// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.


/**
 * @fileoverview Implements an element that is hidden by default, but
 * when shown, dims and (attempts to) disable the main document.
 *
 * You can turn any div into an overlay. Note that while an
 * overlay element is shown, its parent is changed. Hiding the overlay
 * restores its original parentage.
 *
 */
cr.define('gpu', function() {
  /**
   * Manages a full-window div that darkens the window, disables
   * input, and hosts the currently-visible overlays. You shouldn't
   * have to instantiate this directly --- it gets set automatically.
   * @param {Object=} opt_propertyBag Optional properties.
   * @constructor
   * @extends {HTMLDivElement}
   */
  var OverlayRoot = cr.ui.define('div');
  OverlayRoot.prototype = {
    __proto__: HTMLDivElement.prototype,
    decorate: function() {
      this.classList.add('overlay-root');
      this.visible = false;

      this.contentHost = this.ownerDocument.createElement('div');
      this.contentHost.classList.add('content-host');

      this.tabCatcher = this.ownerDocument.createElement('span');
      this.tabCatcher.tabIndex = 0;

      this.appendChild(this.contentHost);

      this.onKeydownBoundToThis_ = this.onKeydown_.bind(this);
      this.onFocusInBoundToThis_ = this.onFocusIn_.bind(this);
      this.addEventListener('mousedown', this.onMousedown_.bind(this));
    },

    /**
     * Adds an overlay, attaching it to the contentHost so that it is visible.
     */
    showOverlay: function(overlay) {
      // Reparent this to the overlay content host.
      overlay.oldParent_ = overlay.parentNode;
      this.contentHost.appendChild(overlay);
      this.contentHost.appendChild(this.tabCatcher);

      // Show the overlay root.
      this.ownerDocument.body.classList.add('disabled-by-overlay');
      this.visible = true;

      // Bring overlay into focus.
      overlay.tabIndex = 0;
      overlay.focus();

      // Listen to key and focus events to prevent focus from
      // leaving the overlay.
      this.ownerDocument.addEventListener('focusin',
          this.onFocusInBoundToThis_, true);
      overlay.addEventListener('keydown', this.onKeydownBoundToThis_);
    },

    /**
     * Clicking outside of the overlay will de-focus the overlay. The
     * next tab will look at the entire document to determine the focus.
     * For certain documents, this can cause focus to "leak" outside of
     * the overlay.
     */
    onMousedown_: function(e) {
      if (e.target == this) {
        e.preventDefault();
      }
    },

    /**
     * Prevents forward-tabbing out of the overlay
     */
    onFocusIn_: function(e) {
      if (e.target == this.tabCatcher) {
        window.setTimeout(this.focusOverlay_.bind(this), 0);
      }
    },

    focusOverlay_: function() {
      this.contentHost.firstChild.focus();
    },

    /**
     * Prevent the user from shift-tabbing backwards out of the overlay.
     */
    onKeydown_: function(e) {
      if (e.keyCode == 9 &&
          e.shiftKey &&
          e.target == this.contentHost.firstChild) {
        e.preventDefault();
      }
    },

    /**
     * Hides an overlay, attaching it to its original parent if needed.
     */
    hideOverlay: function(overlay) {
      // hide the overlay root
      this.visible = false;
      this.ownerDocument.body.classList.remove('disabled-by-overlay');
      this.lastFocusOut_ = undefined;

      // put the overlay back on its previous parent
      overlay.parentNode.removeChild(this.tabCatcher);
      if (overlay.oldParent_) {
        overlay.oldParent_.appendChild(overlay);
        delete overlay.oldParent_;
      } else {
        this.contentHost.removeChild(overlay);
      }

      // remove listeners
      overlay.removeEventListener('keydown', this.onKeydownBoundToThis_);
      this.ownerDocument.removeEventListener('focusin',
          this.onFocusInBoundToThis_);
    }
  };

  cr.defineProperty(OverlayRoot, 'visible', cr.PropertyKind.BOOL_ATTR);

  /**
   * Creates a new overlay element. It will not be visible until shown.
   * @param {Object=} opt_propertyBag Optional properties.
   * @constructor
   * @extends {HTMLDivElement}
   */
  var Overlay = cr.ui.define('div');

  Overlay.prototype = {
    __proto__: HTMLDivElement.prototype,

    /**
     * Initializes the overlay element.
     */
    decorate: function() {
      // create the overlay root on this document if its not present
      if (!this.ownerDocument.querySelector('.overlay-root')) {
        var overlayRoot = this.ownerDocument.createElement('div');
        cr.ui.decorate(overlayRoot, OverlayRoot);
        this.ownerDocument.body.appendChild(overlayRoot);
      }

      this.classList.add('overlay');
      this.visible = false;
    },

    onVisibleChanged_: function() {
      var overlayRoot = this.ownerDocument.querySelector('.overlay-root');
      if (this.visible) {
        overlayRoot.showOverlay(this);
      } else {
        overlayRoot.hideOverlay(this);
      }
    }
  };

  /**
   * Shows and hides the overlay. Note that while visible == true, the overlay
   * element will be tempoarily reparented to another place in the DOM.
   */
  cr.defineProperty(Overlay, 'visible', cr.PropertyKind.BOOL_ATTR,
      Overlay.prototype.onVisibleChanged_);

  return {
    Overlay: Overlay
  };
});