Refactor Diffable Datasources out of the Sidebar

iOS/MasterFeed/Cell/MasterFeedRowIdentifier.swift

@@ -0,0 +1,23 @@
+//
+//  MasterFeedRowIdentifier.swift
+//  NetNewsWire-iOS
+//
+//  Created by Maurice Parker on 10/20/21.
+//  Copyright © 2021 Ranchero Software. All rights reserved.
+//
+
+import Foundation
+
+class MasterFeedRowIdentifier: NSObject, NSCopying {
+
+	var indexPath: IndexPath
+	
+	init(indexPath: IndexPath) {
+		self.indexPath = indexPath
+	}
+	
+	func copy(with zone: NSZone? = nil) -> Any {
+		return self
+	}
+	
+}

iOS/MasterFeed/MasterFeedDataSource.swift

@@ -1,22 +0,0 @@
-//
-//  MasterFeedDataSource.swift
-//  NetNewsWire-iOS
-//
-//  Created by Maurice Parker on 8/28/19.
-//  Copyright © 2019 Ranchero Software. All rights reserved.
-//
-
-import UIKit
-import RSTree
-import Account
-
-class MasterFeedDataSource: UITableViewDiffableDataSource<Int, MasterFeedTableViewIdentifier> {
-
-	override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
-		guard let identifier = itemIdentifier(for: indexPath), identifier.isEditable else {
-			return false
-		}
-		return true
-	}
-	
-}

iOS/MasterFeed/MasterFeedDataSourceOperation.swift

@@ -1,39 +0,0 @@
-//
-//  MasterFeedDataSourceOperation.swift
-//  NetNewsWire-iOS
-//
-//  Created by Maurice Parker on 2/23/20.
-//  Copyright © 2020 Ranchero Software. All rights reserved.
-//
-
-import UIKit
-import RSCore
-import RSTree
-
-class MasterFeedDataSourceOperation: MainThreadOperation {
-	
-	// MainThreadOperation
-	public var isCanceled = false
-	public var id: Int?
-	public weak var operationDelegate: MainThreadOperationDelegate?
-	public var name: String? = "MasterFeedDataSourceOperation"
-	public var completionBlock: MainThreadOperation.MainThreadOperationCompletionBlock?
-
-	private var dataSource: UITableViewDiffableDataSource<Int, MasterFeedTableViewIdentifier>
-	private var snapshot: NSDiffableDataSourceSnapshot<Int, MasterFeedTableViewIdentifier>
-	private var animating: Bool
-	
-	init(dataSource: UITableViewDiffableDataSource<Int, MasterFeedTableViewIdentifier>, snapshot: NSDiffableDataSourceSnapshot<Int, MasterFeedTableViewIdentifier>, animating: Bool) {
-		self.dataSource = dataSource
-		self.snapshot = snapshot
-		self.animating = animating
-	}
-	
-	func run() {
-		dataSource.apply(snapshot, animatingDifferences: animating) { [weak self] in
-			guard let self = self else { return }
-			self.operationDelegate?.operationDidComplete(self)
-		}
-	}
-	
-}

iOS/MasterFeed/MasterFeedViewController+Drag.swift

@@ -13,11 +13,11 @@ import Account
 extension MasterFeedViewController: UITableViewDragDelegate {
 	
 	func tableView(_ tableView: UITableView, itemsForBeginning session: UIDragSession, at indexPath: IndexPath) -> [UIDragItem] {
-		guard let identifier = dataSource.itemIdentifier(for: indexPath), identifier.isWebFeed, let url = identifier.url else {
+		guard let node = coordinator.nodeFor(indexPath), let webFeed = node.representedObject as? WebFeed else {
 			return [UIDragItem]()
 		}
 		
-		let data = url.data(using: .utf8)
+		let data = webFeed.url.data(using: .utf8)
 		let itemProvider = NSItemProvider()
 		  
 		itemProvider.registerDataRepresentation(forTypeIdentifier: kUTTypeURL as String, visibility: .ownProcess) { completion in
@@ -26,7 +26,7 @@ extension MasterFeedViewController: UITableViewDragDelegate {
 		}
 		
 		let dragItem = UIDragItem(itemProvider: itemProvider)
-		dragItem.localObject = identifier
+		dragItem.localObject = node
 		return [dragItem]
 	}
 	

iOS/MasterFeed/MasterFeedViewController+Drop.swift

@@ -22,24 +22,22 @@ extension MasterFeedViewController: UITableViewDropDelegate {
 			return UITableViewDropProposal(operation: .forbidden)
 		}
 			
-		guard let destIdentifier = dataSource.itemIdentifier(for: destIndexPath) else {
-			return UITableViewDropProposal(operation: .move, intent: .insertIntoDestinationIndexPath)
-		}
-		
-		guard let destAccount = destIdentifier.account,	let destCell = tableView.cellForRow(at: destIndexPath) else {
-			return UITableViewDropProposal(operation: .forbidden)
-		}
+		guard let destFeed = coordinator.nodeFor(destIndexPath)?.representedObject as? Feed,
+			  let destAccount = destFeed.account,
+			  let destCell = tableView.cellForRow(at: destIndexPath) else {
+				  return UITableViewDropProposal(operation: .forbidden)
+			  }
 
 		// Validate account specific behaviors...
 		if destAccount.behaviors.contains(.disallowFeedInMultipleFolders),
-		   let sourceFeedID = (session.localDragSession?.items.first?.localObject as? MasterFeedTableViewIdentifier)?.feedID,
-		   let sourceWebFeed = AccountManager.shared.existingFeed(with: sourceFeedID) as? WebFeed,
+		   let sourceNode = session.localDragSession?.items.first?.localObject as? Node,
+		   let sourceWebFeed = sourceNode.representedObject as? WebFeed,
 		   sourceWebFeed.account?.accountID != destAccount.accountID && destAccount.hasWebFeed(withURL: sourceWebFeed.url) {
 			return UITableViewDropProposal(operation: .forbidden)
 		}
 
 		// Determine the correct drop proposal
-		if destIdentifier.isFolder {
+		if destFeed is Folder {
 			if session.location(in: destCell).y >= 0 {
 				return UITableViewDropProposal(operation: .move, intent: .insertIntoDestinationIndexPath)
 			} else {
@@ -53,30 +51,29 @@ extension MasterFeedViewController: UITableViewDropDelegate {
 	
 	func tableView(_ tableView: UITableView, performDropWith dropCoordinator: UITableViewDropCoordinator) {
 		guard let dragItem = dropCoordinator.items.first?.dragItem,
-			let sourceIdentifier = dragItem.localObject as? MasterFeedTableViewIdentifier,
-			let sourceParentContainerID = sourceIdentifier.parentContainerID,
-			let source = AccountManager.shared.existingContainer(with: sourceParentContainerID),
-			let destIndexPath = dropCoordinator.destinationIndexPath else {
-				return
-		}
+			  let dragNode = dragItem.localObject as? Node,
+			  let source = dragNode.parent?.representedObject as? Container,
+			  let destIndexPath = dropCoordinator.destinationIndexPath else {
+				  return
+			  }
 		
 		let isFolderDrop: Bool = {
-			if let propDestIdentifier = dataSource.itemIdentifier(for: destIndexPath), let propCell = tableView.cellForRow(at: destIndexPath) {
-				return propDestIdentifier.isFolder && dropCoordinator.session.location(in: propCell).y >= 0
+			if coordinator.nodeFor(destIndexPath)?.representedObject is Folder, let propCell = tableView.cellForRow(at: destIndexPath) {
+				return dropCoordinator.session.location(in: propCell).y >= 0
 			}
 			return false
 		}()
 		
 		// Based on the drop we have to determine a node to start looking for a parent container.
-		let destIdentifier: MasterFeedTableViewIdentifier? = {
+		let destNode: Node? = {
 			
 			if isFolderDrop {
-				return dataSource.itemIdentifier(for: destIndexPath)
+				return coordinator.nodeFor(destIndexPath)
 			} else {
 				if destIndexPath.row == 0 {
-					return dataSource.itemIdentifier(for: IndexPath(row: 0, section: destIndexPath.section))
+					return coordinator.nodeFor(IndexPath(row: 0, section: destIndexPath.section))
 				} else if destIndexPath.row > 0 {
-					return dataSource.itemIdentifier(for: IndexPath(row: destIndexPath.row - 1, section: destIndexPath.section))
+					return coordinator.nodeFor(IndexPath(row: destIndexPath.row - 1, section: destIndexPath.section))
 				} else {
 					return nil
 				}
@@ -86,25 +83,21 @@ extension MasterFeedViewController: UITableViewDropDelegate {
 
 		// Now we start looking for the parent container
 		let destinationContainer: Container? = {
-			if let containerID = destIdentifier?.containerID ?? destIdentifier?.parentContainerID {
-				return AccountManager.shared.existingContainer(with: containerID)
+			if let container = (destNode?.representedObject as? Container) ?? (destNode?.parent?.representedObject as? Container) {
+				return container
 			} else {
 				// If we got here, we are trying to drop on an empty section header.  Go and find the Account for this section
 				return coordinator.rootNode.childAtIndex(destIndexPath.section)?.representedObject as? Account
 			}
 		}()
 		
-		guard let destination = destinationContainer else { return }
-		guard case .webFeed(_, let webFeedID) = sourceIdentifier.feedID else { return }
-		guard let webFeed = source.existingWebFeed(withWebFeedID: webFeedID) else { return }
+		guard let destination = destinationContainer, let webFeed = dragNode.representedObject as? WebFeed else { return }
 		
 		if source.account == destination.account {
 			moveWebFeedInAccount(feed: webFeed, sourceContainer: source, destinationContainer: destination)
 		} else {
 			moveWebFeedBetweenAccounts(feed: webFeed, sourceContainer: source, destinationContainer: destination)
 		}
-
-
 	}
 
 	func moveWebFeedInAccount(feed: WebFeed, sourceContainer: Container, destinationContainer: Container) {

iOS/MasterFeed/MasterFeedViewController.swift

@@ -27,9 +27,6 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 		}
 	}
 
-	private let operationQueue = MainThreadOperationQueue()
-	lazy var dataSource = makeDataSource()
-	
 	var undoableCommands = [UndoableCommand]()
 	weak var coordinator: SceneCoordinator!
 	
@@ -63,7 +60,6 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 		tableView.tableHeaderView = UIView(frame: frame)
 		
 		tableView.register(MasterFeedTableViewSectionHeader.self, forHeaderFooterViewReuseIdentifier: "SectionHeader")
-		tableView.dataSource = dataSource
 		tableView.dragDelegate = self
 		tableView.dropDelegate = self
 		tableView.dragInteractionEnabled = true
@@ -83,7 +79,6 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 		
 		configureToolbar()
 		becomeFirstResponder()
-
 	}
 
 	override func viewWillAppear(_ animated: Bool) {
@@ -94,7 +89,7 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 	override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
 		IconImageCache.shared.emptyCache()
 		super.traitCollectionDidChange(previousTraitCollection)
-		reloadAllVisibleCells()
+//		reloadAllVisibleCells()
 	}
 
 	// MARK: Notifications
@@ -123,11 +118,8 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 			node = coordinator.rootNode.descendantNodeRepresentingObject(representedObject as AnyObject)
 		}
 
-		guard let unreadCountNode = node else { return }
-		let identifier = makeIdentifier(unreadCountNode)
-		if dataSource.indexPath(for: identifier) != nil {
-			self.reload(identifier)
-		}
+		guard let unreadCountNode = node, let indexPath = coordinator.indexPathFor(unreadCountNode) else { return }
+		tableView.reloadRows(at: [indexPath], with: .middle)
 	}
 
 	@objc func faviconDidBecomeAvailable(_ note: Notification) {
@@ -152,7 +144,7 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 	
 	@objc func contentSizeCategoryDidChange(_ note: Notification) {
 		resetEstimatedRowHeight()
-		applyChanges(animated: false)
+		tableView.reloadData()
 	}
 	
 	@objc func willEnterForeground(_ note: Notification) {
@@ -161,6 +153,20 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 	
 	// MARK: Table View
 	
+	override func numberOfSections(in tableView: UITableView) -> Int {
+		coordinator.numberOfSections()
+	}
+	
+	override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
+		coordinator.numberOfRows(in: section)
+	}
+	
+	override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
+		let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! MasterFeedTableViewCell
+		configure(cell, indexPath)
+		return cell
+	}
+	
 	override func tableView(_ tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {
 
 		guard let nameProvider = coordinator.rootNode.childAtIndex(section)?.representedObject as? DisplayNameProvider else {
@@ -251,13 +257,13 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 		renameAction.backgroundColor = UIColor.systemOrange
 		actions.append(renameAction)
 		
-		if let identifier = dataSource.itemIdentifier(for: indexPath), identifier.isWebFeed {
+		if let webFeed = coordinator.nodeFor(indexPath)?.representedObject as? WebFeed {
 			let moreTitle = NSLocalizedString("More", comment: "More")
 			let moreAction = UIContextualAction(style: .normal, title: moreTitle) { [weak self] (action, view, completion) in
 				
 				if let self = self {
 				
-					let alert = UIAlertController(title: identifier.nameForDisplay, message: nil, preferredStyle: .actionSheet)
+					let alert = UIAlertController(title: webFeed.nameForDisplay, message: nil, preferredStyle: .actionSheet)
 					if let popoverController = alert.popoverPresentationController {
 						popoverController.sourceView = view
 						popoverController.sourceRect = CGRect(x: view.frame.size.width/2, y: view.frame.size.height/2, width: 1, height: 1)
@@ -303,26 +309,25 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 	}
 	
 	override func tableView(_ tableView: UITableView, contextMenuConfigurationForRowAt indexPath: IndexPath, point: CGPoint) -> UIContextMenuConfiguration? {
-		guard let identifier = dataSource.itemIdentifier(for: indexPath) else {
+		guard let feed = coordinator.nodeFor(indexPath)?.representedObject as? Feed else {
 			return nil
 		}
-		if identifier.isWebFeed {
-			return makeWebFeedContextMenu(identifier: identifier, indexPath: indexPath, includeDeleteRename: true)
-		} else if identifier.isFolder {
-			return makeFolderContextMenu(identifier: identifier, indexPath: indexPath)
-		} else if identifier.isPsuedoFeed  {
-			return makePseudoFeedContextMenu(identifier: identifier, indexPath: indexPath)
+		if feed is WebFeed {
+			return makeWebFeedContextMenu(indexPath: indexPath, includeDeleteRename: true)
+		} else if feed is Folder {
+			return makeFolderContextMenu(indexPath: indexPath)
+		} else if feed is PseudoFeed  {
+			return makePseudoFeedContextMenu(indexPath: indexPath)
 		} else {
 			return nil
 		}
 	}
 	
 	override func tableView(_ tableView: UITableView, previewForHighlightingContextMenuWithConfiguration configuration: UIContextMenuConfiguration) -> UITargetedPreview? {
-		guard let identifier = configuration.identifier as? MasterFeedTableViewIdentifier,
-			let indexPath = dataSource.indexPath(for: identifier),
-			let cell = tableView.cellForRow(at: indexPath) else {
-				return nil
-		}
+		guard let identifier = configuration.identifier as? MasterFeedRowIdentifier,
+			  let cell = tableView.cellForRow(at: identifier.indexPath) else {
+				  return nil
+			  }
 
 		return UITargetedPreview(view: cell, parameters: CroppingPreviewParameters(view: cell))
 	}
@@ -342,21 +347,16 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 			return coordinator.cappedIndexPath(proposedDestinationIndexPath)
 		}()
 		
-		guard let draggedIdentifier = dataSource.itemIdentifier(for: sourceIndexPath),
-			let draggedFeedID = draggedIdentifier.feedID,
-			let draggedNode = coordinator.nodeFor(feedID: draggedFeedID) else {
+		guard let draggedNode = coordinator.nodeFor(sourceIndexPath) else {
 			assertionFailure("This should never happen")
 			return sourceIndexPath
 		}
 		
 		// If there is no destination node, we are dragging onto an empty Account
-		guard let destIdentifier = dataSource.itemIdentifier(for: destIndexPath),
-			let destFeedID = destIdentifier.feedID,
-			let destNode = coordinator.nodeFor(feedID: destFeedID),
-			let destParentContainerID = destIdentifier.parentContainerID,
-			let destParentNode = coordinator.nodeFor(containerID: destParentContainerID) else {
-			return proposedDestinationIndexPath
-		}
+		guard let destNode = coordinator.nodeFor(destIndexPath),
+			  let destParentNode = destNode.parent else {
+				  return proposedDestinationIndexPath
+			  }
 		
 		// If this is a folder, let the users drop on it
 		if destNode.representedObject is Folder {
@@ -381,8 +381,7 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 			if destParentNode.representedObject is Account {
 				return IndexPath(row: 0, section: destIndexPath.section)
 			} else {
-				let identifier = makeIdentifier(sortedNodes[index])
-				if let candidateIndexPath = dataSource.indexPath(for: identifier) {
+				if let candidateIndexPath = coordinator.indexPathFor(sortedNodes[index]) {
 					let movementAdjustment = sourceIndexPath < destIndexPath ? 1 : 0
 					return IndexPath(row: candidateIndexPath.row - movementAdjustment, section: candidateIndexPath.section)
 				} else {
@@ -393,8 +392,7 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 		} else {
 			
 			if index >= sortedNodes.count {
-				let identifier = makeIdentifier(sortedNodes[sortedNodes.count - 1])
-				if let lastSortedIndexPath = dataSource.indexPath(for: identifier) {
+				if let lastSortedIndexPath = coordinator.indexPathFor(sortedNodes[sortedNodes.count - 1]) {
 					let movementAdjustment = sourceIndexPath > destIndexPath ? 1 : 0
 					return IndexPath(row: lastSortedIndexPath.row + movementAdjustment, section: lastSortedIndexPath.section)
 				} else {
@@ -402,8 +400,7 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 				}
 			} else {
 				let movementAdjustment = sourceIndexPath < destIndexPath ? 1 : 0
-				let identifer = makeIdentifier(sortedNodes[index - movementAdjustment])
-				return dataSource.indexPath(for: identifer) ?? sourceIndexPath
+				return coordinator.indexPathFor(sortedNodes[index - movementAdjustment]) ?? sourceIndexPath
 			}
 			
 		}
@@ -515,14 +512,14 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 	}
 	
 	@objc func expandSelectedRows(_ sender: Any?) {
-		if let indexPath = coordinator.currentFeedIndexPath, let containerID = dataSource.itemIdentifier(for: indexPath)?.containerID {
-			coordinator.expand(containerID)
+		if let indexPath = coordinator.currentFeedIndexPath, let node = coordinator.nodeFor(indexPath) {
+			coordinator.expand(node)
 		}
 	}
 	
 	@objc func collapseSelectedRows(_ sender: Any?) {
-		if let indexPath = coordinator.currentFeedIndexPath, let containerID = dataSource.itemIdentifier(for: indexPath)?.containerID {
-			coordinator.collapse(containerID)
+		if let indexPath = coordinator.currentFeedIndexPath, let node = coordinator.nodeFor(indexPath) {
+			coordinator.collapse(node)
 		}
 	}
 	
@@ -562,23 +559,54 @@ class MasterFeedViewController: UITableViewController, UndoableCommandRunner {
 	}
 
 	func updateFeedSelection(animations: Animations) {
-		operationQueue.add(UpdateSelectionOperation(coordinator: coordinator, dataSource: dataSource, tableView: tableView, animations: animations))
-	}
-
-	func reloadFeeds(initialLoad: Bool, completion: (() -> Void)? = nil) {
-		updateUI()
-
-		// We have to reload all the visible cells because if we got here by doing a table cell move,
-		// then the table itself is in a weird state.  This is because we do unusual things like allowing
-		// drops on a "folder" that should cause the dropped cell to disappear.
-		applyChanges(animated: !initialLoad) { [weak self] in
-			if !initialLoad {
-				self?.reloadAllVisibleCells(completion: completion)
-			} else {
-				completion?()
+		if let indexPath = coordinator.currentFeedIndexPath {
+			tableView.selectRowAndScrollIfNotVisible(at: indexPath, animations: animations)
+		} else {
+			if let indexPath = tableView.indexPathForSelectedRow {
+				if animations.contains(.select) {
+					tableView.deselectRow(at: indexPath, animated: true)
+				} else {
+					tableView.deselectRow(at: indexPath, animated: false)
+				}
 			}
 		}
 	}
+
+	func reloadFeeds(initialLoad: Bool, changes: [ShadowTableChanges], completion: (() -> Void)? = nil) {
+		updateUI()
+
+		guard !initialLoad else {
+			tableView.reloadData()
+			completion?()
+			return
+		}
+		
+		for change in changes {
+			guard !change.isEmpty else { continue }
+			
+			tableView.performBatchUpdates {
+				if let deletes = change.deleteIndexPaths, !deletes.isEmpty {
+					tableView.deleteRows(at: deletes, with: .middle)
+				}
+				
+				if let inserts = change.insertIndexPaths, !inserts.isEmpty {
+					tableView.insertRows(at: inserts, with: .middle)
+				}
+				
+				if let moves = change.moveIndexPaths, !moves.isEmpty {
+					for move in moves {
+						tableView.moveRow(at: move.0, to: move.1)
+					}
+				}
+				
+				if let reloads = change.reloadIndexPaths, !reloads.isEmpty {
+					tableView.reloadRows(at: reloads, with: .middle)
+				}
+			}
+		}
+		
+		completion?()
+	}
 	
 	func updateUI() {
 		if coordinator.isReadFeedsFiltered {
@@ -741,65 +769,6 @@ private extension MasterFeedViewController {
 		filterButton?.accLabelText = NSLocalizedString("Filter Read Feeds", comment: "Filter Read Feeds")
 	}
 	
-	func makeIdentifier(_ node: Node) -> MasterFeedTableViewIdentifier {
-		let unreadCount = coordinator.unreadCountFor(node)
-		return MasterFeedTableViewIdentifier(node: node, unreadCount: unreadCount)
-	}
-	
-	func reload(_ identifier: MasterFeedTableViewIdentifier) {
-		var snapshot = dataSource.snapshot()
-		snapshot.reloadItems([identifier])
-		queueApply(snapshot: snapshot, animatingDifferences: false) { [weak self] in
-			self?.restoreSelectionIfNecessary(adjustScroll: false)
-		}
-	}
-	
-	func applyChanges(animated: Bool, adjustScroll: Bool = false, completion: (() -> Void)? = nil) {
-        var snapshot = NSDiffableDataSourceSnapshot<Int, MasterFeedTableViewIdentifier>()
-		let sectionIdentifiers = Array(0...coordinator.rootNode.childNodes.count - 1)
-		snapshot.appendSections(sectionIdentifiers)
-
-		for sectionIdentifer in sectionIdentifiers {
-			let identifiers = coordinator.shadowNodesFor(section: sectionIdentifer).map { makeIdentifier($0) }
-			snapshot.appendItems(identifiers, toSection: sectionIdentifer)
-		}
-        
-		queueApply(snapshot: snapshot, animatingDifferences: animated) { [weak self] in
-			self?.restoreSelectionIfNecessary(adjustScroll: adjustScroll)
-			completion?()
-		}
-	}
-	
-	func queueApply(snapshot: NSDiffableDataSourceSnapshot<Int, MasterFeedTableViewIdentifier>, animatingDifferences: Bool = true, completion: (() -> Void)? = nil) {
-		let operation = MasterFeedDataSourceOperation(dataSource: dataSource, snapshot: snapshot, animating: animatingDifferences)
-		operation.completionBlock = { [weak self] _ in
-			self?.enableTableViewSelection()
-			completion?()
-		}
-		disableTableViewSelectionIfNecessary()
-		operationQueue.add(operation)
-	}
-
-	private func disableTableViewSelectionIfNecessary() {
-		// We only need to disable tableView selection if the feeds are filtered by unread
-		guard coordinator.isReadFeedsFiltered else { return }
-		tableView.allowsSelection = false
-	}
-
-	private func enableTableViewSelection() {
-		tableView.allowsSelection = true
-	}
-
-    func makeDataSource() -> MasterFeedDataSource {
-		let dataSource = MasterFeedDataSource(tableView: tableView, cellProvider: { [weak self] tableView, indexPath, cellContents in
-			let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! MasterFeedTableViewCell
-			self?.configure(cell, cellContents)
-			return cell
-		})
-		dataSource.defaultRowAnimation = .middle
-		return dataSource
-    }
-
 	func resetEstimatedRowHeight() {
 		let titleLabel = NonIntrinsicLabel()
 		titleLabel.text = "But I must explain"
@@ -811,27 +780,30 @@ private extension MasterFeedViewController {
 		tableView.estimatedRowHeight = layout.height
 	}
 	
-	func configure(_ cell: MasterFeedTableViewCell, _ identifier: MasterFeedTableViewIdentifier) {
-		
+	func configure(_ cell: MasterFeedTableViewCell, _ indexPath: IndexPath) {
+		guard let node = coordinator.nodeFor(indexPath) else { return }
+
 		cell.delegate = self
-		if identifier.isFolder {
+		if node.representedObject is Folder {
 			cell.indentationLevel = 0
 		} else {
 			cell.indentationLevel = 1
 		}
 		
-		if let containerID = identifier.containerID {
+		if let containerID = (node.representedObject as? Container)?.containerID {
 			cell.setDisclosure(isExpanded: coordinator.isExpanded(containerID), animated: false)
 			cell.isDisclosureAvailable = true
 		} else {
 			cell.isDisclosureAvailable = false
 		}
 		
-		cell.name = identifier.nameForDisplay
-		cell.unreadCount = identifier.unreadCount
-		configureIcon(cell, identifier)
-		
-		guard let indexPath = dataSource.indexPath(for: identifier) else { return }
+		if let feed = node.representedObject as? Feed {
+			cell.name = feed.nameForDisplay
+			cell.unreadCount = feed.unreadCount
+		}
+
+		configureIcon(cell, indexPath)
+
 		let rowsInSection = tableView.numberOfRows(inSection: indexPath.section)
 		if indexPath.row == rowsInSection - 1 {
 			cell.isSeparatorShown = false
@@ -841,8 +813,8 @@ private extension MasterFeedViewController {
 		
 	}
 	
-	func configureIcon(_ cell: MasterFeedTableViewCell, _ identifier: MasterFeedTableViewIdentifier) {
-		guard let feedID = identifier.feedID else {
+	func configureIcon(_ cell: MasterFeedTableViewCell, _ indexPath: IndexPath) {
+		guard let node = coordinator.nodeFor(indexPath), let feed = node.representedObject as? Feed, let feedID = feed.feedID else {
 			return
 		}
 		cell.iconImage = IconImageCache.shared.imageFor(feedID)
@@ -859,35 +831,29 @@ private extension MasterFeedViewController {
 		applyToCellsForRepresentedObject(representedObject, configure)
 	}
 
-	func applyToCellsForRepresentedObject(_ representedObject: AnyObject, _ completion: (MasterFeedTableViewCell, MasterFeedTableViewIdentifier) -> Void) {
-		applyToAvailableCells { (cell, identifier) in
-			if let representedFeed = representedObject as? Feed, representedFeed.feedID == identifier.feedID {
-				completion(cell, identifier)
+	func applyToCellsForRepresentedObject(_ representedObject: AnyObject, _ completion: (MasterFeedTableViewCell, IndexPath) -> Void) {
+		applyToAvailableCells { (cell, indexPath) in
+			if let node = coordinator.nodeFor(indexPath),
+			   let representedFeed = representedObject as? Feed,
+			   let candidate = node.representedObject as? Feed,
+			   representedFeed.feedID == candidate.feedID {
+				completion(cell, indexPath)
 			}
 		}
 	}
 	
-	func applyToAvailableCells(_ completion: (MasterFeedTableViewCell, MasterFeedTableViewIdentifier) -> Void) {
+	func applyToAvailableCells(_ completion: (MasterFeedTableViewCell, IndexPath) -> Void) {
 		tableView.visibleCells.forEach { cell in
-			guard let indexPath = tableView.indexPath(for: cell), let identifier = dataSource.itemIdentifier(for: indexPath) else {
+			guard let indexPath = tableView.indexPath(for: cell) else {
 				return
 			}
-			completion(cell as! MasterFeedTableViewCell, identifier)
+			completion(cell as! MasterFeedTableViewCell, indexPath)
 		}
 	}
 
 	private func reloadAllVisibleCells(completion: (() -> Void)? = nil) {
-		let visibleNodes = tableView.indexPathsForVisibleRows!.compactMap { return dataSource.itemIdentifier(for: $0) }
-		reloadCells(visibleNodes, completion: completion)
-	}
-	
-	private func reloadCells(_ identifiers: [MasterFeedTableViewIdentifier], completion: (() -> Void)? = nil) {
-		var snapshot = dataSource.snapshot()
-		snapshot.reloadItems(identifiers)
-		queueApply(snapshot: snapshot, animatingDifferences: false) { [weak self] in
-			self?.restoreSelectionIfNecessary(adjustScroll: false)
-			completion?()
-		}
+		guard let indexPaths = tableView.indexPathsForVisibleRows else { return }
+		tableView.reloadRows(at: indexPaths, with: .middle)
 	}
 	
 	private func accountForNode(_ node: Node) -> Account? {
@@ -918,21 +884,21 @@ private extension MasterFeedViewController {
 	}
 
 	func expand(_ cell: MasterFeedTableViewCell) {
-		guard let indexPath = tableView.indexPath(for: cell), let containerID = dataSource.itemIdentifier(for: indexPath)?.containerID else {
+		guard let indexPath = tableView.indexPath(for: cell), let node = coordinator.nodeFor(indexPath) else {
 			return
 		}
-		coordinator.expand(containerID)
+		coordinator.expand(node)
 	}
 
 	func collapse(_ cell: MasterFeedTableViewCell) {
-		guard let indexPath = tableView.indexPath(for: cell), let containerID = dataSource.itemIdentifier(for: indexPath)?.containerID else {
+		guard let indexPath = tableView.indexPath(for: cell), let node = coordinator.nodeFor(indexPath) else {
 			return
 		}
-		coordinator.collapse(containerID)
+		coordinator.collapse(node)
 	}
 
-	func makeWebFeedContextMenu(identifier: MasterFeedTableViewIdentifier, indexPath: IndexPath, includeDeleteRename: Bool) -> UIContextMenuConfiguration {
-		return UIContextMenuConfiguration(identifier: identifier as NSCopying, previewProvider: nil, actionProvider: { [ weak self] suggestedActions in
+	func makeWebFeedContextMenu(indexPath: IndexPath, includeDeleteRename: Bool) -> UIContextMenuConfiguration {
+		return UIContextMenuConfiguration(identifier: MasterFeedRowIdentifier(indexPath: indexPath), previewProvider: nil, actionProvider: { [ weak self] suggestedActions in
 			
 			guard let self = self else { return nil }
 			
@@ -976,8 +942,8 @@ private extension MasterFeedViewController {
 		
 	}
 	
-	func makeFolderContextMenu(identifier: MasterFeedTableViewIdentifier, indexPath: IndexPath) -> UIContextMenuConfiguration {
-		return UIContextMenuConfiguration(identifier: identifier as NSCopying, previewProvider: nil, actionProvider: { [weak self] suggestedActions in
+	func makeFolderContextMenu(indexPath: IndexPath) -> UIContextMenuConfiguration {
+		return UIContextMenuConfiguration(identifier: MasterFeedRowIdentifier(indexPath: indexPath), previewProvider: nil, actionProvider: { [weak self] suggestedActions in
 
 			guard let self = self else { return nil }
 			
@@ -999,12 +965,12 @@ private extension MasterFeedViewController {
 		})
 	}
 
-	func makePseudoFeedContextMenu(identifier: MasterFeedTableViewIdentifier, indexPath: IndexPath) -> UIContextMenuConfiguration? {
+	func makePseudoFeedContextMenu(indexPath: IndexPath) -> UIContextMenuConfiguration? {
 		guard let markAllAction = self.markAllAsReadAction(indexPath: indexPath) else {
 			return nil
 		}
 
-		return UIContextMenuConfiguration(identifier: identifier as NSCopying, previewProvider: nil, actionProvider: { suggestedActions in
+		return UIContextMenuConfiguration(identifier: MasterFeedRowIdentifier(indexPath: indexPath), previewProvider: nil, actionProvider: { suggestedActions in
 			return UIMenu(title: "", children: [markAllAction])
 		})
 	}
@@ -1035,11 +1001,10 @@ private extension MasterFeedViewController {
 	}
 	
 	func copyFeedPageAction(indexPath: IndexPath) -> UIAction? {
-		guard let feedID = dataSource.itemIdentifier(for: indexPath)?.feedID,
-			let webFeed = AccountManager.shared.existingFeed(with: feedID) as? WebFeed,
-			let url = URL(string: webFeed.url) else {
-				return nil
-		}
+		guard let webFeed = coordinator.nodeFor(indexPath)?.representedObject as? WebFeed,
+			  let url = URL(string: webFeed.url) else {
+				  return nil
+			  }
 		
 		let title = NSLocalizedString("Copy Feed URL", comment: "Copy Feed URL")
 		let action = UIAction(title: title, image: AppAssets.copyImage) { action in
@@ -1049,12 +1014,11 @@ private extension MasterFeedViewController {
 	}
 	
 	func copyFeedPageAlertAction(indexPath: IndexPath, completion: @escaping (Bool) -> Void) -> UIAlertAction? {
-		guard let feedID = dataSource.itemIdentifier(for: indexPath)?.feedID,
-			let webFeed = AccountManager.shared.existingFeed(with: feedID) as? WebFeed,
-			let url = URL(string: webFeed.url) else {
-				return nil
-		}
-		
+		guard let webFeed = coordinator.nodeFor(indexPath)?.representedObject as? WebFeed,
+			  let url = URL(string: webFeed.url) else {
+				  return nil
+			  }
+
 		let title = NSLocalizedString("Copy Feed URL", comment: "Copy Feed URL")
 		let action = UIAlertAction(title: title, style: .default) { action in
 			UIPasteboard.general.url = url
@@ -1064,12 +1028,11 @@ private extension MasterFeedViewController {
 	}
 	
 	func copyHomePageAction(indexPath: IndexPath) -> UIAction? {
-		guard let feedID = dataSource.itemIdentifier(for: indexPath)?.feedID,
-			let webFeed = AccountManager.shared.existingFeed(with: feedID) as? WebFeed,
-			let homePageURL = webFeed.homePageURL,
-			let url = URL(string: homePageURL) else {
-				return nil
-		}
+		guard let webFeed = coordinator.nodeFor(indexPath)?.representedObject as? WebFeed,
+			  let homePageURL = webFeed.homePageURL,
+			  let url = URL(string: homePageURL) else {
+				  return nil
+			  }
 		
 		let title = NSLocalizedString("Copy Home Page URL", comment: "Copy Home Page URL")
 		let action = UIAction(title: title, image: AppAssets.copyImage) { action in
@@ -1079,13 +1042,12 @@ private extension MasterFeedViewController {
 	}
 	
 	func copyHomePageAlertAction(indexPath: IndexPath, completion: @escaping (Bool) -> Void) -> UIAlertAction? {
-		guard let feedID = dataSource.itemIdentifier(for: indexPath)?.feedID,
-			let webFeed = AccountManager.shared.existingFeed(with: feedID) as? WebFeed,
-			let homePageURL = webFeed.homePageURL,
-			let url = URL(string: homePageURL) else {
-				return nil
-		}
-		
+		guard let webFeed = coordinator.nodeFor(indexPath)?.representedObject as? WebFeed,
+			  let homePageURL = webFeed.homePageURL,
+			  let url = URL(string: homePageURL) else {
+				  return nil
+			  }
+
 		let title = NSLocalizedString("Copy Home Page URL", comment: "Copy Home Page URL")
 		let action = UIAlertAction(title: title, style: .default) { action in
 			UIPasteboard.general.url = url
@@ -1095,16 +1057,14 @@ private extension MasterFeedViewController {
 	}
 	
 	func markAllAsReadAlertAction(indexPath: IndexPath, completion: @escaping (Bool) -> Void) -> UIAlertAction? {
-		guard let identifier = dataSource.itemIdentifier(for: indexPath),
-			identifier.unreadCount > 0,
-			let feedID = identifier.feedID,
-			let feed = AccountManager.shared.existingFeed(with: feedID) as? WebFeed,
-			let articles = try? feed.fetchArticles(), let contentView = self.tableView.cellForRow(at: indexPath)?.contentView else {
+		guard let webFeed = coordinator.nodeFor(indexPath)?.representedObject as? WebFeed,
+			webFeed.unreadCount > 0,
+			let articles = try? webFeed.fetchArticles(), let contentView = self.tableView.cellForRow(at: indexPath)?.contentView else {
 				return nil
 		}
 		
 		let localizedMenuText = NSLocalizedString("Mark All as Read in “%@”", comment: "Command")
-		let title = NSString.localizedStringWithFormat(localizedMenuText as NSString, feed.nameForDisplay) as String
+		let title = NSString.localizedStringWithFormat(localizedMenuText as NSString, webFeed.nameForDisplay) as String
 		let cancel = {
 			completion(true)
 		}
@@ -1137,13 +1097,13 @@ private extension MasterFeedViewController {
 	}
 	
 	func getInfoAction(indexPath: IndexPath) -> UIAction? {
-		guard let feedID = dataSource.itemIdentifier(for: indexPath)?.feedID, let feed = AccountManager.shared.existingFeed(with: feedID) as? WebFeed else {
+		guard let webFeed = coordinator.nodeFor(indexPath)?.representedObject as? WebFeed else {
 			return nil
 		}
 		
 		let title = NSLocalizedString("Get Info", comment: "Get Info")
 		let action = UIAction(title: title, image: AppAssets.infoImage) { [weak self] action in
-			self?.coordinator.showFeedInspector(for: feed)
+			self?.coordinator.showFeedInspector(for: webFeed)
 		}
 		return action
 	}
@@ -1165,41 +1125,25 @@ private extension MasterFeedViewController {
 	}
 
 	func getInfoAlertAction(indexPath: IndexPath, completion: @escaping (Bool) -> Void) -> UIAlertAction? {
-		guard let feedID = dataSource.itemIdentifier(for: indexPath)?.feedID, let feed = AccountManager.shared.existingFeed(with: feedID) as? WebFeed else {
+		guard let webFeed = coordinator.nodeFor(indexPath)?.representedObject as? WebFeed else {
 			return nil
 		}
 
 		let title = NSLocalizedString("Get Info", comment: "Get Info")
 		let action = UIAlertAction(title: title, style: .default) { [weak self] action in
-			self?.coordinator.showFeedInspector(for: feed)
+			self?.coordinator.showFeedInspector(for: webFeed)
 			completion(true)
 		}
 		return action
 	}
 
 	func markAllAsReadAction(indexPath: IndexPath) -> UIAction? {
-		guard let identifier = dataSource.itemIdentifier(for: indexPath), identifier.unreadCount > 0 else {
-			return nil
-		}
+		guard let feed = coordinator.nodeFor(indexPath)?.representedObject as? Feed,
+			  let contentView = self.tableView.cellForRow(at: indexPath)?.contentView,
+			  feed.unreadCount > 0 else {
+				  return nil
+			  }
 		
-		var smartFeed: Feed?
-		if identifier.isPsuedoFeed {
-			if SmartFeedsController.shared.todayFeed.feedID == identifier.feedID {
-				smartFeed = SmartFeedsController.shared.todayFeed
-			} else if SmartFeedsController.shared.unreadFeed.feedID == identifier.feedID {
-				smartFeed = SmartFeedsController.shared.unreadFeed
-			} else if SmartFeedsController.shared.starredFeed.feedID == identifier.feedID  {
-				smartFeed = SmartFeedsController.shared.starredFeed
-			}
-		}
-		
-		guard let feedID = identifier.feedID,
-			  let feed = smartFeed ?? AccountManager.shared.existingFeed(with: feedID),
-			  feed.unreadCount > 0,
-			  let contentView = self.tableView.cellForRow(at: indexPath)?.contentView else {
-			return nil
-		}
-
 		let localizedMenuText = NSLocalizedString("Mark All as Read in “%@”", comment: "Command")
 		let title = NSString.localizedStringWithFormat(localizedMenuText as NSString, feed.nameForDisplay) as String
 		let action = UIAction(title: title, image: AppAssets.markAllAsReadImage) { [weak self] action in
@@ -1236,11 +1180,10 @@ private extension MasterFeedViewController {
 
 
 	func rename(indexPath: IndexPath) {
-		guard let feedID = dataSource.itemIdentifier(for: indexPath)?.feedID, let feed = AccountManager.shared.existingFeed(with: feedID) else { return	}
+		guard let feed = coordinator.nodeFor(indexPath)?.representedObject as? Feed else { return	}
 
-		let name = dataSource.itemIdentifier(for: indexPath)?.nameForDisplay ?? ""
 		let formatString = NSLocalizedString("Rename “%@”", comment: "Rename feed")
-		let title = NSString.localizedStringWithFormat(formatString as NSString, name) as String
+		let title = NSString.localizedStringWithFormat(formatString as NSString, feed.nameForDisplay) as String
 		
 		let alertController = UIAlertController(title: title, message: nil, preferredStyle: .alert)
 		
@@ -1280,7 +1223,7 @@ private extension MasterFeedViewController {
 		alertController.preferredAction = renameAction
 		
 		alertController.addTextField() { textField in
-			textField.text = name
+			textField.text = feed.nameForDisplay
 			textField.placeholder = NSLocalizedString("Name", comment: "Name")
 		}
 		
@@ -1291,7 +1234,7 @@ private extension MasterFeedViewController {
 	}
 	
 	func delete(indexPath: IndexPath) {
-		guard let feedID = dataSource.itemIdentifier(for: indexPath)?.feedID, let feed = AccountManager.shared.existingFeed(with: feedID) else { return	}
+		guard let feed = coordinator.nodeFor(indexPath)?.representedObject as? Feed else { return	}
 
 		let title: String
 		let message: String
@@ -1312,7 +1255,7 @@ private extension MasterFeedViewController {
 		
 		let deleteTitle = NSLocalizedString("Delete", comment: "Delete")
 		let deleteAction = UIAlertAction(title: deleteTitle, style: .destructive) { [weak self] action in
-			self?.delete(indexPath: indexPath, feedID: feedID)
+			self?.performDelete(indexPath: indexPath)
 		}
 		alertController.addAction(deleteAction)
 		alertController.preferredAction = deleteAction
@@ -1320,9 +1263,9 @@ private extension MasterFeedViewController {
 		self.present(alertController, animated: true)
 	}
 	
-	func delete(indexPath: IndexPath, feedID: FeedIdentifier) {
+	func performDelete(indexPath: IndexPath) {
 		guard let undoManager = undoManager,
-			  let deleteNode = coordinator.nodeFor(feedID: feedID),
+			  let deleteNode = coordinator.nodeFor(indexPath),
 			  let deleteCommand = DeleteCommand(nodesToDelete: [deleteNode], undoManager: undoManager, errorHandler: ErrorHandler.present(self)) else {
 			return
 		}

iOS/MasterTimeline/MasterTimelineViewController.swift

@@ -688,7 +688,7 @@ private extension MasterTimelineViewController {
 	
 	func updateTitleUnreadCount() {
 		if let titleView = navigationItem.titleView as? MasterTimelineTitleView {
-			titleView.unreadCountView.unreadCount = coordinator.unreadCount
+			titleView.unreadCountView.unreadCount = coordinator.timelineUnreadCount
 		}
 	}
 	

iOS/SceneCoordinator.swift

@@ -19,6 +19,7 @@ enum PanelMode {
 	case three
 	case standard
 }
+
 enum SearchScope: Int {
 	case timeline = 0
 	case global = 1
@@ -30,7 +31,21 @@ enum ShowFeedName {
 	case feed
 }
 
-class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
+struct FeedNode: Hashable {
+	var node: Node
+	var feedID: FeedIdentifier
+	
+	init(_ node: Node) {
+		self.node = node
+		self.feedID = (node.representedObject as! Feed).feedID!
+	}
+	
+	func hash(into hasher: inout Hasher) {
+		hasher.combine(feedID)
+	}
+}
+
+class SceneCoordinator: NSObject, UndoableCommandRunner {
 	
 	var undoableCommands = [UndoableCommand]()
 	var undoManager: UndoManager? {
@@ -74,7 +89,7 @@ class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
 	
 	private var expandedTable = Set<ContainerIdentifier>()
 	private var readFilterEnabledTable = [FeedIdentifier: Bool]()
-	private var shadowTable = [[Node]]()
+	private var shadowTable = [[FeedNode]]()
 	
 	private(set) var preSearchTimelineFeed: Feed?
 	private var lastSearchString = ""
@@ -285,20 +300,14 @@ class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
 	}
 
 	var isTimelineUnreadAvailable: Bool {
-		return unreadCount > 0
+		return timelineUnreadCount > 0
 	}
 	
 	var isAnyUnreadAvailable: Bool {
 		return appDelegate.unreadCount > 0
 	}
 	
-	var unreadCount: Int = 0 {
-		didSet {
-			if unreadCount != oldValue {
-				postUnreadCountDidChangeNotification()
-			}
-		}
-	}
+	var timelineUnreadCount: Int = 0
 	
 	override init() {
 		treeController = TreeController(delegate: treeControllerDelegate)
@@ -307,7 +316,7 @@ class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
 		
 		for sectionNode in treeController.rootNode.childNodes {
 			markExpanded(sectionNode)
-			shadowTable.append([Node]())
+			shadowTable.append([FeedNode]())
 		}
 		
 		NotificationCenter.default.addObserver(self, selector: #selector(unreadCountDidInitialize(_:)), name: .UnreadCountDidInitialize, object: nil)
@@ -650,20 +659,6 @@ class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
 		
 		refreshTimeline(resetScroll: false)
 	}
-	
-	func shadowNodesFor(section: Int) -> [Node] {
-		return shadowTable[section]
-	}
-	
-	func nodeFor(containerID: ContainerIdentifier) -> Node? {
-		return treeController.rootNode.descendantNode(where: { node in
-			if let container = node.representedObject as? Container {
-				return container.containerID == containerID
-			} else {
-				return false
-			}
-		})
-	}
 
 	func nodeFor(feedID: FeedIdentifier) -> Node? {
 		return treeController.rootNode.descendantNode(where: { node in
@@ -675,6 +670,30 @@ class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
 		})
 	}
 	
+	func numberOfSections() -> Int {
+		return shadowTable.count
+	}
+	
+	func numberOfRows(in section: Int) -> Int {
+		return shadowTable[section].count
+	}
+	
+	func nodeFor(_ indexPath: IndexPath) -> Node? {
+		guard indexPath.section < shadowTable.count && indexPath.row < shadowTable[indexPath.section].count else {
+			return nil
+		}
+		return shadowTable[indexPath.section][indexPath.row].node
+	}
+	
+	func indexPathFor(_ node: Node) -> IndexPath? {
+		for i in 0..<shadowTable.count {
+			if let row = shadowTable[i].firstIndex(of: FeedNode(node)) {
+				return IndexPath(row: row, section: i)
+			}
+		}
+		return nil
+	}
+	
 	func articleFor(_ articleID: String) -> Article? {
 		return idToAticleDictionary[articleID]
 	}
@@ -689,7 +708,7 @@ class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
 	func unreadCountFor(_ node: Node) -> Int {
 		// The coordinator supplies the unread count for the currently selected feed
 		if node.representedObject === timelineFeed as AnyObject {
-			return unreadCount
+			return timelineUnreadCount
 		}
 		if let unreadCountProvider = node.representedObject as? UnreadCountProvider {
 			return unreadCountProvider.unreadCount
@@ -1430,7 +1449,7 @@ private extension SceneCoordinator {
 				count += 1
 			}
 		}
-		unreadCount = count
+		timelineUnreadCount = count
 	}
 	
 	func rebuildArticleDictionaries() {
@@ -1483,8 +1502,8 @@ private extension SceneCoordinator {
 	
 	func addShadowTableToFilterExceptions() {
 		for section in shadowTable {
-			for node in section {
-				if let feed = node.representedObject as? Feed, let feedID = feed.feedID {
+			for feedNode in section {
+				if let feed = feedNode.node.representedObject as? Feed, let feedID = feed.feedID {
 					treeControllerDelegate.addFilterException(feedID)
 				}
 			}
@@ -1501,51 +1520,81 @@ private extension SceneCoordinator {
 	
 	func rebuildBackingStores(initialLoad: Bool = false, updateExpandedNodes: (() -> Void)? = nil, completion: (() -> Void)? = nil) {
 		if !BatchUpdate.shared.isPerforming {
-			
 			addToFilterExeptionsIfNecessary(timelineFeed)
 			treeController.rebuild()
 			treeControllerDelegate.resetFilterExceptions()
 			
 			updateExpandedNodes?()
-			rebuildShadowTable()
-			masterFeedViewController.reloadFeeds(initialLoad: initialLoad, completion: completion)
-			
+			let changes = rebuildShadowTable()
+			masterFeedViewController.reloadFeeds(initialLoad: initialLoad, changes: changes, completion: completion)
 		}
 	}
 	
-	func rebuildShadowTable() {
-		shadowTable = [[Node]]()
+	func rebuildShadowTable() -> [ShadowTableChanges] {
+		var newShadowTable = [[FeedNode]]()
 
 		for i in 0..<treeController.rootNode.numberOfChildNodes {
 			
-			var result = [Node]()
+			var result = [FeedNode]()
 			let sectionNode = treeController.rootNode.childAtIndex(i)!
 			
 			if isExpanded(sectionNode) {
 				for node in sectionNode.childNodes {
-					result.append(node)
+					result.append(FeedNode(node))
 					if isExpanded(node) {
 						for child in node.childNodes {
-							result.append(child)
+							result.append(FeedNode(child))
 						}
 					}
 				}
 			}
 			
-			shadowTable.append(result)
-			
+			newShadowTable.append(result)
 		}
 		
 		// If we have a current Feed IndexPath it is no longer valid and needs reset.
 		if currentFeedIndexPath != nil {
 			currentFeedIndexPath = indexPathFor(timelineFeed as AnyObject)
 		}
+		
+		// Compute the differences in the shadow tables
+		var changes = [ShadowTableChanges]()
+		
+		for (index, newSectionNodes) in newShadowTable.enumerated() {
+			var moves = Set<ShadowTableChanges.Move>()
+			var inserts = Set<Int>()
+			var deletes = Set<Int>()
+			
+			let diff = newSectionNodes.difference(from: shadowTable[index]).inferringMoves()
+			for change in diff {
+				switch change {
+				case .insert(let offset, _, let associated):
+					if let associated = associated {
+						moves.insert(ShadowTableChanges.Move(associated, offset))
+					} else {
+						inserts.insert(offset)
+					}
+				case .remove(let offset, _, let associated):
+					if let associated = associated {
+						moves.insert(ShadowTableChanges.Move(offset, associated))
+					} else {
+						deletes.insert(offset)
+					}
+				}
+			}
+			
+			changes.append(ShadowTableChanges(section: index, deletes: deletes, inserts: inserts, moves: moves))
+		}
+		
+		shadowTable = newShadowTable
+		
+		return changes
 	}
 	
 	func shadowTableContains(_ feed: Feed) -> Bool {
 		for section in shadowTable {
-			for node in section {
-				if let nodeFeed = node.representedObject as? Feed, nodeFeed.feedID == feed.feedID {
+			for feedNode in section {
+				if let nodeFeed = feedNode.node.representedObject as? Feed, nodeFeed.feedID == feed.feedID {
 					return true
 				}
 			}
@@ -1559,22 +1608,6 @@ private extension SceneCoordinator {
 		}
 	}
 
-	func nodeFor(_ indexPath: IndexPath) -> Node? {
-		guard indexPath.section < shadowTable.count && indexPath.row < shadowTable[indexPath.section].count else {
-			return nil
-		}
-		return shadowTable[indexPath.section][indexPath.row]
-	}
-	
-	func indexPathFor(_ node: Node) -> IndexPath? {
-		for i in 0..<shadowTable.count {
-			if let row = shadowTable[i].firstIndex(of: node) {
-				return IndexPath(row: row, section: i)
-			}
-		}
-		return nil
-	}
-
 	func indexPathFor(_ object: AnyObject) -> IndexPath? {
 		guard let node = treeController.rootNode.descendantNodeRepresentingObject(object) else {
 			return nil

iOS/ShadowTableChanges.swift

@@ -0,0 +1,65 @@
+//
+//  ShadowTableChanges.swift
+//  NetNewsWire-iOS
+//
+//  Created by Maurice Parker on 10/20/21.
+//  Copyright © 2021 Ranchero Software. All rights reserved.
+//
+
+import Foundation
+
+public struct ShadowTableChanges {
+	
+	public struct Move: Hashable {
+		public var from: Int
+		public var to: Int
+		
+		init(_ from: Int, _ to: Int) {
+			self.from = from
+			self.to = to
+		}
+	}
+	
+	public var section: Int
+	public var deletes: Set<Int>?
+	public var inserts: Set<Int>?
+	public var moves: Set<Move>?
+	public var reloads: Set<Int>?
+	
+	public var isEmpty: Bool {
+		return (deletes?.isEmpty ?? true) && (inserts?.isEmpty ?? true) && (moves?.isEmpty ?? true) && (reloads?.isEmpty ?? true)
+	}
+	
+	public var isOnlyReloads: Bool {
+		return (deletes?.isEmpty ?? true) && (inserts?.isEmpty ?? true) && (moves?.isEmpty ?? true)
+	}
+	
+	public var deleteIndexPaths: [IndexPath]? {
+		guard let deletes = deletes else { return nil }
+		return deletes.map { IndexPath(row: $0, section: section) }
+	}
+	
+	public var insertIndexPaths: [IndexPath]? {
+		guard let inserts = inserts else { return nil }
+		return inserts.map { IndexPath(row: $0, section: section) }
+	}
+	
+	public var moveIndexPaths: [(IndexPath, IndexPath)]? {
+		guard let moves = moves else { return nil }
+		return moves.map { (IndexPath(row: $0.from, section: section), IndexPath(row: $0.to, section: section)) }
+	}
+	
+	public var reloadIndexPaths: [IndexPath]? {
+		guard let reloads = reloads else { return nil }
+		return reloads.map { IndexPath(row: $0, section: section) }
+	}
+	
+	init(section: Int, deletes: Set<Int>? = nil, inserts: Set<Int>? = nil, moves: Set<Move>? = nil, reloads: Set<Int>? = nil) {
+		self.section = section
+		self.deletes = deletes
+		self.inserts = inserts
+		self.moves = moves
+		self.reloads = reloads
+	}
+	
+}