From 01f824567b380be5c5be8889e22093b2867bdead Mon Sep 17 00:00:00 2001
From: benweet <benoit.schweblin@gmail.com>
Date: Mon, 1 Apr 2013 17:46:48 +0100
Subject: [PATCH] Add down synchronization

---
 cache.manifest     |   2 +-
 css/main.css       |   7 ++
 index.html         |   4 +
 js/gdrive.js       |  98 +++++++++---------
 js/main.js         | 245 +++++++++------------------------------------
 js/synchronizer.js | 189 ++++++++++++++++++++++++++++++++++
 6 files changed, 296 insertions(+), 249 deletions(-)
 create mode 100644 js/synchronizer.js

diff --git a/cache.manifest b/cache.manifest
index 4bb14d3a..39b99cfd 100644
--- a/cache.manifest
+++ b/cache.manifest
@@ -1 +1 @@
-CACHE MANIFEST
# v5

CACHE:
index.html
css/bootstrap.css
css/jgrowl.css
css/main.css
js/async-runner.js
js/base64.js
js/bootstrap.js
js/gdrive.js
js/jquery.jgrowl.js
js/jquery.js
js/jquery.layout.js
js/jquery-ui.custom.js
js/main.js
js/Markdown.Converter.js
js/Markdown.Editor.js
js/Markdown.Sanitizer.js
img/ajax-loader.gif
img/gdrive.png
img/glyphicons-halflings.png
img/glyphicons-halflings-white.png
img/stackedit-16.png
img/stackedit-32.ico

NETWORK:
*
\ No newline at end of file
+CACHE MANIFEST
# v5

CACHE:
index.html
css/bootstrap.css
css/jgrowl.css
css/main.css
js/async-runner.js
js/base64.js
js/bootstrap.js
js/gdrive.js
js/jquery.jgrowl.js
js/jquery.js
js/jquery.layout.js
js/jquery-ui.custom.js
js/main.js
js/Markdown.Converter.js
js/Markdown.Editor.js
js/Markdown.Sanitizer.js
js/synchronizer.js
img/ajax-loader.gif
img/gdrive.png
img/glyphicons-halflings.png
img/glyphicons-halflings-white.png
img/stackedit-16.png
img/stackedit-32.ico

NETWORK:
*
\ No newline at end of file
diff --git a/css/main.css b/css/main.css
index de13f9ff..ed90d78d 100644
--- a/css/main.css
+++ b/css/main.css
@@ -211,6 +211,13 @@ hr {
 	background-position: 0 0;
 }
 
+.icon-dropbox {
+	background-image: url("../img/dropbox.png") !important;
+	width: 16px;
+	height: 16px;
+	background-position: 0 0;
+}
+
 .icon-spinner {
 	background-image: url("../img/ajax-loader.gif");
 	width: 43px;
diff --git a/index.html b/index.html
index f9b84d49..3a13c183 100644
--- a/index.html
+++ b/index.html
@@ -22,6 +22,7 @@
 <script type="text/javascript" src="js/main.js"></script>
 <script type="text/javascript" src="js/async-runner.js"></script>
 <script type="text/javascript" src="js/gdrive.js"></script>
+<script type="text/javascript" src="js/synchronizer.js"></script>
 <script type="text/javascript" src="js/config.custo.js"></script>
 <script>
 	(function(i, s, o, g, r, a, m) {
@@ -71,6 +72,9 @@
 						<li><a class="action-upload-gdrive" href="#"
 							title="Save the current file on Google Drive and synchonize it"><i
 								class="icon-gdrive"></i> Synchronize on Google Drive</a></li>
+						<li><a class="action-upload-dropbox" href="#"
+							title="Save the current file on Dropbox and synchonize it"><i
+								class="icon-dropbox"></i> Synchronize on Dropbox</a></li>
 						<li><a href="#"
 							title="Change the current file synchronized locations"
 							data-toggle="modal" data-target="#modal-manage-sync"
diff --git a/js/gdrive.js b/js/gdrive.js
index 74c763c3..54808002 100644
--- a/js/gdrive.js
+++ b/js/gdrive.js
@@ -31,14 +31,12 @@ var gdrive = (function($) {
 			gdriveDelayedFunction = function() {
 				asyncTask.success();
 			};
-			$
-				.ajax(
-					{
-						url : "https://apis.google.com/js/client.js?onload=runGdriveDelayedFunction",
-						dataType : "script", timeout : AJAX_TIMEOUT }).fail(
-					function() {
-						asyncTask.error();
-					});
+			$.ajax({
+				url : "https://apis.google.com/js/client.js?onload=runGdriveDelayedFunction",
+				dataType : "script", timeout : AJAX_TIMEOUT
+			}).fail(function() {
+				asyncTask.error();
+			});
 		};
 		asyncTask.onSuccess = function() {
 			gdriveDelayedFunction = undefined;
@@ -76,7 +74,7 @@ var gdrive = (function($) {
 					return;
 				}
 				if (immediate === false) {
-					showMessage("Please make sure the Google authorization popup is not blocked by your browser...");
+					showMessage("Please make sure the Google authorization popup is not blocked by your browser.");
 				}
 				gapi.auth.authorize({ 'client_id' : GOOGLE_CLIENT_ID,
 					'scope' : SCOPES, 'immediate' : immediate }, function(
@@ -106,10 +104,9 @@ var gdrive = (function($) {
 		});
 	}
 
-	function handleError(response, asyncTask, callback) {
+	function handleError(error, asyncTask, callback) {
 		var errorMsg = undefined;
-		if (response && response.error) {
-			var error = response.error;
+		if (error) {
 			// Try to analyze the error
 			if (error.code >= 500 && error.code < 600) {
 				errorMsg = "Google Drive is not accessible.";
@@ -119,7 +116,7 @@ var gdrive = (function($) {
 			} else if (error.code === 401) {
 				authenticated = false;
 				errorMsg = "Access to Google Drive is not authorized.";
-			} else if (error.code === -1) {
+			} else if (error.code <= 0) {
 				connected = false;
 				authenticated = false;
 				onOffline();
@@ -190,16 +187,17 @@ var gdrive = (function($) {
 						asyncTask.success();
 						return;
 					}
+					var error = response.error;
 					// If file has been removed from Google Drive
-					if(fileId !== undefined && response.error.code === 404) {
+					if(error !== undefined && fileId !== undefined && error.code === 404) {
 						showMessage('"' + title + '" has been removed from Google Drive.');
 						fileManager.removeSync(SYNC_PROVIDER_GDRIVE + fileId);
 						fileManager.updateFileTitles();
 						// Avoid error analyzed by handleError
-						response = undefined;
+						error = undefined;
 					}
 					// Handle error
-					handleError(response, asyncTask, callback);
+					handleError(error, asyncTask, callback);
 				});
 			};
 			asyncTask.onSuccess = function() {
@@ -223,29 +221,28 @@ var gdrive = (function($) {
 				var nextPageToken = undefined;
 				var asyncTask = {};
 				asyncTask.run = function() {
-					request
-						.execute(function(response) {
-							if (response && response.largestChangeId) {
-								// Retrieve success
-								newChangeId = response.largestChangeId;
-								nextPageToken = response.nextPageToken;
-								if (response.items !== undefined) {
-									for ( var i = 0; i < response.items.length; i++) {
-										var item = response.items[i];
-										var etag = localStorage[SYNC_PROVIDER_GDRIVE
-											+ item.fileId + ".etag"];
-										if (etag
-											&& (item.deleted === true || item.file.etag != etag)) {
-											changes.push(item);
-										}
+					request.execute(function(response) {
+						if (response && response.largestChangeId) {
+							// Retrieve success
+							newChangeId = response.largestChangeId;
+							nextPageToken = response.nextPageToken;
+							if (response.items !== undefined) {
+								for ( var i = 0; i < response.items.length; i++) {
+									var item = response.items[i];
+									var etag = localStorage[SYNC_PROVIDER_GDRIVE
+										+ item.fileId + ".etag"];
+									if (etag
+										&& (item.deleted === true || item.file.etag != etag)) {
+										changes.push(item);
 									}
 								}
-								asyncTask.success();
-								return;
 							}
-							// Handle error
-							handleError(response, asyncTask, callback);
-						});
+							asyncTask.success();
+							return;
+						}
+						// Handle error
+						handleError(response.error, asyncTask, callback);
+					});
 				};
 				asyncTask.onSuccess = function() {
 					if (nextPageToken !== undefined) {
@@ -297,19 +294,22 @@ var gdrive = (function($) {
 			var asyncTask = {};
 			asyncTask.run = function() {
 				var accessToken = gapi.auth.getToken().access_token;
-				$
-					.ajax(
-						{
-							url : file.downloadUrl,
-							headers : { "Authorization" : "Bearer "
-								+ accessToken }, dataType : "text",
-							timeout : AJAX_TIMEOUT }).done(
-						function(data, textStatus, jqXHR) {
-							file.content = data;
-							asyncTask.success();
-						}).fail(function() {
-						asyncTask.error();
-					});
+				$.ajax({
+					url : file.downloadUrl,
+					headers : { "Authorization" : "Bearer "
+						+ accessToken }, dataType : "text",
+					timeout : AJAX_TIMEOUT
+				}).done(function(data, textStatus, jqXHR) {
+					file.content = data;
+					asyncTask.success();
+				}).fail(function(jqXHR) {
+					var error = {
+						code: jqXHR.status,
+						message: jqXHR.statusText
+					};
+					// Handle error
+					handleError(error, asyncTask, callback);
+				});
 			};
 			asyncTask.onSuccess = function() {
 				gdrive.downloadContent(objects, callback, result);
diff --git a/js/main.js b/js/main.js
index 4db5f43a..096ef9e6 100644
--- a/js/main.js
+++ b/js/main.js
@@ -23,19 +23,20 @@ var CHECK_ONLINE_PERIOD = 60000;
 var offline = false;
 var offlineTime = currentTime;
 function onOffline() {
-	offline = true;
 	offlineTime = currentTime;
-	if ($(".msg-offline").length === 0)
+	if(offline === false) {
+		offline = true;
 		showMessage("You are offline.", "icon-exclamation-sign msg-offline", {
 			sticky : true, close : function() {
 				showMessage("You are back online!", "icon-signal");
 			} });
+	}
 }
 
 function onOnline() {
-	offline = false;
 	$(".msg-offline").parents(".jGrowl-notification").trigger(
 		'jGrowl.beforeClose');
+	offline = false;
 }
 
 function checkOnline() {
@@ -52,185 +53,7 @@ function checkOnline() {
 	}
 }
 
-var SYNC_DOWN_PERIOD = 60000;
-var SYNC_PROVIDER_GDRIVE = "sync.gdrive.";
-var syncGoogleDrive = false;
-
-var synchronizer = (function($) {
-	var synchronizer = {};
-
-	// A synchronization queue containing fileIndex that has to be synchronized
-	var syncQueue = undefined;
-	synchronizer.init = function() {
-		syncQueue = ";";
-		// Load the queue from localStorage in case a previous synchronization
-		// was aborted
-		if (localStorage["sync.queue"]) {
-			syncQueue = localStorage["sync.queue"];
-		}
-		if (localStorage["sync.current"]) {
-			this.addFile(localStorage["sync.current"]);
-		}
-	};
-
-	// Add a file to the synchronization queue
-	synchronizer.addFile = function(fileIndex) {
-		if (syncQueue.indexOf(";" + fileIndex + ";") === -1) {
-			syncQueue += fileIndex + ";";
-			localStorage["sync.queue"] = syncQueue;
-		}
-	};
-
-	// Recursive function to upload a single file on multiple locations
-	function fileUp(fileSyncIndexList, content, title) {
-		if (fileSyncIndexList.length === 0) {
-			localStorage.removeItem("sync.current");
-			uploadRunning = false;
-			// run the next file synchronization
-			synchronizer.syncUp();
-			return;
-		}
-		var fileSyncIndex = fileSyncIndexList.pop();
-
-		// Try to find the provider
-		if (fileSyncIndex.indexOf(SYNC_PROVIDER_GDRIVE) === 0) {
-			var id = fileSyncIndex.substring(SYNC_PROVIDER_GDRIVE.length);
-			gdrive.updateFile(id, title, content, function(result) {
-				if (result === undefined && offline === true) {
-					// If we detect offline mode we put the fileIndex back in
-					// the queue
-					synchronizer.addFile(localStorage["sync.current"]);
-					localStorage.removeItem("sync.current");
-					uploadRunning = false;
-					return;
-				}
-				fileUp(fileSyncIndexList, content, title);
-			});
-		} else {
-			fileUp(fileSyncIndexList, content, title);
-		}
-	}
-
-	var uploadRunning = false;
-	synchronizer.syncUp = function() {
-		// If syncUp is already running or nothing to synchronize or offline
-		if (uploadRunning || syncQueue.length === 1 || offline) {
-			return;
-		}
-		uploadRunning = true;
-
-		// Dequeue the fileIndex
-		var separatorPos = syncQueue.indexOf(";", 1);
-		var fileIndex = syncQueue.substring(1, separatorPos);
-		localStorage["sync.current"] = fileIndex;
-		syncQueue = syncQueue.substring(separatorPos);
-		localStorage["sync.queue"] = syncQueue;
-
-		var content = localStorage[fileIndex + ".content"];
-		var title = localStorage[fileIndex + ".title"];
-
-		// Parse the list of synchronized locations associated to the file
-		var fileSyncIndexList = localStorage[fileIndex + ".sync"].split(";");
-		fileUp(fileSyncIndexList, content, title);
-	};
-
-	function syncDownGdrive(callback) {
-		if (syncGoogleDrive === false) {
-			callback();
-			return;
-		}
-		var lastChangeId = parseInt(localStorage[SYNC_PROVIDER_GDRIVE
-			+ "lastChangeId"]);
-		gdrive.checkUpdates(lastChangeId, function(changes, newChangeId) {
-			if (changes === undefined) {
-				callback();
-				return;
-			}
-			gdrive.downloadContent(changes, function(changes) {
-				if (changes === undefined) {
-					callback();
-					return;
-				}
-				var updateFileTitles = false;
-				for ( var i = 0; i < changes.length; i++) {
-					var change = changes[i];
-					var fileSyncIndex = SYNC_PROVIDER_GDRIVE + change.fileId;
-					var fileIndexList = localStorage["file.list"].split(";");
-					var fileIndex = undefined;
-					// Look for local file associated to this synchronized location 
-					for ( var i = 1; i < fileIndexList.length - 1; i++) {
-						var tempFileIndex = fileIndexList[i];
-						var sync = localStorage[tempFileIndex + ".sync"];
-						if (sync.indexOf(";" + fileSyncIndex + ";") !== -1) {
-							fileIndex = tempFileIndex;
-							break;
-						}
-					}
-					// No file corresponding (this should never happen...)
-					if(fileIndex === undefined) {
-						// We can remove the stored etag
-						localStorage.removeItem(fileSyncIndex + ".etag");
-						continue;
-					}
-					var title = localStorage[fileIndex + ".title"];
-					// File deleted
-					if (change.deleted === true) {
-						fileManager.removeSync(fileSyncIndex);
-						updateFileTitles = true;
-						showMessage('"' + title + '" has been removed from Google Drive.');
-						continue;
-					}
-					var content = localStorage[fileIndex + ".content"];
-					var file = change.file;
-					// File title changed
-					if(title != file.title) {
-						localStorage[fileIndex + ".title"] = file.title;
-						updateFileTitles = true;
-						showMessage('"' + title + '" has been renamed to "' + file.title + '" on Google Drive.');
-					}
-					// File content changed
-					if(content != file.content) {
-						localStorage[fileIndex + ".content"] = file.content;
-						showMessage('"' + file.title + '" has been updated from Google Drive.');
-						if(fileIndex == localStorage["file.current"]) {
-							updateFileTitles = false; // Done by next function
-							fileManager.selectFile();
-						}
-					}
-					// Update file etag
-					localStorage[fileSyncIndex + ".etag"] = file.etag;
-					// Synchronize file to others locations
-					synchronizer.addFile(fileIndex);
-				}
-				if(updateFileTitles) {
-					fileManager.updateFileTitles();
-				}
-				localStorage[SYNC_PROVIDER_GDRIVE
-				 			+ "lastChangeId"] = newChangeId;
-				callback();
-			});
-		});
-	}
-
-	var downloadRunning = false;
-	var lastSyncDown = 0;
-	synchronizer.syncDown = function() {
-		// If syncDown is already running or timeout is not reached or offline
-		if (downloadRunning || lastSyncDown + SYNC_DOWN_PERIOD > currentTime
-			|| offline) {
-			return;
-		}
-		downloadRunning = true;
-		lastSyncDown = currentTime;
-
-		syncDownGdrive(function() {
-			downloadRunning = false;
-		});
-	};
-
-	return synchronizer;
-})(jQuery);
-
+var DEFAULT_FILE_TITLE = "Filename";
 var fileManager = (function($) {
 
 	var fileManager = {};
@@ -245,16 +68,15 @@ var fileManager = (function($) {
 		window.setInterval(function() {
 			currentTime = new Date().getTime();
 			fileManager.saveFile();
-			synchronizer.syncDown();
-			synchronizer.syncUp();
+			synchronizer.sync();
 			asyncTaskRunner.runTask();
 			checkOnline();
 		}, 1000);
 
 		$(".action-create-file").click(function() {
 			fileManager.saveFile();
-			fileManager.createFile();
-			fileManager.selectFile();
+			var fileIndex = fileManager.createFile();
+			fileManager.selectFile(fileIndex);
 			$("#file-title").click();
 		});
 		$(".action-remove-file").click(function() {
@@ -294,10 +116,13 @@ var fileManager = (function($) {
 				window.open(uriContent, 'file');
 			});
 		$(".action-upload-gdrive").click(uploadGdrive);
+		$(".action-upload-dropbox").click(function() {
+			showMessage("Sorry, Dropbox synchronization is not yet available.");
+		});
 	};
 
 	var fileDescList = [];
-	fileManager.selectFile = function() {
+	fileManager.selectFile = function(fileIndex) {
 		// If file system does not exist
 		if (!localStorage["file.counter"] || !localStorage["file.list"]) {
 			localStorage.clear();
@@ -306,8 +131,14 @@ var fileManager = (function($) {
 		}
 		// If no file create one
 		if (localStorage["file.list"].length === 1) {
-			this.createFile();
+			fileIndex = this.createFile();
 		}
+		
+		fileIndex = fileIndex || localStorage["file.current"];
+		if(fileIndex !== undefined) {
+			localStorage["file.current"] = fileIndex;
+		}
+
 		// Update the file titles
 		this.updateFileTitles();
 		// Update the editor
@@ -318,20 +149,33 @@ var fileManager = (function($) {
 		});
 	};
 
-	fileManager.createFile = function(title) {
+	fileManager.createFile = function(title, content) {
+		content = content || "";
 		if (!title) {
-			title = "Filename";
+			// Create a file title 
+			title = DEFAULT_FILE_TITLE;
+			function exists(title) {
+				for ( var i = 0; i < fileDescList.length; i++) {
+					if(fileDescList[i].title == title) {
+						return true;
+					}
+				}
+			}
+			var indicator = 2;
+			while(exists(title)) {
+				title = DEFAULT_FILE_TITLE + indicator++;
+			}
 		}
 		// Create the fileIndex
 		var fileCounter = parseInt(localStorage["file.counter"]);
 		var fileIndex = "file." + fileCounter;
 		// Create the file in the localStorage
-		localStorage[fileIndex + ".content"] = "";
+		localStorage[fileIndex + ".content"] = content;
 		localStorage[fileIndex + ".title"] = title;
 		localStorage[fileIndex + ".sync"] = ";";
 		localStorage["file.counter"] = fileCounter + 1;
 		localStorage["file.list"] += fileIndex + ";";
-		localStorage["file.current"] = fileIndex;
+		return fileIndex;
 	};
 
 	fileManager.deleteFile = function() {
@@ -357,7 +201,7 @@ var fileManager = (function($) {
 			var content = $("#wmd-input").val();
 			var fileIndex = localStorage["file.current"];
 			localStorage[fileIndex + ".content"] = content;
-			synchronizer.addFile(fileIndex);
+			synchronizer.addFileForUpload(fileIndex);
 			save = false;
 		}
 	};
@@ -379,9 +223,11 @@ var fileManager = (function($) {
 			return 0;
 		});
 
+		var fileIndex = localStorage["file.current"];
 		// If no default file take first one
-		if (!localStorage["file.current"]) {
-			localStorage["file.current"] = fileDescList[0].index;
+		if (!fileIndex) {
+			fileIndex = fileDescList[0].index;
+			localStorage["file.current"] = fileIndex;
 		}
 		
 		syncGoogleDrive = false;
@@ -395,15 +241,15 @@ var fileManager = (function($) {
 			return result;
 		}
 
-		// Update the the file title and the file selector
-		var fileIndex = localStorage["file.current"];
+		// Update the file title
 		var title = localStorage[fileIndex + ".title"];
 		document.title = "StackEdit - " + title;
 		$("#file-title").html(composeTitle(fileIndex));
 		$(".file-title").text(title);
 		$("#file-title-input").val(title);
+		
+		// Update the file selector
 		$("#file-selector").empty();
-
 		for ( var i = 0; i < fileDescList.length; i++) {
 			var fileDesc = fileDescList[i];
 			var a = $("<a>").html(composeTitle(fileDesc.index));
@@ -595,11 +441,12 @@ var core = (function($) {
 
 	$(function() {
 
+		// jGrowl configuration
 		$.jGrowl.defaults.life = 5000;
 		$.jGrowl.defaults.closer = false;
 		$.jGrowl.defaults.closeTemplate = '';
 		$.jGrowl.defaults.position = 'bottom-right';
-
+		
 		core.init();
 
 		// listen to online/offline events
diff --git a/js/synchronizer.js b/js/synchronizer.js
new file mode 100644
index 00000000..f64e4115
--- /dev/null
+++ b/js/synchronizer.js
@@ -0,0 +1,189 @@
+var SYNC_PERIOD = 30000;
+var SYNC_PROVIDER_GDRIVE = "sync.gdrive.";
+var syncGoogleDrive = false;
+
+var synchronizer = (function() {
+	var synchronizer = {};
+
+	// A synchronization queue containing fileIndex that has to be synchronized
+	var syncUpQueue = undefined;
+	synchronizer.init = function() {
+		syncUpQueue = ";";
+		// Load the queue from localStorage in case a previous synchronization
+		// was aborted
+		if (localStorage["sync.queue"]) {
+			syncUpQueue = localStorage["sync.queue"];
+		}
+		if (localStorage["sync.current"]) {
+			this.addFileForUpload(localStorage["sync.current"]);
+		}
+	};
+
+	// Add a file to the synchronization queue
+	synchronizer.addFileForUpload = function(fileIndex) {
+		if (syncUpQueue.indexOf(";" + fileIndex + ";") === -1) {
+			syncUpQueue += fileIndex + ";";
+			localStorage["sync.queue"] = syncUpQueue;
+		}
+	};
+
+	// Recursive function to upload a single file on multiple locations
+	function fileUp(fileSyncIndexList, content, title, callback) {
+		if (fileSyncIndexList.length === 0) {
+			localStorage.removeItem("sync.current");
+			// run the next file synchronization
+			syncUp(callback);
+			return;
+		}
+		var fileSyncIndex = fileSyncIndexList.pop();
+
+		// Try to find the provider
+		if (fileSyncIndex.indexOf(SYNC_PROVIDER_GDRIVE) === 0) {
+			var id = fileSyncIndex.substring(SYNC_PROVIDER_GDRIVE.length);
+			gdrive.updateFile(id, title, content, function(result) {
+				if (result === undefined && offline === true) {
+					// If we detect offline mode we put the fileIndex back in
+					// the queue
+					synchronizer.addFileForUpload(localStorage["sync.current"]);
+					localStorage.removeItem("sync.current");
+					callback();
+					return;
+				}
+				fileUp(fileSyncIndexList, content, title, callback);
+			});
+		} else {
+			fileUp(fileSyncIndexList, content, title, callback);
+		}
+	}
+
+	function syncUp(callback) {
+		// If nothing to synchronize
+		if (syncUpQueue.length === 1) {
+			callback();
+			return;
+		}
+
+		// Dequeue the fileIndex
+		var separatorPos = syncUpQueue.indexOf(";", 1);
+		var fileIndex = syncUpQueue.substring(1, separatorPos);
+		localStorage["sync.current"] = fileIndex;
+		syncUpQueue = syncUpQueue.substring(separatorPos);
+		localStorage["sync.queue"] = syncUpQueue;
+
+		var content = localStorage[fileIndex + ".content"];
+		var title = localStorage[fileIndex + ".title"];
+
+		// Parse the list of synchronized locations associated to the file
+		var fileSyncIndexList = localStorage[fileIndex + ".sync"].split(";");
+		fileUp(fileSyncIndexList, content, title, callback);
+	};
+
+	function syncDownGdrive(callback) {
+		if (syncGoogleDrive === false) {
+			callback();
+			return;
+		}
+		var lastChangeId = parseInt(localStorage[SYNC_PROVIDER_GDRIVE
+			+ "lastChangeId"]);
+		gdrive.checkUpdates(lastChangeId, function(changes, newChangeId) {
+			if (changes === undefined) {
+				callback();
+				return;
+			}
+			gdrive.downloadContent(changes, function(changes) {
+				if (changes === undefined) {
+					callback();
+					return;
+				}
+				var updateFileTitles = false;
+				for ( var i = 0; i < changes.length; i++) {
+					var change = changes[i];
+					var fileSyncIndex = SYNC_PROVIDER_GDRIVE + change.fileId;
+					var fileIndexList = localStorage["file.list"].split(";");
+					var fileIndex = undefined;
+					// Look for local file associated to this synchronized location 
+					for ( var i = 1; i < fileIndexList.length - 1; i++) {
+						var tempFileIndex = fileIndexList[i];
+						var sync = localStorage[tempFileIndex + ".sync"];
+						if (sync.indexOf(";" + fileSyncIndex + ";") !== -1) {
+							fileIndex = tempFileIndex;
+							break;
+						}
+					}
+					// No file corresponding (this should never happen...)
+					if(fileIndex === undefined) {
+						// We can remove the stored etag
+						localStorage.removeItem(fileSyncIndex + ".etag");
+						continue;
+					}
+					var title = localStorage[fileIndex + ".title"];
+					// File deleted
+					if (change.deleted === true) {
+						fileManager.removeSync(fileSyncIndex);
+						updateFileTitles = true;
+						showMessage('"' + title + '" has been removed from Google Drive.');
+						continue;
+					}
+					var content = localStorage[fileIndex + ".content"];
+					var file = change.file;
+					var titleChanged = title != file.title;
+					var contentChanged = content != file.content;
+					// If file is in the upload queue we have a conflict
+					if ((titleChanged || contentChanged) && syncUpQueue.indexOf(";" + fileIndex + ";") !== -1) {
+						fileManager.createFile(title + " (backup)", content);
+						updateFileTitles = true;
+						showMessage('Conflict detected on "' + title + '". A backup has been created locally.');
+					}
+					// If file title changed
+					if(titleChanged) {
+						localStorage[fileIndex + ".title"] = file.title;
+						updateFileTitles = true;
+						showMessage('"' + title + '" has been renamed to "' + file.title + '" on Google Drive.');
+					}
+					// If file content changed
+					if(contentChanged) {
+						localStorage[fileIndex + ".content"] = file.content;
+						showMessage('"' + file.title + '" has been updated from Google Drive.');
+						if(fileIndex == localStorage["file.current"]) {
+							updateFileTitles = false; // Done by next function
+							fileManager.selectFile();
+						}
+					}
+					// Update file etag
+					localStorage[fileSyncIndex + ".etag"] = file.etag;
+					// Synchronize file to others locations
+					synchronizer.addFileForUpload(fileIndex);
+				}
+				if(updateFileTitles) {
+					fileManager.updateFileTitles();
+				}
+				localStorage[SYNC_PROVIDER_GDRIVE
+				 			+ "lastChangeId"] = newChangeId;
+				callback();
+			});
+		});
+	}
+
+	function syncDown(callback) {
+		syncDownGdrive(callback);
+	};
+		
+	var syncRunning = false;
+	var lastSync = 0;
+	synchronizer.sync = function() {
+		// If sync is already running or timeout is not reached or offline
+		if (syncRunning || lastSync + SYNC_PERIOD > currentTime || offline) {
+			return;
+		}
+		syncRunning = true;
+		lastSync = currentTime;
+
+		syncDown(function() {
+			syncUp(function() {
+				syncRunning = false;
+			});
+		});
+	};
+
+	return synchronizer;
+})();