/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
/* vim: set ts=2 et sw=2 tw=80: */
/* 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/. */

/**
 * Basic use:
 * let spanToEdit = document.getElementById("somespan");
 *
 * editableField({
 *   element: spanToEdit,
 *   done: function(value, commit, direction) {
 *     if (commit) {
 *       spanToEdit.textContent = value;
 *     }
 *   },
 *   trigger: "dblclick"
 * });
 *
 * See editableField() for more options.
 */

"use strict";

const Services = require("Services");
const focusManager = Services.focus;
const {KeyCodes} = require("devtools/client/shared/keycodes");
const EventEmitter = require("devtools/shared/event-emitter");
const { findMostRelevantCssPropertyIndex } = require("./suggestion-picker");

loader.lazyRequireGetter(this, "AppConstants", "resource://gre/modules/AppConstants.jsm", true);

const HTML_NS = "http://www.w3.org/1999/xhtml";
const CONTENT_TYPES = {
  PLAIN_TEXT: 0,
  CSS_VALUE: 1,
  CSS_MIXED: 2,
  CSS_PROPERTY: 3,
};

// The limit of 500 autocomplete suggestions should not be reached but is kept
// for safety.
const MAX_POPUP_ENTRIES = 500;

const FOCUS_FORWARD = focusManager.MOVEFOCUS_FORWARD;
const FOCUS_BACKWARD = focusManager.MOVEFOCUS_BACKWARD;

const WORD_REGEXP = /\w/;
const isWordChar = function(str) {
  return str && WORD_REGEXP.test(str);
};

const GRID_PROPERTY_NAMES = ["grid-area", "grid-row", "grid-row-start",
                             "grid-row-end", "grid-column", "grid-column-start",
                             "grid-column-end"];
const GRID_ROW_PROPERTY_NAMES = ["grid-area", "grid-row", "grid-row-start",
                                 "grid-row-end"];
const GRID_COL_PROPERTY_NAMES = ["grid-area", "grid-column", "grid-column-start",
                                 "grid-column-end"];

/**
 * Helper to check if the provided key matches one of the expected keys.
 * Keys will be prefixed with DOM_VK_ and should match a key in KeyCodes.
 *
 * @param {String} key
 *        the key to check (can be a keyCode).
 * @param {...String} keys
 *        list of possible keys allowed.
 * @return {Boolean} true if the key matches one of the keys.
 */
function isKeyIn(key, ...keys) {
  return keys.some(expectedKey => {
    return key === KeyCodes["DOM_VK_" + expectedKey];
  });
}

/**
 * Mark a span editable.  |editableField| will listen for the span to
 * be focused and create an InlineEditor to handle text input.
 * Changes will be committed when the InlineEditor's input is blurred
 * or dropped when the user presses escape.
 *
 * @param {Object} options
 *    Options for the editable field, including:
 *    {Element} element:
 *      (required) The span to be edited on focus.
 *    {Function} canEdit:
 *       Will be called before creating the inplace editor.  Editor
 *       won't be created if canEdit returns false.
 *    {Function} start:
 *       Will be called when the inplace editor is initialized.
 *    {Function} change:
 *       Will be called when the text input changes.  Will be called
 *       with the current value of the text input.
 *    {Function} done:
 *       Called when input is committed or blurred.  Called with
 *       current value, a boolean telling the caller whether to
 *       commit the change, and the direction of the next element to be
 *       selected. Direction may be one of Services.focus.MOVEFOCUS_FORWARD,
 *       Services.focus.MOVEFOCUS_BACKWARD, or null (no movement).
 *       This function is called before the editor has been torn down.
 *    {Function} destroy:
 *       Called when the editor is destroyed and has been torn down.
 *    {Function} contextMenu:
 *       Called when the user triggers a contextmenu event on the input.
 *    {Object} advanceChars:
 *       This can be either a string or a function.
 *       If it is a string, then if any characters in it are typed,
 *       focus will advance to the next element.
 *       Otherwise, if it is a function, then the function will
 *       be called with three arguments: a key code, the current text,
 *       and the insertion point.  If the function returns true,
 *       then the focus advance takes place.  If it returns false,
 *       then the character is inserted instead.
 *    {Boolean} stopOnReturn:
 *       If true, the return key will not advance the editor to the next
 *       focusable element.
 *    {Boolean} stopOnTab:
 *       If true, the tab key will not advance the editor to the next
 *       focusable element.
 *    {Boolean} stopOnShiftTab:
 *       If true, shift tab will not advance the editor to the previous
 *       focusable element.
 *    {String} trigger: The DOM event that should trigger editing,
 *      defaults to "click"
 *    {Boolean} multiline: Should the editor be a multiline textarea?
 *      defaults to false
 *    {Function or Number} maxWidth:
 *       Should the editor wrap to remain below the provided max width. Only
 *       available if multiline is true. If a function is provided, it will be
 *       called when replacing the element by the inplace input.
 *    {Boolean} trimOutput: Should the returned string be trimmed?
 *      defaults to true
 *    {Boolean} preserveTextStyles: If true, do not copy text-related styles
 *              from `element` to the new input.
 *      defaults to false
 *    {Object} cssProperties: An instance of CSSProperties.
 *    {Object} cssVariables: A Map object containing all CSS variables.
 *    {Number} defaultIncrement: The value by which the input is incremented
 *      or decremented by default (0.1 for properties like opacity and 1 by default)
 *    {Function} getGridLineNames:
 *       Will be called before offering autocomplete sugestions, if the property is
 *       a member of GRID_PROPERTY_NAMES.
 */
function editableField(options) {
  return editableItem(options, function(element, event) {
    if (!options.element.inplaceEditor) {
      new InplaceEditor(options, event);
    }
  });
}

exports.editableField = editableField;

/**
 * Handle events for an element that should respond to
 * clicks and sit in the editing tab order, and call
 * a callback when it is activated.
 *
 * @param {Object} options
 *    The options for this editor, including:
 *    {Element} element: The DOM element.
 *    {String} trigger: The DOM event that should trigger editing,
 *      defaults to "click"
 * @param {Function} callback
 *        Called when the editor is activated.
 * @return {Function} function which calls callback
 */
function editableItem(options, callback) {
  let trigger = options.trigger || "click";
  let element = options.element;
  element.addEventListener(trigger, function(evt) {
    if (evt.target.nodeName !== "a") {
      let win = this.ownerDocument.defaultView;
      let selection = win.getSelection();
      if (trigger != "click" || selection.isCollapsed) {
        callback(element, evt);
      }
      evt.stopPropagation();
    }
  });

  // If focused by means other than a click, start editing by
  // pressing enter or space.
  element.addEventListener("keypress", function(evt) {
    if (isKeyIn(evt.keyCode, "RETURN") || isKeyIn(evt.charCode, "SPACE")) {
      callback(element);
    }
  }, true);

  // Ugly workaround - the element is focused on mousedown but
  // the editor is activated on click/mouseup.  This leads
  // to an ugly flash of the focus ring before showing the editor.
  // So hide the focus ring while the mouse is down.
  element.addEventListener("mousedown", function(evt) {
    if (evt.target.nodeName !== "a") {
      let cleanup = function() {
        element.style.removeProperty("outline-style");
        element.removeEventListener("mouseup", cleanup);
        element.removeEventListener("mouseout", cleanup);
      };
      element.style.setProperty("outline-style", "none");
      element.addEventListener("mouseup", cleanup);
      element.addEventListener("mouseout", cleanup);
    }
  });

  // Mark the element editable field for tab
  // navigation while editing.
  element._editable = true;

  // Save the trigger type so we can dispatch this later
  element._trigger = trigger;

  // Add button semantics to the element, to indicate that it can be activated.
  element.setAttribute("role", "button");

  return function turnOnEditMode() {
    callback(element);
  };
}

exports.editableItem = editableItem;

/*
 * Various API consumers (especially tests) sometimes want to grab the
 * inplaceEditor expando off span elements. However, when each global has its
 * own compartment, those expandos live on Xray wrappers that are only visible
 * within this JSM. So we provide a little workaround here.
 */

function getInplaceEditorForSpan(span) {
  return span.inplaceEditor;
}

exports.getInplaceEditorForSpan = getInplaceEditorForSpan;

function InplaceEditor(options, event) {
  this.elt = options.element;
  let doc = this.elt.ownerDocument;
  this.doc = doc;
  this.elt.inplaceEditor = this;
  this.cssProperties = options.cssProperties;
  this.cssVariables = options.cssVariables || new Map();
  this.change = options.change;
  this.done = options.done;
  this.contextMenu = options.contextMenu;
  this.defaultIncrement = options.defaultIncrement || 1;
  this.destroy = options.destroy;
  this.initial = options.initial ? options.initial : this.elt.textContent;
  this.multiline = options.multiline || false;
  this.maxWidth = options.maxWidth;
  if (typeof this.maxWidth == "function") {
    this.maxWidth = this.maxWidth();
  }

  this.trimOutput = options.trimOutput === undefined
                    ? true
                    : !!options.trimOutput;
  this.stopOnShiftTab = !!options.stopOnShiftTab;
  this.stopOnTab = !!options.stopOnTab;
  this.stopOnReturn = !!options.stopOnReturn;
  this.contentType = options.contentType || CONTENT_TYPES.PLAIN_TEXT;
  this.property = options.property;
  this.popup = options.popup;
  this.preserveTextStyles = options.preserveTextStyles === undefined
                          ? false
                          : !!options.preserveTextStyles;

  this._onBlur = this._onBlur.bind(this);
  this._onWindowBlur = this._onWindowBlur.bind(this);
  this._onKeyPress = this._onKeyPress.bind(this);
  this._onInput = this._onInput.bind(this);
  this._onKeyup = this._onKeyup.bind(this);
  this._onAutocompletePopupClick = this._onAutocompletePopupClick.bind(this);
  this._onContextMenu = this._onContextMenu.bind(this);

  this._createInput();

  // Hide the provided element and add our editor.
  this.originalDisplay = this.elt.style.display;
  this.elt.style.display = "none";
  this.elt.parentNode.insertBefore(this.input, this.elt);

  // After inserting the input to have all CSS styles applied, start autosizing.
  this._autosize();

  this.inputCharDimensions = this._getInputCharDimensions();
  // Pull out character codes for advanceChars, listing the
  // characters that should trigger a blur.
  if (typeof options.advanceChars === "function") {
    this._advanceChars = options.advanceChars;
  } else {
    let advanceCharcodes = {};
    let advanceChars = options.advanceChars || "";
    for (let i = 0; i < advanceChars.length; i++) {
      advanceCharcodes[advanceChars.charCodeAt(i)] = true;
    }
    this._advanceChars = charCode => charCode in advanceCharcodes;
  }

  this.input.focus();

  if (typeof options.selectAll == "undefined" || options.selectAll) {
    this.input.select();
  }

  this.input.addEventListener("blur", this._onBlur);
  this.input.addEventListener("keypress", this._onKeyPress);
  this.input.addEventListener("input", this._onInput);
  this.input.addEventListener("dblclick", this._stopEventPropagation);
  this.input.addEventListener("click", this._stopEventPropagation);
  this.input.addEventListener("mousedown", this._stopEventPropagation);
  this.input.addEventListener("contextmenu", this._onContextMenu);
  this.doc.defaultView.addEventListener("blur", this._onWindowBlur);

  this.validate = options.validate;

  if (this.validate) {
    this.input.addEventListener("keyup", this._onKeyup);
  }

  this._updateSize();

  EventEmitter.decorate(this);

  if (options.start) {
    options.start(this, event);
  }

  this._getGridNamesBeforeCompletion(options.getGridLineNames);
}

exports.InplaceEditor = InplaceEditor;

InplaceEditor.CONTENT_TYPES = CONTENT_TYPES;

InplaceEditor.prototype = {

  get currentInputValue() {
    let val = this.trimOutput ? this.input.value.trim() : this.input.value;
    return val;
  },

  _createInput: function() {
    this.input =
      this.doc.createElementNS(HTML_NS, this.multiline ? "textarea" : "input");
    this.input.inplaceEditor = this;

    if (this.multiline) {
      // Hide the textarea resize handle.
      this.input.style.resize = "none";
      this.input.style.overflow = "hidden";
    }

    this.input.classList.add("styleinspector-propertyeditor");
    this.input.value = this.initial;
    if (!this.preserveTextStyles) {
      copyTextStyles(this.elt, this.input);
    }
  },

  /**
   * Get rid of the editor.
   */
  _clear: function() {
    if (!this.input) {
      // Already cleared.
      return;
    }

    this.input.removeEventListener("blur", this._onBlur);
    this.input.removeEventListener("keypress", this._onKeyPress);
    this.input.removeEventListener("keyup", this._onKeyup);
    this.input.removeEventListener("input", this._onInput);
    this.input.removeEventListener("dblclick", this._stopEventPropagation);
    this.input.removeEventListener("click", this._stopEventPropagation);
    this.input.removeEventListener("mousedown", this._stopEventPropagation);
    this.input.removeEventListener("contextmenu", this._onContextMenu);
    this.doc.defaultView.removeEventListener("blur", this._onWindowBlur);

    this._stopAutosize();

    this.elt.style.display = this.originalDisplay;

    if (this.doc.activeElement == this.input) {
      this.elt.focus();
    }

    this.input.remove();
    this.input = null;

    delete this.elt.inplaceEditor;
    delete this.elt;

    if (this.destroy) {
      this.destroy();
    }
  },

  /**
   * Keeps the editor close to the size of its input string.  This is pretty
   * crappy, suggestions for improvement welcome.
   */
  _autosize: function() {
    // Create a hidden, absolutely-positioned span to measure the text
    // in the input.  Boo.

    // We can't just measure the original element because a) we don't
    // change the underlying element's text ourselves (we leave that
    // up to the client), and b) without tweaking the style of the
    // original element, it might wrap differently or something.
    this._measurement =
      this.doc.createElementNS(HTML_NS, this.multiline ? "pre" : "span");
    this._measurement.className = "autosizer";
    this.elt.parentNode.appendChild(this._measurement);
    let style = this._measurement.style;
    style.visibility = "hidden";
    style.position = "absolute";
    style.top = "0";
    style.left = "0";

    if (this.multiline) {
      style.whiteSpace = "pre-wrap";
      style.wordWrap = "break-word";
      if (this.maxWidth) {
        style.maxWidth = this.maxWidth + "px";
        // Use position fixed to measure dimensions without any influence from
        // the container of the editor.
        style.position = "fixed";
      }
    }

    copyAllStyles(this.input, this._measurement);
    this._updateSize();
  },

  /**
   * Clean up the mess created by _autosize().
   */
  _stopAutosize: function() {
    if (!this._measurement) {
      return;
    }
    this._measurement.remove();
    delete this._measurement;
  },

  /**
   * Size the editor to fit its current contents.
   */
  _updateSize: function() {
    // Replace spaces with non-breaking spaces.  Otherwise setting
    // the span's textContent will collapse spaces and the measurement
    // will be wrong.
    let content = this.input.value;
    let unbreakableSpace = "\u00a0";

    // Make sure the content is not empty.
    if (content === "") {
      content = unbreakableSpace;
    }

    // If content ends with a new line, add a blank space to force the autosize
    // element to adapt its height.
    if (content.lastIndexOf("\n") === content.length - 1) {
      content = content + unbreakableSpace;
    }

    if (!this.multiline) {
      content = content.replace(/ /g, unbreakableSpace);
    }

    this._measurement.textContent = content;

    // Do not use offsetWidth: it will round floating width values.
    let width = this._measurement.getBoundingClientRect().width + 2;
    if (this.multiline) {
      if (this.maxWidth) {
        width = Math.min(this.maxWidth, width);
      }
      let height = this._measurement.getBoundingClientRect().height;
      this.input.style.height = height + "px";
    }
    this.input.style.width = width + "px";
  },

  /**
   * Get the width and height of a single character in the input to properly
   * position the autocompletion popup.
   */
  _getInputCharDimensions: function() {
    // Just make the text content to be 'x' to get the width and height of any
    // character in a monospace font.
    this._measurement.textContent = "x";
    let width = this._measurement.clientWidth;
    let height = this._measurement.clientHeight;
    return { width, height };
  },

   /**
   * Increment property values in rule view.
   *
   * @param {Number} increment
   *        The amount to increase/decrease the property value.
   * @return {Boolean} true if value has been incremented.
   */
  _incrementValue: function(increment) {
    let value = this.input.value;
    let selectionStart = this.input.selectionStart;
    let selectionEnd = this.input.selectionEnd;

    let newValue = this._incrementCSSValue(value, increment, selectionStart,
                                           selectionEnd);

    if (!newValue) {
      return false;
    }

    this.input.value = newValue.value;
    this.input.setSelectionRange(newValue.start, newValue.end);
    this._doValidation();

    // Call the user's change handler if available.
    if (this.change) {
      this.change(this.currentInputValue);
    }

    return true;
  },

  /**
   * Increment the property value based on the property type.
   *
   * @param {String} value
   *        Property value.
   * @param {Number} increment
   *        Amount to increase/decrease the property value.
   * @param {Number} selStart
   *        Starting index of the value.
   * @param {Number} selEnd
   *        Ending index of the value.
   * @return {Object} object with properties 'value', 'start', and 'end'.
   */
  _incrementCSSValue: function(value, increment, selStart, selEnd) {
    let range = this._parseCSSValue(value, selStart);
    let type = (range && range.type) || "";
    let rawValue = range ? value.substring(range.start, range.end) : "";
    let preRawValue = range ? value.substr(0, range.start) : "";
    let postRawValue = range ? value.substr(range.end) : "";
    let info;

    let incrementedValue = null, selection;
    if (type === "num") {
      if (rawValue == "0") {
        info = {};
        info.units = this._findCompatibleUnit(preRawValue, postRawValue);
      }

      let newValue = this._incrementRawValue(rawValue, increment, info);
      if (newValue !== null) {
        incrementedValue = newValue;
        selection = [0, incrementedValue.length];
      }
    } else if (type === "hex") {
      let exprOffset = selStart - range.start;
      let exprOffsetEnd = selEnd - range.start;
      let newValue = this._incHexColor(rawValue, increment, exprOffset,
                                       exprOffsetEnd);
      if (newValue) {
        incrementedValue = newValue.value;
        selection = newValue.selection;
      }
    } else {
      if (type === "rgb" || type === "hsl") {
        info = {};
        let part = value.substring(range.start, selStart).split(",").length - 1;
        if (part === 3) {
          // alpha
          info.minValue = 0;
          info.maxValue = 1;
        } else if (type === "rgb") {
          info.minValue = 0;
          info.maxValue = 255;
        } else if (part !== 0) {
          // hsl percentage
          info.minValue = 0;
          info.maxValue = 100;

          // select the previous number if the selection is at the end of a
          // percentage sign.
          if (value.charAt(selStart - 1) === "%") {
            --selStart;
          }
        }
      }
      return this._incrementGenericValue(value, increment, selStart, selEnd,
                                         info);
    }

    if (incrementedValue === null) {
      return null;
    }

    return {
      value: preRawValue + incrementedValue + postRawValue,
      start: range.start + selection[0],
      end: range.start + selection[1]
    };
  },

  /**
   * Find a compatible unit to use for a CSS number value inserted between the
   * provided beforeValue and afterValue. The compatible unit will be picked
   * from a selection of default units corresponding to supported CSS value
   * dimensions (distance, angle, duration).
   *
   * @param {String} beforeValue
   *        The string preceeding the number value in the current property
   *        value.
   * @param {String} afterValue
   *        The string following the number value in the current property value.
   * @return {String} a valid unit that can be used for this number value or
   *         empty string if no match could be found.
   */
  _findCompatibleUnit: function(beforeValue, afterValue) {
    if (!this.property || !this.property.name) {
      return "";
    }

    // A DOM element is used to test the validity of various units. This is to
    // avoid having to do an async call to the server to get this information.
    let el = this.doc.createElement("div");
    let units = ["px", "deg", "s"];
    for (let unit of units) {
      let value = beforeValue + "1" + unit + afterValue;
      el.style.setProperty(this.property.name, "");
      el.style.setProperty(this.property.name, value);
      if (el.style.getPropertyValue(this.property.name) !== "") {
        return unit;
      }
    }
    return "";
  },

  /**
   * Parses the property value and type.
   *
   * @param {String} value
   *        Property value.
   * @param {Number} offset
   *        Starting index of value.
   * @return {Object} object with properties 'value', 'start', 'end', and
   *         'type'.
   */
  _parseCSSValue: function(value, offset) {
    /* eslint-disable max-len */
    const reSplitCSS = /(url\("?[^"\)]+"?\)?)|(rgba?\([^)]*\)?)|(hsla?\([^)]*\)?)|(#[\dA-Fa-f]+)|(-?\d*\.?\d+(%|[a-z]{1,4})?)|"([^"]*)"?|'([^']*)'?|([^,\s\/!\(\)]+)|(!(.*)?)/;
    /* eslint-enable */
    let start = 0;
    let m;

    // retreive values from left to right until we find the one at our offset
    while ((m = reSplitCSS.exec(value)) &&
          (m.index + m[0].length < offset)) {
      value = value.substr(m.index + m[0].length);
      start += m.index + m[0].length;
      offset -= m.index + m[0].length;
    }

    if (!m) {
      return null;
    }

    let type;
    if (m[1]) {
      type = "url";
    } else if (m[2]) {
      type = "rgb";
    } else if (m[3]) {
      type = "hsl";
    } else if (m[4]) {
      type = "hex";
    } else if (m[5]) {
      type = "num";
    }

    return {
      value: m[0],
      start: start + m.index,
      end: start + m.index + m[0].length,
      type: type
    };
  },

  /**
   * Increment the property value for types other than
   * number or hex, such as rgb, hsl, and file names.
   *
   * @param {String} value
   *        Property value.
   * @param {Number} increment
   *        Amount to increment/decrement.
   * @param {Number} offset
   *        Starting index of the property value.
   * @param {Number} offsetEnd
   *        Ending index of the property value.
   * @param {Object} info
   *        Object with details about the property value.
   * @return {Object} object with properties 'value', 'start', and 'end'.
   */
  _incrementGenericValue: function(value, increment, offset, offsetEnd, info) {
    // Try to find a number around the cursor to increment.
    let start, end;
    // Check if we are incrementing in a non-number context (such as a URL)
    if (/^-?[0-9.]/.test(value.substring(offset, offsetEnd)) &&
      !(/\d/.test(value.charAt(offset - 1) + value.charAt(offsetEnd)))) {
      // We have a number selected, possibly with a suffix, and we are not in
      // the disallowed case of just part of a known number being selected.
      // Use that number.
      start = offset;
      end = offsetEnd;
    } else {
      // Parse periods as belonging to the number only if we are in a known
      // number context. (This makes incrementing the 1 in 'image1.gif' work.)
      let pattern = "[" + (info ? "0-9." : "0-9") + "]*";
      let before = new RegExp(pattern + "$")
        .exec(value.substr(0, offset))[0].length;
      let after = new RegExp("^" + pattern)
        .exec(value.substr(offset))[0].length;

      start = offset - before;
      end = offset + after;

      // Expand the number to contain an initial minus sign if it seems
      // free-standing.
      if (value.charAt(start - 1) === "-" &&
         (start - 1 === 0 || /[ (:,='"]/.test(value.charAt(start - 2)))) {
        --start;
      }
    }

    if (start !== end) {
      // Include percentages as part of the incremented number (they are
      // common enough).
      if (value.charAt(end) === "%") {
        ++end;
      }

      let first = value.substr(0, start);
      let mid = value.substring(start, end);
      let last = value.substr(end);

      mid = this._incrementRawValue(mid, increment, info);

      if (mid !== null) {
        return {
          value: first + mid + last,
          start: start,
          end: start + mid.length
        };
      }
    }

    return null;
  },

  /**
   * Increment the property value for numbers.
   *
   * @param {String} rawValue
   *        Raw value to increment.
   * @param {Number} increment
   *        Amount to increase/decrease the raw value.
   * @param {Object} info
   *        Object with info about the property value.
   * @return {String} the incremented value.
   */
  _incrementRawValue: function(rawValue, increment, info) {
    let num = parseFloat(rawValue);

    if (isNaN(num)) {
      return null;
    }

    let number = /\d+(\.\d+)?/.exec(rawValue);

    let units = rawValue.substr(number.index + number[0].length);
    if (info && "units" in info) {
      units = info.units;
    }

    // avoid rounding errors
    let newValue = Math.round((num + increment) * 1000) / 1000;

    if (info && "minValue" in info) {
      newValue = Math.max(newValue, info.minValue);
    }
    if (info && "maxValue" in info) {
      newValue = Math.min(newValue, info.maxValue);
    }

    newValue = newValue.toString();

    return newValue + units;
  },

  /**
   * Increment the property value for hex.
   *
   * @param {String} value
   *        Property value.
   * @param {Number} increment
   *        Amount to increase/decrease the property value.
   * @param {Number} offset
   *        Starting index of the property value.
   * @param {Number} offsetEnd
   *        Ending index of the property value.
   * @return {Object} object with properties 'value' and 'selection'.
   */
  _incHexColor: function(rawValue, increment, offset, offsetEnd) {
    // Return early if no part of the rawValue is selected.
    if (offsetEnd > rawValue.length && offset >= rawValue.length) {
      return null;
    }
    if (offset < 1 && offsetEnd <= 1) {
      return null;
    }
    // Ignore the leading #.
    rawValue = rawValue.substr(1);
    --offset;
    --offsetEnd;

    // Clamp the selection to within the actual value.
    offset = Math.max(offset, 0);
    offsetEnd = Math.min(offsetEnd, rawValue.length);
    offsetEnd = Math.max(offsetEnd, offset);

    // Normalize #ABC -> #AABBCC.
    if (rawValue.length === 3) {
      rawValue = rawValue.charAt(0) + rawValue.charAt(0) +
                 rawValue.charAt(1) + rawValue.charAt(1) +
                 rawValue.charAt(2) + rawValue.charAt(2);
      offset *= 2;
      offsetEnd *= 2;
    }

    // Normalize #ABCD -> #AABBCCDD.
    if (rawValue.length === 4) {
      rawValue = rawValue.charAt(0) + rawValue.charAt(0) +
                 rawValue.charAt(1) + rawValue.charAt(1) +
                 rawValue.charAt(2) + rawValue.charAt(2) +
                 rawValue.charAt(3) + rawValue.charAt(3);
      offset *= 2;
      offsetEnd *= 2;
    }

    if (rawValue.length !== 6 && rawValue.length !== 8) {
      return null;
    }

    // If no selection, increment an adjacent color, preferably one to the left.
    if (offset === offsetEnd) {
      if (offset === 0) {
        offsetEnd = 1;
      } else {
        offset = offsetEnd - 1;
      }
    }

    // Make the selection cover entire parts.
    offset -= offset % 2;
    offsetEnd += offsetEnd % 2;

    // Remap the increments from [0.1, 1, 10] to [1, 1, 16].
    if (increment > -1 && increment < 1) {
      increment = (increment < 0 ? -1 : 1);
    }
    if (Math.abs(increment) === 10) {
      increment = (increment < 0 ? -16 : 16);
    }

    let isUpper = (rawValue.toUpperCase() === rawValue);

    for (let pos = offset; pos < offsetEnd; pos += 2) {
      // Increment the part in [pos, pos+2).
      let mid = rawValue.substr(pos, 2);
      let value = parseInt(mid, 16);

      if (isNaN(value)) {
        return null;
      }

      mid = Math.min(Math.max(value + increment, 0), 255).toString(16);

      while (mid.length < 2) {
        mid = "0" + mid;
      }
      if (isUpper) {
        mid = mid.toUpperCase();
      }

      rawValue = rawValue.substr(0, pos) + mid + rawValue.substr(pos + 2);
    }

    return {
      value: "#" + rawValue,
      selection: [offset + 1, offsetEnd + 1]
    };
  },

  /**
   * Cycle through the autocompletion suggestions in the popup.
   *
   * @param {Boolean} reverse
   *        true to select previous item from the popup.
   * @param {Boolean} noSelect
   *        true to not select the text after selecting the newly selectedItem
   *        from the popup.
   */
  _cycleCSSSuggestion: function(reverse, noSelect) {
    // selectedItem can be null when nothing is selected in an empty editor.
    let {label, preLabel} = this.popup.selectedItem ||
                            {label: "", preLabel: ""};
    if (reverse) {
      this.popup.selectPreviousItem();
    } else {
      this.popup.selectNextItem();
    }

    this._selectedIndex = this.popup.selectedIndex;
    let input = this.input;
    let pre = "";

    if (input.selectionStart < input.selectionEnd) {
      pre = input.value.slice(0, input.selectionStart);
    } else {
      pre = input.value.slice(0, input.selectionStart - label.length +
                              preLabel.length);
    }

    let post = input.value.slice(input.selectionEnd, input.value.length);
    let item = this.popup.selectedItem;
    let toComplete = item.label.slice(item.preLabel.length);
    input.value = pre + toComplete + post;

    if (!noSelect) {
      input.setSelectionRange(pre.length, pre.length + toComplete.length);
    } else {
      input.setSelectionRange(pre.length + toComplete.length,
                              pre.length + toComplete.length);
    }

    this._updateSize();
    // This emit is mainly for the purpose of making the test flow simpler.
    this.emit("after-suggest");
  },

  /**
   * Call the client's done handler and clear out.
   */
  _apply: function(event, direction) {
    if (this._applied) {
      return null;
    }

    this._applied = true;

    if (this.done) {
      let val = this.cancelled ? this.initial : this.currentInputValue;
      return this.done(val, !this.cancelled, direction);
    }

    return null;
  },

  /**
   * Hide the popup and cancel any pending popup opening.
   */
  _onWindowBlur: function() {
    if (this.popup && this.popup.isOpen) {
      this.popup.hidePopup();
    }

    if (this._openPopupTimeout) {
      this.doc.defaultView.clearTimeout(this._openPopupTimeout);
    }
  },

  /**
   * Event handler called when the inplace-editor's input loses focus.
   */
  _onBlur: function(event) {
    if (event && this.popup && this.popup.isOpen &&
      this.popup.selectedIndex >= 0) {
      this._acceptPopupSuggestion();
    } else {
      this._apply();
      this._clear();
    }
  },

  /**
   * Before offering autocomplete, set this.gridLineNames as the line names
   * of the current grid, if they exist.
   *
   * @param {Function} getGridLineNames
   *        A function which gets the line names of the current grid.
   */
  _getGridNamesBeforeCompletion: async function(getGridLineNames) {
    if (getGridLineNames && this.property &&
        GRID_PROPERTY_NAMES.includes(this.property.name)) {
      this.gridLineNames = await getGridLineNames();
    }

    if (this.contentType == CONTENT_TYPES.CSS_VALUE && this.input &&
        this.input.value == "") {
      this._maybeSuggestCompletion(false);
    }
  },

  /**
   * Event handler called by the autocomplete popup when receiving a click
   * event.
   */
  _onAutocompletePopupClick: function() {
    this._acceptPopupSuggestion();
  },

  _acceptPopupSuggestion: function() {
    let label, preLabel;

    if (this._selectedIndex === undefined) {
      ({label, preLabel} = this.popup.getItemAtIndex(this.popup.selectedIndex));
    } else {
      ({label, preLabel} = this.popup.getItemAtIndex(this._selectedIndex));
    }

    let input = this.input;

    let pre = "";

    // CSS_MIXED needs special treatment here to make it so that
    // multiple presses of tab will cycle through completions, but
    // without selecting the completed text.  However, this same
    // special treatment will do the wrong thing for other editing
    // styles.
    if (input.selectionStart < input.selectionEnd ||
        this.contentType !== CONTENT_TYPES.CSS_MIXED) {
      pre = input.value.slice(0, input.selectionStart);
    } else {
      pre = input.value.slice(0, input.selectionStart - label.length +
                              preLabel.length);
    }
    let post = input.value.slice(input.selectionEnd, input.value.length);
    let item = this.popup.selectedItem;
    this._selectedIndex = this.popup.selectedIndex;
    let toComplete = item.label.slice(item.preLabel.length);
    input.value = pre + toComplete + post;
    input.setSelectionRange(pre.length + toComplete.length,
                            pre.length + toComplete.length);
    this._updateSize();
    // Wait for the popup to hide and then focus input async otherwise it does
    // not work.
    let onPopupHidden = () => {
      this.popup.off("popup-closed", onPopupHidden);
      this.doc.defaultView.setTimeout(()=> {
        input.focus();
        this.emit("after-suggest");
      }, 0);
    };
    this.popup.on("popup-closed", onPopupHidden);
    this._hideAutocompletePopup();
  },

  /**
   * Handle the input field's keypress event.
   */
  _onKeyPress: function(event) {
    let prevent = false;

    let key = event.keyCode;
    let input = this.input;

    // We want to autoclose some characters, remember the pressed key in order to process
    // it later on in maybeSuggestionCompletion().
    this._pressedKey = event.key;

    let multilineNavigation = !this._isSingleLine() &&
      isKeyIn(key, "UP", "DOWN", "LEFT", "RIGHT");
    let isPlainText = this.contentType == CONTENT_TYPES.PLAIN_TEXT;
    let isPopupOpen = this.popup && this.popup.isOpen;

    let increment = 0;
    if (!isPlainText && !multilineNavigation) {
      increment = this._getIncrement(event);
    }

    if (isKeyIn(key, "PAGE_UP", "PAGE_DOWN")) {
      this._preventSuggestions = true;
    }

    let cycling = false;
    if (increment && this._incrementValue(increment)) {
      this._updateSize();
      prevent = true;
      cycling = true;
    }

    if (isPopupOpen && isKeyIn(key, "UP", "DOWN", "PAGE_UP", "PAGE_DOWN")) {
      prevent = true;
      cycling = true;
      this._cycleCSSSuggestion(isKeyIn(key, "UP", "PAGE_UP"));
      this._doValidation();
    }

    if (isKeyIn(key, "BACK_SPACE", "DELETE", "LEFT", "RIGHT", "HOME", "END")) {
      if (isPopupOpen) {
        this._hideAutocompletePopup();
      }
    } else if (!cycling && !multilineNavigation &&
      !event.metaKey && !event.altKey && !event.ctrlKey) {
      this._maybeSuggestCompletion(true);
    }

    if (this.multiline && event.shiftKey && isKeyIn(key, "RETURN")) {
      prevent = false;
    } else if (
      this._advanceChars(event.charCode, input.value, input.selectionStart) ||
      isKeyIn(key, "RETURN", "TAB")) {
      prevent = true;

      let direction;
      if ((this.stopOnReturn && isKeyIn(key, "RETURN")) ||
          (this.stopOnTab && !event.shiftKey && isKeyIn(key, "TAB")) ||
          (this.stopOnShiftTab && event.shiftKey && isKeyIn(key, "TAB"))) {
        direction = null;
      } else if (event.shiftKey && isKeyIn(key, "TAB")) {
        direction = FOCUS_BACKWARD;
      } else {
        direction = FOCUS_FORWARD;
      }

      // Now we don't want to suggest anything as we are moving out.
      this._preventSuggestions = true;
      // But we still want to show suggestions for css values. i.e. moving out
      // of css property input box in forward direction
      if (this.contentType == CONTENT_TYPES.CSS_PROPERTY &&
          direction == FOCUS_FORWARD) {
        this._preventSuggestions = false;
      }

      if (isKeyIn(key, "TAB") && this.contentType == CONTENT_TYPES.CSS_MIXED) {
        if (this.popup && input.selectionStart < input.selectionEnd) {
          event.preventDefault();
          input.setSelectionRange(input.selectionEnd, input.selectionEnd);
          this.emit("after-suggest");
          return;
        } else if (this.popup && this.popup.isOpen) {
          event.preventDefault();
          this._cycleCSSSuggestion(event.shiftKey, true);
          return;
        }
      }

      this._apply(event, direction);

      // Close the popup if open
      if (this.popup && this.popup.isOpen) {
        this._hideAutocompletePopup();
      }

      if (direction !== null && focusManager.focusedElement === input) {
        // If the focused element wasn't changed by the done callback,
        // move the focus as requested.
        let next = moveFocus(this.doc.defaultView, direction);

        // If the next node to be focused has been tagged as an editable
        // node, trigger editing using the configured event
        if (next && next.ownerDocument === this.doc && next._editable) {
          let e = this.doc.createEvent("Event");
          e.initEvent(next._trigger, true, true);
          next.dispatchEvent(e);
        }
      }

      this._clear();
    } else if (isKeyIn(key, "ESCAPE")) {
      // Cancel and blur ourselves.
      // Now we don't want to suggest anything as we are moving out.
      this._preventSuggestions = true;
      // Close the popup if open
      if (this.popup && this.popup.isOpen) {
        this._hideAutocompletePopup();
      }
      prevent = true;
      this.cancelled = true;
      this._apply();
      this._clear();
      event.stopPropagation();
    } else if (isKeyIn(key, "SPACE")) {
      // No need for leading spaces here.  This is particularly
      // noticable when adding a property: it's very natural to type
      // <name>: (which advances to the next property) then spacebar.
      prevent = !input.value;
    }

    if (prevent) {
      event.preventDefault();
    }
  },

  _onContextMenu: function(event) {
    if (this.contextMenu) {
      this.contextMenu(event);
    }
  },

  /**
   * Open the autocomplete popup, adding a custom click handler and classname.
   *
   * @param {Number} offset
   *        X-offset relative to the input starting edge.
   * @param {Number} selectedIndex
   *        The index of the item that should be selected. Use -1 to have no
   *        item selected.
   */
  _openAutocompletePopup: function(offset, selectedIndex) {
    this.popup.on("popup-click", this._onAutocompletePopupClick);
    this.popup.openPopup(this.input, offset, 0, selectedIndex);
  },

  /**
   * Remove the custom classname and click handler and close the autocomplete
   * popup.
   */
  _hideAutocompletePopup: function() {
    this.popup.off("popup-click", this._onAutocompletePopupClick);
    this.popup.hidePopup();
  },

  /**
   * Get the increment/decrement step to use for the provided key event.
   */
  _getIncrement: function(event) {
    const getSmallIncrementKey = (evt) => {
      if (AppConstants.platform === "macosx") {
        return evt.altKey;
      }
      return evt.ctrlKey;
    };

    const largeIncrement = 100;
    const mediumIncrement = 10;
    const smallIncrement = 0.1;

    let increment = 0;
    let key = event.keyCode;

    if (isKeyIn(key, "UP", "PAGE_UP")) {
      increment = 1 * this.defaultIncrement;
    } else if (isKeyIn(key, "DOWN", "PAGE_DOWN")) {
      increment = -1 * this.defaultIncrement;
    }

    if (event.shiftKey && !getSmallIncrementKey(event)) {
      if (isKeyIn(key, "PAGE_UP", "PAGE_DOWN")) {
        increment *= largeIncrement;
      } else {
        increment *= mediumIncrement;
      }
    } else if (getSmallIncrementKey(event) && !event.shiftKey) {
      increment *= smallIncrement;
    }

    return increment;
  },

  /**
   * Handle the input field's keyup event.
   */
  _onKeyup: function() {
    this._applied = false;
  },

  /**
   * Handle changes to the input text.
   */
  _onInput: function() {
    // Validate the entered value.
    this._doValidation();

    // Update size if we're autosizing.
    if (this._measurement) {
      this._updateSize();
    }

    // Call the user's change handler if available.
    if (this.change) {
      this.change(this.currentInputValue);
    }
  },

  /**
   * Stop propagation on the provided event
   */
  _stopEventPropagation: function(e) {
    e.stopPropagation();
  },

  /**
   * Fire validation callback with current input
   */
  _doValidation: function() {
    if (this.validate && this.input) {
      this.validate(this.input.value);
    }
  },

  /**
   * Handles displaying suggestions based on the current input.
   *
   * @param {Boolean} autoInsert
   *        Pass true to automatically insert the most relevant suggestion.
   */
  _maybeSuggestCompletion: function(autoInsert) {
    // Input can be null in cases when you intantaneously switch out of it.
    if (!this.input) {
      return;
    }

    let preTimeoutQuery = this.input.value;

    // Since we are calling this method from a keypress event handler, the
    // |input.value| does not include currently typed character. Thus we perform
    // this method async.
    this._openPopupTimeout = this.doc.defaultView.setTimeout(() => {
      if (this._preventSuggestions) {
        this._preventSuggestions = false;
        return;
      }
      if (this.contentType == CONTENT_TYPES.PLAIN_TEXT) {
        return;
      }
      if (!this.input) {
        return;
      }
      let input = this.input;
      // The length of input.value should be increased by 1
      if (input.value.length - preTimeoutQuery.length > 1) {
        return;
      }
      let query = input.value.slice(0, input.selectionStart);
      let startCheckQuery = query;
      if (query == null) {
        return;
      }
      // If nothing is selected and there is a word (\w) character after the cursor, do
      // not autocomplete.
      if (input.selectionStart == input.selectionEnd &&
          input.selectionStart < input.value.length) {
        let nextChar = input.value.slice(input.selectionStart)[0];
        // Check if the next character is a valid word character, no suggestion should be
        // provided when preceeding a word.
        if (/[\w-]/.test(nextChar)) {
          // This emit is mainly to make the test flow simpler.
          this.emit("after-suggest", "nothing to autocomplete");
          return;
        }
      }

      let list = [];
      let postLabelValues = [];

      if (this.contentType == CONTENT_TYPES.CSS_PROPERTY) {
        list = this._getCSSPropertyList();
      } else if (this.contentType == CONTENT_TYPES.CSS_VALUE) {
        // Get the last query to be completed before the caret.
        let match = /([^\s,.\/]+$)/.exec(query);
        if (match) {
          startCheckQuery = match[0];
        } else {
          startCheckQuery = "";
        }

        // Check if the query to be completed is a CSS variable.
        let varMatch = /^var\(([^\s]+$)/.exec(startCheckQuery);

        if (varMatch && varMatch.length == 2) {
          startCheckQuery = varMatch[1];
          list = this._getCSSVariableNames();
          postLabelValues = list.map(varName => this._getCSSVariableValue(varName));
        } else {
          list = ["!important",
                  ...this._getCSSValuesForPropertyName(this.property.name)];
        }

        if (query == "") {
          // Do not suggest '!important' without any manually typed character.
          list.splice(0, 1);
        }
      } else if (this.contentType == CONTENT_TYPES.CSS_MIXED &&
                 /^\s*style\s*=/.test(query)) {
        // Check if the style attribute is closed before the selection.
        let styleValue = query.replace(/^\s*style\s*=\s*/, "");
        // Look for a quote matching the opening quote (single or double).
        if (/^("[^"]*"|'[^']*')/.test(styleValue)) {
          // This emit is mainly to make the test flow simpler.
          this.emit("after-suggest", "nothing to autocomplete");
          return;
        }

        // Detecting if cursor is at property or value;
        let match = query.match(/([:;"'=]?)\s*([^"';:=]+)?$/);
        if (match && match.length >= 2) {
          if (match[1] == ":") {
            // We are in CSS value completion
            let propertyName =
              query.match(/[;"'=]\s*([^"';:= ]+)\s*:\s*[^"';:=]*$/)[1];
            list = ["!important;",
                    ...this._getCSSValuesForPropertyName(propertyName)];
            let matchLastQuery = /([^\s,.\/]+$)/.exec(match[2] || "");
            if (matchLastQuery) {
              startCheckQuery = matchLastQuery[0];
            } else {
              startCheckQuery = "";
            }
            if (!match[2]) {
              // Don't suggest '!important' without any manually typed character
              list.splice(0, 1);
            }
          } else if (match[1]) {
            // We are in CSS property name completion
            list = this._getCSSPropertyList();
            startCheckQuery = match[2];
          }
          if (startCheckQuery == null) {
            // This emit is mainly to make the test flow simpler.
            this.emit("after-suggest", "nothing to autocomplete");
            return;
          }
        }
      }

      if (!this.popup) {
        // This emit is mainly to make the test flow simpler.
        this.emit("after-suggest", "no popup");
        return;
      }

      let finalList = [];
      let length = list.length;
      for (let i = 0, count = 0; i < length && count < MAX_POPUP_ENTRIES; i++) {
        if (startCheckQuery != null && list[i].startsWith(startCheckQuery)) {
          count++;
          finalList.push({
            preLabel: startCheckQuery,
            label: list[i],
            postLabel: postLabelValues[i] ? postLabelValues[i] : ""
          });
        } else if (count > 0) {
          // Since count was incremented, we had already crossed the entries
          // which would have started with query, assuming that list is sorted.
          break;
        } else if (startCheckQuery != null && list[i][0] > startCheckQuery[0]) {
          // We have crossed all possible matches alphabetically.
          break;
        }
      }

      // Sort items starting with [a-z0-9] first, to make sure vendor-prefixed
      // values and "!important" are suggested only after standard values.
      finalList.sort((item1, item2) => {
        // Get the expected alphabetical comparison between the items.
        let comparison = item1.label.localeCompare(item2.label);
        if (/^\w/.test(item1.label) != /^\w/.test(item2.label)) {
          // One starts with [a-z0-9], one does not: flip the comparison.
          comparison = -1 * comparison;
        }
        return comparison;
      });

      let index = 0;
      if (startCheckQuery) {
        // Only select a "best" suggestion when the user started a query.
        let cssValues = finalList.map(item => item.label);
        index = findMostRelevantCssPropertyIndex(cssValues);
      }

      // Insert the most relevant item from the final list as the input value.
      if (autoInsert && finalList[index]) {
        let item = finalList[index].label;
        input.value = query + item.slice(startCheckQuery.length) +
                      input.value.slice(query.length);
        input.setSelectionRange(query.length, query.length + item.length -
                                              startCheckQuery.length);
        this._updateSize();
      }

      // Display the list of suggestions if there are more than one.
      if (finalList.length > 1) {
        // Calculate the popup horizontal offset.
        let indent = this.input.selectionStart - startCheckQuery.length;
        let offset = indent * this.inputCharDimensions.width;
        offset = this._isSingleLine() ? offset : 0;

        // Select the most relevantItem if autoInsert is allowed
        let selectedIndex = autoInsert ? index : -1;

        // Open the suggestions popup.
        this.popup.setItems(finalList);
        this._openAutocompletePopup(offset, selectedIndex);
      } else {
        this._hideAutocompletePopup();
      }

      this._autocloseParenthesis();

      // This emit is mainly for the purpose of making the test flow simpler.
      this.emit("after-suggest");
      this._doValidation();
    }, 0);
  },

  /**
   * Automatically add closing parenthesis and skip closing parenthesis when needed.
   */
  _autocloseParenthesis: function() {
    // Split the current value at the cursor index to rebuild the string.
    let parts = this._splitStringAt(this.input.value, this.input.selectionStart);

    // Lookup the character following the caret to know if the string should be modified.
    let nextChar = parts[1][0];

    // Autocomplete closing parenthesis if the last key pressed was "(" and the next
    // character is not a "word" character.
    if (this._pressedKey == "(" && !isWordChar(nextChar)) {
      this._updateValue(parts[0] + ")" + parts[1]);
    }

    // Skip inserting ")" if the next character is already a ")" (note that we actually
    // insert and remove the extra ")" here, as the input has already been modified).
    if (this._pressedKey == ")" && nextChar == ")") {
      this._updateValue(parts[0] + parts[1].substring(1));
    }

    this._pressedKey = null;
  },

  /**
   * Update the current value of the input while preserving the caret position.
   */
  _updateValue: function(str) {
    let start = this.input.selectionStart;
    this.input.value = str;
    this.input.setSelectionRange(start, start);
    this._updateSize();
  },

  /**
   * Split the provided string at the provided index. Returns an array of two strings.
   * _splitStringAt("1234567", 3) will return ["123", "4567"]
   */
  _splitStringAt: function(str, index) {
    return [str.substring(0, index), str.substring(index, str.length)];
  },

  /**
   * Check if the current input is displaying more than one line of text.
   *
   * @return {Boolean} true if the input has a single line of text
   */
  _isSingleLine: function() {
    let inputRect = this.input.getBoundingClientRect();
    return inputRect.height < 2 * this.inputCharDimensions.height;
  },

  /**
   * Returns the list of CSS properties to use for the autocompletion. This
   * method is overridden by tests in order to use mocked suggestion lists.
   *
   * @return {Array} array of CSS property names (Strings)
   */
  _getCSSPropertyList: function() {
    return this.cssProperties.getNames().sort();
  },

  /**
   * Returns a list of CSS values valid for a provided property name to use for
   * the autocompletion. This method is overridden by tests in order to use
   * mocked suggestion lists.
   *
   * @param {String} propertyName
   * @return {Array} array of CSS property values (Strings)
   */
  _getCSSValuesForPropertyName: function(propertyName) {
    let gridLineList = [];
    if (this.gridLineNames) {
      if (GRID_ROW_PROPERTY_NAMES.includes(this.property.name)) {
        gridLineList.push(...this.gridLineNames.rows);
      }
      if (GRID_COL_PROPERTY_NAMES.includes(this.property.name)) {
        gridLineList.push(...this.gridLineNames.cols);
      }
    }
    // Must be alphabetically sorted before comparing the results with
    // the user input, otherwise we will lose some results.
    return gridLineList.concat(this.cssProperties.getValues(propertyName)).sort();
  },

  /**
   * Returns the list of all CSS variables to use for the autocompletion.
   *
   * @return {Array} array of CSS variable names (Strings)
   */
  _getCSSVariableNames: function() {
    return Array.from(this.cssVariables.keys()).sort();
  },

  /**
  * Returns the variable's value for the given CSS variable name.
  *
  * @param {String} varName
  *        The variable name to retrieve the value of
  * @return {String} the variable value to the given CSS variable name
  */
  _getCSSVariableValue: function(varName) {
    return this.cssVariables.get(varName);
  },
};

/**
 * Copy text-related styles from one element to another.
 */
function copyTextStyles(from, to) {
  let win = from.ownerDocument.defaultView;
  let style = win.getComputedStyle(from);

  to.style.fontFamily = style.fontFamily;
  to.style.fontSize = style.fontSize;
  to.style.fontWeight = style.fontWeight;
  to.style.fontStyle = style.fontStyle;
}

/**
 * Copy all styles which could have an impact on the element size.
 */
function copyAllStyles(from, to) {
  let win = from.ownerDocument.defaultView;
  let style = win.getComputedStyle(from);

  copyTextStyles(from, to);
  to.style.lineHeight = style.lineHeight;

  // If box-sizing is set to border-box, box model styles also need to be
  // copied.
  let boxSizing = style.boxSizing;
  if (boxSizing === "border-box") {
    to.style.boxSizing = boxSizing;
    copyBoxModelStyles(from, to);
  }
}

/**
 * Copy box model styles that can impact width and height measurements when box-
 * sizing is set to "border-box" instead of "content-box".
 *
 * @param {DOMNode} from
 *        the element from which styles are copied
 * @param {DOMNode} to
 *        the element on which copied styles are applied
 */
function copyBoxModelStyles(from, to) {
  let properties = [
    // Copy all paddings.
    "paddingTop",
    "paddingRight",
    "paddingBottom",
    "paddingLeft",
    // Copy border styles.
    "borderTopStyle",
    "borderRightStyle",
    "borderBottomStyle",
    "borderLeftStyle",
    // Copy border widths.
    "borderTopWidth",
    "borderRightWidth",
    "borderBottomWidth",
    "borderLeftWidth"
  ];

  let win = from.ownerDocument.defaultView;
  let style = win.getComputedStyle(from);
  for (let property of properties) {
    to.style[property] = style[property];
  }
}

/**
 * Trigger a focus change similar to pressing tab/shift-tab.
 */
function moveFocus(win, direction) {
  return focusManager.moveFocus(win, null, direction, 0);
}