Club Drupal

 * Works with a Date argument, the argument filters

 * the view and the pager provides back/next navigation.

 * - The pager id: Set an id to be used as the identifier

 *    in the url for pager values, defaults to 'date'.

 * - Pager position: Choose whether to display the date

 *    pager above, below, or both above and below the content.

 * - Link format: Choose whether the pager links will be in t

 *    he simple 'calendar/2011-12' format or the

 *    more complex 'calendar/?date=2011-12' pager format.

 *    The second one is more likely to work correctly

 *    if the pager is used in blocks and panels.

 * The pager works in combination with a Date argument

 * and it will use the date fields and granularity

 * set in that argument to create its back/next links.

 * If the view has no Date argument, the pager can

 * do nothing. The argument can either be a 'Date' argument

 * that lets you select one or more date fields

 * in the argument, or the simple 'Content' argument for an

 * individual date field. It must be an

 * The pager could technically create a query of its own rather

 * than depending on the date argument to

 * set the query, but it has only a limited set of tools to work

 * with because it is a plugin, not a handler:

 * it has no knowledge about relationships, it cannot use the

 * ensure_my_table() function, plugins are not even invoked in pre_query(),

 * so can't do anything there.

 * My conclusion was that the date pager simply

 * is not powerful enough to create its own queries for

 * date fields, which require very complex queries.

 * Instead, we can combine this with a date argument and

 * let the argument create the query and let the pager

 * just provide the back/next links. If there is no

 * There are still other problems. The pager is not even

 * initialized until after all the handlers

 * have created their queries, so it has no chance

 * to alter values ahead of that. And the argument

 * has no knowledge of the pager, so it can't check

 * for pager values before the query is created.

 * The solution used here is to let the argument create

 * the original query. The pager query

 * runs after that, so the pager checks to see

 * if there is a pager value that needs to be used in the query.

 * The date argument has identified the placeholders

 * it used in the query. So if a change is needed,

 * we can swap the pager value into the query created

 * by the date argument and adjust the

 * $view->date_info values set by the argument accordingly

 * so the theme will pick up the new information.

// @codingStandardsIgnoreStart

    $options['skip_empty_pages'] = array('default' => FALSE);

    $form['skip_empty_pages'] = array(

      '#title' => t('Skip empty pages'),

      '#type' => 'checkbox',

      '#description' => t('When selected, the pager will not display pages with no result for the given date. This causes a slight performance degradation because two additional queries need to be executed.'),

      '#default_value' => $this->options['skip_empty_pages'],

    );

          $this->set_argument_value($argument, $value);

        // Write date_info to store information to be used

        // in the theming functions.

        if (empty($this->view->date_info)) {

          $this->view->date_info = new stdClass();

        }

        $this->view->date_info->limit = $argument->limit;

        $this->view->date_info->url = $this->view->get_url();

        $this->view->date_info->pager_id = $this->options['date_id'];

        $this->view->date_info->date_pager_position = $this->options['pager_position'];

        $this->view->date_info->date_pager_format = $this->options['link_format'];

        $this->view->date_info->skip_empty_pages = $this->options['skip_empty_pages'] == 1;

        // Execute two additional queries to find

        // the previous and next page with values.

        if ($this->view->date_info->skip_empty_pages) {

          $q = clone $argument->query;

          $field = $argument->table_alias . '.' . $argument->real_field;

          $fieldsql = $date_handler->sql_field($field);

          $fieldsql = $date_handler->sql_format($format, $fieldsql);

          $q->clear_fields();

          $q->orderby = array();

          $q->set_distinct(TRUE, TRUE);

          // Date limits of this argument.

          $datelimits = $argument->date_handler->arg_range($argument->limit[0] . '--' . $argument->limit[1]);

          // Find the first two dates between the minimum date

          // and the upper bound of the current value.

          $q->add_orderby(NULL, $fieldsql, 'DESC', 'date');

          $this->set_argument_placeholders($this->view->date_info->placeholders, $datelimits[0], $argument->max_date, $q, $format);

          $compiledquery = $q->query();

          $compiledquery->range(0, 2);

          $results = $compiledquery->execute()->fetchCol(0);

          $prevdate = array_shift($results);

          $prevdatealt = array_shift($results);

          // Find the first two dates between the lower bound

          // of the current value and the maximum date.

          $q->add_orderby(NULL, $fieldsql, 'ASC', 'date');

          $this->set_argument_placeholders($this->view->date_info->placeholders, $argument->min_date, $datelimits[1], $q, $format);

          $compiledquery = $q->query();

          $compiledquery->range(0, 2);

          $results = $compiledquery->execute()->fetchCol(0);

          $nextdate = array_shift($results);

          $nextdatealt = array_shift($results);

          // Set the default value of the query to $prevfirst or $nextfirst

          // when there is no value and $prevsecond or $nextsecond is set.

          if (empty($value)) {

            // @Todo find out which of $prevdate or $nextdate is closest to the

            // default argument date value and choose that one.

            if ($prevdate && $prevdatealt) {

              $this->set_argument_value($argument, $prevdate);

              $value = $prevdate;

              $prevdate = $prevdatealt;

              // If the first next date is the same as the first previous date,

              // move to the following next date.

              if ($value == $nextdate) {

                $nextdate = $nextdatealt;

                $nextdatealt = NULL;

              }

            }

            elseif ($nextdate && $nextdatealt) {

              $this->set_argument_value($argument, $nextdate);

              $value = $nextdate;

              $nextdate = $nextdatealt;

              // If the first previous date is the same as the first next date,

              // move to the following previous date.

              if ($value == $prevdate) {

                $prevdate = $prevdatealt;

                $prevdatealt = NULL;

              }

            }

          }

          else {

            // $prevdate and $nextdate are the same as $value, so move to

            // the next values.

            $prevdate = $prevdatealt;

            $nextdate = $nextdatealt;

          }

          $this->view->date_info->prev_date = $prevdate ? new DateObject($prevdate, NULL, $format) : NULL;

          $this->view->date_info->next_date = $nextdate ? new DateObject($nextdate, NULL, $format) : NULL;

        }

        else {

          $this->view->date_info->prev_date = clone($argument->min_date);

          date_modify($this->view->date_info->prev_date, '-1 ' . $argument->date_handler->granularity);

          $this->view->date_info->next_date = clone($argument->max_date);

          date_modify($this->view->date_info->next_date, '+1 ' . $argument->date_handler->granularity);

        }

        // Write the date_info properties that depend on the current value.

      $this->set_argument_placeholders($this->view->date_info->placeholders, $this->view->date_info->min_date, $this->view->date_info->max_date, $this->view->query, $format);

    }

  }

  function set_argument_value($argument, $value) {

    $argument->argument = $value;

    $argument->date_range = $argument->date_handler->arg_range($value);

    $argument->min_date = $argument->date_range[0];

    $argument->max_date = $argument->date_range[1];

    // $argument->is_default works correctly for normal arguments, but does not

    // work correctly if we are swapping in a new value from the pager.

    $argument->is_default = FALSE;

  }

  function set_argument_placeholders($placeholders, $mindate, $maxdate, $query, $format) {

    $count = count($placeholders);

    foreach ($query->where as $group => $data) {

      foreach ($data['conditions'] as $delta => $condition) {

        if (array_key_exists('value', $condition) && is_array($condition['value'])) {

          foreach ($condition['value'] as $placeholder => $placeholder_value) {

            if (array_key_exists($placeholder, $placeholders)) {

              // If we didn't get a match, this is a > $min < $max query that uses the view

              // min and max dates as placeholders.

              $date = ($count == 2) ? $mindate : $maxdate;

              $next_placeholder = array_shift($placeholders);

              $query->where[$group]['conditions'][$delta]['value'][$placeholder] = $date->format($format);

              $count--;

}

// @codingStandardsIgnoreEnd