<?php

/**
 * `WHERE` keyword parser.
 *
 * @package    SqlParser
 * @subpackage Components
 */
namespace SqlParser\Components;

use SqlParser\Component;
use SqlParser\Parser;
use SqlParser\Token;
use SqlParser\TokensList;

/**
 * `WHERE` keyword parser.
 *
 * @category   Keywords
 * @package    SqlParser
 * @subpackage Components
 * @author     Dan Ungureanu <udan1107@gmail.com>
 * @license    http://opensource.org/licenses/GPL-2.0 GNU Public License
 */
class Condition extends Component
{

    /**
     * Logical operators that can be used to delimit expressions.
     *
     * @var array
     */
    public static $DELIMITERS = array('&&', '||', 'AND', 'OR', 'XOR');

    /**
     * List of allowed reserved keywords in conditions.
     *
     * @var array
     */
    public static $ALLOWED_KEYWORDS = array(
        'AND'                           => 1,
        'BETWEEN'                       => 1,
        'EXISTS'                        => 1,
        'IF'                            => 1,
        'IN'                            => 1,
        'INTERVAL'                      => 1,
        'IS'                            => 1,
        'LIKE'                          => 1,
        'MATCH'                         => 1,
        'NOT IN'                        => 1,
        'NOT NULL'                      => 1,
        'NOT'                           => 1,
        'NULL'                          => 1,
        'OR'                            => 1,
        'XOR'                           => 1,
    );

    /**
     * Identifiers recognized.
     *
     * @var array
     */
    public $identifiers = array();

    /**
     * Whether this component is an operator.
     *
     * @var bool
     */
    public $isOperator = false;

    /**
     * The condition.
     *
     * @var string
     */
    public $expr;

    /**
     * Constructor.
     *
     * @param string $expr The condition or the operator.
     */
    public function __construct($expr = null)
    {
        $this->expr = trim($expr);
    }

    /**
     * @param Parser     $parser  The parser that serves as context.
     * @param TokensList $list    The list of tokens that are being parsed.
     * @param array      $options Parameters for parsing.
     *
     * @return Condition[]
     */
    public static function parse(Parser $parser, TokensList $list, array $options = array())
    {
        $ret = array();

        $expr = new Condition();

        /**
         * Counts brackets.
         *
         * @var int $brackets
         */
        $brackets = 0;

        /**
         * Whether there was a `BETWEEN` keyword before or not.
         *
         * It is required to keep track of them because their structure contains
         * the keyword `AND`, which is also an operator that delimits
         * expressions.
         *
         * @var bool $betweenBefore
         */
        $betweenBefore = false;

        for (; $list->idx < $list->count; ++$list->idx) {

            /**
             * Token parsed at this moment.
             *
             * @var Token $token
             */
            $token = $list->tokens[$list->idx];

            // End of statement.
            if ($token->type === Token::TYPE_DELIMITER) {
                break;
            }

            // Skipping whitespaces and comments.
            if ($token->type === Token::TYPE_COMMENT) {
                continue;
            }

            // Replacing all whitespaces (new lines, tabs, etc.) with a single
            // space character.
            if ($token->type === Token::TYPE_WHITESPACE) {
                $expr->expr .= ' ';
                continue;
            }

            // Conditions are delimited by logical operators.
            if (in_array($token->value, static::$DELIMITERS, true)) {
                if (($betweenBefore) && ($token->value === 'AND')) {
                    // The syntax of keyword `BETWEEN` is hard-coded.
                    $betweenBefore = false;
                } else {
                    // The expression ended.
                    $expr->expr = trim($expr->expr);
                    if (!empty($expr->expr)) {
                        $ret[] = $expr;
                    }

                    // Adding the operator.
                    $expr = new Condition($token->value);
                    $expr->isOperator = true;
                    $ret[] = $expr;

                    // Preparing to parse another condition.
                    $expr = new Condition();
                    continue;
                }
            }

            if (($token->type === Token::TYPE_KEYWORD) && ($token->flags & Token::FLAG_KEYWORD_RESERVED)) {
                if ($token->value === 'BETWEEN') {
                    $betweenBefore = true;
                }
                if (($brackets === 0) && (empty(static::$ALLOWED_KEYWORDS[$token->value]))) {
                    break;
                }
            }

            if ($token->type === Token::TYPE_OPERATOR) {
                if ($token->value === '(') {
                    ++$brackets;
                } elseif ($token->value === ')') {
                    --$brackets;
                }
            }

            $expr->expr .= $token->token;
            if (($token->type === Token::TYPE_NONE)
                || (($token->type === Token::TYPE_KEYWORD)
                && (!($token->flags & Token::FLAG_KEYWORD_RESERVED)))
                || ($token->type === Token::TYPE_STRING)
                || ($token->type === Token::TYPE_SYMBOL)
            ) {
                if (!in_array($token->value, $expr->identifiers)) {
                    $expr->identifiers[] = $token->value;
                }
            }
        }

        // Last iteration was not processed.
        $expr->expr = trim($expr->expr);
        if (!empty($expr->expr)) {
            $ret[] = $expr;
        }

        --$list->idx;
        return $ret;
    }

    /**
     * @param Condition[] $component The component to be built.
     * @param array       $options   Parameters for building.
     *
     * @return string
     */
    public static function build($component, array $options = array())
    {
        if (is_array($component)) {
            return implode(' ', $component);
        } else {
            return $component->expr;
        }
    }
}
