/*!
 * router
 * Copyright(c) 2013 Roman Shtylman
 * Copyright(c) 2014 Douglas Christopher Wilson
 * MIT Licensed
 */

'use strict'

/**
 * Module dependencies.
 * @private
 */

var pathRegexp = require('path-to-regexp')

/**
 * Module variables.
 * @private
 */

var hasOwnProperty = Object.prototype.hasOwnProperty
var TRAILING_SLASH_REGEXP = /\/+$/

/**
 * Expose `Layer`.
 */

module.exports = Layer

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

  var opts = options || {}

  this.handle = fn
  this.keys = []
  this.name = fn.name || '<anonymous>'
  this.params = undefined
  this.path = undefined
  this.regexp = pathRegexp((opts.strict ? path : loosen(path)), this.keys, opts)

  // set fast path flags
  this.regexp._slash = path === '/' && opts.end === false
}

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

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

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

  try {
    // invoke function
    var ret = fn(error, req, res, next)

    // wait for returned promise
    if (isPromise(ret)) {
      ret.then(null, function (error) {
        next(error || new Error('Rejected promise'))
      })
    }
  } catch (err) {
    next(err)
  }
}

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

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

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

  try {
    // invoke function
    var ret = fn(req, res, next)

    // wait for returned promise
    if (isPromise(ret)) {
      ret.then(null, function (error) {
        next(error || new Error('Rejected promise'))
      })
    }
  } 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) {
  var match

  if (path != null) {
    // fast path non-ending match for / (any path matches)
    if (this.regexp._slash) {
      this.params = {}
      this.path = ''
      return true
    }

    // match the path
    match = this.regexp.exec(path)
  }

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

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

  // iterate matches
  var keys = this.keys
  var params = this.params

  for (var i = 1; i < match.length; i++) {
    var key = keys[i - 1]
    var prop = key.name
    var val = decodeParam(match[i])

    if (val !== undefined || !(hasOwnProperty.call(params, prop))) {
      params[prop] = val
    }
  }

  return true
}

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

function decodeParam (val) {
  if (typeof val !== 'string' || val.length === 0) {
    return val
  }

  try {
    return decodeURIComponent(val)
  } catch (err) {
    if (err instanceof URIError) {
      err.message = 'Failed to decode param \'' + val + '\''
      err.status = 400
    }

    throw err
  }
}

/**
 * Returns true if the val is a Promise.
 *
 * @param {*} val
 * @return {boolean}
 * @private
 */

function isPromise (val) {
  return val &&
    typeof val === 'object' &&
    typeof val.then === 'function'
}

/**
 * Loosens the given path for path-to-regexp matching.
 */
function loosen (path) {
  if (path instanceof RegExp) {
    return path
  }

  return Array.isArray(path)
    ? path.map(function (p) { return loosen(p) })
    : String(path).replace(TRAILING_SLASH_REGEXP, '')
}