/**
 * @file
 * JavaScript API for the History module, with client-side caching.
 *
 * May only be loaded for authenticated users, with the History module enabled.
 */

(function ($, Drupal, drupalSettings, storage) {
  const currentUserID = parseInt(drupalSettings.user.uid, 10);

  // Any comment that is older than 30 days is automatically considered read,
  // so for these we don't need to perform a request at all!
  const secondsIn30Days = 2592000;
  const thirtyDaysAgo = Math.round(new Date().getTime() / 1000) - secondsIn30Days;

  // Use the data embedded in the page, if available.
  let embeddedLastReadTimestamps = false;
  if (drupalSettings.history && drupalSettings.history.lastReadTimestamps) {
    embeddedLastReadTimestamps = drupalSettings.history.lastReadTimestamps;
  }

  /**
   * @namespace
   */
  Drupal.history = {

    /**
     * Fetch "last read" timestamps for the given nodes.
     *
     * @param {Array} nodeIDs
     *   An array of node IDs.
     * @param {function} callback
     *   A callback that is called after the requested timestamps were fetched.
     */
    fetchTimestamps(nodeIDs, callback) {
      // Use the data embedded in the page, if available.
      if (embeddedLastReadTimestamps) {
        callback();
        return;
      }

      $.ajax({
        url: Drupal.url('history/get_node_read_timestamps'),
        type: 'POST',
        data: { 'node_ids[]': nodeIDs },
        dataType: 'json',
        success(results) {
          Object.keys(results || {}).forEach((nodeID) => {
            storage.setItem(`Drupal.history.${currentUserID}.${nodeID}`, results[nodeID]);
          });
          callback();
        },
      });
    },

    /**
     * Get the last read timestamp for the given node.
     *
     * @param {number|string} nodeID
     *   A node ID.
     *
     * @return {number}
     *   A UNIX timestamp.
     */
    getLastRead(nodeID) {
      // Use the data embedded in the page, if available.
      if (embeddedLastReadTimestamps && embeddedLastReadTimestamps[nodeID]) {
        return parseInt(embeddedLastReadTimestamps[nodeID], 10);
      }
      return parseInt(storage.getItem(`Drupal.history.${currentUserID}.${nodeID}`) || 0, 10);
    },

    /**
     * Marks a node as read, store the last read timestamp client-side.
     *
     * @param {number|string} nodeID
     *   A node ID.
     */
    markAsRead(nodeID) {
      $.ajax({
        url: Drupal.url(`history/${nodeID}/read`),
        type: 'POST',
        dataType: 'json',
        success(timestamp) {
          // If the data is embedded in the page, don't store on the client
          // side.
          if (embeddedLastReadTimestamps && embeddedLastReadTimestamps[nodeID]) {
            return;
          }

          storage.setItem(`Drupal.history.${currentUserID}.${nodeID}`, timestamp);
        },
      });
    },

    /**
     * Determines whether a server check is necessary.
     *
     * Any content that is >30 days old never gets a "new" or "updated"
     * indicator. Any content that was published before the oldest known reading
     * also never gets a "new" or "updated" indicator, because it must've been
     * read already.
     *
     * @param {number|string} nodeID
     *   A node ID.
     * @param {number} contentTimestamp
     *   The time at which some content (e.g. a comment) was published.
     *
     * @return {bool}
     *   Whether a server check is necessary for the given node and its
     *   timestamp.
     */
    needsServerCheck(nodeID, contentTimestamp) {
      // First check if the content is older than 30 days, then we can bail
      // early.
      if (contentTimestamp < thirtyDaysAgo) {
        return false;
      }

      // Use the data embedded in the page, if available.
      if (embeddedLastReadTimestamps && embeddedLastReadTimestamps[nodeID]) {
        return contentTimestamp > parseInt(embeddedLastReadTimestamps[nodeID], 10);
      }

      const minLastReadTimestamp = parseInt(storage.getItem(`Drupal.history.${currentUserID}.${nodeID}`) || 0, 10);
      return contentTimestamp > minLastReadTimestamp;
    },
  };
}(jQuery, Drupal, drupalSettings, window.localStorage));
