bootstrap.rot.js

const { interfaces: Ci, utils: Cu, classes: Cc } = Components;

Cu.import("resource:///modules/imServices.jsm");

let consoleService = Cc["@mozilla.org/consoleservice;1"]
                       .getService(Ci.nsIConsoleService);

function log(msg) {
  consoleService.logStringMessage(msg);
}

function rot13(aString)
  aString.replace(/[a-zA-Z]/g, function(c)
    String.fromCharCode(c.charCodeAt(0) + (c.toLowerCase() < "n" ? 1 : -1) * 13));

let rotTransform = {
  observe: function(aSubject, aTopic, aData) {
    switch(aTopic) {
    case "sending-message":
      aSubject.message = rot13(aSubject.message);
      break;
    case "receiving-message":
      aSubject.originalMessage = rot13(aSubject.message);
      break;
    default:
      log(aTopic);
    }
  }
};

let originalAddConversation;
function startup() {
  let cs = Services.conversations.wrappedJSObject;
  originalAddConversation = cs.addConversation;
  cs.addConversation = function(prplIConvIM) {
    prplIConvIM.addObserver(rotTransform);
    originalAddConversation.call(cs, prplIConvIM);
  };
}

function shutdown() {
  if (reason === APP_SHUTDOWN)
    return;

  let cs = Services.conversations.wrappedJSObject;
  for each (let prplIConvIM in cs.getUIConversations())
    prplIConvIM.removeObserver(rotTransform);
  cs.addConversation = originalAddConversation;
}