class Subquery

class Subquery extends JoinPluginBase {
  
  /**
   * Constructs a Subquery object.
   */
  public function __construct(array $configuration, $plugin_id, $plugin_definition) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
    $this->left_query = $this->configuration['left_query'];
  }
  
  /**
   * Builds the SQL for the join this object represents.
   *
   * @param \Drupal\Core\Database\Query\SelectInterface $select_query
   *   The select query object.
   * @param string $table
   *   The base table to join.
   * @param \Drupal\views\Plugin\views\query\QueryPluginBase $view_query
   *   The source views query.
   */
  public function buildJoin($select_query, $table, $view_query) {
    if (empty($this->configuration['table formula'])) {
      $right_table = "{" . $this->table . "}";
    }
    else {
      $right_table = $this->configuration['table formula'];
    }
    // Add our join condition, using a subquery on the left instead of a field.
    $condition = "({$this->left_query}) = {$table['alias']}.{$this->field}";
    $arguments = [];
    // Tack on the extra.
    // This is just copied verbatim from the parent class, which itself has a
    // bug: https://www.drupal.org/node/1118100.
    if (isset($this->extra)) {
      if (is_array($this->extra)) {
        $extras = [];
        foreach ($this->extra as $info) {
          // Figure out the table name. Remember, only use aliases provided
          // if at all possible.
          $join_table = '';
          if (!array_key_exists('table', $info)) {
            $join_table = $table['alias'] . '.';
          }
          elseif (isset($info['table'])) {
            $join_table = $info['table'] . '.';
          }
          $placeholder = ':views_join_condition_' . $select_query->nextPlaceholder();
          if (is_array($info['value'])) {
            $operator = !empty($info['operator']) ? $info['operator'] : 'IN';
            // Transform from IN() notation to = notation if just one value.
            if (count($info['value']) == 1) {
              $info['value'] = array_shift($info['value']);
              $operator = $operator == 'NOT IN' ? '!=' : '=';
            }
          }
          else {
            $operator = !empty($info['operator']) ? $info['operator'] : '=';
          }
          $extras[] = "{$join_table}{$info['field']} {$operator} {$placeholder}";
          $arguments[$placeholder] = $info['value'];
        }
        if ($extras) {
          if (count($extras) == 1) {
            $condition .= ' AND ' . array_shift($extras);
          }
          else {
            $condition .= ' AND (' . implode(' ' . $this->extraOperator . ' ', $extras) . ')';
          }
        }
      }
      elseif ($this->extra && is_string($this->extra)) {
        $condition .= " AND ({$this->extra})";
      }
    }
    $select_query->addJoin($this->type, $right_table, $table['alias'], $condition, $arguments);
  }

}