class QueryAggregate

class QueryAggregate extends Query implements QueryAggregateInterface {
    
    /**
     * Stores the sql expressions used to build the sql query.
     *
     * @var array
     *   An array of expressions.
     */
    protected $sqlExpressions = [];
    
    /**
     * {@inheritdoc}
     */
    public function execute() {
        return $this->prepare()
            ->addAggregate()
            ->compile()
            ->compileAggregate()
            ->addGroupBy()
            ->addSort()
            ->addSortAggregate()
            ->finish()
            ->result();
    }
    
    /**
     * {@inheritdoc}
     */
    public function prepare() {
        parent::prepare();
        // Throw away the id fields.
        $this->sqlFields = [];
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function conditionAggregateGroupFactory($conjunction = 'AND') {
        $class = static::getClass($this->namespaces, 'ConditionAggregate');
        return new $class($conjunction, $this, $this->namespaces);
    }
    
    /**
     * {@inheritdoc}
     */
    public function existsAggregate($field, $function, $langcode = NULL) {
        return $this->conditionAggregate
            ->exists($field, $function, $langcode);
    }
    
    /**
     * {@inheritdoc}
     */
    public function notExistsAggregate($field, $function, $langcode = NULL) {
        return $this->conditionAggregate
            ->notExists($field, $function, $langcode);
    }
    
    /**
     * Adds the aggregations to the query.
     *
     * @return $this
     *   Returns the called object.
     */
    protected function addAggregate() {
        if ($this->aggregate) {
            foreach ($this->aggregate as $aggregate) {
                $sql_field = $this->getSqlField($aggregate['field'], $aggregate['langcode']);
                $this->sqlExpressions[$aggregate['alias']] = $aggregate['function'] . "({$sql_field})";
            }
        }
        return $this;
    }
    
    /**
     * Builds the aggregation conditions part of the query.
     *
     * @return $this
     *   Returns the called object.
     */
    protected function compileAggregate() {
        $this->conditionAggregate
            ->compile($this->sqlQuery);
        return $this;
    }
    
    /**
     * Adds the groupby values to the actual query.
     *
     * @return $this
     *   Returns the called object.
     */
    protected function addGroupBy() {
        foreach ($this->groupBy as $group_by) {
            $field = $group_by['field'];
            $sql_field = $this->getSqlField($field, $group_by['langcode']);
            $this->sqlGroupBy[$sql_field] = $sql_field;
            list($table, $real_sql_field) = explode('.', $sql_field);
            $this->sqlFields[$sql_field] = [
                $table,
                $real_sql_field,
                $this->createSqlAlias($field, $real_sql_field),
            ];
        }
        return $this;
    }
    
    /**
     * Builds the aggregation sort part of the query.
     *
     * @return $this
     *   Returns the called object.
     */
    protected function addSortAggregate() {
        if (!$this->count) {
            foreach ($this->sortAggregate as $alias => $sort) {
                $this->sqlQuery
                    ->orderBy($alias, $sort['direction']);
            }
        }
        return $this;
    }
    
    /**
     * Overrides \Drupal\Core\Entity\Query\Sql\Query::finish().
     *
     * Adds the sql expressions to the query.
     */
    protected function finish() {
        foreach ($this->sqlExpressions as $alias => $expression) {
            $this->sqlQuery
                ->addExpression($expression, $alias);
        }
        return parent::finish();
    }
    
    /**
     * Builds a sql alias as expected in the result.
     *
     * @param string $field
     *   The field as passed in by the caller.
     * @param string $sql_field
     *   The sql field as returned by getSqlField.
     *
     * @return string
     *   The SQL alias expected in the return value. The dots in $sql_field are
     *   replaced with underscores and if a default fallback to .value happened,
     *   the _value is stripped.
     */
    public function createSqlAlias($field, $sql_field) {
        $alias = str_replace('.', '_', $sql_field);
        // If the alias contains of field_*_value remove the _value at the end.
        if (substr($alias, 0, 6) === 'field_' && substr($field, -6) !== '_value' && substr($alias, -6) === '_value') {
            $alias = substr($alias, 0, -6);
        }
        return $alias;
    }
    
    /**
     * Overrides \Drupal\Core\Entity\Query\Sql\Query::result().
     *
     * @return array|int
     *   Returns the aggregated result, or a number if it's a count query.
     */
    protected function result() {
        if ($this->count) {
            return parent::result();
        }
        $return = [];
        foreach ($this->sqlQuery
            ->execute() as $row) {
            $return[] = (array) $row;
        }
        return $return;
    }

}