/**
 * Module dependencies.
 */

var pathRegexp = require('path-to-regexp');
var debug = require('debug')('express:router:layer');

/**
 * Expose `Layer`.
 */

module.exports = Layer;

function Layer(path, options, fn) {
  if (!(this instanceof Layer)) {
    return new Layer(path, options, fn);
  }

  debug('new %s', path);
  options = options || {};

  this.handle = fn;
  this.name = fn.name || '<anonymous>';
  this.params = undefined;
  this.path = undefined;
  this.regexp = pathRegexp(path, this.keys = [], options);

  if (path === '/' && options.end === false) {
    this.regexp.fast_slash = true;
  }
}

/**
 * Handle the error for the layer.
 *
 * @param {Error} error
 * @param {Request} req
 * @param {Response} res
 * @param {function} next
 * @api private
 */

Layer.prototype.handle_error = function handle_error(error, req, res, next) {
  var fn = this.handle;

  if (fn.length !== 4) {
    // not a standard error handler
    return next(error);
  }

  try {
    fn(error, req, res, next);
  } catch (err) {
    next(err);
  }
};

/**
 * Handle the request for the layer.
 *
 * @param {Request} req
 * @param {Response} res
 * @param {function} next
 * @api private
 */

Layer.prototype.handle_request = function handle(req, res, next) {
  var fn = this.handle;

  if (fn.length > 3) {
    // not a standard request handler
    return next();
  }

  try {
    fn(req, res, next);
  } catch (err) {
    next(err);
  }
};

/**
 * Check if this route matches `path`, if so
 * populate `.params`.
 *
 * @param {String} path
 * @return {Boolean}
 * @api private
 */

Layer.prototype.match = function match(path) {
  if (this.regexp.fast_slash) {
    // fast path non-ending match for / (everything matches)
    this.params = {};
    this.path = '';
    return true;
  }

  var m = this.regexp.exec(path);

  if (!m) {
    this.params = undefined;
    this.path = undefined;
    return false;
  }

  // store values
  this.params = {};
  this.path = m[0];

  var keys = this.keys;
  var params = this.params;
  var n = 0;
  var key;
  var val;

  for (var i = 1, len = m.length; i < len; ++i) {
    key = keys[i - 1];
    val = decode_param(m[i]);

    if (key) {
      params[key.name] = val;
    } else {
      params[n++] = val;
    }
  }

  return true;
};

/**
 * Decode param value.
 *
 * @param {string} val
 * @return {string}
 * @api private
 */

function decode_param(val){
  if (typeof val !== 'string') {
    return val;
  }

  try {
    return decodeURIComponent(val);
  } catch (e) {
    var err = new TypeError("Failed to decode param '" + val + "'");
    err.status = 400;
    throw err;
  }
}