<?php
/**
 * StatusNet - the distributed open-source microblogging tool
 * Copyright (C) 2011, StatusNet, Inc.
 *
 * URL mapper
 * 
 * PHP version 5
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * @category  Cache
 * @package   StatusNet
 * @author    Evan Prodromou <evan@status.net>
 * @copyright 2011 StatusNet, Inc.
 * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPL 3.0
 * @link      http://status.net/
 */

if (!defined('STATUSNET')) {
    // This check helps protect against security problems;
    // your code file can't be executed directly from the web.
    exit(1);
}

/**
 * URL mapper
 *
 * Converts a path into a set of parameters, and vice versa
 *
 * We used to use Net_URL_Mapper, so there's a wrapper class at Router, q.v.
 * 
 * NUM's vagaries are the main reason we have weirdnesses here.
 *
 * @category  URL
 * @package   StatusNet
 * @author    Evan Prodromou <evan@status.net>
 * @copyright 2011 StatusNet, Inc.
 * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPL 3.0
 * @link      http://status.net/
 */

class URLMapper
{
    const ACTION = 'action';

    protected $statics = array();
    protected $variables = array();
    protected $reverse = array();

    function connect($path, $args, $paramPatterns=array())
    {
        if (!array_key_exists(self::ACTION, $args)) {
            throw new Exception(sprintf("Can't connect %s; path has no action.", $path));
        }

        $action = $args[self::ACTION];

        $paramNames = $this->getParamNames($path);

        if (empty($paramNames)) {
            $this->statics[$path] = $args;
            if (array_key_exists($action, $this->reverse)) {
                $this->reverse[$args[self::ACTION]][] = array($args, $path);
            } else {
                $this->reverse[$args[self::ACTION]] = array(array($args, $path));
            }
        } else {

            // Eff if I understand why some go here and some go there.
            // Anyways, fixup my preconceptions

            foreach ($paramNames as $name) {
                if (!array_key_exists($name, $paramPatterns) &&
                    array_key_exists($name, $args)) {
                    $paramPatterns[$name] = $args[$name];
                    unset($args[$name]);
                }
            }

            $regex = $this->makeRegex($path, $paramPatterns);

            $this->variables[] = array($args, $regex, $paramNames);

            $format = $this->makeFormat($path, $paramPatterns);

            if (array_key_exists($action, $this->reverse)) {
                $this->reverse[$args[self::ACTION]][] = array($args, $format, $paramNames);
            } else {
                $this->reverse[$args[self::ACTION]] = array(array($args, $format, $paramNames));
            }
        }
    }

    function match($path)
    {
        if (array_key_exists($path, $this->statics)) {
            return $this->statics[$path];
        }

        foreach ($this->variables as $pattern) {
            list($args, $regex, $paramNames) = $pattern;
            if (preg_match($regex, $path, $match)) {
                $results = $args;
                foreach ($paramNames as $name) {
                    $results[$name] = $match[$name];
                }
                return $results;
            }
        }
        
        throw new Exception(sprintf('No match for path "%s"', $path));
    }

    function generate($args, $qstring, $fragment)
    {
        if (!array_key_exists(self::ACTION, $args)) {
            throw new Exception("Every path needs an action.");
        }

        $action = $args[self::ACTION];

        if (!array_key_exists($action, $this->reverse)) {
            throw new Exception(sprintf('No candidate paths for action "%s"', $action));
        }

        $candidates = $this->reverse[$action];

        foreach ($candidates as $candidate) {
            if (count($candidate) == 2) { // static
                list($tryArgs, $tryPath) = $candidate;
                foreach ($tryArgs as $key => $value) {
                    if (!array_key_exists($key, $args) || $args[$key] != $value) {
                        // next candidate
                        continue 2;
                    }
                }
                // success
                return $tryPath;
            } else {
                list($tryArgs, $format, $paramNames) = $candidate;

                foreach ($tryArgs as $key => $value) {
                    if (!array_key_exists($key, $args) || $args[$key] != $value) {
                        // next candidate
                        continue 2;
                    }
                }

                // success

                $toFormat = array();

                foreach ($paramNames as $name) {
                    if (!array_key_exists($name, $args)) {
                        // next candidate
                        continue 2;
                    }
                    $toFormat[] = $args[$name];
                }

                $path = vsprintf($format, $toFormat);

                if (!empty($qstring)) {
                    $path .= '?' . http_build_query($qstring);
                }

                return $path;
            }
        }

        unset($args['action']);

        if (empty($args)) {
            throw new Exception(sprintf('No matches for action "%s"', $action));
        }

        $argstring = '';

        foreach ($args as $key => $value) {
            $argstring .= "$key=$value ";
        }

        throw new Exception(sprintf('No matches for action "%s" with arguments "%s"', $action, $argstring));
    }

    protected function getParamNames($path)
    {
        preg_match_all('/:(?P<name>\w+)/', $path, $match);
        return $match['name'];
    }

    protected function makeRegex($path, $paramPatterns)
    {
        $pr = new PatternReplacer($paramPatterns);

        $regex = preg_replace_callback('/:(\w+)/',
                                       array($pr, 'toPattern'),
                                       $path);

        $regex = '#' . str_replace('#', '\#', $regex) . '#';

        return $regex;
    }

    protected function makeFormat($path, $paramPatterns)
    {
        $format = preg_replace('/(:\w+)/', '%s', $path);

        return $format;
    }
}

class PatternReplacer
{
    private $patterns;

    function __construct($patterns)
    {
        $this->patterns = $patterns;
    }

    function toPattern($matches)
    {
        // trim out the :
        $name = $matches[1];
        if (array_key_exists($name, $this->patterns)) {
            $pattern = $this->patterns[$name];
        } else {
            // ???
            $pattern = '\w+';
        }
        return '(?P<'.$name.'>'.$pattern.')';
    }
}