routes.js

/*
 *  Define all routes here for the fly-latex application.
 *  
 */

var mongoose = require("mongoose")
, Schema = mongoose.Schema
, ObjectId = Schema.ObjectId
, app = require("./app")
, io = require("socket.io").listen(app)

// load configurations here
, configs = require("./configs")

, temp = require("temp")
, fs = require("fs-extra")
, util = require("util")
, path = require("path")
, exec = require("child_process").exec
, http = require("http")

// flylatex directory
, flylatexdir = __dirname;

// connect to the flydb app db
mongoose.connect(configs.db.url);

require("./models"); // import the models here

// import the models here
var User = mongoose.model("User")
, Document = mongoose.model("Document")
, DocumentLine = mongoose.model("DocumentLine")
, DocPrivilege = mongoose.model("DocPrivilege")
, Message = mongoose.model("Message")
, PDFDoc = mongoose.model("PDFDoc");


// ================ GLOBAL variables here =============

// maximum number of documents a user can have
var MAX_DOCS = ( configs.docs.MAX_NUM_PER_USER > 0 ? configs.docs.MAX_NUM_PER_USER : 20 );

// messageTypes
var MESSAGE_TYPES = {
    'requestAccess': 0
    , 'shareAccess': 1
};

// currently opened documents
// map of docId : [username]
var openDocuments = {};

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


/*
 * About rendering:
 * the object to pass to the template being rendered has to have:
 * ===== title ======
 * ===== shortTitle ======
 * Optionally can have:
 * * fileSpecificScript
 * * fileSpecificStyle
 * * currentUser
 * * isLoggedIn (should always go together with currentUser)
 * * tagLine
 * * currentDoc
 * * userDocuments - this is an abstraction of the real Document model.
     So it contains different attributes.
     contains: id, name, readAccess, writeAccess, execAccess, canShare
 * * errors
 * * infos
*/


/*
 * preGetIndex -
 * load currentUser's data before loading page
 * if user's not registered, just go to next
 * @param req -> request object
 * @param res -> response object
 * @param next -> next (middleware) function (in callchain) to execute
 */
exports.preIndex = function(req, res, next) {
    if ((req.body.username == undefined
	 && req.body.password == undefined) ||
	(req.body.username.length == 0 
	 && req.body.password.length == 0)) {
	// user's chilling, makes no attempt to log in
	next();

	// seperated the two conditions to make things
	// a lil bit clearer

    } else if (req.session.currentUser && req.session.isLoggedIn) {
	// user's already logged in, so go on
	next();
    } else if (req.body.username && req.body.username.length > 0
	       && req.body.password && req.body.password.length > 0) {

	// user's not logged in, but wants to log in
	User.findOne({userName: req.body.username}
		  , function(err, user) {
		      if (err) {
			  console.log("error: ");
			  console.log(err);
			  req.session.currentUser = null;
			  req.session.isLoggedIn = false;
			  next();
			  return;
		      } 
		  
		      if (!user || typeof user.authenticate != "function") {
			  // is user even in db ? 
			  req.flash("error", "There's no user called " + req.body.username + " in our database");
			  res.redirect('back');
			  return;
		      } else if (!user.authenticate(req.body.password)) {
			  // user's password incorrect
			  req.flash('error', "Password does not match Username entered");
			  res.redirect('back');
			  return;
		      } else {
			  // authenticate user against password entered
			  console.log("==========user successfully logged in========");
			  console.log(user);
			  console.log("=============================================");
			  
			  // user authenticated! Can go in
			  var loadedUser = loadUser(user);
			  for (key in loadedUser) {
			      req.session[key] = loadedUser[key];
			  }
			  
			  next();
		      }
		  });
    } else {
	// user's trying to log in, but didn't enter both username
	// and password
	if (!(req.body.username && req.body.password)) {
	    req.flash('error', "Enter both a username and password");
	    res.redirect('back');
	    return;
	}
	
    }
}

/*
 * index
 * handles both get and post request on the / page
 * @param req -> request object
 * @param res -> response object
 * @param err -> error object
 *
 */
exports.index = function(req, res, err){    
    req.session.currentUser = (req.session.currentUser == undefined ?  "" :
			       req.session.currentUser);

    req.session.isLoggedIn = (req.session.isLoggedIn == undefined ? false :
			      req.session.isLoggedIn);

    req.session.userDocuments = (req.session.userDocuments == undefined ? [] :
				 req.session.userDocuments);


    if (req.session.currentUser && req.session.isLoggedIn) {
	// display the documents for user
	res.render("display-docs",
		   {title: "Fly Latex: Start Editing Documents"
		    , shortTitle: "Fly Latex"
		    , tagLine: "Start Editing Documents with Your Peeps!"
		    , fileSpecificScript: "application.js"
		    , currentUser: req.session.currentUser
		    , isLoggedIn: req.session.isLoggedIn
		    , userDocuments: req.session.userDocuments		    
		   });
	
    } else {
	// user didn't try to log in 
	res.render("not-logged-in",
		   {title: "Log Into/Sign Into to FLY LATEX!"
		    , shortTitle: "FLY LATEX"
		    , tagLine: "Real Time Collaborative editor in node-js"
		    , fileSpecificStyle: "not-logged-in.css"});
    }
};


/*
 * logOutUser -
 * log user out
 * @param req -> request object
 * @param res -> response object
 * @param next -> next (middleware) function (in callchain) to execute
 */
exports.logOutUser = function(req, res, next) {
    if (req.session.currentUser && req.session.isLoggedIn) {
	req.session.regenerate(function(err) {
	    if (err) {
		console.log("==========Error while logging out=============");
	    } 
	    next();
	});
    }
};

/*
 * displaySignUpForm ->
 *  displays sign up form for user to sign up for
 *  fly latex
 * @param req -> request object
 * @param res -> response object
 */
exports.displaySignUpForm = function(req, res) {
    res.render("sign-up",
	       {title: "Sign Up for Fly Latex"
		, shortTitle: "Sign Up"
		, tagLine: "Start Editing Documents with Your Peeps!"
		, fileSpecificStyle: "sign-up.css"
		, fileSpecificScript: "application.js"
	       });
    
};

/*
 * processSignUpData ->
 *  processes the sign up data posted from the sign
 *  up form and logs the user into fly latex
 *  , redirecting him to his home page.
 * @param req -> request object
 * @param res -> response object
 */
exports.processSignUpData = function(req, res) {
    var errors = {}; // key-value pair -> error Type : error Message
    var isError = false;
    var newUser = req.body.newUser;

    // validate userName: make sure no one else has that username
    if (newUser.userName.length == 0) {
	errors["userNameToken"] = "Enter a username";
    }

    // make sure valid password
    if (!(newUser.password.length > 4 // password has to be at least 5 chars 
	  && /\d+/.test(newUser.password))) { // password has to have at least one digit
	errors["passwordInvalid"] = "Password must be at least 5 chars and must contain at least one digit";
	isError = true;
    }

    // make sure password == confirmPassword
    if (newUser.password != newUser.confirmPassword) {
	errors["passwordNoMatch"] = "The Confirm Password should match the initial password entry";
	isError = true;
    }


    // make sure email is valid
    if (!(/^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$/.test(newUser.email))) {
	errors["emailInvalid"] = "Enter a valid email address";
	isError = true;
    }

    // make sure names are valid
    if (!(newUser.firstName.length > 0
	  && newUser.lastName.length > 0)) {
	errors["namesInvalid"] = "Enter a first Name and a Last Name";
	isError = true;
    }

    // optional params
    if (newUser.githubId.length == 0) {
	delete newUser["githubId"];
    }
    if (newUser.twitterId.length == 0) {
	delete newUser["twitterId"];
    }
    
    if (!isError) {
	// there's no error. Save the new user
	// only if someone else doesn't have his username
	User.find({userName: newUser.userName}
	      , function(err, users) {
		  if (users.length > 0) {
		      errors["userNameTaken"] = "The username " + newUser.userName + " is already taken";
		      isError = true;

		      displayErrorsForSignUp(res, errors);
		  } else {
		      // save the user
		      var newFlyUser = new User();
		      for (var key in newUser) {
			  newFlyUser[key] = newUser[key];
		      }
		      newFlyUser.documentsPriv = [];
		      newFlyUser.save(function(err) {
			  if (err) {
			      console.log("==============Error in saving user======"); 
			  } else  {
			      console.log("================saved user=============");
			  }
			  console.log(newFlyUser);
			  console.log("======================================");
		      });
		      
		      // load user here
		      var loadedUser = loadUser(newFlyUser);
		      for (var key in loadedUser) {
			  req.session[key] = loadedUser[key];
		      }
		      
		      // redirect to home page with user
		      // logged in and ready to rumble!
		      res.redirect("home");     
		  }
	      });
    
	
    } else {
	// there's an error. Return error message(s) to user
	displayErrorsForSignUp(res, errors);
    }
};

/*
 * createDoc ->
 * creates a new document for the current user.
 * error if user not logged in.
 * @note
 * this function is called asynchronous and should
 * sennd back a json response
 * and not redirect or reload page.
 *
 * @param req -> request object
 * @param res -> response object
 */
exports.createDoc = function(req, res) {
    // prepare response object
    var response = {infos:[]
		    , errors: []
		    , code:200
		    , newDocument: {id:null
				    , name:null
				    , readAccess: true
				    , writeAccess: true
				    , execAccess: true
				    , canShare: true}
		   }
    
    var docName = req.body.docName;

    if (!(docName.length && docName.length > 0)) {
	// check that document's name is not empty
	response.errors.push("Error in creating document with no title or name");
	res.json(response);
	return;
    } else if (!(req.session.isLoggedIn && req.session.currentUser)) {
	// user is not logged in
	response.errors.push("You're not not logged in. Please log in!");
	res.json(response);
	return;
    }

    // check the list of documents
    // verify that this new document doesn't
    // have the same name as the old ones
    var found = false;
    for (var i = 0; i < req.session.userDocuments.length; i++) {
	if (req.session.userDocuments[i].name == docName) {
	    found = true;
	    break;
	}
    }
    if (found) {
	response.errors.push("Error in creating document that shares its name with an already existing document you have.");
	res.json(response);
	return;
    } else {
	// then check that the user doesn't have up to MAX_DOCS documents yet
	if (req.session.userDocuments.length >= MAX_DOCS) {
	    response.errors.push("You can't have more than " + MAX_DOCS + " documents. Delete some documents to create space. Or contact the Administrator.");
	    res.json(response);
	    return;		
	} else {
	    // so we can create a new document 
	    // the new document will have only one line for starters
	    var newDoc = createNewDocument(req.body.docName, req.session.currentUser);

	    // by default, document privilege for the
	    // current user is 7 (full access)
	    var docPriv = new DocPrivilege();
	    docPriv.documentId = newDoc._id;
	    docPriv.documentName = newDoc.name;
	    
	    // new user document to send off to front end for display
	    var newUserDocument = {};
	    
	    User.findOne({"userName": req.session.currentUser}, function(err, user) {
		if (err || !user) {
		    response.errors.push("error", "Couldn't find you. Weird.");
		    res.json(response);
		    return;
		}
		
		console.log("Document Priv Object created===============");
		console.log(docPriv);
		console.log("===========================================");
		
		// add to user's documentsPriv
		user.documentsPriv.push(docPriv);
		
		// save the document
		user.save();
		
		// add to the user's session data
		newUserDocument.id = docPriv.documentId;
		newUserDocument.name = docPriv.documentName;
		
		// user creating document should have full access to document
		// R,W,X (and so can share the document with anyone)
		newUserDocument.readAccess = true;
		newUserDocument.writeAccess = true;
		newUserDocument.execAccess = true;
		newUserDocument.canShare = true;
		
		req.session.userDocuments.push(newUserDocument);
		response.newDocument = newUserDocument;
		
		// inform user of new document creation
		response.infos.push("Just created the new Document: " + req.body.docName + " Hooray!");
		res.json(response);
	    });
	}
    }    
};
		      
/**
 * deleteDoc -
 * delete the document from the user's list of documents
 * both in the session data and on the database (his/her docPrivileges)
 * then delete the document from the Documents collection.
 * 
 * @note
 * this method is called asynchronously and should not redirect the user
 * or reload the page under any circumstances.
 * @param req -> request object
 * @param res -> response object
 */
exports.deleteDoc = function(req, res) {
    // response to send back to user after successful deletion (or error)
    var response = {errors:[], infos:[], code:200};

    // get document id,name for document to delete
    var docId = req.body.docId
    , docName;

    if (!(req.session.currentUser && req.session.isLoggedIn)) {
	response.errors.push("Weird. Seems like you're not logged in.");
	res.json(response);
	return;
    }
    // remove the document from Users collections
    User.findOne({userName: req.session.currentUser}, function(err, user) {
	if (err || !user) {
	    console.log("unable to delete doc from " + user.userName + "'s list of documents");
	    response.errors.push("Had problems processing your deletion. Try again.");
	    res.json(response);
	    return;
	}
	for (var i = 0; i < user.documentsPriv.length; i++) {
	    if (user.documentsPriv[i].documentId == docId) {
		docName = user.documentsPriv[i].documentName;
		user.documentsPriv.splice(i, 1);

		console.log("Removed documentsPriv with documentId: " + docId);
	    }
	}
	
	// save a document
	user.save();

	// change session object to reflect new change in user's documents
	for (var i = 0; i < req.session.userDocuments.length; i++) {	    
	    if (req.session.userDocuments[i].id == docId) {
		req.session.userDocuments.splice(i,1);
		
		console.log("Removed userDocument with id: " + docId + " from session object");
	    }
	}
		
	// remove the document from Documents collections
	// if no other user has it
	DocPrivilege.find({documentId:docId}, function(err, docs) {
	    if (docs.length == 0) {
		// no other user has this document
		Document.findOne({_id:docId}).remove(function(err) {
		    if (!err) 
			console.log("Removed document with _id " + docId + " completely from the database");
		    else
			console.log("Error while deleting document with id " + docId + " completely from the database");
		});
	    } else {
		// some other user(s) has access to this document
		console.log("Document(docId="+docId+") not deleted because some other users still have access to this document");

		// then remove the current userName from the the list of users
		// with share (full) access, if there
		Document.findOne({_id: docId}, function(err, doc) {
		    if (!err) {
			var found = false
			, i; // loop variable
			
			for (i = 0; i < doc.usersWithShareAccess.length; i++) {
			    if (doc.usersWithShareAccess[i] == req.session.currentUser) {
				found = true;
				break;
			    }
			}
			if (found) {
			    doc.usersWithShareAccess.splice(i, 1);
			    
			    // save the document
			    doc.save();
			}
		    }
		});
	    }
	});
	if (response.errors.length == 0 && docName.length > 0) {
	    response.infos.push("Successfully deleted the document " + docName);
	    res.json(response);
	}
    });
};

/**
 * shareAccess -> share access to a document
 * @param req -> request object
 * @param res -> response object
 */
exports.shareAccess = function(req, res) {
    var response = {errors:[], infos:[], code: 200};

    // get share options
    var options = req.body.options;

    var priv = ((options.withReadAccess == "true" ? 4 : 0) +
		(options.withWriteAccess == "true" ? 2 : 0) +
		(options.withExecAccess == "true" ? 1 : 0));

    // try to return error messages if any errors found
    if (!(req.session.currentUser && req.session.isLoggedIn)) {
	response.errors.push("You are not logged in. So you can't share access");
    }
    if (priv == 0) {
	response.errors.push("You can't try to share no privilege Dude/Dudette");
    }
    if (!(options.docId
	  && options.docName
	  && options.userToShare)) {
	response.errors.push("Options passed in are incomplete");
    }
    if (priv < 4) {
	response.errors.push("You should share at least 'Read' privilege");
	res.json(response);
	return;
    }

    User.findOne({userName: options.userToShare}, function(err, user) {
	if (err) {
	    console.log("An error occured");
	}
	if (!user) {
	    response.errors.push("The user you want to send a message to doesn't exist");
	}
	if (response.errors.length > 0) {
	    // if any errors
	    res.json(response);
	} else {
	    // if no errors found yet
	    // make the message to send
	    var newMessage = new Message();
	    newMessage.messageType = MESSAGE_TYPES.shareAccess;
	    newMessage.fromUser = req.session.currentUser;
	    newMessage.toUser = options.userToShare;	
	    newMessage.documentId = options.docId;
	    newMessage.documentName = options.docName;
	    newMessage.access = priv;
	    
	    // save the message to the messages collection
	    newMessage.save();
	    
	    var withReadAccess = (options.withReadAccess == 'true')
	    , withWriteAccess = (options.withWriteAccess == 'true')
	    , withExecAccess = (options.withExecAccess == 'true');

	    // send success message
	    response.infos.push("You just invited "+options.userToShare+" to have "+
				(withReadAccess ? "Read" +
				 ((!withWriteAccess && !withExecAccess) 
				  ? " ": ", ") :"")+
				(withWriteAccess ? "Write" +
				 (!withExecAccess ? " ": ", ") : "") +
				(withExecAccess ? "Exec " : " ") +
				"Access to " + options.docName);
	    // let the recipient of the message know that he has a new
	    // message
	   
	    io.sockets.volatile.emit("newMessage", JSON.stringify(newMessage));


	    // send response back to the client
	    res.json(response);
	}
    });    
};
/**
 * ajaxAutoComplete ->
 * returns json of auto-complete results based on the purpose
 * 
 * @param req -> request object
 * @param res -> response object
 */
exports.ajaxAutoComplete = function(req, res) {
    /*
     * ====data to get ======
     * word -> word to search for
     * purpose -> usernames, and so on.
     */
    // get the purpose of the auto-complete mission
    var purpose = req.query.purpose;
    // get the word to autocomplete for
    var word = req.query.word;
    
    switch (purpose) {
    case "usernames":
	// get word user has typed so far
	var typed = req.query.word
	, data = {code:200, results:[]};
	
	// query the users collection for usernames
	User.find({userName: new RegExp(typed)}, function(err, users) {
	    if (!err) {
		users.forEach(function(item, index) {
		    if (item.userName != req.session.currentUser) {
			data.results.push(item.userName);
		    }
		});
	    }
	    res.json(data);
	});
	break;
    default:
	console.log("It's either you're trying to mess with me or I messed up.");
    };
};

/**
 * requestAccess -> request access to a document
 * @param req -> request object
 * @param res -> response object
 */
exports.requestAccess = function(req, res) {
    var response = {errors:[], infos:[], code: 200};

    // get request access options
    var options = req.body.options;

    var priv = ((options.withReadAccess == "true" ? 4 : 0) +
		(options.withWriteAccess == "true" ? 2 : 0) +
		(options.withExecAccess == "true" ? 1 : 0));

    // try to return error messages if any errors found
    if (!(req.session.currentUser && req.session.isLoggedIn)) {
	response.errors.push("You are not logged in. So you can't share access");
    }
    if (priv == 0) {
	response.errors.push("You can't try to request for no privilege");
    }
    if (!(options.docId
	  && options.docName)) {
	response.errors.push("Options passed in are incomplete");
    }

    if (priv < 4) {
	response.errors.push("You should request for at least read access to a document ");
    }

    if (response.errors.length > 0) {
	res.json(response);
	return;
    }
    // first find the users that have share access (7:R,W,X) to the document
    Document.findOne({_id: options.docId}, function(err, doc) {
	if (err) {
	    console.log("An error occured while trying to request access for " 
			+ req.session.currentUser);
	} else {	    
	    if (doc.usersWithShareAccess.length > 0) {
		var newMessage, i;
		
		for (i = 0; i < doc.usersWithShareAccess.length; i++) {
		    newMessage = new Message();
		    newMessage.messageType = MESSAGE_TYPES.requestAccess;
		    newMessage.fromUser = req.session.currentUser;
		    newMessage.toUser = doc.usersWithShareAccess[i];
		    newMessage.documentId = options.docId;
		    newMessage.documentName = options.docName;
		    newMessage.access = priv;
		    
		    // save the message in the messages collection
		    newMessage.save();
		    
		    // alert users that are logged in about message
		    io.sockets.volatile.emit("newMessage", JSON.stringify(newMessage));
		    
 		}
		response.infos.push("Sent a 'Request More Privileges' message to all the users who have share access to the document, " + options.docName);
		
		res.json(response);
	    } else {
		response.errors.push("No user currently has Share Access to that document");
		
		// send response back
		res.json(response);
	    }
	}
    });
};

/**
 * getMessages ->
 * get the messages for the current user
 * @param req -> request object
 * @param res -> response object
 *
 * @jsonreturn returns a list of user's messages
 *  each message object is of the form
 *  {messageType:, fromUser:, toUser:, documentId:, documentName:,access:}
 */
exports.getMessages = function(req, res) {
    var response = {errors:[], infos:[], messages:[]};
    
    // try to find messages for the current user
    Message.find({toUser:req.session.currentUser}, function(err, messages) {
	if (err) {
	    response.errors.push("Error while retrieving messages. Try again later.");
	    res.json(response);
	} else if (messages.length == 0) {
	    response.infos.push("You have no messages!");
	    res.json(response);
	} else {
	    // get the messages
	    messages.forEach(function(item, index) {
		var priv = item.access;
		// set privileges fromUser is requesting
		item.readAccess = false;
		item.writeAccess = false;
		item.execAccess = false;
		
		if (priv >= 4) {
		    item.readAccess = true;
		    priv -= 4;
		} 
		if (priv >= 2) {
		    item.writeAccess = true;
		    priv -= 2;
		}
		if (priv == 1) {
		    item.execAccess = true;
		}
		response.messages.push(item);
	    });

	    // send back messages
	    res.json(response);
	}
    });
};

/**
 * grantAccess ->
 * grant another user access to some document
 * @param req : request object
 * @param res: response object
 */
exports.grantAccess = function(req, res) {
    var response = {errors: [], infos:[]}
    
    /**
     * options passed in: userToGrant, documentId, documentName, access
     */
    if (!(req.session.currentUser && req.session.isLoggedIn)) {
	response.errors.push("You cannot grant access since you are not logged in.");
	res.json(response);
	return;
    }
    
    User.findOne({"userName":req.body.userToGrant}, function(err, user) {
	if (err || !user) {
	    response.errors.push("No user " + req.body.userToGrant + " exists or an error occured while looking for this user");
	    res.json(response);
	} else {
	    // make sure the user's granting at least read access 
	    if (req.body.access < 4) {
		response.errors. push("You should grant a user at least 'Read' privilge");
		res.json(response);
		return;
	    }
	    
	    // first make sure that userToGrant doesn't already have some access
	    // to the document
	    var userHasDoc = false;
	    
	    user.documentsPriv.forEach(function(item, index) {
		if (item.documentId == req.body.documentId) {
		    userHasDoc = true;
		}
	    });

	    var priv = req.body.access
	    , readAccess = false
	    , writeAccess = false
	    , execAccess = false
	    , canShare = false;

	    // give user power to be able to share the document with other users
	    // if he/she has full access
	    if (priv == 7) {
		canShare = true;

		// give user R, W, X access
		giveUserSharePower(req.body.userToGrant, req.body.documentId);
	    }

	    // de-couple privileges here
	    if (priv >= 4) {
		readAccess = true;
		priv -= 4;
	    }
	    if (priv >= 2) {
		writeAccess = true;
		priv -= 2;
	    }
	    if (priv == 1) {
		execAccess = true;
	    }

	    // create new user document
	    var newUserDocument = {
		"id": req.body.documentId
		, "name": req.body.documentName
		, "readAccess" : readAccess
		, "writeAccess" : writeAccess
		, "execAccess" : execAccess
		, "canShare" : canShare
		, "forUser" : req.body.userToGrant
	    };
	    
	    
	    if (userHasDoc) {
		var upgrading = false;
		
		// if userToShare already has the document, upgrade access if possible
		for (var i = 0; i < user.documentsPriv.length; i++) {
		    if (user.documentsPriv[i].documentId == newUserDocument.id
		       && user.documentsPriv[i].access < req.body.access) {
			upgrading = true;

			// userToShare should reload his/her list of documents
			response.reloadDocs = true;

			user.documentsPriv[i].access = parseInt(req.body.access);
			
			user.save(function(err) {
			    if (!err) 
				console.log("user successfully saved!");
			    else
				console.log("error occured while trying to save user");
			});
			
			// send back message
			response.infos.push("You just upgraded the privileges of "
					   + req.body.userToGrant + " for the document "
					   + req.body.documentName);

			// notify userToShare you just upgraded his privileges on some document
			io.sockets.volatile.emit("changedDocument", JSON.stringify(newUserDocument));
			res.json(response);
	    
			break;		
		    }
		}
		if (!upgrading) {
		    // send back duplicate message
		    response.infos.push(req.body.userToGrant + " already has higher or equal access to the document, " + req.body.documentName);
		    res.json(response);
		}
	    } else {
		// userToShare should definitely redisplay his list of documents
		response.reloadDocs = true;
		
		var newDocPriv = new DocPrivilege();
		newDocPriv.access = parseInt(req.body.access);
		newDocPriv.documentName = req.body.documentName;
		newDocPriv.documentId = req.body.documentId;
		
		// save
		newDocPriv.save();
	    
		// save to user's list of document privileges
		user.documentsPriv.push(newDocPriv);
		user.save(); // save user

		
		response.infos.push("You just granted "+req.body.userToGrant+" "+
				    (readAccess ? "Read" +
				     ((!writeAccess && !execAccess) 
				      ? " ": ", ") :"")+
				    (writeAccess ? "Write" +
				     (!execAccess ? " ": ", ") : "") +
				    (execAccess ? "Exec " : " ") +
				    "Access to " + req.body.documentName);
		
		// notify the user just granted access that his/her request
		// has been granted immediately via socket.io
		io.sockets.volatile.emit("changedDocument", JSON.stringify(newUserDocument));

		
		// send response
		res.json(response);
	    }	
	}
    });
};

/**
 * acceptAccess ->
 * accept another user's offer to have  
 * access to a document
 * @param req : request object
 * @param res: response object
 */
exports.acceptAccess = function(req, res) {
    var response = {errors:[], infos:[]
		    , newDocument:null
		    , reDisplay:false
		    , userDocuments: req.session.userDocuments};

    /**
     * options passed in: acceptFromUser, documentId, documentName, access
     */    
    if (!(req.session.currentUser && req.session.isLoggedIn)) {
	response.errors.push("You cannot accept the invitation since you aren't logged in");
	res.json(response);
	return;
    }

    // make sure the privilege to accept is at least read privilege
    if (parseInt(req.body.access) < 4) {
	response.errors.push("You should accept at least 'Read' privilege");
	res.json(response);
    }
   
    User.findOne({"userName":req.session.currentUser}, function(err, user) {
	// first make sure the user doesn't already have some access to the document
	// in that case, bump up the user's access
	var userHasDoc = false;
	req.session.userDocuments.forEach(function(item, index) {	    
	    if (item.id == req.body.documentId) {
		userHasDoc = true;
	    }
	});

	var priv = req.body.access 
	, readAccess = false
	, writeAccess = false
	, execAccess = false
	, canShare = false;
	// give user power to be able to share the document with other users
	// if he/she has full access
	if (priv == 7) {
	    canShare = true;
	    
	    // give user share power
	    // a user can only get share access when he's given access of 7
	    // which corresponds to R, W, X
	    giveUserSharePower(req.session.currentUser, req.body.documentId);
	}
	
	// de-couple privileges
	if (priv >= 4) {
	    readAccess = true;
	    priv -= 4;
	}
	if (priv >= 2) {
	    writeAccess = true;
	    priv -= 2;
	}
	if (priv == 1) {
	    execAccess = true;
	}
	
	// new user document
	var newUserDocument = {
	    "id": req.body.documentId
	    , "name": req.body.documentName
	    , "readAccess" : readAccess
	    , "writeAccess" : writeAccess
	    , "execAccess" : execAccess
	    , "canShare" : canShare
	};

	if (userHasDoc) {
	    // if user already has the document, upgrade access if possible
	    var upgrading = false;

	    for (var i = 0; i < user.documentsPriv.length; i++) {
		if (user.documentsPriv[i].documentId == newUserDocument.id
		    && user.documentsPriv[i].access < req.body.access) {
		    upgrading = true;

		    // user should redisplay list of documents
		    response.reDisplay = true;

		    user.documentsPriv[i].access = parseInt(req.body.access);
		    user.save();
		    
		    // send back  message
		    response.infos.push("You just upgraded your rights to the document " + newUserDocument.name);
		    break;
		}
	    }
	    if (upgrading) {
		for (var i = 0; i < req.session.userDocuments.length; i++) {
		    if (req.session.userDocuments[i].id == newUserDocument.id) {
			// upgrade all we've got
			req.session.userDocuments[i] = newUserDocument;
		    }
		}
		res.json(response);
		return;
	    }
	    // send back duplicate message
	    response.infos.push("You already have higher or equal access to the document " + newUserDocument.name);
	    res.json(response);	    
	} else {	    
	    // user should redisplay list of documents
	    response.reDisplay = true;

	    // user doesn't already have access to document
	    var newDocPriv = new DocPrivilege();
	    newDocPriv.access = parseInt(req.body.access);
	    newDocPriv.documentName = req.body.documentName;
	    newDocPriv.documentId = req.body.documentId;
	    
	    // save
	    newDocPriv.save();
	    
	    // save to user's list of document privileges
	    user.documentsPriv.push(newDocPriv);
	    user.save(); // save user
	    
	    // add to my session if I don't have the document yet
	    req.session.userDocuments.push(newUserDocument);
	    
	    // also send back so user can display in his/her DOM
	    response.newDocument = newUserDocument;
	    
	    // send acceptance message to user
	    response.infos.push("You just accepted "+
				(readAccess ? "Read" +
				 ((!writeAccess && !execAccess) 
				  ? " ": ", ") :"")+
				(writeAccess ? "Write" +
				 (!execAccess ? " ": ", ") : "") +
				(execAccess ? "Exec " : " ") +
				"Access to " + req.body.documentName +
				" from " + req.body.acceptFromUser);
	    res.json(response);
	}
    });
};

/**
 * exports.reloadSession -
 * reload the user's documents and send back the new documents
 *
 * @param req : request object
 * @param res : result object
 */
exports.reloadSession = function(req, res) {
    var response = {infos: [], errors: [], userDocuments: null};
    
    if (!(req.session.currentUser && req.session.isLoggedIn)) {
	response.errors.push("You are not logged in.");
	res.json(response);
	return;
    } else if (req.session.currentUser == req.body.document.forUser) {
	User.findOne({userName: req.session.currentUser}, function(err, user) {
	    // reload user
	    var loadedUser = loadUser(user);
	    for (var key in loadedUser) {
		req.session[key] = loadedUser[key];
	    }
	    
	    // load userDocuments
	    response.userDocuments = req.session.userDocuments;
	    
	    res.json(response);
	});
    }
};

/**
 * exports.servePDF ->
 * @param req : request Object
 * @param res : result Object
 *
 */
exports.servePDF = function(req, res) {
    var documentId = req.params.documentId
    , options;

    // find the pdf
    PDFDoc.findOne({forDocument:documentId}, function(err, doc) {
	if (err || !doc) {
	    req.flash("error", "PDF not found or an error occured while reading the pdf");
	    res.redirect("back");
	    return;
	}
	// write pdf file to user
	fs.createReadStream(configs.pdfs.path+documentId+".pdf").pipe(res);
    });
};

/**
 * exports.compileDoc
 * @param req : request object
 * @param res : response object
 */
exports.compileDoc = function(req, res) {
    // initialize the 'response' JS object to send back
    var response = {infos:[], errors: [], logs:"", compiledDocURI:null}
    , documentId = req.body.documentId;

    if (!(req.session.currentUser && req.session.isLoggedIn)) {
	response.errors.push("You are not logged in");
	res.json(response);
	return;
    } 
    
    // first load the text of the document from the database
    Document.findOne({_id:documentId}, function(err, doc) {
	if (err || !doc) {
	    response.errors.push("An Error Occured while trying to open the document");
	    res.json(response);
	    return;
	}

	// assemble the document lines
	var docLines = []
	, lastModified
	, docText;

	// get document lines
	doc.lines.forEach(function(item, index) {
	    docLines.push(item.data.toString());
	    
	    if (!lastModified || lastModified < item.lastModified) {
		lastModified = item.lastModified;
	    }
	});

	// get the document text
	docText = docLines.join();

	// make temporary directory to create and compile latex pdf
	temp.mkdir("pdfcreator", function(err, dirPath){
	    var inputPath = path.join(dirPath, documentId+".tex");
	    
	    fs.writeFile(inputPath, docText, function(err) {
		if (err) {
		    response.errors.push("An error occured even before compiling");
		    res.json(response);
		    return;
		}
		process.chdir(dirPath);

		// copy files from the packages folder
		// to the temp directory for compiling
		console.log("From: " + configs.includes.path+"*");
		console.log("To: " + dirPath+"/");
		exec("cp -r " + configs.includes.path+"*  " + dirPath+"/", function(err) {
		    if (err) {
			response.errors.push("Error copying additional packages to use in compilation");
			return;
		    } 
		    // compile the document (or at least try)
		    // redirect the stdin, stderr results of compilation
		    // since the results of compilation will eventually be
		    // written to the log file
		    exec("pdflatex -interaction=nonstopmode "+ inputPath +" > /dev/null 2>&1", function(err) {
			// store the logs for the user here
			fs.readFile(path.join(dirPath, documentId+".log"), function(err, data){
			    if (err) {
				response.errors.push("Error while trying to read logs.");
			    }
			    
			    // store the 'logs' from the compile
			    response.logs = (data ? data.toString() : "");
			    
			    var errorStr = "An error occured before or during compilation";
			    if (err) {
				console.log(err);
				response.errors.push(errorStr);
				res.json(response);
				return;
			    }
			    
			    // store the compile pdf document in the cloud
			    
			    // create new PDFDoc
			    var newpdf = new PDFDoc();
			    newpdf.forDocument = documentId;
			    newpdf.title = documentId+".pdf";
			    tempfile = path.join(dirPath, newpdf.title);
			    fs.copy(tempfile
				    , configs.pdfs.path + newpdf.title
				    , function(err){
					if (err) {
					    console.log(err);
					    response.errors.push(errorStr);
					    res.json(response);
					    return;
					} else {
					    console.log("Successfully saved "+newpdf.title+" in "+configs.pdfs.path);
					    newpdf.save(function(err) {
						if (err) {
						    console.log(err);
						    response.errors.push(errorStr);
						    res.json(response);
						    return;
						}
						response.infos.push("Successfully compiled "+ req.body.documentName);
						// make the compiledDocURI
						response.compiledDocURI = "/servepdf/"+documentId;
						// send response back to user
						res.json(response);
			    		    });
					}
				    });
			});
		    });
		});
	    });
	});
    });
};


/**
 * exports.addNewDocument -
 * add a new document to my list of documents in my session
 * @param req : request object
 * @param res : response object
 */
exports.addNewDocument = function(req, res) {
    var response = {infos:[], errors: []};
    
    if (!(req.session.currentUser && req.session.isLoggedIn)) {
	response.errors.push("You are not logged in.");
	res.json(response);
	return;
    } else if (req.session.currentUser === req.body.document.forUser) {
	// add to user's list of documents
	var document = req.body.document;
	
	req.session.userDocuments.push(document);
	
	response.infos.push(document.fromUser + " just added " + document.name + " to your list of documents");
	
	res.json(response);
    }

};

/**
 * exports.deleteMessage ->
 * delete a message from messages collections
 * @jsonparam -> fromUser
 * @jsonparam -> documentId
 * @jsonparam -> access
 */
exports.deleteMessage = function(req, res) {
    var response = {infos:[], errors:[]};

    if (!(req.session.currentUser && req.session.isLoggedIn)) {
	response.errors.push("Ya not logged in");
	res.json(response);
    } else {
	Message.findOne({fromUser: req.body.fromUser
			 , documentId: req.body.documentId
			 , access: parseInt(req.body.access)
			 , toUser: req.session.currentUser}).remove(function(err) {
	    if (!err) {
		console.log("You just deleted a message");
		
		res.json(response);
	    } else {
		console.log("Error while deleting a message");
	    }
	});
    }
};

/**
 * openDocument ->
 * opens a document
 *
 * @param req : request object
 * @param res : response object
 * 
 * @getparam documentId : id of document to open
 */
exports.openDocument = function(req, res) {
    // retrieve the document id from url
    var documentId = req.params.documentId;

    // first retrieve the name of the document
    Document.findOne({_id:documentId}, function(err, doc) {
	if (err || !doc) {
	    req.flash("error", "An Error Occured while trying to open the document");
	    res.redirect('back');
	    return;
	}

	// assemble the document lines
	var docLines = []
	, lastModified
	, userDoc
	, docInSession
	, writeable
	, sharesWith;

	// retrieve the document from the current user session
	docInSession = searchForDocsInSession(documentId, req.session);	
	// handle lag in findOne callback execution
	if (docInSession == null) {
	    return;
	}

	// get document lines
	doc.lines.forEach(function(item, index) {
	    docLines.push(item.data.toString());
	    
	    if (!lastModified || lastModified < item.lastModified) {
		lastModified = item.lastModified;
	    }
	});
	
	sharesWith = (openDocuments[documentId] ?
		      openDocuments[documentId] : []);

	if (openDocuments[documentId] && openDocuments[documentId].indexOf(req.session.currentUser) == -1) {
	    openDocuments[documentId].push(req.session.currentUser);
	}
	
	// then record that this document is now opened by the current user
	if (!openDocuments[documentId]) {
	    openDocuments[documentId] = [req.session.currentUser];
	}
	
	// construct a user document
	userDoc = {
	    "id" : documentId
	    , "name" : doc.name
	    , "text" : escape(docLines.join()) // escape special characters
	    , "lastSaved" : lastModified
	    , "sharesWith" : sharesWith
	    , "readAccess" : docInSession.readAccess
	    , "writeAccess" : docInSession.writeAccess
	    , "execAccess" : docInSession.execAccess
	    , "canShare" : docInSession.canShare
	};
	
	// render the document you just opened
	res.render("open-document",{
	    title: "Viewing the document, "+ doc.name
	    , shortTitle: "Fly Latex"
	    , tagLine: "Viewing the document, " + doc.name
	    , fileSpecificStyle: "open-document.css"
	    , fileSpecificScript: "open-document.js"
	    , userDocument: userDoc
	    , currentUser: req.session.currentUser
	    , isLoggedIn: req.session.isLoggedIn
	    , userDocuments: req.session.userDocuments
	});
    });
};

/**
 * saveDocument - 
 * saves the document in DB
 *
 * @param req : request object
 * @param res : response object
 */
exports.saveDocument = function(req, res) {
    var response = {code: 400, errors: [], infos: []}
    , documentId = req.body.documentId
    , documentName = req.body.documentName
    , documentText = req.body.documentText
    , maxDocLine = 1024 // a document line has max. length of 1024 
    , lineNum = 0; // keep track of the current line number

    Document.findOne({_id:documentId}, function(err, doc){
	var newLine; 
	
	if (err || !doc) {
	    response.errors.push("Error in finding document to save");
	    res.json(response);
	    return;
	}
		
	// save document text in form of document lines
	while (documentText.length > 0) {
	    newLine = new DocumentLine();
	    
	    newLine.lineNum = lineNum;
	    
	    newLine.data = new Buffer(documentText.slice(0, maxDocLine));
	    newLine.lastModified = new Date();
	    
	    newLine.save(function(err) {
		if (!err) 
		    console.log("new line saved successfully!");
	    });
	    
	    doc.lines[lineNum] = newLine;
    
	    documentText = documentText.slice(maxDocLine);
	    lineNum++;	
	}
	
	if (doc.lines[lineNum]) {
	    doc.lines.splice(lineNum);
	}
	// save the document
	doc.save();

	var savedDocMessage = {
	    "sharesWith" : openDocuments[documentId]
	    , "lastModified" : (newLine ? newLine.lastModified : new Date())
	};

	// send a message to all users that are currently viewing the saved doc
	io.sockets.volatile.emit("savedDocument", JSON.stringify(savedDocMessage));


	// after save
	response.code = 200;
	response.infos.push("Successfully saved the document");
	res.json(response);
    });
};

// ============== Helper functions here ==========
/**
 * searchForDocsInSession
 * search for document in session.userDocuments
 *
 * @param documentId - id of document to search for
 * @param session - session object for current user
 * @return document
 */
var searchForDocsInSession = function(documentId, session) {
    if (session.userDocuments != undefined) {
	for (var i = 0; i < session.userDocuments.length; i++) {
	    if (session.userDocuments[i].id == documentId) {
		return session.userDocuments[i];
	    }
	}
    }
    return null;
};

/**
 * giveUserSharePower
 *
 * if user has full access to doc, give user power to be able to 
 * share the document with other users
 *
 * @param fromUser -> user to give full access to
 * @param documentId -> document id of document concerned
 */
var giveUserSharePower = function(fromUser, documentId) {
    Document.findOne({_id: documentId}, function(err, doc) {
	if (!err) {
	    if (doc.usersWithShareAccess.indexOf(fromUser) == -1) {
		doc.usersWithShareAccess.push(fromUser);
		
		// save doc
		doc.save();
	    }
	} else {
	    console.log("An error occured while trying to note " 
			+ "in document model that "
			+ req.body.fromUser + " has full access to the doc");  
	}
    });
};

/**
 * createNewDocument
 * create a new document for the current user
 *
 * @param docName -> document name
 * @param currentUser -> created by
 * @return DocPrivilege -> representing new document
 */
var createNewDocument = function(docName, currentUser) {
    // create the first document line
    // of the document
    var newDocLine = new DocumentLine();
    var newDocLineObj = {lineNum: 0
			 , data: new Buffer(0)
			};
    for (var key in newDocLineObj) {
	newDocLine[key] = newDocLineObj[key];
    }
    // save the document line
    newDocLine.save();
    
    // create the document (with some properties)
    var newDoc = new Document();
    var newDocObj = {name: docName
		     , lines: [newDocLine]
		     , lastModified: new Date()
		     , usersWithShareAccess: [currentUser]
		     , documentType: 0 // latex document
		    };
    
    for (var key in newDocObj) {
	newDoc[key] = newDocObj[key];
    }
    // save the document
    newDoc.save();
    
    return newDoc;
};

/*
 * Helper function
 * displayErrorsForSignUp
*/
var displayErrorsForSignUp = function(res, errors) {
    res.render("sign-up",
	       {title: "Sign Up for Fly Latex"
		, shortTitle: "Sign Up"
		, tagLine: "Start Editing Documents with Your Peeps!"
		, fileSpecificStyle: "sign-up.css"
		, fileSpecificScript: "application.js"
		, errors: errors
	       });
};

/*
 * Helper function to loadUser onto app
 * Returns an object containing user credentials
 * like username and what not.
 */
var loadUser = function(user) {
    var obj = {};
    
    obj.currentUser = user.userName;
    obj.isLoggedIn = true;
    obj.userDocuments = [];
    obj.userDocumentsPriv = user.documentsPriv;
    
    // user document to send off to front end for display
    var userDocument = {}
    , priv;

    user.documentsPriv.forEach(function(item, i) {
	userDocument.id = item.documentId;
	userDocument.name = item.documentName;
	// set defaults here
	userDocument.readAccess = false;
	userDocument.writeAccess = false;
	userDocument.execAccess = false;
	userDocument.canShare = false;
	
	// set privileges here
	priv = item.access;
	
	if (priv >= 4) {
	    userDocument.readAccess = true;
	    priv -= 4;
	}
	if (priv >= 2) {
	    userDocument.writeAccess = true;
	    priv -= 2;
	}
	if (priv == 1) {
	    userDocument.execAccess = true;
	}

	// if user has R, W, X access, he can share the document
	// else he cannot
	if (item.access == 7) {
	    userDocument.canShare = true;
	}
	
	obj.userDocuments.push(userDocument);
	userDocument = {};
    });

    return obj;
}

/**
 * Helper function to clone an object (deep copy)
 * cloneObject
 * @param obj : object to clone
 */
function cloneObject(obj) {
    var clone = {};
    for(var i in obj) {
        if(typeof(obj[i])=="object")
            clone[i] = cloneObject(obj[i]);
        else
            clone[i] = obj[i];
    }
    return clone;
}