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<?php

/**
 * The Gravity Forms Query Call class.
 */
class GF_Query_Call {
    /**
     * @var string The function name.
     */
    private $_function_name = null;

    /**
     * @var array The parameters.
     */
    private $_parameters = array();

    /**
     * A function call.
     *
     * @param string $function_name The function to call.
     * @param array $parameters The function parameters. Default: []
     */
    public function __construct( $function_name, $parameters = array() ) {
        $this->_function_name = $function_name;
        $this->_parameters = $parameters;
    }

    /**
     * Generate the SQL.
     *
     * The default behavior is to just plop function_name( implode( ', ', $parameters ) ).
     * For other cases, like CAST, check the derived classes.
     *
     * @param GF_Query $query The query.
     *
     * @return string The generated SQL.
     */
    public function sql( $query ) {
        if ( method_exists( $this, strtolower( $this->function_name ) . '_sql' ) ) {
            return call_user_func( array( $this, strtolower( $this->function_name ) . '_sql' ), $query );
        }
        return sprintf( "{$this->function_name}(%s)", implode( ', ', $this->parameters ) );
    }

    /**
     * A cast call.
     *
     * @param GF_Query_Column $column The column to cast.
     * @param string $type The type to cast to.
     *
     * @return GF_Query_Call|null instance or null.
     */
    public static function CAST( $column, $type ) {
        if ( ! $column instanceof GF_Query_Column ) {
            return null;
        }

        return new self( 'CAST', array( $column, $type ) );
    }

    /**
     * A RAND call.
     *
     * @return GF_Query_Call|null instance or null.
     */
    public static function RAND( ) {
        return new self( 'RAND' );
    }

    /**
     * Generate the RAND call SQL.
     *
     * @return string The generated SQL.
     */
    private function rand_sql() {
        return 'RAND()';
    }

    /**
     * Generate the CAST call SQL.
     *
     * @param GF_Query $query The query.
     *
     * @return string The generated SQL.
     */
    private function cast_sql( $query ) {
        if ( ! $this->parameters || count( $this->parameters ) != 2 ) {
            return '';
        }

        list( $column, $type ) = $this->parameters;

        if ( ! in_array( $type, array( GF_Query::TYPE_SIGNED, GF_Query::TYPE_UNSIGNED ) ) ) {
            return '';
        }

        if ( ! $column->field_id || ! $column->source ) {
            return '';
        }

        $id = $column->is_entry_column() ? $column->field_id : 'meta_value';
        return sprintf( 'CAST(`%s`.`%s` AS %s)', $query->_alias( $column->field_id, $column->source, 'c' ), $id, $type );
    }

    /**
     * Retrieve all the columns from the parameters of this call.
     *
     * @return array The columns.
     */
    private function get_columns() {
        $columns = array();
        foreach ( $this->parameters as $p ) {
            if ( $p instanceof GF_Query_Column ) {
                $columns[] = $p;
            }
        }
        return $columns;
    }

    /**
     * Proxy read-only values.
     */
    public function __get( $key ) {
        switch ( $key ):
            case 'parameters':
                return $this->_parameters;
            case 'function_name':
                return $this->_function_name;
            case 'columns':
                return $this->get_columns();
        endswitch;
    }
}