Refactoring Status Menu

baRSS/Core Data/Feed+Ext.h

@@ -0,0 +1,40 @@
+//
+//  The MIT License (MIT)
+//  Copyright (c) 2018 Oleg Geier
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy of
+//  this software and associated documentation files (the "Software"), to deal in
+//  the Software without restriction, including without limitation the rights to
+//  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+//  of the Software, and to permit persons to whom the Software is furnished to do
+//  so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+
+#import "Feed+CoreDataClass.h"
+#import <Cocoa/Cocoa.h>
+
+@class RSParsedFeed;
+
+@interface Feed (Ext)
+// Generator methods / Feed update
++ (instancetype)newFeedAndMetaInContext:(NSManagedObjectContext*)context;
++ (instancetype)appendToRootWithDefaultIntervalInContext:(NSManagedObjectContext*)moc;
+- (void)updateWithRSS:(RSParsedFeed*)obj postUnreadCountChange:(BOOL)flag;
+- (void)calculateAndSetIndexPathString;
+- (NSMenuItem*)newMenuItem;
+// Article properties
+- (NSArray<FeedArticle*>*)sortedArticles;
+// Icon
+- (NSImage*)iconImage16;
+- (BOOL)setIconImage:(NSImage*)img;
+@end

baRSS/Core Data/Feed+Ext.m

@@ -0,0 +1,248 @@
+//
+//  The MIT License (MIT)
+//  Copyright (c) 2018 Oleg Geier
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy of
+//  this software and associated documentation files (the "Software"), to deal in
+//  the Software without restriction, including without limitation the rights to
+//  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+//  of the Software, and to permit persons to whom the Software is furnished to do
+//  so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+
+#import "Feed+Ext.h"
+#import "Constants.h"
+#import "UserPrefs.h"
+#import "DrawImage.h"
+#import "FeedMeta+Ext.h"
+#import "FeedGroup+Ext.h"
+#import "FeedArticle+Ext.h"
+#import "StoreCoordinator.h"
+
+#import <RSXML/RSXML.h>
+
+@implementation Feed (Ext)
+
+/// Instantiates new @c Feed and @c FeedMeta entities in context.
++ (instancetype)newFeedAndMetaInContext:(NSManagedObjectContext*)moc {
+	Feed *feed = [[Feed alloc] initWithEntity:Feed.entity insertIntoManagedObjectContext:moc];
+	feed.meta = [[FeedMeta alloc] initWithEntity:FeedMeta.entity insertIntoManagedObjectContext:moc];
+	return feed;
+}
+
+/// Instantiates new @c FeedGroup with @c FEED type, set the update interval to @c 30min and @c sortIndex to last root index.
++ (instancetype)appendToRootWithDefaultIntervalInContext:(NSManagedObjectContext*)moc {
+	NSUInteger lastIndex = [StoreCoordinator countRootItemsInContext:moc];
+	FeedGroup *fg = [FeedGroup newGroup:FEED inContext:moc];
+	[fg setParent:nil andSortIndex:(int32_t)lastIndex];
+	[fg.feed.meta setRefreshAndSchedule:kDefaultFeedRefreshInterval];
+	return fg.feed;
+}
+
+/// Call @c indexPathString on @c .group and update @c .indexPath if current value is different.
+- (void)calculateAndSetIndexPathString {
+	NSString *pthStr = [self.group indexPathString];
+	if (![self.indexPath isEqualToString:pthStr])
+		self.indexPath = pthStr;
+}
+
+/// @return Fully initialized @c NSMenuItem with @c title, @c tooltip, @c image, and @c action.
+- (NSMenuItem*)newMenuItem {
+	NSMenuItem *item = [NSMenuItem new];
+	item.title = self.group.nameOrError;
+	item.toolTip = self.subtitle;
+	item.enabled = (self.articles.count > 0);
+	item.image = [self iconImage16];
+	item.representedObject = self.indexPath;
+	item.target = [self class];
+	item.action = @selector(didClickOnMenuItem:);
+	return item;
+}
+
+/// Callback method for @c NSMenuItem. Will open url associated with @c Feed.
++ (void)didClickOnMenuItem:(NSMenuItem*)sender {
+	NSString *url = [StoreCoordinator urlForFeedWithIndexPath:sender.representedObject];
+	if (url && url.length > 0)
+		[UserPrefs openURLsWithPreferredBrowser:@[[NSURL URLWithString:url]]];
+}
+
+
+#pragma mark - Update Feed Items -
+
+
+/**
+ Replace feed title, subtitle and link (if changed). Also adds new articles and removes old ones.
+ */
+- (void)updateWithRSS:(RSParsedFeed*)obj postUnreadCountChange:(BOOL)flag {
+	if (![self.title isEqualToString:obj.title])       self.title = obj.title;
+	if (![self.subtitle isEqualToString:obj.subtitle]) self.subtitle = obj.subtitle;
+	if (![self.link isEqualToString:obj.link])         self.link = obj.link;
+	
+	if (self.group.name.length == 0) // in case a blank group was initialized
+		self.group.name = obj.title;
+	
+	// Add and remove articles
+	NSMutableSet<NSString*> *urls = [[self.articles valueForKeyPath:@"link"] mutableCopy];
+	NSInteger diff = [self addMissingArticles:obj updateLinks:urls]; // will remove links in 'urls' that should be kept
+	diff -= [self deleteArticlesWithLink:urls]; // remove old, outdated articles
+	// Get new total article count and post unread-count-change notification
+	if (flag && diff != 0) {
+		[[NSNotificationCenter defaultCenter] postNotificationName:kNotificationTotalUnreadCountChanged object:@(diff)];
+	}
+}
+
+/**
+ Append new articles and increment their sortIndex. Update unread counter on the way.
+ 
+ @note
+ New articles should be in ascending order without any gaps in between.
+ If new article is disjunct from the article before, assume a deleted article re-appeared and mark it as read.
+ 
+ @param urls Input will be used to identify new articles. Output will contain URLs that aren't present in the feed anymore.
+ */
+- (NSInteger)addMissingArticles:(RSParsedFeed*)obj updateLinks:(NSMutableSet<NSString*>*)urls {
+	NSInteger newOnes = 0;
+	int32_t currentIndex = [[self.articles valueForKeyPath:@"@min.sortIndex"] intValue];
+	FeedArticle *lastInserted = nil;
+	BOOL hasGapBetweenNewArticles = NO;
+	
+	for (RSParsedArticle *article in [obj.articles reverseObjectEnumerator]) {
+		// reverse enumeration ensures correct article order
+		if ([urls containsObject:article.link]) {
+			[urls removeObject:article.link];
+			FeedArticle *storedArticle = [self findArticleWithLink:article.link]; // TODO: use two synced arrays?
+			if (storedArticle && storedArticle.sortIndex != currentIndex) {
+				storedArticle.sortIndex = currentIndex;
+			}
+			hasGapBetweenNewArticles = YES;
+		} else {
+			newOnes += 1;
+			if (hasGapBetweenNewArticles && lastInserted) { // gap with at least one article inbetween
+				lastInserted.unread = NO;
+				newOnes -= 1;
+			}
+			hasGapBetweenNewArticles = NO;
+			lastInserted = [FeedArticle newArticle:article inContext:self.managedObjectContext];
+			lastInserted.sortIndex = currentIndex;
+			[self addArticlesObject:lastInserted];
+		}
+		currentIndex += 1;
+	}
+	if (hasGapBetweenNewArticles && lastInserted) {
+		lastInserted.unread = NO;
+		newOnes -= 1;
+	}
+	return newOnes;
+}
+
+/**
+ Delete all items where @c link matches one of the URLs in the @c NSSet.
+ */
+- (NSUInteger)deleteArticlesWithLink:(NSMutableSet<NSString*>*)urls {
+	if (!urls || urls.count == 0)
+		return 0;
+	NSUInteger c = 0;
+	for (FeedArticle *fa in self.articles) {
+		if ([urls containsObject:fa.link]) {
+			[urls removeObject:fa.link];
+			if (fa.unread) ++c;
+			// TODO: keep unread articles?
+			[self.managedObjectContext deleteObject:fa];
+			if (urls.count == 0)
+				break;
+		}
+	}
+	NSSet<FeedArticle*> *delArticles = [self.managedObjectContext deletedObjects];
+	if (delArticles.count > 0) {
+		[self removeArticles:delArticles];
+	}
+	return c;
+}
+
+
+#pragma mark - Article Properties -
+
+
+/**
+ @return Articles sorted by attribute @c sortIndex with descending order (newest items first).
+ */
+- (NSArray<FeedArticle*>*)sortedArticles {
+	if (self.articles.count == 0)
+		return nil;
+	return [self.articles sortedArrayUsingDescriptors:@[[NSSortDescriptor sortDescriptorWithKey:@"sortIndex" ascending:NO]]];
+}
+
+/**
+ Iterate over all Articles and return the one where @c .link matches. Or @c nil if no matching article found.
+ */
+- (FeedArticle*)findArticleWithLink:(NSString*)url {
+	for (FeedArticle *a in self.articles) {
+		if ([a.link isEqualToString:url])
+			return a;
+	}
+	return nil;
+}
+
+
+#pragma mark - Icon -
+
+
+/**
+ @return Return @c 16x16px image. Either from core data storage or generated default RSS icon.
+ */
+- (NSImage*)iconImage16 {
+	NSData *imgData = self.icon.icon;
+	if (imgData)
+	{
+		NSImage *img = [[NSImage alloc] initWithData:imgData];
+		[img setSize:NSMakeSize(16, 16)];
+		return img;
+	}
+	else if (self.articles.count == 0)
+	{
+		static NSImage *warningIcon;
+		if (!warningIcon) {
+			warningIcon = [NSImage imageNamed:NSImageNameCaution];
+			[warningIcon setSize:NSMakeSize(16, 16)];
+		}
+		return warningIcon;
+	}
+	else
+	{
+		static NSImage *defaultRSSIcon; // TODO: setup imageNamed: for default rss icon
+		if (!defaultRSSIcon)
+			defaultRSSIcon = [RSSIcon iconWithSize:16];
+		return defaultRSSIcon;
+	}
+}
+
+/**
+ Set favicon icon or delete relationship if @c img is not a valid image.
+ 
+ @return @c YES if icon was updated (core data did change).
+*/
+- (BOOL)setIconImage:(NSImage*)img {
+	if (img && [img isValid]) {
+		if (!self.icon)
+			self.icon = [[FeedIcon alloc] initWithEntity:FeedIcon.entity insertIntoManagedObjectContext:self.managedObjectContext];
+		self.icon.icon = [img TIFFRepresentation];
+		return YES;
+	} else if (self.icon) {
+		[self.managedObjectContext deleteObject:self.icon];
+		self.icon = nil;
+		return YES;
+	}
+	return NO;
+}
+
+@end

baRSS/Core Data/FeedArticle+Ext.h

@@ -0,0 +1,31 @@
+//
+//  The MIT License (MIT)
+//  Copyright (c) 2019 Oleg Geier
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy of
+//  this software and associated documentation files (the "Software"), to deal in
+//  the Software without restriction, including without limitation the rights to
+//  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+//  of the Software, and to permit persons to whom the Software is furnished to do
+//  so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+
+#import "FeedArticle+CoreDataClass.h"
+#import <Cocoa/Cocoa.h>
+
+@class RSParsedArticle;
+
+@interface FeedArticle (Ext)
++ (instancetype)newArticle:(RSParsedArticle*)entry inContext:(NSManagedObjectContext*)moc;
+- (NSMenuItem*)newMenuItem;
+@end

baRSS/Core Data/FeedArticle+Ext.m

@@ -0,0 +1,94 @@
+//
+//  The MIT License (MIT)
+//  Copyright (c) 2019 Oleg Geier
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy of
+//  this software and associated documentation files (the "Software"), to deal in
+//  the Software without restriction, including without limitation the rights to
+//  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+//  of the Software, and to permit persons to whom the Software is furnished to do
+//  so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+
+#import "FeedArticle+Ext.h"
+#import "Constants.h"
+#import "UserPrefs.h"
+#import "StoreCoordinator.h"
+
+#import <RSXML/RSParsedArticle.h>
+
+@implementation FeedArticle (Ext)
+
+/// Create new article based on RSXML article input.
++ (instancetype)newArticle:(RSParsedArticle*)entry inContext:(NSManagedObjectContext*)moc {
+	FeedArticle *fa = [[FeedArticle alloc] initWithEntity:FeedArticle.entity insertIntoManagedObjectContext:moc];
+	fa.unread = YES;
+	fa.guid = entry.guid;
+	fa.title = entry.title;
+	fa.abstract = entry.abstract;
+	fa.body = entry.body;
+	fa.author = entry.author;
+	fa.link = entry.link;
+	fa.published = entry.datePublished;
+	if (!fa.published)
+		fa.published = entry.dateModified;
+	return fa;
+}
+
+/// @return Full or truncated article title, based on user preference in settings.
+- (NSString*)shortArticleName {
+	NSString *title = self.title;
+	if (!title) return @"";
+	// TODO: It should be enough to get user prefs once per menu build
+	if ([UserPrefs defaultNO:@"feedShortNames"]) {
+		NSUInteger limit = [UserPrefs shortArticleNamesLimit];
+		if (title.length > limit)
+			title = [NSString stringWithFormat:@"%@…", [title substringToIndex:limit-1]];
+	}
+	return title;
+}
+
+/// @return Fully initialized @c NSMenuItem with @c title, @c tooltip, @c tickmark, and @c action.
+- (NSMenuItem*)newMenuItem {
+	NSMenuItem *item = [NSMenuItem new];
+	item.title = [self shortArticleName];
+	item.enabled = (self.link.length > 0);
+	item.state = (self.unread && [UserPrefs defaultYES:@"feedTickMark"] ? NSControlStateValueOn : NSControlStateValueOff);
+	//mi.toolTip = item.abstract;
+	// TODO: Do regex during save, not during display. Its here for testing purposes ...
+	if (self.abstract.length > 0) {
+		NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"<[^>]*>" options:kNilOptions error:nil];
+		item.toolTip = [regex stringByReplacingMatchesInString:self.abstract options:kNilOptions range:NSMakeRange(0, self.abstract.length) withTemplate:@""];
+	}
+	item.representedObject = self.objectID;
+	item.target = [self class];
+	item.action = @selector(didClickOnMenuItem:);
+	return item;
+}
+
+/// Callback method for @c NSMenuItem. Will open url associated with @c FeedArticle and mark it read.
++ (void)didClickOnMenuItem:(NSMenuItem*)sender {
+	NSManagedObjectContext *moc = [StoreCoordinator createChildContext];
+	FeedArticle *fa = [moc objectWithID:sender.representedObject];
+	NSString *url = fa.link;
+	if (fa.unread) {
+		fa.unread = NO;
+		[StoreCoordinator saveContext:moc andParent:YES];
+		[[NSNotificationCenter defaultCenter] postNotificationName:kNotificationTotalUnreadCountChanged object:@-1];
+	}
+	[moc reset];
+	if (url && url.length > 0)
+		[UserPrefs openURLsWithPreferredBrowser:@[[NSURL URLWithString:url]]];
+}
+
+@end

baRSS/Core Data/FeedGroup+Ext.h

@@ -0,0 +1,51 @@
+//
+//  The MIT License (MIT)
+//  Copyright (c) 2018 Oleg Geier
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy of
+//  this software and associated documentation files (the "Software"), to deal in
+//  the Software without restriction, including without limitation the rights to
+//  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+//  of the Software, and to permit persons to whom the Software is furnished to do
+//  so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+
+#import "FeedGroup+CoreDataClass.h"
+#import <Cocoa/Cocoa.h>
+
+/// Enum type to distinguish different @c FeedGroup types: @c GROUP, @c FEED, @c SEPARATOR
+typedef NS_ENUM(int16_t, FeedGroupType) {
+	/// Other types: @c GROUP, @c FEED, @c SEPARATOR
+	GROUP = 0, FEED = 1, SEPARATOR = 2
+};
+
+
+@interface FeedGroup (Ext)
+/// Overwrites @c type attribute with enum. Use one of: @c GROUP, @c FEED, @c SEPARATOR.
+@property (nonatomic) FeedGroupType type;
+@property (nonnull, readonly) NSString *nameOrError;
+
++ (instancetype)newGroup:(FeedGroupType)type inContext:(NSManagedObjectContext*)context;
+- (void)setParent:(FeedGroup *)parent andSortIndex:(int32_t)sortIndex;
+- (void)setNameIfChanged:(NSString*)name;
+- (NSImage*)groupIconImage16;
+- (NSMenuItem*)newMenuItem;
+// Handle children and parents
+- (NSString*)indexPathString;
+- (NSArray<FeedGroup*>*)sortedChildren;
+- (NSMutableArray<FeedGroup*>*)allParents;
+- (BOOL)iterateSorted:(BOOL)ordered overDescendantFeeds:(void(^)(Feed *feed, BOOL* cancel))block;
+// Printing
+- (NSString*)readableDescription;
+- (nonnull NSString*)refreshString;
+@end

baRSS/Core Data/FeedGroup+Ext.m

@@ -0,0 +1,150 @@
+//
+//  The MIT License (MIT)
+//  Copyright (c) 2018 Oleg Geier
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy of
+//  this software and associated documentation files (the "Software"), to deal in
+//  the Software without restriction, including without limitation the rights to
+//  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+//  of the Software, and to permit persons to whom the Software is furnished to do
+//  so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+
+#import "FeedGroup+Ext.h"
+#import "FeedMeta+Ext.h"
+#import "Feed+Ext.h"
+#import "NSDate+Ext.h"
+
+@implementation FeedGroup (Ext)
+
+/// Create new instance and set @c Feed and @c FeedMeta if group type is @c FEED
++ (instancetype)newGroup:(FeedGroupType)type inContext:(NSManagedObjectContext*)moc {
+	FeedGroup *fg = [[FeedGroup alloc] initWithEntity: FeedGroup.entity insertIntoManagedObjectContext:moc];
+	fg.type = type;
+	if (type == FEED)
+		fg.feed = [Feed newFeedAndMetaInContext:moc];
+	return fg;
+}
+
+- (void)setParent:(FeedGroup *)parent andSortIndex:(int32_t)sortIndex {
+	self.parent = parent;
+	self.sortIndex = sortIndex;
+	if (self.type == FEED)
+		[self.feed calculateAndSetIndexPathString];
+}
+
+/// Set @c name attribute but only if value differs.
+- (void)setNameIfChanged:(NSString*)name {
+	if (![self.name isEqualToString: name])
+		self.name = name;
+}
+
+/// @return Return static @c 16x16px NSImageNameFolder image.
+- (NSImage*)groupIconImage16 {
+	static NSImage *groupIcon;
+	if (!groupIcon) {
+		groupIcon = [NSImage imageNamed:NSImageNameFolder];
+		groupIcon.size = NSMakeSize(16, 16);
+	}
+	return groupIcon;
+}
+
+/// @return Returns "(error)" if @c self.name is @c nil.
+- (nonnull NSString*)nameOrError {
+	return (self.name ? self.name : NSLocalizedString(@"(error)", nil));
+}
+
+/// @return Fully initialized @c NSMenuItem with @c title and @c image.
+- (NSMenuItem*)newMenuItem {
+	NSMenuItem *item = [NSMenuItem new];
+	item.title = self.nameOrError;
+	item.enabled = (self.children.count > 0);
+	item.image = [self groupIconImage16];
+	item.representedObject = self.objectID;
+	return item;
+}
+
+
+#pragma mark - Handle Children And Parents -
+
+
+/// @return IndexPath as semicolon separated string for sorted children starting with root index.
+- (NSString*)indexPathString {
+	if (self.parent == nil)
+		return [NSString stringWithFormat:@"%d", self.sortIndex];
+	return [[self.parent indexPathString] stringByAppendingFormat:@".%d", self.sortIndex];
+}
+
+/// @return Children sorted by attribute @c sortIndex (same order as in preferences).
+- (NSArray<FeedGroup*>*)sortedChildren {
+	if (self.children.count == 0)
+		return nil;
+	return [self.children sortedArrayUsingDescriptors:@[[NSSortDescriptor sortDescriptorWithKey:@"sortIndex" ascending:YES]]];
+}
+
+/// @return @c NSArray of all ancestors: First object is root. Last object is the @c FeedGroup that executed the command.
+- (NSMutableArray<FeedGroup*>*)allParents {
+	if (self.parent == nil)
+		return [NSMutableArray arrayWithObject:self];
+	NSMutableArray *arr = [self.parent allParents];
+	[arr addObject:self];
+	return arr;
+}
+
+/**
+ Iterate over all descenden feeds.
+
+ @param ordered If @c YES items are executed in the same order they are listed in the menu. Pass @n NO for a speed-up.
+ @param block Set @c cancel to @c YES to stop execution of further descendants.
+ @return @c NO if execution was stopped with @c cancel @c = @c YES in @c block.
+ */
+- (BOOL)iterateSorted:(BOOL)ordered overDescendantFeeds:(void(^)(Feed*,BOOL*))block  {
+	if (self.feed) {
+		BOOL stopEarly = NO;
+		block(self.feed, &stopEarly);
+		if (stopEarly) return NO;
+	} else {
+		for (FeedGroup *fg in (ordered ? [self sortedChildren] : self.children)) {
+			if (![fg iterateSorted:ordered overDescendantFeeds:block])
+				return NO;
+		}
+	}
+	return YES;
+}
+
+
+#pragma mark - Printing -
+
+
+/// @return Simplified description of the feed object.
+- (NSString*)readableDescription {
+	switch (self.type) {
+		case SEPARATOR: return @"-------------";
+		case GROUP: return [NSString stringWithFormat:@"%@", self.name];
+		case FEED:
+			return [NSString stringWithFormat:@"%@ (%@) - %@", self.name, self.feed.meta.url, [self refreshString]];
+	}
+}
+
+/// @return Formatted string for update interval ( e.g., @c 30m or @c 12h )
+- (nonnull NSString*)refreshString {
+	if (self.type == FEED) {
+		int32_t refresh = self.feed.meta.refresh;
+		if (refresh <= 0)
+			return @"∞"; // ∞ ƒ Ø
+		return [NSDate stringForInterval:refresh rounded:NO];
+	}
+	return @"";
+}
+
+@end

baRSS/Core Data/FeedMeta+Ext.h

@@ -0,0 +1,35 @@
+//
+//  The MIT License (MIT)
+//  Copyright (c) 2018 Oleg Geier
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy of
+//  this software and associated documentation files (the "Software"), to deal in
+//  the Software without restriction, including without limitation the rights to
+//  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+//  of the Software, and to permit persons to whom the Software is furnished to do
+//  so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+
+#import "FeedMeta+CoreDataClass.h"
+
+static const int32_t kDefaultFeedRefreshInterval = 30 * 60;
+
+@interface FeedMeta (Ext)
+// HTTP response
+- (void)setErrorAndPostponeSchedule;
+- (void)setSucessfulWithResponse:(NSHTTPURLResponse*)response;
+// Setter
+- (void)setUrlIfChanged:(NSString*)url;
+- (void)setEtag:(NSString*)etag modified:(NSString*)modified;
+- (BOOL)setRefreshAndSchedule:(int32_t)refresh;
+@end

baRSS/Core Data/FeedMeta+Ext.m

@@ -0,0 +1,89 @@
+//
+//  The MIT License (MIT)
+//  Copyright (c) 2018 Oleg Geier
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy of
+//  this software and associated documentation files (the "Software"), to deal in
+//  the Software without restriction, including without limitation the rights to
+//  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+//  of the Software, and to permit persons to whom the Software is furnished to do
+//  so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+
+#import "FeedMeta+Ext.h"
+#import "Feed+Ext.h"
+#import "FeedGroup+Ext.h"
+
+@implementation FeedMeta (Ext)
+
+#pragma mark - HTTP response
+
+/// Increment @c errorCount and set new @c scheduled date (2^N minutes, max. 5.7 days).
+- (void)setErrorAndPostponeSchedule {
+	if (self.errorCount < 0)
+		self.errorCount = 0;
+	int16_t n = self.errorCount + 1; // always increment errorCount (can be used to indicate bad feeds)
+	// TODO: remove logging
+	NSLog(@"ERROR: Feed download failed: %@ (errorCount: %d)", self.url, n);
+	if ([self.scheduled timeIntervalSinceNow] > 30) // forced, early update. Scheduled is still in the futute.
+		return; // Keep error counter low. Not enough time has passed (e.g., temporary server outage)
+	NSTimeInterval retryWaitTime = pow(2, (n > 13 ? 13 : n)) * 60; // 2^N (between: 2 minutes and 5.7 days)
+	self.errorCount = n;
+	[self scheduleNow:retryWaitTime];
+}
+
+- (void)setSucessfulWithResponse:(NSHTTPURLResponse*)response {
+	self.errorCount = 0; // reset counter
+	NSDictionary *header = [response allHeaderFields];
+	[self setEtag:header[@"Etag"] modified:header[@"Date"]]; // @"Expires", @"Last-Modified"
+	[self scheduleNow:self.refresh];
+}
+
+#pragma mark - Setter
+
+/// Set @c url attribute but only if value differs.
+- (void)setUrlIfChanged:(NSString*)url {
+	if (![self.url isEqualToString:url]) self.url = url;
+}
+
+/// Set @c etag and @c modified attributes. Only values that differ will be updated.
+- (void)setEtag:(NSString*)etag modified:(NSString*)modified {
+	if (![self.etag isEqualToString:etag])         self.etag = etag;
+	if (![self.modified isEqualToString:modified]) self.modified = modified;
+}
+
+/**
+ Set @c refresh and calculate new @c scheduled date.
+
+ @return @c YES if refresh interval has changed
+ */
+- (BOOL)setRefreshAndSchedule:(int32_t)refresh {
+	if (self.refresh != refresh) {
+		self.refresh = refresh;
+		[self scheduleNow:self.refresh];
+		return YES;
+	}
+	return NO;
+}
+
+/// Set next scheduled feed update or @c nil if @c refresh @c <= @c 0.
+- (void)scheduleNow:(NSTimeInterval)future {
+	if (self.refresh <= 0) { // update deactivated; manually update with force update all
+		if (self.scheduled != nil) // already nil? Avoid unnecessary core data edits
+			self.scheduled = nil;
+	} else {
+		self.scheduled = [NSDate dateWithTimeIntervalSinceNow:future];
+	}
+}
+
+@end

baRSS/Core Data/NSFetchRequest+Ext.h

@@ -0,0 +1,38 @@
+//
+//  The MIT License (MIT)
+//  Copyright (c) 2019 Oleg Geier
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy of
+//  this software and associated documentation files (the "Software"), to deal in
+//  the Software without restriction, including without limitation the rights to
+//  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+//  of the Software, and to permit persons to whom the Software is furnished to do
+//  so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+
+#import <CoreData/CoreData.h>
+
+@interface NSFetchRequest<ResultType> (Ext)
+// Perform core data request and fetch data
+- (NSArray<ResultType>*)fetchAllRows:(NSManagedObjectContext*)moc;
+- (NSArray<NSManagedObjectID*>*)fetchIDs:(NSManagedObjectContext*)moc;
+- (NSUInteger)fetchCount:(NSManagedObjectContext*)moc;
+- (id)fetchFirst:(NSManagedObjectContext*)moc; // limit 1
+
+// Selecting, filtering, sorting results
+- (instancetype)select:(NSArray<NSString*>*)cols; // sets .propertiesToFetch
+- (instancetype)where:(NSString*)format, ...; // sets .predicate
+- (instancetype)sortASC:(NSString*)key; // add .sortDescriptors -> ascending:YES
+- (instancetype)sortDESC:(NSString*)key; // add .sortDescriptors -> ascending:NO
+- (instancetype)addFunctionExpression:(NSString*)fn onKeyPath:(NSString*)keyPath name:(NSString*)name type:(NSAttributeType)type; // add .propertiesToFetch -> (expressionForFunction:@[expressionForKeyPath:])
+@end

baRSS/Core Data/NSFetchRequest+Ext.m

@@ -0,0 +1,133 @@
+//
+//  The MIT License (MIT)
+//  Copyright (c) 2019 Oleg Geier
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy of
+//  this software and associated documentation files (the "Software"), to deal in
+//  the Software without restriction, including without limitation the rights to
+//  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+//  of the Software, and to permit persons to whom the Software is furnished to do
+//  so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+
+#import "NSFetchRequest+Ext.h"
+
+@implementation NSFetchRequest (Ext)
+
+/// Perform fetch and return result. If an error occurs, print it to the console.
+- (NSArray*)fetchAllRows:(NSManagedObjectContext*)moc {
+	NSError *err;
+	NSArray *fetchResults = [moc executeFetchRequest:self error:&err];
+	if (err) NSLog(@"ERROR: Fetch request failed: %@", err);
+	//NSLog(@"%@ ==> %@", self, fetchResults); // debugging
+	return fetchResults;
+}
+
+/// Set @c resultType to @c NSManagedObjectIDResultType and return list of object ids.
+- (NSArray<NSManagedObjectID*>*)fetchIDs:(NSManagedObjectContext*)moc {
+	self.includesPropertyValues = NO;
+	self.resultType = NSManagedObjectIDResultType;
+	return [self fetchAllRows:moc];
+}
+
+/// Set @c limit to @c 1 and fetch first objcect. May return object type or @c NSDictionary if @c resultType @c = @c NSManagedObjectIDResultType.
+- (id)fetchFirst:(NSManagedObjectContext*)moc {
+	self.fetchLimit = 1;
+	return [[self fetchAllRows:moc] firstObject];
+}
+
+/// Convenient method to return the number of rows that match the request.
+- (NSUInteger)fetchCount:(NSManagedObjectContext*)moc {
+	return [moc countForFetchRequest:self error:nil];
+}
+
+#pragma mark - Selecting, Filtering, Sorting
+
+/**
+ Set @c self.propertiesToFetch = @c cols and @c self.resultType = @c NSDictionaryResultType.
+ @return @c self (e.g., method chaining)
+ */
+- (instancetype)select:(NSArray<NSString*>*)cols {
+	self.propertiesToFetch = cols;
+	self.resultType = NSDictionaryResultType;
+	return self;
+}
+
+/**
+ Set @c self.predicate = [NSPredicate predicateWithFormat: @c format ]
+ @return @c self (e.g., method chaining)
+ */
+- (instancetype)where:(NSString*)format, ... {
+	va_list arguments;
+	va_start(arguments, format);
+	self.predicate = [NSPredicate predicateWithFormat:format arguments:arguments];
+	va_end(arguments);
+	return self;
+}
+
+/**
+ Add new [NSSortDescriptor sortDescriptorWithKey: @c key ascending:YES] to @c self.sortDescriptors.
+ @return @c self (e.g., method chaining)
+ */
+- (instancetype)sortASC:(NSString*)key {
+	[self addSortingKey:key asc:YES];
+	return self;
+}
+
+/**
+ Add new [NSSortDescriptor sortDescriptorWithKey: @c key ascending:NO] to @c self.sortDescriptors.
+ @return @c self (e.g., method chaining)
+ */
+- (instancetype)sortDESC:(NSString*)key {
+	[self addSortingKey:key asc:NO];
+	return self;
+}
+
+/**
+ Add new [NSExpression expressionForFunction: @c fn arguments: [NSExpression expressionForKeyPath: @c keyPath ]] to @c self.propertiesToFetch.
+ Also set @c self.includesPropertyValues @c = @c NO and @c self.resultType @c = @c NSDictionaryResultType.
+ @return @c self (e.g., method chaining)
+ */
+- (instancetype)addFunctionExpression:(NSString*)fn onKeyPath:(NSString*)keyPath name:(NSString*)name type:(NSAttributeType)type {
+	[self addExpression:[NSExpression expressionForFunction:fn arguments:@[[NSExpression expressionForKeyPath:keyPath]]] name:name type:type];
+	return self;
+}
+
+#pragma mark - Helper
+
+/// Add @c NSSortDescriptor to existing list of @c sortDescriptors.
+- (void)addSortingKey:(NSString*)key asc:(BOOL)flag {
+	NSSortDescriptor *sd = [NSSortDescriptor sortDescriptorWithKey:key ascending:flag];
+	if (!self.sortDescriptors) {
+		self.sortDescriptors = @[ sd ];
+	} else {
+		self.sortDescriptors = [self.sortDescriptors arrayByAddingObject:sd];
+	}
+}
+
+/// Add @c NSExpressionDescription to existing list of @c propertiesToFetch.
+- (void)addExpression:(NSExpression*)exp name:(NSString*)name type:(NSAttributeType)type {
+	self.includesPropertyValues = NO;
+	self.resultType = NSDictionaryResultType;
+	NSExpressionDescription *expDesc = [[NSExpressionDescription alloc] init];
+	[expDesc setName:name];
+	[expDesc setExpression:exp];
+	[expDesc setExpressionResultType:type];
+	if (!self.propertiesToFetch) {
+		self.propertiesToFetch = @[ expDesc ];
+	} else {
+		self.propertiesToFetch = [self.propertiesToFetch arrayByAddingObject:expDesc];
+	}
+}
+
+@end

baRSS/Core Data/StoreCoordinator.h

@@ -0,0 +1,55 @@
+//
+//  The MIT License (MIT)
+//  Copyright (c) 2018 Oleg Geier
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy of
+//  this software and associated documentation files (the "Software"), to deal in
+//  the Software without restriction, including without limitation the rights to
+//  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+//  of the Software, and to permit persons to whom the Software is furnished to do
+//  so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+
+#import <Foundation/Foundation.h>
+#import "DBv1+CoreDataModel.h"
+
+@interface StoreCoordinator : NSObject
+// Managing contexts
++ (NSManagedObjectContext*)createChildContext;
++ (void)saveContext:(NSManagedObjectContext*)context andParent:(BOOL)flag;
+
+// Feed update
++ (NSDate*)nextScheduledUpdate;
++ (NSArray<Feed*>*)getListOfFeedsThatNeedUpdate:(BOOL)forceAll inContext:(NSManagedObjectContext*)moc;
+
+// Count elements
++ (NSUInteger)countTotalUnread;
++ (NSUInteger)countRootItemsInContext:(NSManagedObjectContext*)moc;
++ (NSArray<NSDictionary*>*)countAggregatedUnread;
+
+// Get List Of Elements
++ (NSArray<FeedGroup*>*)sortedFeedGroupsWithParent:(id)parent inContext:(NSManagedObjectContext*)moc;
++ (NSArray<FeedArticle*>*)sortedArticlesWithParent:(id)parent inContext:(NSManagedObjectContext*)moc;
++ (NSArray<Feed*>*)listOfFeedsMissingArticlesInContext:(NSManagedObjectContext*)moc;
++ (NSArray<Feed*>*)listOfFeedsMissingIconsInContext:(NSManagedObjectContext*)moc;
++ (Feed*)feedWithIndexPath:(nonnull NSString*)path inContext:(NSManagedObjectContext*)moc;
++ (NSString*)urlForFeedWithIndexPath:(nonnull NSString*)path;
+
+// Unread articles list & mark articled read
++ (NSArray<FeedArticle*>*)articlesAtPath:(nullable NSString*)path isFeed:(BOOL)feedFlag sorted:(BOOL)sortFlag unread:(BOOL)readFlag inContext:(NSManagedObjectContext*)moc limit:(NSUInteger)limit;
+
+// Restore sound state
++ (void)restoreFeedIndexPaths;
++ (NSUInteger)deleteUnreferenced;
++ (NSUInteger)deleteAllGroups;
+@end

baRSS/Core Data/StoreCoordinator.m

@@ -0,0 +1,253 @@
+//
+//  The MIT License (MIT)
+//  Copyright (c) 2018 Oleg Geier
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy of
+//  this software and associated documentation files (the "Software"), to deal in
+//  the Software without restriction, including without limitation the rights to
+//  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+//  of the Software, and to permit persons to whom the Software is furnished to do
+//  so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+
+#import "StoreCoordinator.h"
+#import "NSFetchRequest+Ext.h"
+#import "AppHook.h"
+#import "Feed+Ext.h"
+
+@implementation StoreCoordinator
+
+#pragma mark - Managing contexts
+
+/// @return The application main persistent context.
++ (NSManagedObjectContext*)getMainContext {
+	return [(AppHook*)NSApp persistentContainer].viewContext;
+}
+
+/// New child context with @c NSMainQueueConcurrencyType and without undo manager.
++ (NSManagedObjectContext*)createChildContext {
+	NSManagedObjectContext *context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
+	[context setParentContext:[self getMainContext]];
+	context.undoManager = nil;
+	//context.automaticallyMergesChangesFromParent = YES;
+	return context;
+}
+
+/**
+ Commit changes and perform save operation on @c context.
+
+ @param flag If @c YES save any parent context as well (recursive).
+ */
++ (void)saveContext:(NSManagedObjectContext*)context andParent:(BOOL)flag {
+	// Performs the save action for the application, which is to send the save: message to the application's managed object context. Any encountered errors are presented to the user.
+	if (![context commitEditing]) {
+		NSLog(@"%@:%@ unable to commit editing before saving", [self class], NSStringFromSelector(_cmd));
+	}
+	NSError *error = nil;
+	if (context.hasChanges && ![context save:&error]) {
+		// Customize this code block to include application-specific recovery steps.
+		[[NSApplication sharedApplication] presentError:error];
+	}
+	if (flag && context.parentContext) {
+		[self saveContext:context.parentContext andParent:flag];
+	}
+}
+
+
+#pragma mark - Feed Update
+
+/// @return @c NSDate of next (earliest) feed update. May be @c nil.
++ (NSDate*)nextScheduledUpdate {
+	NSFetchRequest *fr = [FeedMeta fetchRequest];
+	[fr addFunctionExpression:@"min:" onKeyPath:@"scheduled" name:@"minDate" type:NSDateAttributeType];
+	return [fr fetchAllRows: [self getMainContext]].firstObject[@"minDate"];
+}
+
+/**
+ List of @c Feed items that need to be updated. Scheduled time is now (or in past).
+
+ @param forceAll If @c YES get a list of all @c Feed regardless of schedules time.
+ */
++ (NSArray<Feed*>*)getListOfFeedsThatNeedUpdate:(BOOL)forceAll inContext:(NSManagedObjectContext*)moc {
+	NSFetchRequest *fr = [Feed fetchRequest];
+	if (!forceAll) {
+		// when fetching also get those feeds that would need update soon (now + 10s)
+		[fr where:@"meta.scheduled <= %@", [NSDate dateWithTimeIntervalSinceNow:+10]];
+	}
+	return [fr fetchAllRows:moc];
+}
+
+
+#pragma mark - Count Elements
+
+/// @return Sum of all unread @c FeedArticle items.
++ (NSUInteger)countTotalUnread {
+	return [[[FeedArticle fetchRequest] where:@"unread = YES"] fetchCount: [self getMainContext]];
+}
+
+/// @return Count of objects at root level. Aka @c sortIndex for the next @c FeedGroup item.
++ (NSUInteger)countRootItemsInContext:(NSManagedObjectContext*)moc {
+	return [[[FeedGroup fetchRequest] where:@"parent = NULL"] fetchCount:moc];
+}
+
+/// @return Unread and total count grouped by @c Feed item.
++ (NSArray<NSDictionary*>*)countAggregatedUnread {
+	NSFetchRequest *fr = [Feed fetchRequest];
+	fr.propertiesToGroupBy = @[ @"indexPath" ];
+	fr.propertiesToFetch = @[ @"indexPath" ];
+	[fr addFunctionExpression:@"sum:" onKeyPath:@"articles.unread" name:@"unread" type:NSInteger32AttributeType];
+	[fr addFunctionExpression:@"count:" onKeyPath:@"articles.unread" name:@"total" type:NSInteger32AttributeType];
+	return [fr fetchAllRows: [self getMainContext]];
+}
+
+
+#pragma mark - Get List Of Elements
+
+/// @return Sorted list of @c FeedGroup items where @c FeedGroup.parent @c = @c parent.
++ (NSArray<FeedGroup*>*)sortedFeedGroupsWithParent:(id)parent inContext:(NSManagedObjectContext*)moc {
+	return [[[[FeedGroup fetchRequest] where:@"parent = %@", parent] sortASC:@"sortIndex"] fetchAllRows:moc];
+}
+
+/// @return Sorted list of @c FeedArticle items where @c FeedArticle.feed @c = @c parent.
++ (NSArray<FeedArticle*>*)sortedArticlesWithParent:(id)parent inContext:(NSManagedObjectContext*)moc {
+	return [[[[FeedArticle fetchRequest] where:@"feed = %@", parent] sortDESC:@"sortIndex"] fetchAllRows:moc];
+}
+
+/// @return Unsorted list of @c Feed items where @c articles.count @c == @c 0.
++ (NSArray<Feed*>*)listOfFeedsMissingArticlesInContext:(NSManagedObjectContext*)moc {
+	return [[[Feed fetchRequest] where:@"articles.@count == 0"] fetchAllRows:moc];
+}
+
+/// @return Unsorted list of @c Feed items where @c icon is @c nil.
++ (NSArray<Feed*>*)listOfFeedsMissingIconsInContext:(NSManagedObjectContext*)moc {
+	return [[[Feed fetchRequest] where:@"icon = NULL"] fetchAllRows:moc];
+}
+
+/// @return Single @c Feed item where @c Feed.indexPath @c = @c path.
++ (Feed*)feedWithIndexPath:(nonnull NSString*)path inContext:(NSManagedObjectContext*)moc {
+	return [[[Feed fetchRequest] where:@"indexPath = %@", path] fetchFirst:moc];
+}
+
+/// @return URL of @c Feed item where @c Feed.indexPath @c = @c path.
++ (NSString*)urlForFeedWithIndexPath:(nonnull NSString*)path {
+	return [[[[Feed fetchRequest] where:@"indexPath = %@", path] select:@[@"link"]] fetchFirst: [self getMainContext]][@"link"];
+}
+
+/// @return Unsorted list of object IDs where @c Feed.indexPath begins with @c path @c + @c "."
++ (NSArray<NSManagedObjectID*>*)feedIDsForIndexPath:(nonnull NSString*)path inContext:(NSManagedObjectContext*)moc {
+	return [[[Feed fetchRequest] where:@"indexPath BEGINSWITH %@", [path stringByAppendingString:@"."]] fetchIDs:moc];
+}
+
+
+#pragma mark - Unread Articles List & Mark Read
+
+/// @return Return predicate that will match either exactly one, @b or a list of, @b or all @c Feed items.
++ (nullable NSPredicate*)predicateWithPath:(nullable NSString*)path isFeed:(BOOL)flag inContext:(NSManagedObjectContext*)moc {
+	if (!path) return nil; // match all
+	if (flag) {
+		Feed *obj = [self feedWithIndexPath:path inContext:moc];
+		return [NSPredicate predicateWithFormat:@"feed = %@", obj.objectID];
+	}
+	NSArray *list = [self feedIDsForIndexPath:path inContext:moc];
+	if (list && list.count > 0) {
+		return [NSPredicate predicateWithFormat:@"feed IN %@", list];
+	}
+	return [NSPredicate predicateWithValue:NO]; // match none
+}
+
+/**
+ Return object list with @c FeedArticle where @c unread @c = @c YES. In the same order the user provided.
+
+ @param path Match @c Feed items where @c indexPath string matches @c path.
+ @param feedFlag If @c YES path must match exactly. If @c NO match items that begin with @c path + @c "."
+ @param sortFlag Whether articles should be returned in sorted order (e.g., for 'open all unread').
+ @param readFlag Match @c FeedArticle where @c unread @c = @c readFlag.
+ @param limit Only return first @c X articles that match the criteria.
+ @return Sorted list of @c FeedArticle with @c unread @c = @c YES.
+ */
++ (NSArray<FeedArticle*>*)articlesAtPath:(nullable NSString*)path isFeed:(BOOL)feedFlag sorted:(BOOL)sortFlag unread:(BOOL)readFlag inContext:(NSManagedObjectContext*)moc limit:(NSUInteger)limit {
+	NSFetchRequest<FeedArticle*> *fr = [[FeedArticle fetchRequest] where:@"unread = %d", readFlag];
+	fr.fetchLimit = limit;
+	if (sortFlag) {
+		if (!path || !feedFlag)
+			[fr sortASC:@"feed.indexPath"];
+		[fr sortDESC:@"sortIndex"];
+	}
+	/* UNUSED. Batch updates will break NSUndoManager in preferences. Fix that before usage.
+	 NSBatchUpdateRequest *bur = [NSBatchUpdateRequest batchUpdateRequestWithEntityName: FeedArticle.entity.name];
+	 bur.propertiesToUpdate = @{ @"unread": @(!readFlag) };
+	 bur.resultType = NSUpdatedObjectIDsResultType;
+	 bur.predicate = [NSPredicate predicateWithFormat:@"unread = %d", readFlag];*/
+	NSPredicate *feedFilter = [self predicateWithPath:path isFeed:feedFlag inContext:moc];
+	if (feedFilter)
+		fr.predicate = [NSCompoundPredicate andPredicateWithSubpredicates:@[fr.predicate, feedFilter]];
+	return [fr fetchAllRows:moc];
+}
+
+
+#pragma mark - Restore Sound State
+
+/// Iterate over all @c Feed and re-calculate @c indexPath.
++ (void)restoreFeedIndexPaths {
+	NSManagedObjectContext *moc = [self getMainContext];
+	for (Feed *f in [[Feed fetchRequest] fetchAllRows:moc]) {
+		[f calculateAndSetIndexPathString];
+	}
+	[self saveContext:moc andParent:YES];
+	[moc reset];
+}
+
+/**
+ Delete all @c Feed items where @c group @c = @c NULL and all @c FeedMeta, @c FeedIcon, @c FeedArticle where @c feed @c = @c NULL.
+ */
++ (NSUInteger)deleteUnreferenced {
+	NSUInteger deleted = 0;
+	NSManagedObjectContext *moc = [self getMainContext];
+	deleted += [self batchDelete:Feed.entity nullAttribute:@"group" inContext:moc];
+	deleted += [self batchDelete:FeedMeta.entity nullAttribute:@"feed" inContext:moc];
+	deleted += [self batchDelete:FeedIcon.entity nullAttribute:@"feed" inContext:moc];
+	deleted += [self batchDelete:FeedArticle.entity nullAttribute:@"feed" inContext:moc];
+	if (deleted > 0) {
+		[self saveContext:moc andParent:YES];
+		[moc reset];
+	}
+	return deleted;
+}
+
+/// Delete all @c FeedGroup items.
++ (NSUInteger)deleteAllGroups {
+	NSManagedObjectContext *moc = [self getMainContext];
+	NSUInteger deleted = [self batchDelete:FeedGroup.entity nullAttribute:nil inContext:moc];
+	[self saveContext:moc andParent:YES];
+	[moc reset];
+	return deleted;
+}
+
+/**
+ Perform batch delete on entities of type @c entity where @c column @c IS @c NULL. If @c column is @c nil, delete all rows.
+ */
++ (NSUInteger)batchDelete:(NSEntityDescription*)entity nullAttribute:(NSString*)column inContext:(NSManagedObjectContext*)moc {
+	NSFetchRequest *fr = [NSFetchRequest fetchRequestWithEntityName: entity.name];
+	if (column && column.length > 0) {
+		// using @count here to also find items where foreign key is set but referencing a non-existing object.
+		fr.predicate = [NSPredicate predicateWithFormat:@"count(%K) == 0", column];
+	}
+	NSBatchDeleteRequest *bdr = [[NSBatchDeleteRequest alloc] initWithFetchRequest:fr];
+	bdr.resultType = NSBatchDeleteResultTypeCount;
+	NSError *err;
+	NSBatchDeleteResult *res = [moc executeRequest:bdr error:&err];
+	if (err) NSLog(@"%@", err);
+	return [res.result unsignedIntegerValue];
+}
+
+@end