<?php

/*

 * This file is part of the Symfony package.

 * (c) Fabien Potencier <fabien@symfony.com>

 *

 * For the full copyright and license information, please view the LICENSE

 * file that was distributed with this source code.

 */

namespace Symfony\Component\Yaml;

/**

 * Unescaper encapsulates unescaping rules for single and double-quoted

 * YAML strings.

 *

 * @author Matthew Lewinski <matthew@lewinski.org>

 */

class Unescaper

{

    // Parser and Inline assume UTF-8 encoding, so escaped Unicode characters

    // must be converted to that encoding.

    const ENCODING = 'UTF-8';

    // Regex fragment that matches an escaped character in a double quoted

    // string.

    const REGEX_ESCAPED_CHARACTER = "\\\\([0abt\tnvfre \\\"\\/\\\\N_LP]|x[0-9a-fA-F]{2}|u[0-9a-fA-F]{4}|U[0-9a-fA-F]{8})";

    /**

     * Unescapes a single quoted string.

     *

     * @param string $value A single quoted string.

     *

     * @return string The unescaped string.

     */

    public function unescapeSingleQuotedString($value)

    {

        return str_replace('\'\'', '\'', $value);

    }

    /**

     * Unescapes a double quoted string.

     *

     * @param string $value A double quoted string.

     *

     * @return string The unescaped string.

     */

    public function unescapeDoubleQuotedString($value)

    {

        $self = $this;

        $callback = function($match) use($self) {

            return $self->unescapeCharacter($match[0]);

        };

        // evaluate the string

        return preg_replace_callback('/'.self::REGEX_ESCAPED_CHARACTER.'/u', $callback, $value);

    }

    /**

     * Unescapes a character that was found in a double-quoted string

     *

     * @param string $value An escaped character

     *

     * @return string The unescaped character

     */

    public function unescapeCharacter($value)

    {

        switch ($value{1}) {

            case '0':

                return "\x0";

            case 'a':

                return "\x7";

            case 'b':

                return "\x8";

            case 't':

                return "\t";

            case "\t":

                return "\t";

            case 'n':

                return "\n";

            case 'v':

                return "\xb";

            case 'f':

                return "\xc";

            case 'r':

                return "\xd";

            case 'e':

                return "\x1b";

            case ' ':

                return ' ';

            case '"':

                return '"';

            case '/':

                return '/';

            case '\\':

                return '\\';

            case 'N':

                // U+0085 NEXT LINE

                return $this->convertEncoding("\x00\x85", self::ENCODING, 'UCS-2BE');

            case '_':

                // U+00A0 NO-BREAK SPACE

                return $this->convertEncoding("\x00\xA0", self::ENCODING, 'UCS-2BE');

            case 'L':

                // U+2028 LINE SEPARATOR

                return $this->convertEncoding("\x20\x28", self::ENCODING, 'UCS-2BE');

            case 'P':

                // U+2029 PARAGRAPH SEPARATOR

                return $this->convertEncoding("\x20\x29", self::ENCODING, 'UCS-2BE');

            case 'x':

                $char = pack('n', hexdec(substr($value, 2, 2)));

                return $this->convertEncoding($char, self::ENCODING, 'UCS-2BE');

            case 'u':

                $char = pack('n', hexdec(substr($value, 2, 4)));

                return $this->convertEncoding($char, self::ENCODING, 'UCS-2BE');

            case 'U':

                $char = pack('N', hexdec(substr($value, 2, 8)));

                return $this->convertEncoding($char, self::ENCODING, 'UCS-4BE');

        }

    }

    /**

     * Convert a string from one encoding to another.

     *

     * @param string $value The string to convert

     * @param string $to    The input encoding

     * @param string $from  The output encoding

     *

     * @return string The string with the new encoding

     *

     * @throws \RuntimeException if no suitable encoding function is found (iconv or mbstring)

     */

    private function convertEncoding($value, $to, $from)

    {

        if (function_exists('iconv')) {

            return iconv($from, $to, $value);

        } elseif (function_exists('mb_convert_encoding')) {

            return mb_convert_encoding($value, $to, $from);

        }

        throw new \RuntimeException('No suitable convert encoding function (install the iconv or mbstring extension).');

    }

}