'use strict'

var net = require('net')
  , tls = require('tls')
  , http = require('http')
  , https = require('https')
  , events = require('events')
  , assert = require('assert')
  , util = require('util')
  ;

exports.httpOverHttp = httpOverHttp
exports.httpsOverHttp = httpsOverHttp
exports.httpOverHttps = httpOverHttps
exports.httpsOverHttps = httpsOverHttps


function httpOverHttp(options) {
  var agent = new TunnelingAgent(options)
  agent.request = http.request
  return agent
}

function httpsOverHttp(options) {
  var agent = new TunnelingAgent(options)
  agent.request = http.request
  agent.createSocket = createSecureSocket
  return agent
}

function httpOverHttps(options) {
  var agent = new TunnelingAgent(options)
  agent.request = https.request
  return agent
}

function httpsOverHttps(options) {
  var agent = new TunnelingAgent(options)
  agent.request = https.request
  agent.createSocket = createSecureSocket
  return agent
}


function TunnelingAgent(options) {
  var self = this
  self.options = options || {}
  self.proxyOptions = self.options.proxy || {}
  self.maxSockets = self.options.maxSockets || http.Agent.defaultMaxSockets
  self.requests = []
  self.sockets = []

  self.on('free', function onFree(socket, host, port) {
    for (var i = 0, len = self.requests.length; i < len; ++i) {
      var pending = self.requests[i]
      if (pending.host === host && pending.port === port) {
        // Detect the request to connect same origin server,
        // reuse the connection.
        self.requests.splice(i, 1)
        pending.request.onSocket(socket)
        return
      }
    }
    socket.destroy()
    self.removeSocket(socket)
  })
}
util.inherits(TunnelingAgent, events.EventEmitter)

TunnelingAgent.prototype.addRequest = function addRequest(req, host, port) {
  var self = this

  if (self.sockets.length >= this.maxSockets) {
    // We are over limit so we'll add it to the queue.
    self.requests.push({host: host, port: port, request: req})
    return
  }

  // If we are under maxSockets create a new one.
  self.createSocket({host: host, port: port, request: req}, function(socket) {
    socket.on('free', onFree)
    socket.on('close', onCloseOrRemove)
    socket.on('agentRemove', onCloseOrRemove)
    req.onSocket(socket)

    function onFree() {
      self.emit('free', socket, host, port)
    }

    function onCloseOrRemove(err) {
      self.removeSocket()
      socket.removeListener('free', onFree)
      socket.removeListener('close', onCloseOrRemove)
      socket.removeListener('agentRemove', onCloseOrRemove)
    }
  })
}

TunnelingAgent.prototype.createSocket = function createSocket(options, cb) {
  var self = this
  var placeholder = {}
  self.sockets.push(placeholder)

  var connectOptions = mergeOptions({}, self.proxyOptions, 
    { method: 'CONNECT'
    , path: options.host + ':' + options.port
    , agent: false
    }
  )
  if (connectOptions.proxyAuth) {
    connectOptions.headers = connectOptions.headers || {}
    connectOptions.headers['Proxy-Authorization'] = 'Basic ' +
        new Buffer(connectOptions.proxyAuth).toString('base64')
  }

  debug('making CONNECT request')
  var connectReq = self.request(connectOptions)
  connectReq.useChunkedEncodingByDefault = false // for v0.6
  connectReq.once('response', onResponse) // for v0.6
  connectReq.once('upgrade', onUpgrade)   // for v0.6
  connectReq.once('connect', onConnect)   // for v0.7 or later
  connectReq.once('error', onError)
  connectReq.end()

  function onResponse(res) {
    // Very hacky. This is necessary to avoid http-parser leaks.
    res.upgrade = true
  }

  function onUpgrade(res, socket, head) {
    // Hacky.
    process.nextTick(function() {
      onConnect(res, socket, head)
    })
  }

  function onConnect(res, socket, head) {
    connectReq.removeAllListeners()
    socket.removeAllListeners()

    if (res.statusCode === 200) {
      assert.equal(head.length, 0)
      debug('tunneling connection has established')
      self.sockets[self.sockets.indexOf(placeholder)] = socket
      cb(socket)
    } else {
      debug('tunneling socket could not be established, statusCode=%d', res.statusCode)
      var error = new Error('tunneling socket could not be established, ' + 'statusCode=' + res.statusCode)
      error.code = 'ECONNRESET'
      options.request.emit('error', error)
      self.removeSocket(placeholder)
    }
  }

  function onError(cause) {
    connectReq.removeAllListeners()

    debug('tunneling socket could not be established, cause=%s\n', cause.message, cause.stack)
    var error = new Error('tunneling socket could not be established, ' + 'cause=' + cause.message)
    error.code = 'ECONNRESET'
    options.request.emit('error', error)
    self.removeSocket(placeholder)
  }
}

TunnelingAgent.prototype.removeSocket = function removeSocket(socket) {
  var pos = this.sockets.indexOf(socket)
  if (pos === -1) return
  
  this.sockets.splice(pos, 1)

  var pending = this.requests.shift()
  if (pending) {
    // If we have pending requests and a socket gets closed a new one
    // needs to be created to take over in the pool for the one that closed.
    this.createSocket(pending, function(socket) {
      pending.request.onSocket(socket)
    })
  }
}

function createSecureSocket(options, cb) {
  var self = this
  TunnelingAgent.prototype.createSocket.call(self, options, function(socket) {
    // 0 is dummy port for v0.6
    var secureSocket = tls.connect(0, mergeOptions({}, self.options, 
      { servername: options.host
      , socket: socket
      }
    ))
    cb(secureSocket)
  })
}


function mergeOptions(target) {
  for (var i = 1, len = arguments.length; i < len; ++i) {
    var overrides = arguments[i]
    if (typeof overrides === 'object') {
      var keys = Object.keys(overrides)
      for (var j = 0, keyLen = keys.length; j < keyLen; ++j) {
        var k = keys[j]
        if (overrides[k] !== undefined) {
          target[k] = overrides[k]
        }
      }
    }
  }
  return target
}


var debug
if (process.env.NODE_DEBUG && /\btunnel\b/.test(process.env.NODE_DEBUG)) {
  debug = function() {
    var args = Array.prototype.slice.call(arguments)
    if (typeof args[0] === 'string') {
      args[0] = 'TUNNEL: ' + args[0]
    } else {
      args.unshift('TUNNEL:')
    }
    console.error.apply(console, args)
  }
} else {
  debug = function() {}
}
exports.debug = debug // for test