<?php

class RouterException extends Exception {}

class NotFound extends RouterException {}

class Router {
    protected
        $_routes = array(),
        $_path;

    function __construct($routes = null, $path = null) {
        if (is_array($routes)) {
            foreach ($routes as $pattern => $handler) {
                $this->addRoute($pattern, $handler);
            }
        }
        $this->_path = $path;
    }

    function compileRoute($pattern) {
        $replacements = array(
            'num' => '\d+',
            'alphanum' => '\w+',
            'id' => '[1-9]\d*',
            'any' => '.*'
        );
        $pattern = '/^' . preg_quote($pattern, '/') . '$/';
        foreach ($replacements as $k => $v) {
            $pattern = str_replace("<$k>", $v, $pattern);
        }
        return $pattern;
    }

    function addRoute($pattern, $handler) {
        $pattern = $this->compileRoute($pattern);
        $this->_routes[$pattern] = $handler;
    }

    function serve($path = null) {
        $path = $path ? $path : $this->_path;
        if (!$path) {
            throw new RouterException('Need path');
        }
        foreach ($this->_routes as $pattern => $handler) {
            if (preg_match($pattern, $path, $matches)) {
                return call_user_func_array($handler, array_slice($matches, 1));
            }
        }
        throw new NotFound();
    }
}