safechat/nodejs/public/javascripts/safechat.js

/*! @file

   @id $Id$

   This is the main application as it is fully run in the user's browser.

   @dot
   digraph X {

   start [URL="\ref start()"];
   newuser [URL="\ref newuser()"];
   login [URL="\ref login()"];
   createkeypair [URL="\ref createkeypair()"];
   chat [URL="\ref chat()"];
   getpwd [URL="\ref getpwd()"];
   setpw [URL="\ref setpw()"];
   get [URL="\ref get()"];
   sendmessage [URL="\ref sendmessage()"];
   
   start -> newuser [label="if no keys exist"];
   start -> login [label="if keys exist"];
   newuser -> createkeypair [label="on submit"];
   createkeypair -> "openpgp.generateKey";
   "openpgp.generateKey" -> login [label="keys generated in local store"];
   login -> chat [label="user is valid on server"];
   chat -> getpwd [label="password not yet entered"];
   getpwd -> setpw [label="on input"];
   setpw -> chat [label="password is valid"];
   chat -> chat [label="remain in chat"];
   chat -> get [label="start timer"];
   get -> get [label="restart timer"];
   chat -> sendmessage [label="on submit"];
   sendmessage -> chat [label="remain in chat"];
   }
   @enddot
 */
//       1         2         3         4         5         6         7         8
// 45678901234567890123456789012345678901234567890123456789012345678901234567890

function SafeChat() {

  /// Create UID from a name by appending an E-Mail
  function uid(name) {
    return name+' <'+name+'@'+hostname+'>'
  }

  /// @class Crypto cryptographic functions
  /** @param view is of class SafeChat.View */
  function Crypto(view) {

    /// cache client's key from local strorage
    var k = null

    /// detect hosstname, default to safechat.ch
    var hostname = window.location.hostname!='localhost'?window.location.hostname:'safechat.ch'
    
    /// get user key
    /** @internal key ist cached in k
       @return key */
    function key() {
      if (k) return k
      if (typeof localStorage.key == 'undefined') return null
      return k = openpgp.key.readArmored(localStorage.key)
    }

    /// get own user name
    /** get user name as user id of first public key */
    function user() {
      if (k || key()) return k.pub.keys[0].getUserIds()[0]
      return null
    }

    /// create New User
    function createuser(user, email, pwd) {
      view.notice("generating keys")
      openpgp.generateKey({
        numBits: 4096,
        userIds: [{name: user, email: email}],
        passphrase: pwd
      }).then(function(keyPair) {
        view.success("keys generated")
        localStorage.key = keyPair.privateKeyArmored
        k = keyPair.key
      }).catch(function(e) {
        console.log(e)
        view.fatal("generating key pairs failed")
      })
    }

    /// open private key with password
    /** @return @c true if password matches */
    function password(pwd) {
      return (k || keys()) && k.keys[0].decrypt(pwd)
    }

    /// Encrypt Message
    function encrypt(message, targetkeys, done, failed) {
      if (!k) return false
      openpgp.encrypt({
        publicKeys: targetkeys.keys.concat(k.keys),
        privateKeys: k,
        data: message,
        armor: false
      }).then(done).else(failed)
      return true
    }

    /// Decrypt Message
    function decrypt(message, sourcekeys, done, failed) {
      if (!k) return false
      openpgp.decrypt({
        privateKeys: k.keys,
        publicKeys: sourcekeys.keys,
        message: message
      }).then(done).else(failed)
      return true
    }

  }

  /// database that stores in indexed db
  function DataBase() {

    function user(name, key) {
    }
    
  }

  /// manage local copy of users
  function Users() {
    
    var users = new Map()
    
    function add(usr) {
      if (!users[usr.name])
        users[usr.name].valid = true
      else
        users[usr.name].valid = users[usr.name].valid && users[usr.name].key == usr.key
      users[usr.name].key = usr.key
      users[usr.name].online = usr.online
    }
    
  }

  /// manage local copy of messages
  function Messages() {
    
    var messages = {};

    function add() {
    }
    
  }

  /// @class Communication client socket communication
  /** @param view is of class SafeChat.View */
  function Communication(controller) {
    
    var socket = io.connect()
    
    function broadcast(signal, data) {
      console.log("<=snd "+signal)
      socket.broadcast.emit(signal, data)
    }

    function emit(signal, data) {
      console.log("<-snd "+signal)
      socket.emit(signal, data)
    }

    socket
      .on("login", controller.loggedin)
      .on("fail", controller.fail)
      .on("user", controller.user)
      .on("users", controller.users)
      .on("message", controller.message)
      .on("messages", controller.messages)
      .io
      .on("connect", controller.connected)
      .on("reconnect", controller.connected)
      .on("disconnect", controller.disconnected)
      .on("error", controller.disconnected)
    
  }

  /// @class View provides the glue to the GUI in the index.ejs file
  /** View provides the following callbacks:
     - status updates:
     - @c notice(msg) to display information 
     - @c warning(msg) 
     - @c error(msg)
     - @c fatal(msg) */
  function View() {

    var nexttimer = null

    /// Padding for numbers in dates
    function pad(n) {
      return n<10 ? '0'+n : n
    }

    /// escape text to show in html @see htmldec
    function htmlenc(html) {
      return $('<div/>').text(html).html()
    }

    /// decode html encoded text @see htmlenc
    function htmldec(data) {
      return $('<div/>').html(data).text()
    }

    /// alert user accoustically or by vibration
    /** alert user, e.g. that a new message has arrived. */
    function beep() {
      if (navigator.vibrate) navigator.vibrate(1000)
      (new Audio("sounds/beep.mp3")).play()
    }

    /// show fatal error
    /** something completely failed, abort
        @param msg  */
    function fatal(msg) {
      if (nexttimer) clearTimeout(nexttimer)
      if (msg) {
        error(msg)
        $('#fatal-msg').html(msg)
      }
      show('fatal')
    }
    
    /// show error messsage
    /** shows an error message and logs to console.
        @param data (optional) The error can be a string or any structure.
               Strings are shown to the user, structures are logged only.
        @param next (optional) next function to call */
    function error(data, next) {
      if (nexttimer) clearTimeout(nexttimer)
      $("#status").hide()
      $("#status").addClass("error")
      $("#status").removeClass("notice")
      $("#status").removeClass("success")
      if (data) {
        if (typeof data == 'string') {
          $("#status").html(data)
          console.log("error: "+data)
        } else {
          $("#status").html('error')
          console.log("error: "+JSON.stringify(data))
        }
      } else {
        $("#status").html('error')
        console.log("error")
      }
      $("#status").show()
      if (next) nexttimer = setTimeout(function() {
        nexttimer = null
        next()
      }, 5000)
    }

    /// show notice messsage
    /** shows an notice message and logs to console.
        @param text (optional) The data is a string. */
    function notice(text) {
      $("#status").hide()
      $("#status").addClass("notice")
      $("#status").removeClass("error")
      $("#status").removeClass("success")
      if (text) {
        $("#status").html(text)
        console.log("notice: "+text)
      } else {
        $("#status").html('')
        console.log("notice")
      }
      $("#status").show()
    }

    /// show success messsage
    /** shows an success message and logs to console.
        @param text (optional) The data is a string. */
    function success(text) {
      $("#status").hide()
      $("#status").addClass("success")
      $("#status").removeClass("error")
      $("#status").removeClass("notice")
      if (text) {
        $("#status").html(text)
        console.log("success: "+text)
      } else {
        $("#status").html('')
        console.log("success")
      }
      $("#status").show()
    }

    /// show a specific screen given the element id
    /** @param id html id to be shown.
        @param msg (optional) the success message text */
    function show(id, msg) {
      console.log("state: "+id)
      if (msg) success(msg) else $("#status").hide()
      $("#main").children(":not(#"+id+")").hide()
      $("#main #"+id).show()
      $("#main #"+id+" form input:first-child").focus()
    }

    /// show server connected status
    function connected() {
      console.log("server connected")
      $("#connectionstatus #bad").hide()
      $("#connectionstatus #good").show()
      success("server connected")
    }

    /// show server disconnected status
    function disconnected() {
      console.log("server disconnected")
      $("#connectionstatus #good").hide()
      $("#connectionstatus #bad").show()
      error("server disconnected", true)
    }
    
    /// toggle menu display
    function togglemenu() {
      $("#menu").toggle()
    }

    function checkFeature(id, query) {
      if (query) $('#'+id+':before')
        .css('color', 'green')
        .css('content', '&#x2714;')
      else $('#'+id+':before')
        .css('color', 'red')
        .css('content', '&#x2718;')
      if (query) $('#'+id)
        .css('color', 'green')
        .css('text-decoration', 'line-through')
      else $('#'+id)
        .css('color', 'red')
        .css('text-decoration', 'none')
    }

    function checkFeatures() {
      $('ul.features').css('list-style-type', 'none')
      checkFeature("localstorage", Storage)
      checkFeature("indexeddb", window.indexedDB)
      checkFeature("randomvalues", window.crypto.getRandomValues)
      checkFeature("vibrate", navigator.vibrate)
      checkFeature("filereader", window.FileReader)
    }

    function DataTransfer() {
      
      var reboottimer = null
      var data = new DataTransfer()

      /// download profile backup
      function backup() {
        var download = document.createElement('a')
        download.href = 'data:attachment/text,'+encodeURI(JSON.stringify(localStorage))
        download.target = '_blank'
        var now = new Date()
        download.download =
        pad(now.getFullYear())+pad(now.getMonth()+1)+pad(now.getDate())+
        "-"+userid()+"@"+hostname+".bak"
        var clickEvent = new MouseEvent("click", {
          "view": window,
          "bubbles": true,
          "cancelable": false
        })
        download.dispatchEvent(clickEvent)
        togglemenu()
      }
      
      /// Upload Profile Backup
      function restore(evt) {
        for (var i=0, f; f=evt.target.files[i]; ++i) {
          var file = f
          var reader = new FileReader()
          reader.onload = function(evt) {
            if (evt.target.error) return error("error reading file")
            if (evt.target.readyState==0) return notice("waiting for data …")
            if (evt.target.readyState==1) return notice("loading data …")
            var parsed=JSON.parse(evt.target.result)
            togglemenu()
            localStorage.pubkey = parsed.pubkey
            localStorage.privkey = parsed.privkey
            success("backup is restored")
            console.log("reboot after restore in 2s")
            if (!reboottimer && reboot) reboottimer = setTimeout(function() {
              reboottimer = null
            }, 2000)
          }
          reader.readAsText(file)
        }
      }

      if (!window.FileReader) {
        $('restore-menu-item').hide()
        error("your browser does not support file upload")
      }

    }

  }

  /// @class Controller defines the programm flow
  function Controller(view) {
    
    var db = new Database()
    var communication = new Communication(this)
    var users = new Users()
    
    function fail(msg) {
      console.log('rcv-> fail('+msg+')')
      error(msg)
    }

    function loggedin() {
      console.log("rcv-> login")
      success("login successful")
      chat()
    }
    
    function user(usr) {
      console.log("rcv-> user")
      if (usr.exits) users.add(usr)
    }

    function users() {
      console.log("rcv-> users")
    }
    
    function message(msg) {
      console.log("rcv-> message")
    }
    
    function messages(msgs) {
      console.log("rcv-> messages")
    }

    this.connected = view.connected
    this.reconnect = view.connected
    this.disconnect = view.disconnected
    this.error = view.disconnected

    function login() {
    }

    function user(usr) {
      if (usr.exists) db.adduser
    }

    function initBrowser() {
      window.indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB
      window.IDBTransaction = window.IDBTransaction || window.webkitIDBTransaction || window.msIDBTransaction
      window.IDBKeyRange = window.IDBKeyRange || window.webkitIDBKeyRange || window.msIDBKeyRange
      navigator.vibrate = navigator.vibrate || navigator.webkitVibrate || navigator.mozVibrate || navigator.msVibrate
      return window.indexedDB && window.crypto.getRandomValues && Storage
    }

    function run() {
    }

    function start() {
      view.reboot = run
      var compatible = initBrowser()
      view.checkFeatures()
      if (!compatible)
        view.fatal("your browser is not supported")
      else
        run()
    }

  }

  //==============================================================================

  //------------------------------------------------------------------------------
  return new Controller(new View())

}
  
  var filecontent = new Array() ///< temporary storage for attachments
  var reboottimer = null

  function connectionstatus() {
    if (socket.connected) connected() else disconnected()
  }

  /// Configure local groups
  /** … */
  function groups() {
  }

  /// Check if password is set and matches the repeated password
  /** Checks if both passwords are identical and valid and gives
     feedback to the user.

     Called when user edits the password fields.

     Sets @ref username and checks @ref password - if both are well
     defined, enables the submit button.

     @param pwd The password.
     @param pwd2 The repeated password. */
  function checkpwd(pwd, pwd2) {
    $("#register").submit(function(event) {
      return false
    })
    if (pwd==pwd2) password=pwd
    else password=null
    if (!password||password.length<1) password=null
    $("#createuser").prop("disabled", !(username && password))
    if (password) {
      if (username) success("user is ready to be created")
      else notice("password matches, please chose a valid user name")
    } else {
      if (username) notice("passwords don't match")
      else if ($('#user').val()) notice("user name is already in use")
      else notice("please chose a user name")
      
    }
  }

  /// Checks if the receiver of a message exists on server.
  /** Calls checknewuser.php on server and enables the message submit
     button if the receiver of the message exists on the server. */
  function checkpartner(user) {
    $("#chat").submit(function(event) {
      return false
    })
    emit("user", uid(user))
  }

  /// Create Local Public-/Private-Key Pair
  /** Called if user has not yet his keys, just generates a new key pair. */
  function createkeypair(user, pwd) {
    notice("generating keys")
    openpgp.generateKey({
      numBits: 4096,
      userIds: [{name: user, email: user+'@'+hostname}],
      passphrase: pwd
    }).then(function(keyPair) {
      success("keys generated")
      localStorage.pubkey = keyPair.publicKeyArmored
      localStorage.privkey = keyPair.privateKeyArmored
      login()
    }).catch(function(e) {
      console.log(e)
      error("generating key pairs failed")
    })
  }

  /// Get Own Public Key
  /** @return public key object */
  function publicKey() {
    if (typeof localStorage.pubkey == 'undefined') {
      if (typeof localStorage.pubKey == 'undefined') {
        return null
      } else {
        localStorage.pubkey = localStorage.pubKey
        localStorage.removeItem(pubKey)
      }
    }
    return openpgp.key.readArmored(localStorage.pubkey)
  }

  /// Get Own Private Key
  /** @return private key object */
  function privateKey() {
    if (typeof localStorage.privkey == 'undefined') {
      if (typeof localStorage.privKey == 'undefined') {
        return null
      } else {
        localStorage.privkey = localStorage.privKey
        localStorage.removeItem(privKey)
      }
    }
    return openpgp.key.readArmored(localStorage.privkey)
  }

  /// Get Own User Name
  /** Get user name as user id of first public key */
  function userid() {
    if (!publicKey() ||
        publicKey().keys.length < 1 ||
        publicKey().keys[0].getUserIds().length < 1) return null
    return publicKey().keys[0].getUserIds()[0]
  }

  /// Clear Message Text And Attachments
  /** Does not remove the receiver's name */
  function clearmessage() {
    $("#message").prop(":disabled", true)
    filecontent = new Array()
    $('#preview').empty()
    $("#msg").val("")
    $("#message").prop(":disabled", false)
  }

  function guessfilename(mimetype, user, date) {
    if (!user) user = userid()
    if (!date) date = new Date()
    var ext = mimetype.replace(/.*\/(x-)?/i, "")
    return pad(date.getFullYear())+pad(date.getMonth()+1)+pad(date.getDate())
          +"-"+ext+"-"+user+"@"+hostname+'.'+ext
  }

  /// Display Image Attachments
  function attachments(files, id, from, date) {
    if (files) files.forEach(function(file) {
      console.log(file)
      if (!file.name) file.name = guessfilename(file.type, from, date)
      var a = document.createElement('a')
      a.href = file.content
      a.download = file.name
      a.target = '_blank'
      if (file.type.match('^image/')) {
        var img = document.createElement('img')
        img.title = file.name
        img.src = file.content
        a.appendChild(img)
      } else if (file.type.match('^video/')) {
        var video = document.createElement('video')
        video.controls = true
        video.title = file.name
        video.src = file.content
        a.appendChild(video)
      } else {
        var img = document.createElement('img')
        img.title = file.name
        img.src = "images/Document_sans_PICOL-PIctorial-COmmunication-Language.svg"
        a.appendChild(img)
      }
      $(id).append(a)            
    })
  }

  var recorder

  function done() {
    if (recorder) {
      recorder.stop()
      recorder.recording(function(data) {
        previewfile(data, "video/webm")
        abort()
      })
    }
  }

  function abort() {
    if (recorder) {
      $("#videorecorder").hide()
      recorder.release()
      delete recorder recorder = null
    }
  }

  /// Record Video from builtin camera
  function recordvideo() {
    try {
      abort()
      $("#videorecorder").show()
      recorder = new MediaStreamRecorder({
        video: {
          width: {ideal: 180},
          height: {ideal: 160}
        },
        audio: true
      })
      recorder.on("ready", function() {
        $("#videorecorder video").attr("src", recorder.preview())
        $("#videorecorder video").css("width", 180)
        $("#videorecorder video").css("height", 160)
        $("#videorecorder video").attr("width", 180)
        $("#videorecorder video").attr("height", 160)
        recorder.start()
      })
    } catch (e) {
      console.log(e)
      error("cannot access camera", true)
    }
  }

  function previewfile(content, type, name) {
    if (!name) name = guessfilename(type)
    if (type.match('^image/')) {
      var img = document.createElement("img")
      img.onload = function() { // resize image to maximum 400px
        var MAX = 400
        var width = img.width
        var height = img.height
        if (width > MAX) {
          height *= MAX / width
          width = MAX
        }
        if (height > MAX) {
          width *= MAX / height
          height = MAX
        }
        var canvas = document.createElement("canvas")
        canvas.width = width
        canvas.height = height
        var ctx = canvas.getContext("2d")
        ctx.drawImage(img, 0, 0, width, height)
        img.onload = function() {
          filecontent.push({name: name, type: type, content: img.src})
          $("#preview").append(img)
          success('image is ready to be sent')
        }
        img.src = canvas.toDataURL(file.type)
        img.title = name+"\n"+size(img.src.length)
      }
      img.src=content
    } else if (type.match('^video/')) {
      filecontent.push({name: name, type: type, content: content})
      var video = document.createElement("video")
      video.setAttribute("controls", "controls")
      video.setAttribute("loop", "loop")
      video.setAttribute("src", content)
      video.setAttribute("title", name+"\n"+size(content.length))
      $("#preview").append(video)
    } else {
      filecontent.push({name: name, type: type, content: content})
      var img = document.createElement("img")
      img.src = "images/Document_sans_PICOL-PIctorial-COmmunication-Language.svg"
      img.title = name+"\n"+size(content.length)
      $("#preview").append(img)
    }
  }

  /// Upload Attachment
  /** Prepares attachment to be sent in a message. If the attachment is
     an image, it resizes the image to 400px on the lager side.

     By now, only images are supported.

     Stores data in global variable @ref filecontent. */
  function fileupload(evt) {
    if (!window.FileReader)
      return error("your browser does not support file upload", true)
    for (var i=0, f; f=evt.target.files[i]; ++i) {
      var file = f
      var reader = new FileReader()
      reader.onload = function(evt) {
        if (evt.target.error) return error("error reading file", true)
        if (evt.target.readyState==0) return notice("waiting for data …")
        if (evt.target.readyState==1) return notice("loading data …")
        previewfile(evt.target.result, file.type, file.name)
      }
      reader.readAsDataURL(file)
    }
  }

  /// Sets Receiver's Name
  /** Called when clicked on a receiver's name. Sets focus to the
     message text field.

     @param name The receiver's name. */
  function setreceiver(name) {
    $("#recv").val(name)
    checkpartner(name)
    $("#msg").focus()
  }

  var userMap = null
  function users(userlist) {
    console.log("rcv-> users")
    userMap = new Array()
    $("#allusers").empty()
    userlist.forEach(function(usr) {
      userMap[usr.name] = usr.pubkey
      $("#allusers").append('<option value="'+htmlenc(usr.name)+'">')
      $("#allusers").hide()
      console.log("   user: "+usr.name)
    })
    localStorage.userMap = JSON.stringify(userMap)
  }

  function user(usr) {
    if (usr.exists) console.log("rcv-> user("+usr.name+")")
    else console.log("rcv-> user("+usr.name+"): name is available")
    if ($("#newuser").is(":visible") && usr.name==uid($('#user').val())) {
      // same username as in the create user form
      $("#createuser").prop("disabled", usr.exists) // todo: check password
      if (!usr.exists) {
        username = usr.name
        success("user name "+usr.name+" is available")
      } else {
        username = null
        error("user name "+usr.name+" is in use", true)
      }
    }
    if ($("#chat").is(":visible") && usr.name==uid($("#recv").val())) { // same username as in receiver
      $('#send').prop("disabled", !usr.exists)
      $("label[for=send] img").css("opacity", usr.exists?"1.0":"0.4")
      $("label[for=send] img").css("filter", usr.exists?"alpha(opacity=100)":"alpha(opacity=40)")
      if (usr.exists) success("recipient exists")
      else error("unknown recipient", true)
    }
    if (userMap == null) {
      if (localStorage.userMap) {
        userMap = JSON.parse(localStorage.userMap)
      } else {
        userMap = new Array()
      }
    }
    if (usr.exists && usr.pubkey && userMap[usr.name] != usr.pubkey) {
      userMap[usr.name] = usr.pubkey
      $("#allusers").append('option value="'+htmlenc(usr.name)+'"')
      localStorage.userMap = JSON.stringify(userMap)
    }
  }

  function queryuser(usr) {
    console.log("query user: "+uid(usr))
    socket.emit("user", uid(usr))
  }

  /// Get a user's public key.
  /** The first time, gets it from the server, later from the cache. */
  function getPublicKey(user) {
    var deferredObject = $.Deferred()
    if (userMap && userMap[user]) deferredObject.resolve(userMap[user])
    else deferredObject.reject("unknown user")
    return deferredObject.promise()
  }

  /// Received a list of messages from server
  function messages(msgs) {
    console.log("rcv-> messages("+msgs.length+")")
    if (!password || !privateKey())
      return setTimeout(function() {emit("messages")}, 1000) // try again later
    status("allmessages")
    notice("load messages, please wait …")
    msgs.forEach(function(msg) {message(msg, true)})
    status("chat")
  }

  /// Received a message from server
  function message(m, internal) {
    if (!internal) console.log("rcv-> message("+m.user+")")
    if (!password || !privateKey()) return
    var key=openpgp.key.readArmored(m.pubkey)
    if (key.err) return error("key of sender unreadable", true)
    var message = openpgp.message.readArmored(m.msg)
    var privkey = privateKey().keys[0]
    if (privkey.decrypt(password)) // prepare own key
      openpgp.decrypt({
        privateKeys: privkey,
        publicKeys: key.keys,
        message: message
      }).then(function(msg) { // decryption succeded
        openpgp.decrypt({
          privateKeys: privkey,
          publicKeys: key.keys,
          message: message
        }).then(function(msg) { // decryption succeded
          // prepend message to list of messages
          var message = JSON.parse(msg.text)
          $("#msgs") // todo: check msg.signatures[0].valid
            .prepend('<div id="id'+(m.id)+'" class="msg '+
                            (m.user==userid()?"me":"other")+
                     '"><div class="header">'+
                     '<span class="date">'+
                            (new Date(m.time)).toLocaleString()+
                     '</span><span class="sender">'+
                     '<a href="javascript:void(0)" '+
                     'onclick="setreceiver(this.innerHTML)">'+
                     htmlenc(m.user)+
                     '</a>'+(message.receiver?' → <a href="javascript:void(0)" '+
                                              'onclick="setreceiver(this.innerHTML)">'
                                             +htmlenc(message.receiver)+'</a>':"")+
                     '</span></div>'+
                     '<div class="text">'+
                     htmlenc(message.text)+
                     '</div></div><div class="clear"/>')
          // show attachments
          attachments(message.files, '#id'+m.id+' .text', m.user, new Date(m.time))
          // calculate and show emoticons
          $('#id'+m.id).emoticonize()
          if (!internal) beep(m.user)
        }).catch(function(e) {
          // not for me
          success()
        })
      }

        /// Send Message To Server
        /** User wants to send a message. Encrypt message with own private and
           the receiver's public key, then send it to the server. */
        function sendmessage(recv, txt) {
          notice("1/3 preparing message …")
          $("#message").prop(":disabled", true)
          getPublicKey(recv) // get receiver's public key
            .done(function(pk) {
              var key=openpgp.key.readArmored(pk)
              if (!pk||key.err) {
                $("#message").prop(":disabled", false)
                error("receiver's key not found", true)
                return
              }
              var privkey = privateKey().keys[0]
              privkey.decrypt(password) // get own private key ready
              var message = JSON.stringify({receiver: recv, text: txt, files: filecontent})
              notice("2/3 encrypting message …")
              openpgp.encrypt({publicKeys: key.keys.concat(publicKey().keys),
                               privateKeys: privkey,
                               data: message,
                               armor: false})
                     .then(function(msg) { // message is encrypted
                       notice("3/3 sending message …")
                       emit("message", {user: userid(), content: msg})
                       clearmessage()
                     })
                     .catch(function(e) {
                       $("#message").prop(":disabled", false)
                       error("encryption of message failed", true)
                     })
            })
            .fail(function(e) {
              $("#message").prop(":disabled", false)
              error("user not found", true)
            })
        }

        /// Check And Set Password
        /** Check if given password matches to decrypt the private key. If so,
           store it in global temporary variable @ref password and start the
           chat. The password matches, when the private key can be decrypted.

           @param pwd The password to check. */
        function setpw(pwd) {
          if (privateKey().keys[0].decrypt(pwd)) {
            success("password matches")
            $("#removeKey").hide()
            password = pwd
            chat()
          } else {
            notice("password does not match")
          }
        }

        /// Create Password Entry Field
        /** Asks user for password. When user starts to enter it, it is
           permanentely checked in setpw(). As soon as the password matches,
           setpw() continues automatically. No submit is required by the
           user. */
        function getpwd() {
          if (password) return
          $("#removeKey").show()
          status("getpwd")
        }

        function deleteUser() {
          var uid = userid()
          localStorage.removeItem(pubkey)
          localStorage.removeItem(privkey)
          error("user "+uid+" permanentely lost")
        }

        function removeKey() {
          togglemenu()
          $("#removeKey").hide()
          status('forgotpassword')
        }

        /// Main Chat Window
        /** Gets chat widgets from server and displays them. Starts timer for
           get() which polls for new messages. */
        var firsttime = true
        function chat() {
          if (!password) return getpwd()
          status("chat")
          if (firsttime && $('#msgs').is(':empty')) {
            firsttime = false
            notice("getting previous messages, please wait …")
            emit("messages")
          }
        }

        /// Login User
        /** This is not really a login, it is just some kind of validation.
           The server does not care if a user is online or not, it is only
           interesting to the client to make sure, everything is fine. User
           is logged in the following way: User name and public key are sent
           to the server. If the user name exists on the server and the
           public key is the same, the user is considered logged in, his
           credentials seem to be valid. If user does not yet exits on
           server, it is created now. If user exists, but public key is
           different, then this is a complete failure, something went
           terribly wrong. */
        function login() {
          $("#username").html(userid()+"@"+hostname)
          emit("login", {name: userid(),
                         pubkey: localStorage.pubkey})
          success("login sent to server")
        }

        /// Get And Display Form To Create New User
        /** Shows user creation form. On submit, a private key is generated in
           createkeypair(), then login() creates the user. */
        function newuser() {
          status("newuser")
        }

        /// Check if local storage is available
        function checkLocalStorage() {
          var test = 'test'
          try {
            localStorage.setItem(test, test)
            localStorage.removeItem(test)
            return true
          } catch(e) {
            status("nolocalstorage")
            error("local storage not available")
          }
          return false
        }

        /// Initial Function: Startup
        /** Decide whether to login or to create a new user */
        function start() {
          $("#menu").hide()
          //status("startup")
          if (checkLocalStorage())
            try {
              if (!userid()) {
                newuser()
              } else {
                login()
              }
            } catch (m) {
              console.log(m.stack)
              error(m)
            }
        }

        function init() {
          /// On Load, Call @ref start
          $(window.onbeforeunload = function() {
            return "Are you sure you want to navigate away?"
          })
          /// Allow Running in Background on Android
          document.addEventListener('deviceready', function () {
            if (cordova && cordova.plugins.backgroundMode) {
              cordova.plugins.backgroundMode.enable()
            }
          }, false)
          connectionstatus()
          if (openpgp.initWorker("openpgp.worker.min.js"))
            console.log("asynchronous openpgp enabled")
          else
            console.log("asynchronous openpgp failed")
          emit('users')
          start()
        }

        /// Start Main Loop
        $(init)