<!--
@license
Copyright (c) 2015 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
-->

<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="../iron-menu-behavior/iron-menu-behavior.html">
<link rel="import" href="../iron-behaviors/iron-control-state.html">
<link rel="import" href="../iron-collapse/iron-collapse.html">
<link rel="import" href="../iron-flex-layout/iron-flex-layout.html">
<link rel="import" href="../paper-styles/default-theme.html">
<link rel="import" href="../paper-styles/color.html">
<link rel="import" href="paper-menu-shared-styles.html">

<!--
`<paper-submenu>` is a nested menu inside of a parent `<paper-menu>`. It
consists of a trigger that expands or collapses another `<paper-menu>`:

    <paper-menu>
      <paper-submenu>
        <paper-item class="menu-trigger">Topics</paper-item>
        <paper-menu class="menu-content">
          <paper-item>Topic 1</paper-item>
          <paper-item>Topic 2</paper-item>
          <paper-item>Topic 3</paper-item>
        </paper-menu>
      </paper-submenu>
      <paper-submenu>
        <paper-item class="menu-trigger">Faves</paper-item>
        <paper-menu class="menu-content">
          <paper-item>Fave 1</paper-item>
          <paper-item>Fave 2</paper-item>
        </paper-menu>
      </paper-submenu>
      <paper-submenu disabled>
        <paper-item class="menu-trigger">Unavailable</paper-item>
        <paper-menu class="menu-content">
          <paper-item>Disabled 1</paper-item>
          <paper-item>Disabled 2</paper-item>
        </paper-menu>
      </paper-submenu>
    </paper-menu>

Just like in `<paper-menu>`, the focused item is highlighted, and the selected
item has bolded text. Please see the `<paper-menu>` docs for which attributes
(such as `multi` and `selected`), and styling options are available for the
`menu-content` menu.

@group Paper Elements
@element paper-submenu
@hero hero.svg
@demo demo/index.html
-->

<dom-module id="paper-submenu">
  <template>
    <style include="paper-menu-shared-styles"></style>

    <div class="selectable-content" on-tap="_onTap">
      <content id="trigger" select=".menu-trigger"></content>
    </div>
    <iron-collapse id="collapse" opened="{{opened}}">
      <content id="content" select=".menu-content"></content>
    </iron-collapse>
  </template>

  <script>

  (function() {

    Polymer({

      is: 'paper-submenu',

      properties: {
        /**
         * Fired when the submenu is opened.
         *
         * @event paper-submenu-open
         */

        /**
         * Fired when the submenu is closed.
         *
         * @event paper-submenu-close
         */

        /**
         * Set opened to true to show the collapse element and to false to hide it.
         *
         * @attribute opened
         */
        opened: {
          type: Boolean,
          value: false,
          notify: true,
          observer: '_openedChanged'
        }
      },

      behaviors: [
        Polymer.IronControlState
      ],

      listeners: {
        'focus': '_onFocus'
      },

      get __parent() {
        return Polymer.dom(this).parentNode;
      },

      get __trigger() {
        return Polymer.dom(this.$.trigger).getDistributedNodes()[0];
      },

      get __content() {
        return Polymer.dom(this.$.content).getDistributedNodes()[0];
      },

      attached: function() {
        this.listen(this.__parent, 'iron-activate', '_onParentIronActivate');
      },

      dettached: function() {
        this.unlisten(this.__parent, 'iron-activate', '_onParentIronActivate');
      },

      /**
       * Expand the submenu content.
       */
      open: function() {
        if (!this.disabled && !this._active) {
          this.$.collapse.show();
          this._active = true;
          this.__trigger && this.__trigger.classList.add('iron-selected');
          this.__content && this.__content.focus();
        }
      },

      /**
       * Collapse the submenu content.
       */
      close: function() {
        if (this._active) {
          this.$.collapse.hide();
          this._active = false;
          this.__trigger && this.__trigger.classList.remove('iron-selected');
        }
      },

      /**
       * Toggle the submenu.
       */
      toggle: function() {
        if (this._active) {
          this.close();
        } else {
          this.open();
        }
      },

      /**
       * A handler that is called when the trigger is tapped.
       */
      _onTap: function(e) {
        if (!this.disabled) {
          this.toggle();
        }
      },

      /**
       * Toggles the submenu content when the trigger is tapped.
       */
      _openedChanged: function(opened, oldOpened) {
        if (opened) {
          this.fire('paper-submenu-open');
        } else if (oldOpened != null) {
          this.fire('paper-submenu-close');
        }
      },

      /**
       * A handler that is called when `iron-activate` is fired.
       *
       * @param {CustomEvent} event An `iron-activate` event.
       */
      _onParentIronActivate: function(event) {
        var parent = this.__parent;
        if (Polymer.dom(event).localTarget === parent) {
          // The activated item can either be this submenu, in which case it
          // should be expanded, or any of the other sibling submenus, in which
          // case this submenu should be collapsed.
          if (event.detail.item !== this && !parent.multi) {
            this.close();
          }
        }
      },

      /**
       * If the dropdown is open when disabled becomes true, close the
       * dropdown.
       *
       * @param {boolean} disabled True if disabled, otherwise false.
       */
      _disabledChanged: function(disabled) {
        Polymer.IronControlState._disabledChanged.apply(this, arguments);
        if (disabled && this._active) {
          this.close();
        }
      },

      /**
       * Handler that is called when the menu receives focus.
       *
       * @param {FocusEvent} event A focus event.
       */
      _onFocus: function(event) {
        this.__trigger && this.__trigger.focus();
      }

    });

  })();
</script>
</dom-module>