(function ($, Drupal) {

"use strict";

var autocomplete;

/**
 * Helper splitting terms from the autocomplete value.
 *
 * @param {String} value
 *
 * @return {Array}
 */
function autocompleteSplitValues (value) {
  // We will match the value against comma-seperated terms.
  var result = [];
  var quote = false;
  var current = '';
  var valueLength = value.length;
  var i, character;

  for (i = 0; i < valueLength; i++) {
    character = value.charAt(i);
    if (character === '"') {
      current += character;
      quote = !quote;
    }
    else if (character === ',' && !quote) {
      result.push(current.trim());
      current = '';
    }
    else {
      current += character;
    }
  }
  if (value.length > 0) {
    result.push($.trim(current));
  }

  return result;
}

/**
 * Returns the last value of an multi-value textfield.
 *
 * @param {String} terms
 *
 * @return {String}
 */
function extractLastTerm (terms) {
  return autocomplete.splitValues(terms).pop();
}

/**
 * The search handler is called before a search is performed.
 *
 * @param {Object} event
 *
 * @return {Boolean}
 */
function searchHandler (event) {
  // Only search when the term is two characters or larger.
  var term = autocomplete.extractLastTerm(event.target.value);
  return term.length >= autocomplete.minLength;
}

/**
 * jQuery UI autocomplete source callback.
 *
 * @param {Object} request
 * @param {Function} response
 */
function sourceData (request, response) {
  /*jshint validthis:true */
  var elementId = this.element.attr('id');

  if (!(elementId in autocomplete.cache)) {
    autocomplete.cache[elementId] = {};
  }

  /**
   * Filter through the suggestions removing all terms already tagged and
   * display the available terms to the user.
   *
   * @param {Object} suggestions
   */
  function showSuggestions (suggestions) {
    var tagged = autocomplete.splitValues(request.term);
    for (var i = 0, il = tagged.length; i < il; i++) {
      var index = suggestions.indexOf(tagged[i]);
      if (index >= 0) {
        suggestions.splice(index, 1);
      }
    }
    response(suggestions);
  }

  /**
   * Transforms the data object into an array and update autocomplete results.
   *
   * @param {Object} data
   */
  function sourceCallbackHandler (data) {
    autocomplete.cache[elementId][term] = data;

    // Send the new string array of terms to the jQuery UI list.
    showSuggestions(data);
  }

  // Get the desired term and construct the autocomplete URL for it.
  var term = autocomplete.extractLastTerm(request.term);

  // Check if the term is already cached.
  if (autocomplete.cache[elementId].hasOwnProperty(term)) {
    showSuggestions(autocomplete.cache[elementId][term]);
  }
  else {
    var options = $.extend({ success: sourceCallbackHandler, data: { q: term } }, autocomplete.ajax);
    /*jshint validthis:true */
    $.ajax(this.element.attr('data-autocomplete-path'), options);
  }
}

/**
 * Handles an autocompletefocus event.
 *
 * @return {Boolean}
 */
function focusHandler () {
  return false;
}

/**
 * Handles an autocompleteselect event.
 *
 * @param {Object} event
 * @param {Object} ui
 *
 * @return {Boolean}
 */
function selectHandler (event, ui) {
  var terms = autocomplete.splitValues(event.target.value);
  // Remove the current input.
  terms.pop();
  // Add the selected item.
  if (ui.item.value.search(",") > 0) {
    terms.push('"' + ui.item.value + '"');
  }
  else {
    terms.push(ui.item.value);
  }
  event.target.value = terms.join(', ');
  // Return false to tell jQuery UI that we've filled in the value already.
  return false;
}

/**
 * Attaches the autocomplete behavior to all required fields.
 */
Drupal.behaviors.autocomplete = {
  attach: function (context) {
    // Act on textfields with the "form-autocomplete" class.
    var $autocomplete = $(context).find('input.form-autocomplete').once('autocomplete');
    if ($autocomplete.length) {
      // Use jQuery UI Autocomplete on the textfield.
      $autocomplete.autocomplete(autocomplete.options);
    }
  },
  detach: function (context, settings, trigger) {
    if (trigger === 'unload') {
      $(context).find('input.form-autocomplete')
        .removeOnce('autocomplete')
        .autocomplete('destroy');
    }
  }
};

/**
 * Autocomplete object implementation.
 */
autocomplete = {
  cache: {},
  // Exposes methods to allow overriding by contrib.
  minLength: 1,
  splitValues: autocompleteSplitValues,
  extractLastTerm: extractLastTerm,
  // jQuery UI autocomplete options.
  options: {
    source: sourceData,
    focus: focusHandler,
    search: searchHandler,
    select: selectHandler
  },
  ajax: {
    dataType: 'json'
  }
};

Drupal.autocomplete = autocomplete;

})(jQuery, Drupal);