var URL = require('url')

module.exports = function(/* fn1, fn2, ... */) {
  var handle = function (req, res, out) {
    var i = 0
    function next(err) {
      var layer = handle.layers[i++]

      if (!layer || res.headersSent) {
        // all done
        if (out) return out(err) // delegate to parent

        if (err && res.statusCode < 400) res.statusCode = err.status || 500
        else res.statusCode = 404

        return res.end()
      }

      try {
        layer(req, res, next)
      }
      catch (e) {
        next(e)
      }
    }
    next()
  }

  handle.layers = Array.prototype.slice.call(arguments)

  handle.use = function(fn) {
    if (typeof fn == 'object' && fn.handle) fn = fn.handle.bind(fn)
    handle.layers.push(fn)
    return this
  }

  handle.mount = function(path, fn) {
    return this.use(sub(path, fn))
  }

  return handle
}

function sub(mount, fn) {
  if (mount.substr(-1) != '/') mount += '/'
  if (typeof fn == 'object' && fn.handle) fn = fn.handle.bind(fn)

  return function(req, res, next) {
    var url = req.url
      , uri = req.uri

    if (url.substr(0, mount.length) !== mount && url.substr(0, mount.length) + '/' !== mount) return next()

    // modify the URL
    if (!req.realUrl) req.realUrl = url

    req.url = url.substr(mount.length-1)
    if (req.uri) req.uri = URL.parse(req.url)

    fn(req, res, function(err) {
      // reset the URL
      req.url = url
      req.uri = uri
      next(err)
    })
  }
}