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);
    }

}