(function(window) {
  'use strict'

  var htmlEscapes = {
    '&': '&',
    '<': '&lt;',
    '>': '&gt;',
    '"': '&quot;',
    '\'': '&#x27;',
    '`': '&#x60;'
  }

  var escapeHtmlChar = function(chr) {
    return htmlEscapes[chr]
  }

  var reUnescapedHtml = /[&<>"'`]/g
  var reHasUnescapedHtml = new RegExp(reUnescapedHtml.source)

  var escape = function(string) {
    return (string && reHasUnescapedHtml.test(string)) ?
      string.replace(reUnescapedHtml, escapeHtmlChar) :
      string
  }

  /**
   * Sets up defaults for all the Template methods such as a default template
   *
   * @constructor
   */
  function Template() {
    this.defaultTemplate = '<li data-id="{{id}}" class="{{completed}}">' +
      '<div class="view">' +
      '<input class="toggle" type="checkbox" {{checked}}>' +
      '<label>{{title}}</label>' +
      '<button class="destroy"></button>' +
      '</div>' +
      '</li>'
  }

  /**
   * Creates an <li> HTML string and returns it for placement in your app.
   *
   * NOTE: In real life you should be using a templating engine such as Mustache
   * or Handlebars, however, this is a vanilla JS example.
   *
   * @param {object} data The object containing keys you want to find in the
   *                      template to replace.
   * @returns {string} HTML String of an <li> element
   *
   * @example
   * view.show({
	 *	id: 1,
	 *	title: "Hello World",
	 *	completed: 0,
	 * });
   */
  Template.prototype.show = function(data) {
    var i, l
    var view = ''

    for (i = 0, l = data.length; i < l; i++) {
      var template = this.defaultTemplate
      var completed = ''
      var checked = ''

      if (data[i].completed) {
        completed = 'completed'
        checked = 'checked'
      }

      template = template.replace('{{id}}', data[i].id)
      template = template.replace('{{title}}', escape(data[i].title))
      template = template.replace('{{completed}}', completed)
      template = template.replace('{{checked}}', checked)

      view = view + template
    }

    return view
  }

  /**
   * Displays a counter of how many to dos are left to complete
   *
   * @param {number} activeTodos The number of active todos.
   * @returns {string} String containing the count
   */
  Template.prototype.itemCounter = function(activeTodos) {
    var plural = activeTodos === 1 ? '' : 's'

    return '<strong>' + activeTodos + '</strong> item' + plural + ' left'
  }

  /**
   * Updates the text within the "Clear completed" button
   *
   * @param  {[type]} completedTodos The number of completed todos.
   * @returns {string} String containing the count
   */
  Template.prototype.clearCompletedButton = function(completedTodos) {
    if (completedTodos > 0) {
      return 'Clear completed'
    } else {
      return ''
    }
  }

  // Export to window
  window.app = window.app || {}
  window.app.Template = Template
})(window)