konami-code.html

<!--
@license
Copyright (c) 2016 Abdón Rodríguez Davila (@abdonrd). All rights reserved.
This code may only be used under the MIT style license found at https://abdonrd.github.io/LICENSE.txt
-->

<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="../iron-a11y-keys-behavior/iron-a11y-keys-behavior.html">

<!--
Web Component (with Polymer) to listen the Konami Code (↑↑↓↓←→←→BA).

@demo demo/index.html
-->

<dom-module id="konami-code">
  <script>
    Polymer({
      is: 'konami-code',

      properties: {
        _konamiCode: {
          type: Array,
          value: function() {
            return [
              'up',
              'up',
              'down',
              'down',
              'left',
              'right',
              'left',
              'right',
              'b',
              'a'
            ];
          }
        },

        _nextCodeIndex: {
          type: Number,
          value: 0
        },

        _keydownListener: {
          type: Object
        }
      },

      attached: function() {
        this._keydownListener = this.__onBodyKeydown.bind(this);
        document.body.addEventListener('keydown', this._keydownListener);
      },

      detached: function() {
        document.body.removeEventListener('keydown', this._keydownListener);
      },

      __onBodyKeydown: function(event) {
        if (this._isExpectedKey(event)) {
          this._nextCodeIndex += 1;
        } else {
          this._nextCodeIndex = 0;
        }

        if (this._isCodeComplete()) {
          this.fire('code-completed');
          this._nextCodeIndex = 0;
        }
      },

      _isExpectedKey: function(event) {
        var expectedKey = this._konamiCode[this._nextCodeIndex];

        // eslint-disable-next-line max-len
        return Polymer.IronA11yKeysBehavior.keyboardEventMatchesKeys(event, expectedKey);
      },

      _isCodeComplete: function() {
        return this._nextCodeIndex === this._konamiCode.length;
      }

      /**
       * Fired when the code is completed.
       *
       * @event code-completed
       */
    });
  </script>
</dom-module>