Refactoring Part 4: Update Timer and Pausing

baRSS/Categories/FeedMeta+Ext.h

@@ -27,6 +27,7 @@
 - (void)calculateAndSetScheduled;
 
 - (void)setEtag:(NSString*)etag modified:(NSString*)modified;
+- (void)setEtagAndModified:(NSHTTPURLResponse*)http;
 - (BOOL)setURL:(NSString*)url refresh:(int32_t)refresh unit:(int16_t)unit;
 
 - (NSString*)readableRefreshString;

baRSS/Categories/FeedMeta+Ext.m

@@ -24,12 +24,16 @@
 
 @implementation FeedMeta (Ext)
 
-/// Increment @c errorCount (max. 19) and set new @c scheduled (2^N seconds, max. 6 days).
+/// Increment @c errorCount and set new @c scheduled date (2^N minutes, max. 5.7 days).
 - (void)setErrorAndPostponeSchedule {
-	int16_t n = self.errorCount + 1;
+	if (self.errorCount < 0)
-	self.errorCount = (n < 1 ? 1 : (n > 19 ? 19 : n)); // between: 2 sec and 6 days
+		self.errorCount = 0;
-	NSTimeInterval retryWaitTime = pow(2, self.errorCount); // 2^n seconds
+	int16_t n = self.errorCount + 1; // always increment errorCount (can be used to indicate bad feeds)
+	NSTimeInterval retryWaitTime = pow(2, (n > 13 ? 13 : n)) * 60; // 2^N (between: 2 minutes and 5.7 days)
+	self.errorCount = n;
 	self.scheduled = [NSDate dateWithTimeIntervalSinceNow:retryWaitTime];
+	// TODO: remove logging
+	NSLog(@"ERROR: Feed download failed: %@ (errorCount: %d)", self.url, n);
 }
 
 /// Calculate date from @c refreshNum and @c refreshUnit and set as next scheduled feed update.
@@ -44,6 +48,12 @@
 	if (![self.modified isEqualToString:modified]) self.modified = modified;
 }
 
+/// Read header field "Etag" and "Date" and set @c .etag and @c .modified.
+- (void)setEtagAndModified:(NSHTTPURLResponse*)http {
+	NSDictionary *header = [http allHeaderFields];
+	[self setEtag:header[@"Etag"] modified:header[@"Date"]]; // @"Expires", @"Last-Modified"
+}
+
 /**
  Set download url and refresh interval (popup button selection). @note Only values that differ will be updated.
 

baRSS/Constants.h

@@ -23,6 +23,10 @@
 #ifndef Constants_h
 #define Constants_h
 
+// TODO: Add support for media player?
+// <enclosure url="https://url.mp3" length="63274022" type="audio/mpeg" />
+// TODO: Disable 'update all' menu item during update?
+
 static NSString *kNotificationFeedUpdated = @"baRSS-notification-feed-updated";
 static NSString *kNotificationNetworkStatusChanged = @"baRSS-notification-network-status-changed";
 static NSString *kNotificationTotalUnreadCountChanged = @"baRSS-notification-total-unread-count-changed";

baRSS/FeedDownload.h

@@ -24,9 +24,15 @@
 #import <RSXML/RSXML.h>
 
 @interface FeedDownload : NSObject
-+ (void)newFeed:(NSString *)url block:(void(^)(RSParsedFeed *feed, NSError* error, NSHTTPURLResponse* response))block;
+// Register for network change notifications
 + (void)registerNetworkChangeNotification;
 + (void)unregisterNetworkChangeNotification;
-+ (BOOL)isNetworkReachable;
+// Scheduled feed update
-+ (void)scheduleNextUpdateForced:(BOOL)flag;
++ (void)newFeed:(NSString *)url block:(void(^)(RSParsedFeed *feed, NSError* error, NSHTTPURLResponse* response))block;
++ (void)scheduleUpdateForUpcomingFeeds;
++ (void)forceUpdateAllFeeds;
+// User interaction
++ (BOOL)allowNetworkConnection;
++ (BOOL)isPaused;
++ (void)setPaused:(BOOL)flag;
 @end

baRSS/FeedDownload.m

@@ -30,10 +30,126 @@
 
 static SCNetworkReachabilityRef _reachability = NULL;
 static BOOL _isReachable = NO;
+static BOOL _updatePaused = NO;
+static BOOL _nextUpdateIsForced = NO;
 
 
 @implementation FeedDownload
 
+#pragma mark - User Interaction -
+
+/// @return @c YES if current network state is reachable and updates are not paused by user.
++ (BOOL)allowNetworkConnection {
+	return (_isReachable && !_updatePaused);
+}
+
+/// @return @c YES if update is paused by user.
++ (BOOL)isPaused {
+	return _updatePaused;
+}
+
+/// Set paused flag and cancel timer regardless of network connectivity.
++ (void)setPaused:(BOOL)flag {
+	_updatePaused = flag;
+	if (_updatePaused)
+		[self pauseUpdates];
+	else
+		[self resumeUpdates];
+}
+
+/// Cancel current timer and stop any updates until enabled again.
++ (void)pauseUpdates {
+	[self scheduleTimer:nil];
+}
+
+/// Start normal (non forced) schedule if network is reachable.
++ (void)resumeUpdates {
+	if (_isReachable)
+		[self scheduleUpdateForUpcomingFeeds];
+}
+
+
+#pragma mark - Update Feed Timer -
+
+
+/**
+ Get date of next up feed and start the timer.
+ */
++ (void)scheduleUpdateForUpcomingFeeds {
+	if (![self allowNetworkConnection]) // timer will restart once connection exists
+		return;
+	NSDate *nextTime = [StoreCoordinator nextScheduledUpdate];
+	if (!nextTime) return; // no timer means no feeds to update
+	if ([nextTime timeIntervalSinceNow] < 1) { // mostly, if app was closed for a long time
+		nextTime = [NSDate dateWithTimeIntervalSinceNow:1];
+	}
+	[self scheduleTimer:nextTime];
+}
+
+/**
+ Start download of all feeds (immediatelly) regardless of @c .scheduled property.
+ */
++ (void)forceUpdateAllFeeds {
+	if (![self allowNetworkConnection]) // timer will restart once connection exists
+		return;
+	_nextUpdateIsForced = YES;
+	[self scheduleTimer:[NSDate dateWithTimeIntervalSinceNow:0.2]];
+}
+
+/**
+ Set new @c .fireDate and @c .tolerance for update timer.
+
+ @param nextTime If @c nil timer will be disabled with a @c .fireDate very far in the future.
+ */
++ (void)scheduleTimer:(NSDate*)nextTime {
+	static NSTimer *timer;
+	if (!timer) {
+		timer = [NSTimer timerWithTimeInterval:NSTimeIntervalSince1970 target:[self class] selector:@selector(updateTimerCallback) userInfo:nil repeats:YES];
+		[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
+	}
+	if (!nextTime)
+		nextTime = [NSDate dateWithTimeIntervalSinceNow:NSTimeIntervalSince1970];
+	NSTimeInterval tolerance = [nextTime timeIntervalSinceNow] * 0.15;
+	timer.tolerance = (tolerance < 1 ? 1 : tolerance); // at least 1 sec
+	timer.fireDate = nextTime;
+}
+
+/**
+ Called when schedule timer runs out (earliest @c .schedule date). Or if forced by user request.
+ */
++ (void)updateTimerCallback {
+	if (![self allowNetworkConnection])
+		return;
+	NSLog(@"fired");
+	
+	__block NSManagedObjectContext *childContext = [StoreCoordinator createChildContext];
+	NSArray<Feed*> *list = [StoreCoordinator getListOfFeedsThatNeedUpdate:_nextUpdateIsForced inContext:childContext];
+	_nextUpdateIsForced = NO;
+	if (list.count == 0) {
+		NSLog(@"ERROR: Something went wrong, timer fired too early.");
+		[childContext reset];
+		childContext = nil;
+		// thechnically should never happen, anyway we need to reset the timer
+		[self resumeUpdates];
+		return; // nothing to do here
+	}
+	dispatch_group_t group = dispatch_group_create();
+	for (Feed *feed in list) {
+		[self downloadFeed:feed group:group];
+	}
+	dispatch_group_notify(group, dispatch_get_main_queue(), ^{
+		[StoreCoordinator saveContext:childContext andParent:YES];
+		[[NSNotificationCenter defaultCenter] postNotificationName:kNotificationFeedUpdated object:[list valueForKeyPath:@"objectID"]];
+		[childContext reset];
+		childContext = nil;
+		[self resumeUpdates];
+	});
+}
+
+
+#pragma mark - Download RSS Feed -
+
+
 /// @return New request with no caching policy and timeout interval of 30 seconds.
 + (NSMutableURLRequest*)newRequestURL:(NSString*)url {
 	NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:url]];
@@ -76,72 +192,6 @@ static BOOL _isReachable = NO;
 	}] resume];
 }
 
-
-#pragma mark - Update existing feeds -
-
-
-/**
- Get date of next update schedule and start @c updateTimer.
-
- @param forceUpdate If @c YES all feeds will be downloaded regardless of scheduled date.
- */
-+ (void)scheduleNextUpdateForced:(BOOL)forceUpdate {
-	static NSTimer *_updateTimer;
-	@synchronized (_updateTimer) { // TODO: dig into analyzer warning
-		if (_updateTimer) {
-			[_updateTimer invalidate];
-			_updateTimer = nil;
-		}
-	}
-	if (!_isReachable) return; // cancel timer entirely (will be restarted once connection exists)
-	NSDate *nextTime = [NSDate dateWithTimeIntervalSinceNow:0.2];
-	if (!forceUpdate) {
-		nextTime = [StoreCoordinator nextScheduledUpdate];
-		if (!nextTime) return; // no timer means no feeds to update
-		if ([nextTime timeIntervalSinceNow] < 0) { // mostly, if app was closed for a long time
-			nextTime = [NSDate dateWithTimeIntervalSinceNow:2]; // TODO: retry in 2 sec?
-		}
-	}
-	NSTimeInterval tolerance = [nextTime timeIntervalSinceNow] * 0.15;
-	_updateTimer = [NSTimer timerWithTimeInterval:0 target:[self class] selector:@selector(scheduledUpdateTimer:) userInfo:@(forceUpdate) repeats:NO];
-	_updateTimer.fireDate = nextTime;
-	_updateTimer.tolerance = (tolerance < 1 ? 1 : tolerance); // at least 1 sec
-	[[NSRunLoop mainRunLoop] addTimer:_updateTimer forMode:NSRunLoopCommonModes];
-}
-
-/**
- Called when schedule timer has run out (earliest scheduled date). Or if forced by user request.
-
- @param timer @c NSTimer @c .userInfo should contain a @c BOOL value whether to force an update of all feeds @c (YES).
- */
-+ (void)scheduledUpdateTimer:(NSTimer*)timer {
-	NSLog(@"fired");
-	BOOL forceAll = [timer.userInfo boolValue];
-	// TODO: check internet connection
-	// TODO: disable menu item 'update all' during update
-	__block NSManagedObjectContext *childContext = [StoreCoordinator createChildContext];
-	NSArray<Feed*> *list = [StoreCoordinator getListOfFeedsThatNeedUpdate:forceAll inContext:childContext];
-	if (list.count == 0) {
-		NSLog(@"ERROR: Something went wrong, timer fired too early.");
-		[childContext reset];
-		childContext = nil;
-		// thechnically should never happen, anyway we need to reset the timer
-		[self scheduleNextUpdateForced:NO]; // NO, since forceAll will get ALL items and shouldn't be 0
-		return; // nothing to do here
-	}
-	dispatch_group_t group = dispatch_group_create();
-	for (Feed *feed in list) {
-		[self downloadFeed:feed group:group];
-	}
-	dispatch_group_notify(group, dispatch_get_main_queue(), ^{
-		[StoreCoordinator saveContext:childContext andParent:YES];
-		[[NSNotificationCenter defaultCenter] postNotificationName:kNotificationFeedUpdated object:[list valueForKeyPath:@"objectID"]];
-		[childContext reset];
-		childContext = nil;
-		[self scheduleNextUpdateForced:NO]; // after forced update, continue regular cycle
-	});
-}
-
 /**
  Start download request with existing @c Feed object. Reuses etag and modified headers.
 
@@ -149,56 +199,41 @@ static BOOL _isReachable = NO;
  @param group Mutex to count completion of all downloads.
  */
 + (void)downloadFeed:(Feed*)feed group:(dispatch_group_t)group {
-	if (!_isReachable) return;
+	if (![self allowNetworkConnection])
+		return;
 	dispatch_group_enter(group);
 	[[[NSURLSession sharedSession] dataTaskWithRequest:[self newRequest:feed.meta] completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
 		[feed.managedObjectContext performBlock:^{
 			// core data block inside of url session block; otherwise access will EXC_BAD_INSTRUCTION
 			if (error) {
 				[feed.meta setErrorAndPostponeSchedule];
-				// TODO: remove logging
-				NSLog(@"Error loading: %@ (%d)", response.URL, feed.meta.errorCount);
 			} else {
+				[feed.meta setEtagAndModified:(NSHTTPURLResponse*)response];
+				[feed.meta calculateAndSetScheduled];
+				
+				if ([(NSHTTPURLResponse*)response statusCode] != 304) { // only parse if modified
+					// should be fine to call synchronous since dataTask is already in the background (always? proof?)
+					RSXMLData *xml = [[RSXMLData alloc] initWithData:data urlString:feed.meta.url];
+					RSParsedFeed *parsed = RSParseFeedSync(xml, NULL);
+					if (parsed && parsed.articles.count > 0) {
+						[feed updateWithRSS:parsed postUnreadCountChange:YES];
 						feed.meta.errorCount = 0; // reset counter
-				[self downloadSuccessful:data forFeed:feed response:(NSHTTPURLResponse*)response];
+					} else {
+						[feed.meta setErrorAndPostponeSchedule]; // replaces date of 'calculateAndSetScheduled'
+					}
+				}
+				// TODO: save changes for this feed only?
+				//[[NSNotificationCenter defaultCenter] postNotificationName:kNotificationFeedUpdated object:feed.objectID];
 			}
 			dispatch_group_leave(group);
 		}];
 	}] resume];
 }
 
-/**
- Parse RSS feed data and save to persistent store. If HTTP 304 (not modified) skip feed evaluation.
 
- @param data Raw data from request.
+#pragma mark - Network Connection & Reachability -
- @param feed @c Feed on which the update is executed.
- @param http Download response containing the statusCode and etag / modified headers.
- */
-+ (void)downloadSuccessful:(NSData*)data forFeed:(Feed*)feed response:(NSHTTPURLResponse*)http {
-	if ([http statusCode] != 304) {
-		// should be fine to call synchronous since dataTask is already in the background (always? proof?)
-		RSXMLData *xml = [[RSXMLData alloc] initWithData:data urlString:feed.meta.url];
-		RSParsedFeed *parsed = RSParseFeedSync(xml, NULL);
-		if (parsed) {
-			// TODO: add support for media player?
-			// <enclosure url="https://url.mp3" length="63274022" type="audio/mpeg" />
-			[feed updateWithRSS:parsed postUnreadCountChange:YES];
-		}
-	}
-	[feed.meta setEtag:[http allHeaderFields][@"Etag"] modified:[http allHeaderFields][@"Date"]]; // @"Expires", @"Last-Modified"
-	// Don't update redirected url since it happened in the background; User may not recognize url
-	[feed.meta calculateAndSetScheduled];
-	// TODO: save changes for this feed only?
-//	[[NSNotificationCenter defaultCenter] postNotificationName:kNotificationFeedUpdated object:feed.objectID];
-}
 
 
-#pragma mark - Network Connection -
-
-
-/// External getter to check wheter current network state is reachable.
-+ (BOOL)isNetworkReachable { return _isReachable; }
-
 /// Set callback on @c self to listen for network reachability changes.
 + (void)registerNetworkChangeNotification {
 	// https://stackoverflow.com/questions/11240196/notification-when-wifi-connected-os-x
@@ -229,18 +264,16 @@ static BOOL _isReachable = NO;
 
 /// Called when network interface or reachability changes.
 static void networkReachabilityCallback(SCNetworkReachabilityRef target, SCNetworkConnectionFlags flags, void *object) {
-	if (_reachability == NULL)
+	if (_reachability == NULL) return;
-		return;
 	_isReachable = [FeedDownload hasConnectivity:flags];
-	[[NSNotificationCenter defaultCenter] postNotificationName:kNotificationNetworkStatusChanged
+	[[NSNotificationCenter defaultCenter] postNotificationName:kNotificationNetworkStatusChanged object:@(_isReachable)];
-														object:[NSNumber numberWithBool:_isReachable]];
 	if (_isReachable) {
 		NSLog(@"reachable");
+		[FeedDownload resumeUpdates];
 	} else {
 		NSLog(@"not reachable");
+		[FeedDownload pauseUpdates];
 	}
-	// schedule regardless of state (if not reachable timer will be canceled)
-	[FeedDownload scheduleNextUpdateForced:NO];
 }
 
 /// @return @c YES if network connection established.

baRSS/Preferences/Feeds Tab/SettingsFeeds.m

@@ -181,7 +181,6 @@ static NSString *dragNodeType = @"baRSS-feed-drag";
 		FeedGroup *fg = [children objectAtIndex:i].representedObject;
 		if (fg.sortIndex != (int32_t)i)
 			fg.sortIndex = (int32_t)i;
-		NSLog(@"%@ - %d", fg.name, fg.sortIndex);
 		[fg iterateSorted:NO overDescendantFeeds:^(Feed *feed, BOOL *cancel) {
 			[feed calculateAndSetIndexPathString];
 		}];
@@ -259,13 +258,14 @@ static NSString *dragNodeType = @"baRSS-feed-drag";
 	BOOL isFeed = (fg.typ == FEED);
 	BOOL isSeperator = (fg.typ == SEPARATOR);
 	BOOL isRefreshColumn = [tableColumn.identifier isEqualToString:@"RefreshColumn"];
+	BOOL refreshDisabled = (!isFeed || fg.refreshStr.length == 0 || [fg.refreshStr characterAtIndex:0] == '0');
 	
 	NSString *cellIdent = (isRefreshColumn ? @"cellRefresh" : (isSeperator ? @"cellSeparator" : @"cellFeed"));
 	// owner is nil to prohibit repeated awakeFromNib calls
 	NSTableCellView *cellView = [self.outlineView makeViewWithIdentifier:cellIdent owner:nil];
 	
 	if (isRefreshColumn) {
-		cellView.textField.stringValue = (isFeed && fg.refreshStr.length > 0 ? fg.refreshStr : @"");
+		cellView.textField.stringValue = (refreshDisabled ? (isFeed ? @"--" : @"") : fg.refreshStr);
 	} else if (isSeperator) {
 		return cellView; // the refresh cell is already skipped with the above if condition
 	} else {
@@ -281,10 +281,8 @@ static NSString *dragNodeType = @"baRSS-feed-drag";
 			cellView.imageView.image = defaultRSSIcon;
 		}
 	}
-	if (isFeed) {// also for refresh column
+	// also for refresh column
-		BOOL feedDisbaled = (fg.refreshStr.length == 0 || [fg.refreshStr characterAtIndex:0] == '0');
+	cellView.textField.textColor = (isFeed && refreshDisabled ? [NSColor disabledControlTextColor] : [NSColor controlTextColor]);
-		cellView.textField.textColor = (feedDisbaled ? [NSColor disabledControlTextColor] : [NSColor controlTextColor]);
-	}
 	return cellView;
 }
 

baRSS/Status Bar Menu/BarMenu.m

@@ -89,7 +89,7 @@
 		} else {
 			self.barItem.title = @"";
 		}
-		// BOOL hasNet = [FeedDownload isNetworkReachable];
+		// BOOL hasNet = [FeedDownload allowNetworkConnection];
 		if (self.unreadCountTotal > 0 && [UserPrefs defaultYES:@"tintMenuBarIcon"]) {
 			self.barItem.image = [RSSIcon templateIcon:16 tint:[NSColor rssOrange]];
 		} else {
@@ -281,13 +281,14 @@
  Insert default menu items for the main menu only. Like 'Pause Updates', 'Update all feeds', 'Preferences' and 'Quit'.
  */
 - (void)insertMainMenuHeader:(NSMenu*)menu {
-	NSMenuItem *item1 = [NSMenuItem itemWithTitle:NSLocalizedString(@"Pause Updates", nil)
+	NSMenuItem *item1 = [NSMenuItem itemWithTitle:@"" action:@selector(pauseUpdates:) target:self tag:TagPauseUpdates];
-										   action:@selector(pauseUpdates:) target:self tag:TagPauseUpdates];
 	NSMenuItem *item2 = [NSMenuItem itemWithTitle:NSLocalizedString(@"Update all feeds", nil)
 										   action:@selector(updateAllFeeds:) target:self tag:TagUpdateFeed];
+	item1.title = ([FeedDownload isPaused] ?
+				   NSLocalizedString(@"Resume Updates", nil) : NSLocalizedString(@"Pause Updates", nil));
 	if ([UserPrefs defaultYES:@"globalUpdateAll"] == NO)
 		item2.hidden = YES;
-	if (![FeedDownload isNetworkReachable])
+	if (![FeedDownload allowNetworkConnection])
 		item2.enabled = NO;
 	[menu insertItem:item1 atIndex:0];
 	[menu insertItem:item2 atIndex:1];
@@ -325,22 +326,21 @@
 - (void)preferencesClosed:(id)sender {
 	[[NSNotificationCenter defaultCenter] removeObserver:self name:NSWindowWillCloseNotification object:self.prefWindow.window];
 	self.prefWindow = nil;
-	[FeedDownload scheduleNextUpdateForced:NO];
+	[FeedDownload scheduleUpdateForUpcomingFeeds];
 }
 
 /**
  Called when user clicks on 'Pause Updates' in the main menu (only).
  */
 - (void)pauseUpdates:(NSMenuItem*)sender {
-	NSLog(@"1pause");
+	[FeedDownload setPaused:![FeedDownload isPaused]];
 }
 
 /**
  Called when user clicks on 'Update all feeds' in the main menu (only).
  */
 - (void)updateAllFeeds:(NSMenuItem*)sender {
-	// TODO: Disable 'update all' menu item during update?
+	[FeedDownload forceUpdateAllFeeds];
-	[FeedDownload scheduleNextUpdateForced:YES];
 }
 
 /**