<?php
/**
 * ExplainProcessor.php
 *
 * This file implements the processor for the EXPLAIN statements.
 *
 * Copyright (c) 2010-2012, Justin Swanhart
 * with contributions by André Rothe <arothe@phosco.info, phosco@gmx.de>
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright notice,
 *     this list of conditions and the following disclaimer in the documentation
 *     and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */

require_once(dirname(__FILE__) . '/AbstractProcessor.php');
require_once(dirname(__FILE__) . '/../utils/ExpressionType.php');

/**
 * 
 * This class processes the EXPLAIN statements.
 * 
 * @author arothe
 * 
 */
class ExplainProcessor extends AbstractProcessor {

    protected function isStatement($keys, $needle = "EXPLAIN") {
        $pos = array_search($needle, $keys);
        if (isset($keys[$pos + 1])) {
            return in_array($keys[$pos + 1], array('SELECT', 'DELETE', 'INSERT', 'REPLACE', 'UPDATE'), true);
        }
        return false;
    }

    // TODO: refactor that function
    public function process($tokens, $keys = array()) {

        $base_expr = "";
        $expr = array();
        $currCategory = "";

        if ($this->isStatement($keys)) {
            foreach ($tokens as $token) {

                $trim = trim($token);
                $base_expr .= $token;

                if ($trim === '') {
                    continue;
                }

                $upper = strtoupper($trim);

                switch ($upper) {

                case 'EXTENDED':
                case 'PARTITIONS':
                    return array('expr_type' => ExpressionType::RESERVED, 'base_expr' => $token);
                    break;

                case 'FORMAT':
                    if ($currCategory === '') {
                        $currCategory = $upper;
                        $expr[] = array('expr_type' => ExpressionType::RESERVED, 'base_expr' => $trim);
                    }
                    // else?
                    break;

                case '=':
                    if ($currCategory === 'FORMAT') {
                        $expr[] = array('expr_type' => ExpressionType::OPERATOR, 'base_expr' => $trim);
                    }
                    // else?
                    break;

                case 'TRADITIONAL':
                case 'JSON':
                    if ($currCategory === 'FORMAT') {
                        $expr[] = array('expr_type' => ExpressionType::RESERVED, 'base_expr' => $trim);
                        return array('expr_type' => ExpressionType::EXPRESSION, 'base_expr' => trim($base_expr),
                                     'sub_tree' => $expr);
                    }
                    // else?
                    break;

                default:
                // ignore the other stuff
                    break;
                }
            }
            return empty($expr) ? null : $expr;
        }

        foreach ($tokens as $token) {

            $trim = trim($token);

            if ($trim === '') {
                continue;
            }

            switch ($currCategory) {

            case 'TABLENAME':
                $currCategory = 'WILD';
                $expr[] = array('expr_type' => ExpressionType::COLREF, 'base_expr' => $trim);
                break;

            case '':
                $currCategory = 'TABLENAME';
                $expr[] = array('expr_type' => ExpressionType::TABLE, 'base_expr' => $trim);
                break;

            default:
                break;
            }
        }
        return empty($expr) ? null : $expr;
    }
}
?>