/**
* Builds a regex from a tokens structure array.
*
* @param array $token A tokens structure root node.
* @return array An array containing the regex pattern and its associated variable names.
*/
public static function compile($token)
{
$variables = [];
$regex = '';
foreach ($token['tokens'] as $child) {
if (is_string($child)) {
$regex .= preg_quote($child, '~');
} elseif (isset($child['tokens'])) {
$rule = static::compile($child);
if ($child['repeat']) {
if (count($rule[1]) > 1) {
throw ParserException::placeholderExceeded();
}
$regex .= '((?:' . $rule[0] . ')' . $child['greedy'] . ')';
} elseif ($child['optional']) {
$regex .= '(?:' . $rule[0] . ')?';
}
foreach ($rule[1] as $name => $pattern) {
if (isset($variables[$name])) {
throw ParserException::duplicatePlaceholder($name);
}
$variables[$name] = $pattern;
}
} else {
$name = $child['name'];
if (isset($variables[$name])) {
throw ParserException::duplicatePlaceholder($name);
}
if ($token['repeat']) {
$variables[$name] = $token['pattern'];
$regex .= $child['pattern'];
} else {
$variables[$name] = false;
$regex .= '(' . $child['pattern'] . ')';
}
}
}
return [$regex, $variables];
}
