Implement drag and drop feed arrangement

iOS/MasterFeed/MasterFeedViewController+Drop.swift

@@ -0,0 +1,167 @@
+//
+//  MasterFeedViewController+Drop.swift
+//  NetNewsWire-iOS
+//
+//  Created by Maurice Parker on 11/20/19.
+//  Copyright © 2019 Ranchero Software. All rights reserved.
+//
+
+import UIKit
+import RSCore
+import Account
+import RSTree
+
+extension MasterFeedViewController: UITableViewDropDelegate {
+	
+	func tableView(_ tableView: UITableView, canHandle session: UIDropSession) -> Bool {
+		return session.localDragSession != nil //&& session.canLoadObjects(ofClass: URL.self)
+	}
+	
+	func tableView(_ tableView: UITableView, dropSessionDidUpdate session: UIDropSession, withDestinationIndexPath destinationIndexPath: IndexPath?) -> UITableViewDropProposal {
+		if tableView.hasActiveDrag {
+			if let destIndexPath = destinationIndexPath, let destNode = dataSource.itemIdentifier(for: destIndexPath) {
+				if destNode.representedObject is Folder {
+					return UITableViewDropProposal(operation: .move, intent: .insertIntoDestinationIndexPath)
+				} else {
+					return UITableViewDropProposal(operation: .move, intent: .insertAtDestinationIndexPath)
+				}
+			}
+		}
+		return UITableViewDropProposal(operation: .forbidden)
+	}
+	
+	func tableView(_ tableView: UITableView, performDropWith dropCoordinator: UITableViewDropCoordinator) {
+		guard let dragItem = dropCoordinator.items.first?.dragItem,
+			let sourceNode = dragItem.localObject as? Node,
+			let sourceIndexPath = dataSource.indexPath(for: sourceNode),
+			let webFeed = sourceNode.representedObject as? WebFeed,
+			let destinationIndexPath = dropCoordinator.destinationIndexPath else {
+				return
+		}
+		
+		// Based on the drop we have to determine a node to start looking for a parent container.
+		let destNode: Node = {
+			if destinationIndexPath.row == 0 {
+				return coordinator.rootNode.childAtIndex(destinationIndexPath.section)!
+			} else {
+				let movementAdjustment = sourceIndexPath > destinationIndexPath ? 1 : 0
+				let adjustedDestIndexPath = IndexPath(row: destinationIndexPath.row - movementAdjustment, section: destinationIndexPath.section)
+				return dataSource.itemIdentifier(for: adjustedDestIndexPath)!
+			}
+		}()
+
+		// Now we start looking for the parent container
+		let destParentNode: Node? = {
+			if destNode.representedObject is Container {
+				return destNode
+			} else {
+				if destNode.parent?.representedObject is Container {
+					return destNode.parent!
+				} else {
+					return nil
+				}
+			}
+		}()
+		
+		// Move the Web Feed
+		guard let source = sourceNode.parent?.representedObject as? Container, let destination = destParentNode?.representedObject as? Container else {
+			return
+		}
+		
+		if sameAccount(sourceNode, destParentNode!) {
+			moveWebFeedInAccount(feed: webFeed, sourceContainer: source, destinationContainer: destination)
+		} else {
+			moveWebFeedBetweenAccounts(feed: webFeed, sourceContainer: source, destinationContainer: destination)
+		}
+
+
+	}
+
+	private func sameAccount(_ node: Node, _ parentNode: Node) -> Bool {
+		if let accountID = nodeAccountID(node), let parentAccountID = nodeAccountID(parentNode) {
+			if accountID == parentAccountID {
+				return true
+			}
+		}
+		return false
+	}
+	
+	private func nodeAccount(_ node: Node) -> Account? {
+		if let account = node.representedObject as? Account {
+			return account
+		} else if let folder = node.representedObject as? Folder {
+			return folder.account
+		} else if let webFeed = node.representedObject as? WebFeed {
+			return webFeed.account
+		} else {
+			return nil
+		}
+
+	}
+
+	private func nodeAccountID(_ node: Node) -> String? {
+		return nodeAccount(node)?.accountID
+	}
+
+	func moveWebFeedInAccount(feed: WebFeed, sourceContainer: Container, destinationContainer: Container) {
+		BatchUpdate.shared.start()
+		sourceContainer.account?.moveWebFeed(feed, from: sourceContainer, to: destinationContainer) { result in
+			BatchUpdate.shared.end()
+			switch result {
+			case .success:
+				break
+			case .failure(let error):
+				self.presentError(error)
+			}
+		}
+	}
+	
+	func moveWebFeedBetweenAccounts(feed: WebFeed, sourceContainer: Container, destinationContainer: Container) {
+		
+		if let existingFeed = destinationContainer.account?.existingWebFeed(withURL: feed.url) {
+			
+			BatchUpdate.shared.start()
+			destinationContainer.account?.addWebFeed(existingFeed, to: destinationContainer) { result in
+				switch result {
+				case .success:
+					sourceContainer.account?.removeWebFeed(feed, from: sourceContainer) { result in
+						BatchUpdate.shared.end()
+						switch result {
+						case .success:
+							break
+						case .failure(let error):
+							self.presentError(error)
+						}
+					}
+				case .failure(let error):
+					BatchUpdate.shared.end()
+					self.presentError(error)
+				}
+			}
+			
+		} else {
+			
+			BatchUpdate.shared.start()
+			destinationContainer.account?.createWebFeed(url: feed.url, name: feed.editedName, container: destinationContainer) { result in
+				switch result {
+				case .success:
+					sourceContainer.account?.removeWebFeed(feed, from: sourceContainer) { result in
+						BatchUpdate.shared.end()
+						switch result {
+						case .success:
+							break
+						case .failure(let error):
+							self.presentError(error)
+						}
+					}
+				case .failure(let error):
+					BatchUpdate.shared.end()
+					self.presentError(error)
+				}
+			}
+			
+		}
+	}
+
+
+}