<?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 Kant\Routing\Symfony;

/**
 * RouteCompiler compiles Route instances to CompiledRoute instances.
 *
 * @author Fabien Potencier <fabien@symfony.com>
 * @author Tobias Schultze <http://tobion.de>
 */
class RouteCompiler implements RouteCompilerInterface
{

    const REGEX_DELIMITER = '#';

    /**
     * This string defines the characters that are automatically considered separators in front of
     * optional placeholders (with default and no static text following).
     * Such a single separator
     * can be left out together with the optional placeholder from matching and generating URLs.
     */
    const SEPARATORS = '/,;.:-_~+*=@|';

    /**
     * The maximum supported length of a PCRE subpattern name
     * http://pcre.org/current/doc/html/pcre2pattern.html#SEC16.
     *
     * @internal
     *
     */
    const VARIABLE_MAXIMUM_LENGTH = 32;

    /**
     *
     * {@inheritdoc}
     *
     * @throws \InvalidArgumentException If a path variable is named _fragment
     * @throws \LogicException If a variable is referenced more than once
     * @throws \DomainException If a variable name starts with a digit or if it is too long to be successfully used as
     *         a PCRE subpattern.
     */
    public static function compile(Route $route)
    {
        $hostVariables = array();
        $variables = array();
        $hostRegex = null;
        $hostTokens = array();
        
        if ('' !== $host = $route->getHost()) {
            $result = self::compilePattern($route, $host, true);
            
            $hostVariables = $result['variables'];
            $variables = $hostVariables;
            
            $hostTokens = $result['tokens'];
            $hostRegex = $result['regex'];
        }
        
        $path = $route->getPath();
        
        $result = self::compilePattern($route, $path, false);
        
        $staticPrefix = $result['staticPrefix'];
        
        $pathVariables = $result['variables'];
        
        foreach ($pathVariables as $pathParam) {
            if ('_fragment' === $pathParam) {
                throw new \InvalidArgumentException(sprintf('Route pattern "%s" cannot contain "_fragment" as a path parameter.', $route->getPath()));
            }
        }
        
        $variables = array_merge($variables, $pathVariables);
        
        $tokens = $result['tokens'];
        $regex = $result['regex'];
        
        return new CompiledRoute($staticPrefix, $regex, $tokens, $pathVariables, $hostRegex, $hostTokens, $hostVariables, array_unique($variables));
    }

    private static function compilePattern(Route $route, $pattern, $isHost)
    {
        $tokens = array();
        $variables = array();
        $matches = array();
        $pos = 0;
        $defaultSeparator = $isHost ? '.' : '/';
        $useUtf8 = preg_match('//u', $pattern);
        $needsUtf8 = $route->getOption('utf8');
        
        if (!$needsUtf8 && $useUtf8 && preg_match('/[\x80-\xFF]/', $pattern)) {
            $needsUtf8 = true;
            @trigger_error(sprintf('Using UTF-8 route patterns without setting the "utf8" option is deprecated since Symfony 3.2 and will throw a LogicException in 4.0. Turn on the "utf8" route option for pattern "%s".', $pattern), E_USER_DEPRECATED);
        }
        if (!$useUtf8 && $needsUtf8) {
            throw new \LogicException(sprintf('Cannot mix UTF-8 requirements with non-UTF-8 pattern "%s".', $pattern));
        }
        
        // Match all variables enclosed in "{}" and iterate over them. But we only want to match the innermost variable
        // in case of nested "{}", e.g. {foo{bar}}. This in ensured because \w does not match "{" or "}" itself.
        preg_match_all('#\{\w+\}#', $pattern, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER);
        foreach ($matches as $match) {
            $varName = substr($match[0][0], 1, - 1);
            // get all static text preceding the current variable
            $precedingText = substr($pattern, $pos, $match[0][1] - $pos);
            $pos = $match[0][1] + strlen($match[0][0]);
            
            if (!strlen($precedingText)) {
                $precedingChar = '';
            } elseif ($useUtf8) {
                preg_match('/.$/u', $precedingText, $precedingChar);
                $precedingChar = $precedingChar[0];
            } else {
                $precedingChar = substr($precedingText, - 1);
            }
            $isSeparator = '' !== $precedingChar && false !== strpos(static::SEPARATORS, $precedingChar);
            
            // A PCRE subpattern name must start with a non-digit. Also a PHP variable cannot start with a digit so the
            // variable would not be usable as a Controller action argument.
            if (preg_match('/^\d/', $varName)) {
                throw new \DomainException(sprintf('Variable name "%s" cannot start with a digit in route pattern "%s". Please use a different name.', $varName, $pattern));
            }
            if (in_array($varName, $variables)) {
                throw new \LogicException(sprintf('Route pattern "%s" cannot reference variable name "%s" more than once.', $pattern, $varName));
            }
            
            if (strlen($varName) > self::VARIABLE_MAXIMUM_LENGTH) {
                throw new \DomainException(sprintf('Variable name "%s" cannot be longer than %s characters in route pattern "%s". Please use a shorter name.', $varName, self::VARIABLE_MAXIMUM_LENGTH, $pattern));
            }
            
            if ($isSeparator && $precedingText !== $precedingChar) {
                $tokens[] = array(
                    'text',
                    substr($precedingText, 0, - strlen($precedingChar))
                );
            } elseif (!$isSeparator && strlen($precedingText) > 0) {
                $tokens[] = array(
                    'text',
                    $precedingText
                );
            }
            
            $regexp = $route->getRequirement($varName);
            if (null === $regexp) {
                $followingPattern = (string) substr($pattern, $pos);
                // Find the next static character after the variable that functions as a separator. By default, this separator and '/'
                // are disallowed for the variable. This default requirement makes sure that optional variables can be matched at all
                // and that the generating-matching-combination of URLs unambiguous, i.e. the params used for generating the URL are
                // the same that will be matched. Example: new Route('/{page}.{_format}', array('_format' => 'html'))
                // If {page} would also match the separating dot, {_format} would never match as {page} will eagerly consume everything.
                // Also even if {_format} was not optional the requirement prevents that {page} matches something that was originally
                // part of {_format} when generating the URL, e.g. _format = 'mobile.html'.
                $nextSeparator = self::findNextSeparator($followingPattern, $useUtf8);
                $regexp = sprintf('[^%s%s]+', preg_quote($defaultSeparator, self::REGEX_DELIMITER), $defaultSeparator !== $nextSeparator && '' !== $nextSeparator ? preg_quote($nextSeparator, self::REGEX_DELIMITER) : '');
                if (('' !== $nextSeparator && ! preg_match('#^\{\w+\}#', $followingPattern)) || '' === $followingPattern) {
                    // When we have a separator, which is disallowed for the variable, we can optimize the regex with a possessive
                    // quantifier. This prevents useless backtracking of PCRE and improves performance by 20% for matching those patterns.
                    // Given the above example, there is no point in backtracking into {page} (that forbids the dot) when a dot must follow
                    // after it. This optimization cannot be applied when the next char is no real separator or when the next variable is
                    // directly adjacent, e.g. '/{x}{y}'.
                    $regexp .= '+';
                }
            } else {
                if (!preg_match('//u', $regexp)) {
                    $useUtf8 = false;
                } elseif (!$needsUtf8 && preg_match('/[\x80-\xFF]|(?<!\\\\)\\\\(?:\\\\\\\\)*+(?-i:X|[pP][\{CLMNPSZ]|x\{[A-Fa-f0-9]{3})/', $regexp)) {
                    $needsUtf8 = true;
                    @trigger_error(sprintf('Using UTF-8 route requirements without setting the "utf8" option is deprecated since Symfony 3.2 and will throw a LogicException in 4.0. Turn on the "utf8" route option for variable "%s" in pattern "%s".', $varName, $pattern), E_USER_DEPRECATED);
                }
                if (!$useUtf8 && $needsUtf8) {
                    throw new \LogicException(sprintf('Cannot mix UTF-8 requirement with non-UTF-8 charset for variable "%s" in pattern "%s".', $varName, $pattern));
                }
            }
            
            $tokens[] = array(
                'variable',
                $isSeparator ? $precedingChar : '',
                $regexp,
                $varName
            );
            $variables[] = $varName;
        }
        
        if ($pos < strlen($pattern)) {
            $tokens[] = array(
                'text',
                substr($pattern, $pos)
            );
        }
        
        // find the first optional token
        $firstOptional = PHP_INT_MAX;
        if (!$isHost) {
            for ($i = count($tokens) - 1; $i >= 0; -- $i) {
                $token = $tokens[$i];
                if ('variable' === $token[0] && $route->hasDefault($token[3])) {
                    $firstOptional = $i;
                } else {
                    break;
                }
            }
        }
        
        // compute the matching regexp
        $regexp = '';
        for ($i = 0, $nbToken = count($tokens); $i < $nbToken; ++ $i) {
            $regexp .= self::computeRegexp($tokens, $i, $firstOptional);
        }
        $regexp = self::REGEX_DELIMITER . '^' . $regexp . '$' . self::REGEX_DELIMITER . 's' . ($isHost ? 'i' : '');
        
        // enable Utf8 matching if really required
        if ($needsUtf8) {
            $regexp .= 'u';
            for ($i = 0, $nbToken = count($tokens); $i < $nbToken; ++ $i) {
                if ('variable' === $tokens[$i][0]) {
                    $tokens[$i][] = true;
                }
            }
        }
        
        return array(
            'staticPrefix' => 'text' === $tokens[0][0] ? $tokens[0][1] : '',
            'regex' => $regexp,
            'tokens' => array_reverse($tokens),
            'variables' => $variables
        );
    }

    /**
     * Returns the next static character in the Route pattern that will serve as a separator.
     *
     * @param string $pattern
     *            The route pattern
     * @param bool $useUtf8
     *            Whether the character is encoded in UTF-8 or not
     *            
     * @return string The next static character that functions as separator (or empty string when none available)
     */
    private static function findNextSeparator($pattern, $useUtf8)
    {
        if ('' == $pattern) {
            // return empty string if pattern is empty or false (false which can be returned by substr)
            return '';
        }
        // first remove all placeholders from the pattern so we can find the next real static character
        if ('' === $pattern = preg_replace('#\{\w+\}#', '', $pattern)) {
            return '';
        }
        if ($useUtf8) {
            preg_match('/^./u', $pattern, $pattern);
        }
        
        return false !== strpos(static::SEPARATORS, $pattern[0]) ? $pattern[0] : '';
    }

    /**
     * Computes the regexp used to match a specific token.
     * It can be static text or a subpattern.
     *
     * @param array $tokens
     *            The route tokens
     * @param int $index
     *            The index of the current token
     * @param int $firstOptional
     *            The index of the first optional token
     *            
     * @return string The regexp pattern for a single token
     */
    private static function computeRegexp(array $tokens, $index, $firstOptional)
    {
        $token = $tokens[$index];
        if ('text' === $token[0]) {
            // Text tokens
            return preg_quote($token[1], self::REGEX_DELIMITER);
        } else {
            // Variable tokens
            if (0 === $index && 0 === $firstOptional) {
                // When the only token is an optional variable token, the separator is required
                return sprintf('%s(?P<%s>%s)?', preg_quote($token[1], self::REGEX_DELIMITER), $token[3], $token[2]);
            } else {
                $regexp = sprintf('%s(?P<%s>%s)', preg_quote($token[1], self::REGEX_DELIMITER), $token[3], $token[2]);
                if ($index >= $firstOptional) {
                    // Enclose each optional token in a subpattern to make it optional.
                    // "?:" means it is non-capturing, i.e. the portion of the subject string that
                    // matched the optional subpattern is not passed back.
                    $regexp = "(?:$regexp";
                    $nbTokens = count($tokens);
                    if ($nbTokens - 1 == $index) {
                        // Close the optional subpatterns
                        $regexp .= str_repeat(')?', $nbTokens - $firstOptional - (0 === $firstOptional ? 1 : 0));
                    }
                }
                
                return $regexp;
            }
        }
    }
}
