<!--
@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
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-->

<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="../iron-validatable-behavior/iron-validatable-behavior.html">
<link rel="import" href="../iron-form-element-behavior/iron-form-element-behavior.html">

<script>

  /**
   * Use `Polymer.IronCheckedElementBehavior` to implement a custom element
   * that has a `checked` property, which can be used for validation if the
   * element is also `required`. Element instances implementing this behavior
   * will also be registered for use in an `iron-form` element.
   *
   * @demo demo/index.html
   * @polymerBehavior Polymer.IronCheckedElementBehavior
   */
  Polymer.IronCheckedElementBehaviorImpl = {

    properties: {
      /**
       * Fired when the checked state changes.
       *
       * @event iron-change
       */

      /**
       * Gets or sets the state, `true` is checked and `false` is unchecked.
       */
      checked: {
        type: Boolean,
        value: false,
        reflectToAttribute: true,
        notify: true,
        observer: '_checkedChanged'
      },

      /**
       * If true, the button toggles the active state with each tap or press
       * of the spacebar.
       */
      toggles: {
        type: Boolean,
        value: true,
        reflectToAttribute: true
      },

      /* Overriden from Polymer.IronFormElementBehavior */
      value: {
        type: String,
        value: ''
      }
    },

    observers: [
      '_requiredChanged(required)'
    ],

    /**
     * Returns false if the element is required and not checked, and true otherwise.
     * @return {boolean} true if `required` is false, or if `required` and `checked` are both true.
     */
    _getValidity: function(_value) {
      return this.disabled || !this.required || (this.required && this.checked);
    },

    /**
     * Update the aria-required label when `required` is changed.
     */
    _requiredChanged: function() {
      if (this.required) {
        this.setAttribute('aria-required', 'true');
      } else {
        this.removeAttribute('aria-required');
      }
    },

    /**
     * Update the element's value when checked.
     */
    _checkedChanged: function() {
      this.active = this.checked;
      // Unless the user has specified a value, a checked element has the
      // default value "on" when checked.
      if (this.value === '')
        this.value = this.checked ? 'on' : '';
      this.fire('iron-change');
    }
  };

  /** @polymerBehavior Polymer.IronCheckedElementBehavior */
  Polymer.IronCheckedElementBehavior = [
    Polymer.IronFormElementBehavior,
    Polymer.IronValidatableBehavior,
    Polymer.IronCheckedElementBehaviorImpl
  ];

</script>