class SelectExtender

class SelectExtender implements SelectInterface {
    
    /**
     * The Select query object we are extending/decorating.
     *
     * @var \Drupal\Core\Database\Query\SelectInterface
     */
    protected $query;
    
    /**
     * The connection object on which to run this query.
     *
     * @var \Drupal\Core\Database\Connection
     */
    protected $connection;
    
    /**
     * A unique identifier for this query object.
     *
     * @var string
     */
    protected $uniqueIdentifier;
    
    /**
     * The placeholder counter.
     *
     * @var int
     */
    protected $placeholder = 0;
    public function __construct(SelectInterface $query, Connection $connection) {
        $this->uniqueIdentifier = uniqid('', TRUE);
        $this->query = $query;
        $this->connection = $connection;
    }
    
    /**
     * {@inheritdoc}
     */
    public function uniqueIdentifier() {
        return $this->uniqueIdentifier;
    }
    
    /**
     * {@inheritdoc}
     */
    public function nextPlaceholder() {
        return $this->placeholder++;
    }
    
    /**
     * {@inheritdoc}
     */
    public function addTag($tag) {
        $this->query
            ->addTag($tag);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasTag($tag) {
        return $this->query
            ->hasTag($tag);
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasAllTags() {
        return call_user_func_array([
            $this->query,
            'hasAllTags',
        ], func_get_args());
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasAnyTag() {
        return call_user_func_array([
            $this->query,
            'hasAnyTag',
        ], func_get_args());
    }
    
    /**
     * {@inheritdoc}
     */
    public function addMetaData($key, $object) {
        $this->query
            ->addMetaData($key, $object);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getMetaData($key) {
        return $this->query
            ->getMetaData($key);
    }
    
    /**
     * {@inheritdoc}
     */
    public function condition($field, $value = NULL, $operator = '=') {
        $this->query
            ->condition($field, $value, $operator);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function &conditions() {
        return $this->query
            ->conditions();
    }
    
    /**
     * {@inheritdoc}
     */
    public function arguments() {
        return $this->query
            ->arguments();
    }
    
    /**
     * {@inheritdoc}
     */
    public function where($snippet, $args = []) {
        $this->query
            ->where($snippet, $args);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function compile(Connection $connection, PlaceholderInterface $queryPlaceholder) {
        return $this->query
            ->compile($connection, $queryPlaceholder);
    }
    
    /**
     * {@inheritdoc}
     */
    public function compiled() {
        return $this->query
            ->compiled();
    }
    
    /**
     * {@inheritdoc}
     */
    public function havingCondition($field, $value = NULL, $operator = '=') {
        $this->query
            ->havingCondition($field, $value, $operator);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function &havingConditions() {
        return $this->query
            ->havingConditions();
    }
    
    /**
     * {@inheritdoc}
     */
    public function havingArguments() {
        return $this->query
            ->havingArguments();
    }
    
    /**
     * {@inheritdoc}
     */
    public function having($snippet, $args = []) {
        $this->query
            ->having($snippet, $args);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function havingCompile(Connection $connection) {
        return $this->query
            ->havingCompile($connection);
    }
    
    /**
     * {@inheritdoc}
     */
    public function havingIsNull($field) {
        $this->query
            ->havingIsNull($field);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function havingIsNotNull($field) {
        $this->query
            ->havingIsNotNull($field);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function havingExists(SelectInterface $select) {
        $this->query
            ->havingExists($select);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function havingNotExists(SelectInterface $select) {
        $this->query
            ->havingNotExists($select);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function extend($extender_name) {
        // We cannot call $this->query->extend(), because with multiple extenders
        // you will replace all the earlier extenders with the last extender,
        // instead of creating list of objects that extend each other.
        $parts = explode('\\', $extender_name);
        $class = end($parts);
        $driver_class = $this->connection
            ->getDriverClass($class);
        if ($driver_class !== $class) {
            return new $driver_class($this, $this->connection);
        }
        return new $extender_name($this, $this->connection);
    }
    
    /* Alter accessors to expose the query data to alter hooks. */
    
    /**
     * {@inheritdoc}
     */
    public function &getFields() {
        return $this->query
            ->getFields();
    }
    
    /**
     * {@inheritdoc}
     */
    public function &getExpressions() {
        return $this->query
            ->getExpressions();
    }
    
    /**
     * {@inheritdoc}
     */
    public function &getOrderBy() {
        return $this->query
            ->getOrderBy();
    }
    
    /**
     * {@inheritdoc}
     */
    public function &getGroupBy() {
        return $this->query
            ->getGroupBy();
    }
    
    /**
     * {@inheritdoc}
     */
    public function &getTables() {
        return $this->query
            ->getTables();
    }
    
    /**
     * {@inheritdoc}
     */
    public function &getUnion() {
        return $this->query
            ->getUnion();
    }
    
    /**
     * {@inheritdoc}
     */
    public function escapeLike($string) {
        return $this->query
            ->escapeLike($string);
    }
    
    /**
     * {@inheritdoc}
     */
    public function escapeField($string) {
        $this->query
            ->escapeField($string);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getArguments(?PlaceholderInterface $queryPlaceholder = NULL) {
        return $this->query
            ->getArguments($queryPlaceholder);
    }
    
    /**
     * {@inheritdoc}
     */
    public function isPrepared() {
        return $this->query
            ->isPrepared();
    }
    
    /**
     * {@inheritdoc}
     */
    public function preExecute(?SelectInterface $query = NULL) {
        // If no query object is passed in, use $this.
        if (!isset($query)) {
            $query = $this;
        }
        return $this->query
            ->preExecute($query);
    }
    
    /**
     * {@inheritdoc}
     */
    public function execute() {
        // By calling preExecute() here, we force it to preprocess the extender
        // object rather than just the base query object.  That means
        // hook_query_alter() gets access to the extended object.
        if (!$this->preExecute($this)) {
            return NULL;
        }
        return $this->query
            ->execute();
    }
    
    /**
     * {@inheritdoc}
     */
    public function distinct($distinct = TRUE) {
        $this->query
            ->distinct($distinct);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function addField($table_alias, $field, $alias = NULL) {
        return $this->query
            ->addField($table_alias, $field, $alias);
    }
    
    /**
     * {@inheritdoc}
     */
    public function fields($table_alias, array $fields = []) {
        $this->query
            ->fields($table_alias, $fields);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function addExpression($expression, $alias = NULL, $arguments = []) {
        return $this->query
            ->addExpression($expression, $alias, $arguments);
    }
    
    /**
     * {@inheritdoc}
     */
    public function join($table, $alias = NULL, $condition = NULL, $arguments = []) {
        return $this->query
            ->join($table, $alias, $condition, $arguments);
    }
    
    /**
     * {@inheritdoc}
     */
    public function innerJoin($table, $alias = NULL, $condition = NULL, $arguments = []) {
        return $this->query
            ->innerJoin($table, $alias, $condition, $arguments);
    }
    
    /**
     * {@inheritdoc}
     */
    public function leftJoin($table, $alias = NULL, $condition = NULL, $arguments = []) {
        return $this->query
            ->leftJoin($table, $alias, $condition, $arguments);
    }
    
    /**
     * {@inheritdoc}
     */
    public function addJoin($type, $table, $alias = NULL, $condition = NULL, $arguments = []) {
        return $this->query
            ->addJoin($type, $table, $alias, $condition, $arguments);
    }
    
    /**
     * {@inheritdoc}
     */
    public function orderBy($field, $direction = 'ASC') {
        $this->query
            ->orderBy($field, $direction);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function orderRandom() {
        $this->query
            ->orderRandom();
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function range($start = NULL, $length = NULL) {
        $this->query
            ->range($start, $length);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function union(SelectInterface $query, $type = '') {
        $this->query
            ->union($query, $type);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function groupBy($field) {
        $this->query
            ->groupBy($field);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function forUpdate($set = TRUE) {
        $this->query
            ->forUpdate($set);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function countQuery() {
        return $this->query
            ->countQuery();
    }
    
    /**
     * {@inheritdoc}
     */
    public function isNull($field) {
        $this->query
            ->isNull($field);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isNotNull($field) {
        $this->query
            ->isNotNull($field);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function exists(SelectInterface $select) {
        $this->query
            ->exists($select);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function notExists(SelectInterface $select) {
        $this->query
            ->notExists($select);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function alwaysFalse() {
        $this->query
            ->alwaysFalse();
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function __toString() {
        return (string) $this->query;
    }
    
    /**
     * {@inheritdoc}
     */
    public function __clone() {
        $this->uniqueIdentifier = uniqid('', TRUE);
        // We need to deep-clone the query we're wrapping, which in turn may
        // deep-clone other objects.  Exciting!
        $this->query = clone $this->query;
    }
    
    /**
     * Magic override for undefined methods.
     *
     * If one extender extends another extender, then methods in the inner extender
     * will not be exposed on the outer extender.  That's because we cannot know
     * in advance what those methods will be, so we cannot provide wrapping
     * implementations as we do above.  Instead, we use this slower catch-all method
     * to handle any additional methods.
     */
    public function __call($method, $args) {
        $return = call_user_func_array([
            $this->query,
            $method,
        ], $args);
        // Some methods will return the called object as part of a fluent interface.
        // Others will return some useful value.  If it's a value, then the caller
        // probably wants that value.  If it's the called object, then we instead
        // return this object.  That way we don't "lose" an extender layer when
        // chaining methods together.
        if ($return instanceof SelectInterface) {
            return $this;
        }
        else {
            return $return;
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function conditionGroupFactory($conjunction = 'AND') {
        return $this->connection
            ->condition($conjunction);
    }
    
    /**
     * {@inheritdoc}
     */
    public function andConditionGroup() {
        return $this->conditionGroupFactory('AND');
    }
    
    /**
     * {@inheritdoc}
     */
    public function orConditionGroup() {
        return $this->conditionGroupFactory('OR');
    }

}