/**
 * @file
 * Machine name functionality.
 */

(function ($, Drupal, drupalSettings) {
  /**
   * Attach the machine-readable name form element behavior.
   *
   * @type {Drupal~behavior}
   *
   * @prop {Drupal~behaviorAttach} attach
   *   Attaches machine-name behaviors.
   */
  Drupal.behaviors.machineName = {

    /**
     * Attaches the behavior.
     *
     * @param {Element} context
     *   The context for attaching the behavior.
     * @param {object} settings
     *   Settings object.
     * @param {object} settings.machineName
     *   A list of elements to process, keyed by the HTML ID of the form
     *   element containing the human-readable value. Each element is an object
     *   defining the following properties:
     *   - target: The HTML ID of the machine name form element.
     *   - suffix: The HTML ID of a container to show the machine name preview
     *     in (usually a field suffix after the human-readable name
     *     form element).
     *   - label: The label to show for the machine name preview.
     *   - replace_pattern: A regular expression (without modifiers) matching
     *     disallowed characters in the machine name; e.g., '[^a-z0-9]+'.
     *   - replace: A character to replace disallowed characters with; e.g.,
     *     '_' or '-'.
     *   - standalone: Whether the preview should stay in its own element
     *     rather than the suffix of the source element.
     *   - field_prefix: The #field_prefix of the form element.
     *   - field_suffix: The #field_suffix of the form element.
     */
    attach(context, settings) {
      const self = this;
      const $context = $(context);
      let timeout = null;
      let xhr = null;

      function clickEditHandler(e) {
        const data = e.data;
        data.$wrapper.removeClass('visually-hidden');
        data.$target.trigger('focus');
        data.$suffix.hide();
        data.$source.off('.machineName');
      }

      function machineNameHandler(e) {
        const data = e.data;
        const options = data.options;
        const baseValue = $(e.target).val();

        const rx = new RegExp(options.replace_pattern, 'g');
        const expected = baseValue.toLowerCase().replace(rx, options.replace).substr(0, options.maxlength);

        // Abort the last pending request because the label has changed and it
        // is no longer valid.
        if (xhr && xhr.readystate !== 4) {
          xhr.abort();
          xhr = null;
        }

        // Wait 300 milliseconds for Ajax request since the last event to update
        // the machine name i.e., after the user has stopped typing.
        if (timeout) {
          clearTimeout(timeout);
          timeout = null;
        }
        if (baseValue.toLowerCase() !== expected) {
          timeout = setTimeout(() => {
            xhr = self.transliterate(baseValue, options).done((machine) => {
              self.showMachineName(machine.substr(0, options.maxlength), data);
            });
          }, 300);
        }
        else {
          self.showMachineName(expected, data);
        }
      }

      Object.keys(settings.machineName).forEach((source_id) => {
        let machine = '';
        let eventData;
        const options = settings.machineName[source_id];

        const $source = $context.find(source_id).addClass('machine-name-source').once('machine-name');
        const $target = $context.find(options.target).addClass('machine-name-target');
        const $suffix = $context.find(options.suffix);
        const $wrapper = $target.closest('.js-form-item');
        // All elements have to exist.
        if (!$source.length || !$target.length || !$suffix.length || !$wrapper.length) {
          return;
        }
        // Skip processing upon a form validation error on the machine name.
        if ($target.hasClass('error')) {
          return;
        }
        // Figure out the maximum length for the machine name.
        options.maxlength = $target.attr('maxlength');
        // Hide the form item container of the machine name form element.
        $wrapper.addClass('visually-hidden');
        // Determine the initial machine name value. Unless the machine name
        // form element is disabled or not empty, the initial default value is
        // based on the human-readable form element value.
        if ($target.is(':disabled') || $target.val() !== '') {
          machine = $target.val();
        }
        else if ($source.val() !== '') {
          machine = self.transliterate($source.val(), options);
        }
        // Append the machine name preview to the source field.
        const $preview = $(`<span class="machine-name-value">${options.field_prefix}${Drupal.checkPlain(machine)}${options.field_suffix}</span>`);
        $suffix.empty();
        if (options.label) {
          $suffix.append(`<span class="machine-name-label">${options.label}: </span>`);
        }
        $suffix.append($preview);

        // If the machine name cannot be edited, stop further processing.
        if ($target.is(':disabled')) {
          return;
        }

        eventData = {
          $source,
          $target,
          $suffix,
          $wrapper,
          $preview,
          options,
        };
        // If it is editable, append an edit link.
        const $link = $(`<span class="admin-link"><button type="button" class="link">${Drupal.t('Edit')}</button></span>`).on('click', eventData, clickEditHandler);
        $suffix.append($link);

        // Preview the machine name in realtime when the human-readable name
        // changes, but only if there is no machine name yet; i.e., only upon
        // initial creation, not when editing.
        if ($target.val() === '') {
          $source.on('formUpdated.machineName', eventData, machineNameHandler)
            // Initialize machine name preview.
            .trigger('formUpdated.machineName');
        }

        // Add a listener for an invalid event on the machine name input
        // to show its container and focus it.
        $target.on('invalid', eventData, clickEditHandler);
      });
    },

    showMachineName(machine, data) {
      const settings = data.options;
      // Set the machine name to the transliterated value.
      if (machine !== '') {
        if (machine !== settings.replace) {
          data.$target.val(machine);
          data.$preview.html(settings.field_prefix + Drupal.checkPlain(machine) + settings.field_suffix);
        }
        data.$suffix.show();
      }
      else {
        data.$suffix.hide();
        data.$target.val(machine);
        data.$preview.empty();
      }
    },

    /**
     * Transliterate a human-readable name to a machine name.
     *
     * @param {string} source
     *   A string to transliterate.
     * @param {object} settings
     *   The machine name settings for the corresponding field.
     * @param {string} settings.replace_pattern
     *   A regular expression (without modifiers) matching disallowed characters
     *   in the machine name; e.g., '[^a-z0-9]+'.
     * @param {string} settings.replace_token
     *   A token to validate the regular expression.
     * @param {string} settings.replace
     *   A character to replace disallowed characters with; e.g., '_' or '-'.
     * @param {number} settings.maxlength
     *   The maximum length of the machine name.
     *
     * @return {jQuery}
     *   The transliterated source string.
     */
    transliterate(source, settings) {
      return $.get(Drupal.url('machine_name/transliterate'), {
        text: source,
        langcode: drupalSettings.langcode,
        replace_pattern: settings.replace_pattern,
        replace_token: settings.replace_token,
        replace: settings.replace,
        lowercase: true,
      });
    },
  };
}(jQuery, Drupal, drupalSettings));
