<!--
Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
Code distributed by Google as part of the polymer project is also
subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
-->

<!--
`core-drawer-panel` contains a drawer panel and a main panel.  The drawer
and the main panel are side-by-side with drawer on the left.  When browser
window size is smaller than the `responsiveWidth`, `core-drawer-panel`
changes to narrow layout.  In narrow layout, the drawer will be stacked on top
of the main panel.  The drawer will be slided in/out to hide/reveal the main
panel.

Use the attribute `drawer` to indicate the element is a drawer panel and
`main` to indicate is a main panel.

Example:

    <core-drawer-panel>
      <div drawer> Drawer panel... </div>
      <div main> Main panel... </div>
    </core-drawer-panel>

The drawer and the main panels are not scrollable.  You can set CSS overflow
property on the elements to make them scrollable or use `core-header-panel`.

Example:

    <core-drawer-panel>
      <core-header-panel drawer>
        <core-toolbar></core-toolbar>
        <div> Drawer content... </div>
      </core-header-panel>
      <core-header-panel main>
        <core-toolbar></core-toolbar>
        <div> Main content... </div>
      </core-header-panel>
    </core-drawer-panel>

To position the drawer to the right, add `rightDrawer` attribute.

    <core-drawer-panel rightDrawer>
      <div drawer> Drawer panel... </div>
      <div main> Main panel... </div>
    </core-drawer-panel>

@group Polymer Core Elements
@element core-drawer-panel
@homepage github.io
-->

<link rel="import" href="../core-media-query/core-media-query.html">
<link rel="import" href="../core-selector/core-selector.html">

<polymer-element name="core-drawer-panel" touch-action="auto">
<template>

  <link rel="stylesheet" href="core-drawer-panel.css">

  <core-media-query query="max-width: {{responsiveWidth}}" queryMatches="{{queryMatches}}"></core-media-query>

  <core-selector class="{{ {'narrow-layout' : queryMatches, transition : transition, dragging : dragging, 'right-drawer': rightDrawer} | tokenList }}" valueattr="id" selected="{{selected}}">

    <div id="main" _style="left: {{ narrow || rightDrawer ? '0' : drawerWidth }}; right: {{ rightDrawer ? (narrow ? '' : drawerWidth) : '' }};">
      <content select="[main]"></content>
      <div id="scrim" on-tap="{{togglePanel}}"></div>
    </div>

    <div id="drawer" _style="width: {{ drawerWidth }}">
      <content select="[drawer]"></content>
    </div>

  </core-selector>

</template>
<script>

  Polymer('core-drawer-panel', {

    /**
     * Fired when the narrow layout changes.
     *
     * @event core-responsive-change
     * @param {Object} detail
     * @param {boolean} detail.narrow true if the panel is in narrow layout.
     */

    publish: {

      /**
       * Width of the drawer panel.
       *
       * @attribute drawerWidth
       * @type string
       * @default '256px'
       */
      drawerWidth: '256px',

      /**
       * Max-width when the panel changes to narrow layout.
       *
       * @attribute responsiveWidth
       * @type string
       * @default '640px'
       */
      responsiveWidth: '640px',

      /**
       * The panel that is being selected. `drawer` for the drawer panel and
       * `main` for the main panel.
       *
       * @attribute selected
       * @type string
       * @default null
       */
      selected: {value: null, reflect: true},

      /**
       * The panel to be selected when `core-drawer-panel` changes to narrow
       * layout.
       *
       * @attribute defaultSelected
       * @type string
       * @default 'main'
       */
      defaultSelected: 'main',

      /**
       * Returns true if the panel is in narrow layout.  This is useful if you
       * need to show/hide elements based on the layout.
       *
       * @attribute narrow
       * @type boolean
       * @default false
       */
      narrow: {value: false, reflect: true},

      /**
       * If true, position the drawer to the right.
       *
       * @attribute rightDrawer
       * @type boolean
       * @default false
       */
      rightDrawer: false,

      /**
       * If true, swipe to open/close the drawer is disabled.
       *
       * @attribute disableSwipe
       * @type boolean
       * @default false
       */
      disableSwipe: false
    },

    eventDelegates: {
      trackstart: 'trackStart',
      trackx: 'trackx',
      trackend: 'trackEnd',
      down: 'touchStart',
      up: 'touchEnd'
    },

    // Whether the transition is enabled.
    transition: false,

    // How many pixels on the side of the screen are sensitive to edge swipes and peek.
    edgeSwipeSensitivity: 15,

    // Whether the drawer is peeking out from the edge.
    peeking: false,

    // Whether the user is dragging the drawer interactively.
    dragging: false,

    // Whether the browser has support for the transform CSS property.
    hasTransform: true,

    // Whether the browser has support for the will-change CSS property.
    hasWillChange: true,

    created: function() {
      this.hasTransform = 'transform' in this.style;
      this.hasWillChange = 'willChange' in this.style;
    },

    domReady: function() {
      // to avoid transition at the beginning e.g. page loads
      // NOTE: domReady is already raf delayed and delaying another frame
      // ensures a layout has occurred.
      this.async(function() {
        this.transition = true;
      });
    },

    /**
     * Toggles the panel open and closed.
     *
     * @method togglePanel
     */
    togglePanel: function() {
      this.selected = this.selected === 'main' ? 'drawer' : 'main';
    },

    /**
     * Opens the drawer.
     *
     * @method openDrawer
     */
    openDrawer: function() {
      this.selected = 'drawer';
    },

    /**
     * Closes the drawer.
     *
     * @method closeDrawer
     */
    closeDrawer: function() {
      this.selected = 'main';
    },

    queryMatchesChanged: function() {
      if (this.queryMatches) {
        this.selected = this.defaultSelected;
      }
      this.narrow = this.queryMatches;
      this.setAttribute('touch-action', this.swipeAllowed() ? 'pan-y' : '');
      this.fire('core-responsive-change', {narrow: this.narrow});
    },

    swipeAllowed: function() {
      return this.narrow && !this.disableSwipe;
    },

    startEdgePeek: function() {
      this.width = this.$.drawer.offsetWidth;
      this.moveDrawer(this.translateXForDeltaX(this.rightDrawer ?
          -this.edgeSwipeSensitivity : this.edgeSwipeSensitivity));
      this.peeking = true;
    },

    stopEdgePeak: function() {
      if (this.peeking) {
        this.peeking = false;
        this.moveDrawer(null);
      }
    },

    touchStart: function(e) {
      if (!this.dragging && this.selected === 'main' && this.isEdgeTouch(e))
        this.startEdgePeek();
    },

    touchEnd: function(e) {
      this.stopEdgePeak();
    },

    isEdgeTouch: function(e) {
      return this.swipeAllowed() && (this.rightDrawer ?
        e.pageX >= this.offsetWidth - this.edgeSwipeSensitivity :
        e.pageX <= this.edgeSwipeSensitivity);
    },

    // swipe support for the drawer, inspired by
    // https://github.com/Polymer/core-drawer-panel/pull/6
    trackStart : function(e) {
      if (this.swipeAllowed()) {
        this.dragging = true;

        if (this.selected === 'main')
          this.dragging = this.peeking || this.isEdgeTouch(e);

        if (this.dragging) {
          this.width = this.$.drawer.offsetWidth;
          this.transition = false;
          e.preventTap();
        }
      }
    },

    translateXForDeltaX: function(deltaX) {
      if (this.rightDrawer) {
        return Math.max(0, (this.selected === 'main') ? this.width + deltaX : deltaX);
      } else {
        return Math.min(0, (this.selected === 'main') ? deltaX - this.width : deltaX);
      }
    },

    trackx : function(e) {
      if (this.dragging) {
        if (this.peeking) {
          if (Math.abs(e.dx) <= this.edgeSwipeSensitivity)
            return; // Ignore trackx until we move past the edge peek.
          this.peeking = false;
        }
        this.moveDrawer(this.translateXForDeltaX(e.dx));
      }
    },

    trackEnd : function(e) {
      if (this.dragging) {
        this.dragging = false;
        this.transition = true;
        this.moveDrawer(null);

        if (this.rightDrawer) {
          this.selected = e.xDirection > 0 ? 'main' : 'drawer';
        } else {
          this.selected = e.xDirection > 0 ? 'drawer' : 'main';
        }
      }
    },

    transformForTranslateX: function (translateX) {
      if (translateX === null)
        return '';
      return this.hasWillChange ? 'translateX(' + translateX + 'px)' : 'translate3d(' + translateX + 'px, 0, 0)';
    },

    moveDrawer: function(translateX) {
      var s = this.$.drawer.style;

      if (this.hasTransform) {
        s.transform = this.transformForTranslateX(translateX);
      } else {
        s.webkitTransform = this.transformForTranslateX(translateX);
      }
    },

  });

</script>
</polymer-element>
