allow starting offline in monitor mode

src/main.d

@@ -183,9 +183,11 @@ int main(string[] args)
 	} catch (CurlException e) {
 		// No network connection to OneDrive Service
 		log.error("No network connection to Microsoft OneDrive Service");
-		return EXIT_FAILURE;
-	} 
-
+		if (!monitor) {
+			return EXIT_FAILURE;
+		}
+	}
+
 	// Initialize OneDrive, check for authorization
 	auto onedrive = new OneDriveApi(cfg, debugHttp);
 	onedrive.printAccessToken = printAccessToken;
@@ -256,21 +258,18 @@ int main(string[] args)
 	auto sync = new SyncEngine(cfg, onedrive, itemdb, selectiveSync);
 
 	try {
-		sync.init();
-	} catch (OneDriveException e) {
-		if (e.httpStatusCode == 400 || e.httpStatusCode == 401) {
-			// Authorization is invalid
-			log.log("\nAuthorization token invalid, use --logout to authorize the client again\n");
+		if (!initSyncEngine(sync)) {
 			onedrive.http.shutdown();
 			return EXIT_FAILURE;
 		}
-		if (e.httpStatusCode >= 500) {
-			// There was a HTTP 5xx Server Side Error, message already printed
+	} catch (CurlException e) {
+		if (!monitor) {
+			log.log("\nNo internet connection.");
 			onedrive.http.shutdown();
 			return EXIT_FAILURE;
 		}
 	}
-	
+
 	// We should only set noRemoteDelete in an upload-only scenario
 	if ((uploadOnly)&&(noRemoteDelete)) sync.setNoRemoteDelete();
 
@@ -375,23 +374,20 @@ int main(string[] args)
 				auto currTime = MonoTime.currTime();
 				if (currTime - lastCheckTime > checkInterval) {
 					try {
-						online = testNetwork();
+						if (!initSyncEngine(sync)) {
+							onedrive.http.shutdown();
+							return EXIT_FAILURE;
+						}
+						performSync(sync, singleDirectory, downloadOnly, localFirst, uploadOnly);
+						if (!downloadOnly) {
+							// discard all events that may have been generated by the sync
+							m.update(false);
+						}
 					} catch (CurlException e) {
+						// TODO better check of type of exception from Curl
+						// could be either timeout of operation of connection error
 						// No network connection to OneDrive Service
 						log.log("No network connection to Microsoft OneDrive Service, skipping sync");
-						online = false;
-					}
-					if (online) {
-						try {
-							performSync(sync, singleDirectory, downloadOnly, localFirst, uploadOnly);
-							if (!downloadOnly) {
-								// discard all events that may have been generated by the sync
-								m.update(false);
-							}
-						} catch (CurlException e) {
-							// TODO better check of type of exception from Curl
-							log.log("No network connection to Microsoft OneDrive Service, skipping sync");
-						}
 					}
 					// performSync complete, set lastCheckTime to current time
 					lastCheckTime = MonoTime.currTime();
@@ -407,6 +403,24 @@ int main(string[] args)
 	return EXIT_SUCCESS;
 }
 
+bool initSyncEngine(SyncEngine sync)
+{
+	try {
+		sync.init();
+	} catch (OneDriveException e) {
+		if (e.httpStatusCode == 400 || e.httpStatusCode == 401) {
+			// Authorization is invalid
+			log.log("\nAuthorization token invalid, use --logout to authorize the client again\n");
+			return false;
+		}
+		if (e.httpStatusCode >= 500) {
+			// There was a HTTP 5xx Server Side Error, message already printed
+			return false;
+		}
+	}
+	return true;
+}
+
 // try to synchronize the folder three times
 void performSync(SyncEngine sync, string singleDirectory, bool downloadOnly, bool localFirst, bool uploadOnly)
 {

src/sync.d

@@ -167,6 +167,8 @@ final class SyncEngine
 	private bool malwareDetected = false;
 	// download filesystem issue flag
 	private bool downloadFailed = false;
+	// initialization has been done
+	private bool initDone = false;
 
 	this(Config cfg, OneDriveApi onedrive, ItemDatabase itemdb, SelectiveSync selectiveSync)
 	{
@@ -183,6 +185,11 @@ final class SyncEngine
 		// Set accountType, defaultDriveId, defaultRootId & remainingFreeSpace once and reuse where possible
 		JSONValue oneDriveDetails;
 
+
+		if (initDone) {
+			return;
+		}
+
 		// Need to catch 400 or 5xx server side errors at initialization
 		try {
 			oneDriveDetails	= onedrive.getDefaultDrive();
@@ -239,6 +246,7 @@ final class SyncEngine
 			auto item = session.upload();
 			saveItem(item);
 		}		
+		initDone = true;
 	}
 
 	// Configure noRemoteDelete if function is called