.keyCode - 64);
          } else if (ev.keyCode === 32) {
            // NUL
            result.key = String.fromCharCode(0);
          } else if (ev.keyCode >= 51 && ev.keyCode <= 55) {
            // escape, file sep, group sep, record sep, unit sep
            result.key = String.fromCharCode(ev.keyCode - 51 + 27);
          } else if (ev.keyCode === 56) {
            // delete
            result.key = String.fromCharCode(127);
          } else if (ev.keyCode === 219) {
            // ^[ - Control Sequence Introducer (CSI)
            result.key = String.fromCharCode(27);
          } else if (ev.keyCode === 220) {
            // ^\ - String Terminator (ST)
            result.key = String.fromCharCode(28);
          } else if (ev.keyCode === 221) {
            // ^] - Operating System Command (OSC)
            result.key = String.fromCharCode(29);
          }
        } else if (!this.browser.isMac && ev.altKey && !ev.ctrlKey && !ev.metaKey) {
          // On Mac this is a third level shift. Use <Esc> instead.
          if (ev.keyCode >= 65 && ev.keyCode <= 90) {
            result.key = C0.ESC + String.fromCharCode(ev.keyCode + 32);
          } else if (ev.keyCode === 192) {
            result.key = C0.ESC + '`';
          } else if (ev.keyCode >= 48 && ev.keyCode <= 57) {
            result.key = C0.ESC + (ev.keyCode - 48);
          }
        } else if (this.browser.isMac && !ev.altKey && !ev.ctrlKey && ev.metaKey) {
          if (ev.keyCode === 65) { // cmd + a
            this.selectAll();
          }
        }
        break;
    }

    return result;
  }

  /**
   * Set the G level of the terminal
   * @param g
   */
  public setgLevel(g: number): void {
    this.glevel = g;
    this.charset = this.charsets[g];
  }

  /**
   * Set the charset for the given G level of the terminal
   * @param g
   * @param charset
   */
  public setgCharset(g: number, charset: Charset): void {
    this.charsets[g] = charset;
    if (this.glevel === g) {
      this.charset = charset;
    }
  }

  /**
   * Handle a keypress event.
   * Key Resources:
   *   - https://developer.mozilla.org/en-US/docs/DOM/KeyboardEvent
   * @param {KeyboardEvent} ev The keypress event to be handled.
   */
  protected _keyPress(ev: KeyboardEvent): boolean {
    let key;

    if (this.customKeyEventHandler && this.customKeyEventHandler(ev) === false) {
      return false;
    }

    this.cancel(ev);

    if (ev.charCode) {
      key = ev.charCode;
    } else if (ev.which == null) {
      key = ev.keyCode;
    } else if (ev.which !== 0 && ev.charCode !== 0) {
      key = ev.which;
    } else {
      return false;
    }

    if (!key || (
      (ev.altKey || ev.ctrlKey || ev.metaKey) && !isThirdLevelShift(this.browser, ev)
    )) {
      return false;
    }

    key = String.fromCharCode(key);

    this.emit('keypress', key, ev);
    this.emit('key', key, ev);
    this.showCursor();
    this.handler(key);

    return true;
  }

  /**
   * Send data for handling to the terminal
   * @param {string} data
   */
  public send(data: string): void {
    if (!this.sendDataQueue) {
      setTimeout(() => {
        this.handler(this.sendDataQueue);
        this.sendDataQueue = '';
      }, 1);
    }

    this.sendDataQueue += data;
  }

  /**
   * Ring the bell.
   * Note: We could do sweet things with webaudio here
   */
  public bell(): void {
    this.emit('bell');
    if (this.soundBell()) this.bellAudioElement.play();

    if (this.visualBell()) {
      this.element.classList.add('visual-bell-active');
      clearTimeout(this.visualBellTimer);
      this.visualBellTimer = window.setTimeout(() => {
        this.element.classList.remove('visual-bell-active');
      }, 200);
    }
  }

  /**
   * Log the current state to the console.
   */
  public log(text: string, data?: any): void {
    if (!this.options.debug) return;
    if (!this.context.console || !this.context.console.log) return;
    this.context.console.log(text, data);
  }

  /**
   * Log the current state as error to the console.
   */
  public error(text: string, data?: any): void {
    if (!this.options.debug) return;
    if (!this.context.console || !this.context.console.error) return;
    this.context.console.error(text, data);
  }

  /**
   * Resizes the terminal.
   *
   * @param {number} x The number of columns to resize to.
   * @param {number} y The number of rows to resize to.
   */
  public resize(x: number, y: number): void {
    if (isNaN(x) || isNaN(y)) {
      return;
    }

    if (x === this.cols && y === this.rows) {
      // Check if we still need to measure the char size (fixes #785).
      if (!this.charMeasure.width || !this.charMeasure.height) {
        this.charMeasure.measure(this.options);
      }
      return;
    }

    if (x < 1) x = 1;
    if (y < 1) y = 1;

    this.buffers.resize(x, y);

    this.cols = x;
    this.rows = y;
    this.buffers.setupTabStops(this.cols);

    this.charMeasure.measure(this.options);

    this.refresh(0, this.rows - 1);
    this.emit('resize', {cols: x, rows: y});
  }

  /**
   * Updates the range of rows to refresh
   * @param {number} y The number of rows to refresh next.
   */
  public updateRange(y: number): void {
    if (y < this.refreshStart) this.refreshStart = y;
    if (y > this.refreshEnd) this.refreshEnd = y;
    // if (y > this.refreshEnd) {
    //   this.refreshEnd = y;
    //   if (y > this.rows - 1) {
    //     this.refreshEnd = this.rows - 1;
    //   }
    // }
  }

  /**
   * Set the range of refreshing to the maximum value
   */
  public maxRange(): void {
    this.refreshStart = 0;
    this.refreshEnd = this.rows - 1;
  }

  /**
   * Erase in the identified line everything from "x" to the end of the line (right).
   * @param {number} x The column from which to start erasing to the end of the line.
   * @param {number} y The line in which to operate.
   */
  public eraseRight(x: number, y: number): void {
    const line = this.buffer.lines.get(this.buffer.ybase + y);
    if (!line) {
      return;
    }
    const ch: CharData = [this.eraseAttr(), ' ', 1, 32 /* ' '.charCodeAt(0) */]; // xterm
    for (; x < this.cols; x++) {
      line[x] = ch;
    }
    this.updateRange(y);
  }

  /**
   * Erase in the identified line everything from "x" to the start of the line (left).
   * @param {number} x The column from which to start erasing to the start of the line.
   * @param {number} y The line in which to operate.
   */
  public eraseLeft(x: number, y: number): void {
    const line = this.buffer.lines.get(this.buffer.ybase + y);
    if (!line) {
      return;
    }
    const ch: CharData = [this.eraseAttr(), ' ', 1, 32 /* ' '.charCodeAt(0) */]; // xterm
    x++;
    while (x--) {
      line[x] = ch;
    }
    this.updateRange(y);
  }

  /**
   * Clear the entire buffer, making the prompt line the new first line.
   */
  public clear(): void {
    if (this.buffer.ybase === 0 && this.buffer.y === 0) {
      // Don't clear if it's already clear
      return;
    }
    this.buffer.lines.set(0, this.buffer.lines.get(this.buffer.ybase + this.buffer.y));
    this.buffer.lines.length = 1;
    this.buffer.ydisp = 0;
    this.buffer.ybase = 0;
    this.buffer.y = 0;
    for (let i = 1; i < this.rows; i++) {
      this.buffer.lines.push(this.blankLine());
    }
    this.refresh(0, this.rows - 1);
    this.emit('scroll', this.buffer.ydisp);
  }

  /**
   * Erase all content in the given line
   * @param {number} y The line to erase all of its contents.
   */
  public eraseLine(y: number): void {
    this.eraseRight(0, y);
  }

  /**
   * Return the data array of a blank line
   * @param {boolean} cur First bunch of data for each "blank" character.
   * @param {boolean} isWrapped Whether the new line is wrapped from the previous line.
   * @param {boolean} cols The number of columns in the terminal, if this is not
   * set, the terminal's current column count would be used.
   */
  public blankLine(cur?: boolean, isWrapped?: boolean, cols?: number): LineData {
    const attr = cur ? this.eraseAttr() : this.defAttr;

    const ch: CharData = [attr, ' ', 1, 32 /* ' '.charCodeAt(0) */]; // width defaults to 1 halfwidth character
    const line: LineData = [];

    // TODO: It is not ideal that this is a property on an array, a buffer line
    // class should be added that will hold this data and other useful functions.
    if (isWrapped) {
      (<any>line).isWrapped = isWrapped;
    }

    cols = cols || this.cols;
    for (let i = 0; i < cols; i++) {
      line[i] = ch;
    }

    return line;
  }

  /**
   * If cur return the back color xterm feature attribute. Else return defAttr.
   * @param cur
   */
  public ch(cur?: boolean): CharData {
    if (cur) {
      return [this.eraseAttr(), ' ', 1, 32 /* ' '.charCodeAt(0) */];
    }
    return [this.defAttr, ' ', 1, 32 /* ' '.charCodeAt(0) */];
  }

  /**
   * Evaluate if the current terminal is the given argument.
   * @param term The terminal name to evaluate
   */
  public is(term: string): boolean {
    return (this.options.termName + '').indexOf(term) === 0;
  }

  /**
   * Emit the 'data' event and populate the given data.
   * @param {string} data The data to populate in the event.
   */
  public handler(data: string): void {
    // Prevents all events to pty process if stdin is disabled
    if (this.options.disableStdin) {
      return;
    }

    // Clear the selection if the selection manager is available and has an active selection
    if (this.selectionManager && this.selectionManager.hasSelection) {
      this.selectionManager.clearSelection();
    }

    // Input is being sent to the terminal, the terminal should focus the prompt.
    if (this.buffer.ybase !== this.buffer.ydisp) {
      this.scrollToBottom();
    }
    this.emit('data', data);
  }

  /**
   * Emit the 'title' event and populate the given title.
   * @param {string} title The title to populate in the event.
   */
  private handleTitle(title: string): void {
    /**
     * This event is emitted when the title of the terminal is changed
     * from inside the terminal. The parameter is the new title.
     *
     * @event title
     */
    this.emit('title', title);
  }

  /**
   * ESC
   */

  /**
   * ESC D Index (IND is 0x84).
   */
  public index(): void {
    this.buffer.y++;
    if (this.buffer.y > this.buffer.scrollBottom) {
      this.buffer.y--;
      this.scroll();
    }
    // If the end of the line is hit, prevent this action from wrapping around to the next line.
    if (this.buffer.x >= this.cols) {
      this.buffer.x--;
    }
  }

  /**
   * ESC M Reverse Index (RI is 0x8d).
   *
   * Move the cursor up one row, inserting a new blank line if necessary.
   */
  public reverseIndex(): void {
    if (this.buffer.y === this.buffer.scrollTop) {
      // possibly move the code below to term.reverseScroll();
      // test: echo -ne '\e[1;1H\e[44m\eM\e[0m'
      // blankLine(true) is xterm/linux behavior
      const scrollRegionHeight = this.buffer.scrollBottom - this.buffer.scrollTop;
      this.buffer.lines.shiftElements(this.buffer.y + this.buffer.ybase, scrollRegionHeight, 1);
      this.buffer.lines.set(this.buffer.y + this.buffer.ybase, this.blankLine(true));
      this.updateRange(this.buffer.scrollTop);
      this.updateRange(this.buffer.scrollBottom);
    } else {
      this.buffer.y--;
    }
  }

  /**
   * ESC c Full Reset (RIS).
   */
  public reset(): void {
    this.options.rows = this.rows;
    this.options.cols = this.cols;
    const customKeyEventHandler = this.customKeyEventHandler;
    const inputHandler = this.inputHandler;
    const buffers = this.buffers;
    this.setup();
    this.customKeyEventHandler = customKeyEventHandler;
    this.inputHandler = inputHandler;
    this.buffers = buffers;
    this.refresh(0, this.rows - 1);
    this.viewport.syncScrollArea();
  }


  /**
   * ESC H Tab Set (HTS is 0x88).
   */
  private tabSet(): void {
    this.buffer.tabs[this.buffer.x] = true;
  }

  // TODO: Remove cancel function and cancelEvents option
  public cancel(ev: Event, force?: boolean): boolean {
    if (!this.options.cancelEvents && !force) {
      return;
    }
    ev.preventDefault();
    ev.stopPropagation();
    return false;
  }

  // TODO: Remove when true color is implemented
  public matchColor(r1: number, g1: number, b1: number): number {
    return matchColor_(r1, g1, b1);
  }

  private visualBell(): boolean {
    return this.options.bellStyle === 'visual' ||
        this.options.bellStyle === 'both';
  }

  private soundBell(): boolean {
    return this.options.bellStyle === 'sound' ||
        this.options.bellStyle === 'both';
  }

  private syncBellSound(): void {
    // Don't update anything if the terminal has not been opened yet
    if (!this.element) {
      return;
    }

    if (this.soundBell() && this.bellAudioElement) {
      this.bellAudioElement.setAttribute('src', this.options.bellSound);
    } else if (this.soundBell()) {
      this.bellAudioElement = document.createElement('audio');
      this.bellAudioElement.setAttribute('preload', 'auto');
      this.bellAudioElement.setAttribute('src', this.options.bellSound);
      this.helperContainer.appendChild(this.bellAudioElement);
    } else if (this.bellAudioElement) {
      this.helperContainer.removeChild(this.bellAudioElement);
    }
  }
}

/**
 * Helpers
 */

function globalOn(el: any, type: string, handler: (event: Event) => any, capture?: boolean): void {
  if (!Array.isArray(el)) {
    el = [el];
  }
  el.forEach((element: HTMLElement) => {
    element.addEventListener(type, handler, capture || false);
  });
}
// TODO: Remove once everything is typed
const on = globalOn;

function off(el: any, type: string, handler: (event: Event) => any, capture: boolean = false): void {
  el.removeEventListener(type, handler, capture);
}

function isThirdLevelShift(browser: IBrowser, ev: KeyboardEvent): boolean {
  const thirdLevelKey =
      (browser.isMac && ev.altKey && !ev.ctrlKey && !ev.metaKey) ||
      (browser.isMSWindows && ev.altKey && ev.ctrlKey && !ev.metaKey);

  if (ev.type === 'keypress') {
    return thirdLevelKey;
  }

  // Don't invoke for arrows, pageDown, home, backspace, etc. (on non-keypress events)
  return thirdLevelKey && (!ev.keyCode || ev.keyCode > 47);
}

function wasMondifierKeyOnlyEvent(ev: KeyboardEvent): boolean {
  return ev.keyCode === 16 || // Shift
    ev.keyCode === 17 || // Ctrl
    ev.keyCode === 18; // Alt
}

/**
 * TODO:
 * The below color-related code can be removed when true color is implemented.
 * It's only purpose is to match true color requests with the closest matching
 * ANSI color code.
 */

// Colors 0-15 + 16-255
// Much thanks to TooTallNate for writing this.
const vcolors: number[][] = (function(): number[][] {
  const result = DEFAULT_ANSI_COLORS.map(c => {
    c = c.substring(1);
    return [
      parseInt(c.substring(0, 2), 16),
      parseInt(c.substring(2, 4), 16),
      parseInt(c.substring(4, 6), 16)
    ];
  });
  const r = [0x00, 0x5f, 0x87, 0xaf, 0xd7, 0xff];

  // 16-231
  for (let i = 0; i < 216; i++) {
    result.push([
      r[(i / 36) % 6 | 0],
      r[(i / 6) % 6 | 0],
      r[i % 6]
    ]);
  }

  // 232-255 (grey)
  let c: number;
  for (let i = 0; i < 24; i++) {
    c = 8 + i * 10;
    result.push([c, c, c]);
  }

  return result;
})();

const matchColorCache: {[colorRGBHash: number]: number} = {};

// http://stackoverflow.com/questions/1633828
function matchColorDistance(r1: number, g1: number, b1: number, r2: number, g2: number, b2: number): number {
  return Math.pow(30 * (r1 - r2), 2)
    + Math.pow(59 * (g1 - g2), 2)
    + Math.pow(11 * (b1 - b2), 2);
};


function matchColor_(r1: number, g1: number, b1: number): number {
  const hash = (r1 << 16) | (g1 << 8) | b1;

  if (matchColorCache[hash] != null) {
    return matchColorCache[hash];
  }

  let ldiff = Infinity;
  let li = -1;
  let i = 0;
  let c: number[];
  let r2: number;
  let g2: number;
  let b2: number;
  let diff: number;

  for (; i < vcolors.length; i++) {
    c = vcolors[i];
    r2 = c[0];
    g2 = c[1];
    b2 = c[2];

    diff = matchColorDistance(r1, g1, b1, r2, g2, b2);

    if (diff === 0) {
      li = i;
      break;
    }

    if (diff < ldiff) {
      ldiff = diff;
      li = i;
    }
  }

  return matchColorCache[hash] = li;
}