/**
 * FireChat constructor, user joins chatroom after successful initialization
 * @param {String} screenName The nickname of the chat user that's displayed 
 * on the screen. A 3-character random string is used if undefined
 * @param {String} username The username that the user publishes chat data with; 
 * In the tutorial's case it's the user's email. A 10-character string is used 
 * if undefined.
 * @param {String} chatroom The name of the chatroom/channel
 * @param {Function} onChatData, onUserLeave, onUserJoin, updateRosterm onChatDataVerified; UI callbacks
 * @param {Bool} usePersistentStorage Set true for this app to use an indexeddb
 * based persistent chat data storage; defaults to False
 * @param {Bool} requireVerification Set true for this app to ignore unverified
 * sync messages; defaults to False
 */
var FireChat = function
   (screenName, username, chatroom,
    onChatData, onUserLeave, onUserJoin, updateRoster, onChatDataVerified
    usePersistentStorage, requireVerification)

/**
 * This user's join; called automatically in constructor for now.
 */
FireChat.prototype.join = function()

/**
 * Append a message to the message cache, and publish new sync state upon calling
 * @param {String} msg The message to send
 */
FireChat.prototype.send = function(msg)

/**
 * This user's leave; not called for now.
 */
FireChat.prototype.leave = function()

/**
 * User join callback to pass into FireChat class
 * @param {String} from The screen name of the user that joined
 * @param {Number} time The receive time of join message
 * @param {String} msg The message that comes with the join message, ignored
 * @param {Bool} verified Since we decided to move this out of onVerified to onData, other user join will always be unverified
 * @param {String} name The user name of the user that joined
 * @param {String} session The session name of the user that joined
 * @param {Number} seqNo The sequence number of this join message; this concatenated with name and session is used to identify an html element if needed, so that we can change the style of that element upon verification or verification failed; alternative: expose verify method (with NDN data as parameter?) and call verify inline
 */
function onUserJoin(from, time, msg, verified, name, session, seqNo)

/**
 * Same parameters as onUserJoin
 */
function onUserLeave(from, time, msg, verified, name, session, seqNo)

/**
 * Same parameters as onUserJoin
 */
function onChatData(from, time, msg, verified, name, session, seqNo)

/**
 * Update roster function, usually called right after onUserJoin, or onUserLeave
 * @param {Object} roster, the roster is a dictionary keyed by "username + session", value is an object of {"screenName": "XXX", lastReceivedSeqNo: XX}
 */
function updateRoster(roster)

/**
 * onChatDataVerified is called when a piece of data is successfully verified
 * @param {String} name The username of the verified data
 * @param {String} session The session name of the verified data
 * @param {Number} seqNo The sequence number of the verified data; this concatenated with name and session is used to identify an html element if needed
 */
function onChatDataVerified(name, session, seqNo)

/**
 * Library interface for getting current ID cert
 * @return {String} The (base64 encoded) default certificate of this instance's
 */
FireChat.prototype.getBase64CertString = function()

/**
 * Library interface for installing ID cert
 * @param {String} signedCertString The signed certificate string encoded in base64
 * @param {Function} onSuccess() Success callback for id cert installed
 * @param {Function} onError(error) Error callback
 */
FireChat.prototype.installIdentityCertificate = function(signedCertString, onSuccess, onError)

  // Create the FireChat class and join the given chatroom
  var chronoChat = new FireChat
    (screenName, username, chatroom, 
     onChatData, onUserLeave, onUserJoin, updateRoster, onChatDataVerified,
     true, false);
  ...
  
  var unsignedCert = chronoChat.getBase64CertString();
  ...
  chronoChat.installIdentityCertificate(signedCert, function () {
      console.log("Cert installation ready.");
      ...
  });
  ...

  // Sending chat messages
  chronoChat.send("Hi there");
  ...
  
  // Leave before window unloads
  chronoChat.leave();

    "validator"                   + "\n" +
    "{"                           + "\n" +
    "  rule"                      + "\n" +
    "  {"                         + "\n" +
    "    id \"Chat Rule\""        + "\n" +
    "    for data"                + "\n" +
    "    filter"                  + "\n" +
    "    {"                       + "\n" +
    "      type name"             + "\n" +
    "      name /ndn/org/icn"     + "\n" +
    "      relation is-prefix-of" + "\n" +
    "    }"                       + "\n" +
    "    checker"                 + "\n" +
    "    {"                       + "\n" +
    "      type hierarchical"     + "\n" +
    "      sig-type rsa-sha256"   + "\n" +
    "    }"                       + "\n" +
    "  }"                         + "\n" +

    "  rule"                      + "\n" +
    "  {"                         + "\n" +
    "    id \"Sync Rule\""        + "\n" +
    "    for data"                + "\n" +
    "    filter"                  + "\n" +
    "    {"                       + "\n" +
    "      type name"             + "\n" +
    "      name /ndn/multicast/CHAT/CHANNEL" + "\n" +
    "      relation is-prefix-of" + "\n" +
    "    }"                       + "\n" +
    "    checker"                 + "\n" +
    "    {"                       + "\n" +
    "      type customized"       + "\n" +
    "      sig-type rsa-sha256"   + "\n" +
    "      key-locator"           + "\n" +
    "      {"                     + "\n" +
    "        type name"           + "\n" +
    "        regex ^<ndn><org><icn><USER><><KEY><><ID-CERT>$" + "\n" +
    "      }"                     + "\n" +
    "    }"                       + "\n" +
    "  }"                         + "\n" +

    "  trust-anchor"              + "\n" +
    "  {"                         + "\n" +
    "    type base64"             + "\n" +
    "    base64-string \"" + trustAnchorBase64 + "\"" + "\n" +
    "  }"                         + "\n" +
    "}"                           + "\n";