<?php

/*
 * This file is part of SwiftMailer.
 * (c) 2004-2009 Chris Corbyn
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

/**
 * Defines the grammar to use for validation, implements the RFC 2822 (and friends) ABNF grammar definitions.
 *
 * @author     Fabien Potencier
 * @author     Chris Corbyn
 */
class Swift_Mime_Grammar
{
    /**
     * Special characters used in the syntax which need to be escaped.
     *
     * @var string[]
     */
    private static $_specials = array();

    /**
     * Tokens defined in RFC 2822 (and some related RFCs).
     *
     * @var string[]
     */
    private static $_grammar = array();

    /**
     * Initialize some RFC 2822 (and friends) ABNF grammar definitions.
     */
    public function __construct()
    {
        $this->init();
    }

    public function __wakeup()
    {
        $this->init();
    }

    protected function init()
    {
        if (count(self::$_specials) > 0) {
            return;
        }

        self::$_specials = array(
            '(', ')', '<', '>', '[', ']',
            ':', ';', '@', ',', '.', '"'
            );

        /*** Refer to RFC 2822 for ABNF grammar ***/

        // All basic building blocks
        self::$_grammar['NO-WS-CTL'] = '[\x01-\x08\x0B\x0C\x0E-\x19\x7F]';
        self::$_grammar['WSP'] = '[ \t]';
        self::$_grammar['CRLF'] = '(?:\r\n)';
        self::$_grammar['FWS'] = '(?:(?:' . self::$_grammar['WSP'] . '*' .
                self::$_grammar['CRLF'] . ')?' . self::$_grammar['WSP'] . ')';
        self::$_grammar['text'] = '[\x00-\x08\x0B\x0C\x0E-\x7F]';
        self::$_grammar['quoted-pair'] = '(?:\\\\' . self::$_grammar['text'] . ')';
        self::$_grammar['ctext'] = '(?:' . self::$_grammar['NO-WS-CTL'] .
                '|[\x21-\x27\x2A-\x5B\x5D-\x7E])';
        // Uses recursive PCRE (?1) -- could be a weak point??
        self::$_grammar['ccontent'] = '(?:' . self::$_grammar['ctext'] . '|' .
                self::$_grammar['quoted-pair'] . '|(?1))';
        self::$_grammar['comment'] = '(\((?:' . self::$_grammar['FWS'] . '|' .
                self::$_grammar['ccontent']. ')*' . self::$_grammar['FWS'] . '?\))';
        self::$_grammar['CFWS'] = '(?:(?:' . self::$_grammar['FWS'] . '?' .
                self::$_grammar['comment'] . ')*(?:(?:' . self::$_grammar['FWS'] . '?' .
                self::$_grammar['comment'] . ')|' . self::$_grammar['FWS'] . '))';
        self::$_grammar['qtext'] = '(?:' . self::$_grammar['NO-WS-CTL'] .
                '|[\x21\x23-\x5B\x5D-\x7E])';
        self::$_grammar['qcontent'] = '(?:' . self::$_grammar['qtext'] . '|' .
                self::$_grammar['quoted-pair'] . ')';
        self::$_grammar['quoted-string'] = '(?:' . self::$_grammar['CFWS'] . '?"' .
                '(' . self::$_grammar['FWS'] . '?' . self::$_grammar['qcontent'] . ')*' .
                self::$_grammar['FWS'] . '?"' . self::$_grammar['CFWS'] . '?)';
        self::$_grammar['atext'] = '[a-zA-Z0-9!#\$%&\'\*\+\-\/=\?\^_`\{\}\|~]';
        self::$_grammar['atom'] = '(?:' . self::$_grammar['CFWS'] . '?' .
                self::$_grammar['atext'] . '+' . self::$_grammar['CFWS'] . '?)';
        self::$_grammar['dot-atom-text'] = '(?:' . self::$_grammar['atext'] . '+' .
                '(\.' . self::$_grammar['atext'] . '+)*)';
        self::$_grammar['dot-atom'] = '(?:' . self::$_grammar['CFWS'] . '?' .
                self::$_grammar['dot-atom-text'] . '+' . self::$_grammar['CFWS'] . '?)';
        self::$_grammar['word'] = '(?:' . self::$_grammar['atom'] . '|' .
                self::$_grammar['quoted-string'] . ')';
        self::$_grammar['phrase'] = '(?:' . self::$_grammar['word'] . '+?)';
        self::$_grammar['no-fold-quote'] = '(?:"(?:' . self::$_grammar['qtext'] .
                '|' . self::$_grammar['quoted-pair'] . ')*")';
        self::$_grammar['dtext'] = '(?:' . self::$_grammar['NO-WS-CTL'] .
                '|[\x21-\x5A\x5E-\x7E])';
        self::$_grammar['no-fold-literal'] = '(?:\[(?:' . self::$_grammar['dtext'] .
                '|' . self::$_grammar['quoted-pair'] . ')*\])';

        // Message IDs
        self::$_grammar['id-left'] = '(?:' . self::$_grammar['dot-atom-text'] . '|' .
                self::$_grammar['no-fold-quote'] . ')';
        self::$_grammar['id-right'] = '(?:' . self::$_grammar['dot-atom-text'] . '|' .
                self::$_grammar['no-fold-literal'] . ')';

        // Addresses, mailboxes and paths
        self::$_grammar['local-part'] = '(?:' . self::$_grammar['dot-atom'] . '|' .
                self::$_grammar['quoted-string'] . ')';
        self::$_grammar['dcontent'] = '(?:' . self::$_grammar['dtext'] . '|' .
                self::$_grammar['quoted-pair'] . ')';
        self::$_grammar['domain-literal'] = '(?:' . self::$_grammar['CFWS'] . '?\[(' .
                self::$_grammar['FWS'] . '?' . self::$_grammar['dcontent'] . ')*?' .
                self::$_grammar['FWS'] . '?\]' . self::$_grammar['CFWS'] . '?)';
        self::$_grammar['domain'] = '(?:' . self::$_grammar['dot-atom'] . '|' .
                self::$_grammar['domain-literal'] . ')';
        self::$_grammar['addr-spec'] = '(?:' . self::$_grammar['local-part'] . '@' .
                self::$_grammar['domain'] . ')';
    }

    /**
     * Get the grammar defined for $name token.
     *
     * @param string $name exactly as written in the RFC
     *
     * @return string
     */
    public function getDefinition($name)
    {
        if (array_key_exists($name, self::$_grammar)) {
            return self::$_grammar[$name];
        } else {
            throw new Swift_RfcComplianceException(
                "No such grammar '" . $name . "' defined."
                );
        }
    }

    /**
     * Returns the tokens defined in RFC 2822 (and some related RFCs).
     *
     * @return array
     */
    public function getGrammarDefinitions()
    {
        return self::$_grammar;
    }

    /**
     * Returns the current special characters used in the syntax which need to be escaped.
     *
     * @return array
     */
    public function getSpecials()
    {
        return self::$_specials;
    }

    /**
     * Escape special characters in a string (convert to quoted-pairs).
     *
     * @param string   $token
     * @param string[] $include additional chars to escape
     * @param string[] $exclude chars from escaping
     *
     * @return string
     */
    public function escapeSpecials($token, $include = array(), $exclude = array())
    {
        foreach (array_merge(array('\\'), array_diff(self::$_specials, $exclude), $include) as $char) {
            $token = str_replace($char, '\\' . $char, $token);
        }

        return $token;
    }
}