<?php

/*
 * This file is part of the Pagerfanta package.
 *
 * (c) Pablo Díez <pablodip@gmail.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Pagerfanta\Adapter\DoctrineORM;

use Doctrine\ORM\Query\TreeWalkerAdapter,
    Doctrine\ORM\Query\AST\SelectStatement,
    Doctrine\ORM\Query\AST\SimpleSelectExpression,
    Doctrine\ORM\Query\AST\PathExpression,
    Doctrine\ORM\Query\AST\AggregateExpression;

/**
 * Replaces the selectClause of the AST with a SELECT DISTINCT root.id equivalent
 *
 * @category    DoctrineExtensions
 * @package     DoctrineExtensions\Paginate
 * @author      David Abdemoulaie <dave@hobodave.com>
 * @copyright   Copyright (c) 2010 David Abdemoulaie (http://hobodave.com/)
 * @license     http://hobodave.com/license.txt New BSD License
 */
class LimitSubqueryWalker extends TreeWalkerAdapter
{

    /**
     * Walks down a SelectStatement AST node, modifying it to retrieve DISTINCT ids
     * of the root Entity
     *
     * @param SelectStatement $AST
     * @return void
     */
    public function walkSelectStatement(SelectStatement $AST)
    {
        $parent = null;
        $parentName = null;
        foreach ($this->_getQueryComponents() AS $dqlAlias => $qComp) {

            // skip mixed data in query
            if (isset($qComp['resultVariable'])) {
                continue;
            }

            if ($qComp['parent'] === null && $qComp['nestingLevel'] == 0) {
                $parent = $qComp;
                $parentName = $dqlAlias;
                break;
            }
        }

        $pathExpression = new PathExpression(
                        PathExpression::TYPE_STATE_FIELD | PathExpression::TYPE_SINGLE_VALUED_ASSOCIATION, $parentName,
                        $parent['metadata']->getSingleIdentifierFieldName()
        );
        $pathExpression->type = PathExpression::TYPE_STATE_FIELD;

        $AST->selectClause->selectExpressions = array(
            new SimpleSelectExpression($pathExpression)
        );

        if (isset($AST->orderByClause)) {
            foreach ($AST->orderByClause->orderByItems as $item) {
                $pathExpression = new PathExpression(
                                PathExpression::TYPE_STATE_FIELD | PathExpression::TYPE_SINGLE_VALUED_ASSOCIATION,
                                $item->expression->identificationVariable,
                                $item->expression->field
                );
                $pathExpression->type = PathExpression::TYPE_STATE_FIELD;
                $AST->selectClause->selectExpressions[] = new SimpleSelectExpression($pathExpression);
            }
        }

        $AST->selectClause->isDistinct = true;
    }

}
