mjackson/mach

var escapeRegExp = require('../utils/escapeRegExp');
var isRegExp = require('../utils/isRegExp');

/**
 * A middleware that provides URL rewriting behavior similar to Apache's
 * mod_rewrite. The pathname of requests that match the given pattern is
 * overwritten with the replacement using a simple String#replace.
 */
function rewrite(app, pattern, replacement) {
  if (typeof pattern === 'string')
    pattern = new RegExp('^' + escapeRegExp(pattern) + '$');

  if (!isRegExp(pattern))
    throw new Error('Rewrite pattern must be a RegExp or String');

  replacement = replacement || '';

  return function (conn) {
    var pathname = conn.pathname;

    // Modify the pathname if the pattern matches.
    if (pattern.test(pathname))
      conn.location.properties.pathname = conn.basename + pathname.replace(pattern, replacement);

    return conn.call(app);
  };
}

module.exports = rewrite;