WIP: do not use yet

Sources/Internals.DiffDelegate.swift

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+//
+//  Internals.FetchedResultsControllerDelegate.swift
+//  CoreStore
+//
+//  Copyright © 2018 John Rommel Estropia
+//
+//  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
+import CoreData
+
+
+// MARK: - FetchedResultsControllerHandler
+
+@available(macOS 10.12, *)
+internal protocol FetchedResultsControllerHandler: AnyObject {
+    
+    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeObject anObject: Any, atIndexPath indexPath: IndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: IndexPath?)
+    
+    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType)
+    
+    func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>)
+    
+    func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>)
+    
+    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, sectionIndexTitleForSectionName sectionName: String?) -> String?
+}
+
+
+// MARK: - Internal
+
+extension Internals {
+
+    // MARK: - FetchedResultsControllerDelegate
+
+    @available(macOS 10.12, *)
+    internal final class FetchedResultsControllerDelegate: NSObject, NSFetchedResultsControllerDelegate {
+
+        // MARK: Internal
+
+        @nonobjc
+        internal var enabled = true
+
+        @nonobjc
+        internal let taskGroup = DispatchGroup()
+
+        @nonobjc
+        internal weak var handler: FetchedResultsControllerHandler?
+
+        @nonobjc
+        internal weak var fetchedResultsController: Internals.CoreStoreFetchedResultsController? {
+
+            didSet {
+
+                oldValue?.delegate = nil
+                self.fetchedResultsController?.delegate = self
+            }
+        }
+
+        deinit {
+
+            self.fetchedResultsController?.delegate = nil
+        }
+
+
+        // MARK: NSFetchedResultsControllerDelegate
+        
+        @available(iOS 13.0, *)
+        dynamic func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: NSDiffableDataSourceSnapshot) {
+            
+        }
+
+        @objc
+        dynamic func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
+
+            self.taskGroup.enter()
+            guard self.enabled else {
+
+                return
+            }
+
+            if #available(iOS 10.3, tvOS 10.3, watchOS 3.2, macOS 10.13, *) {}
+            else {
+
+                self.deletedSections = []
+                self.insertedSections = []
+            }
+
+            self.handler?.controllerWillChangeContent(controller)
+        }
+
+        @objc
+        dynamic func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
+
+            defer {
+
+                self.taskGroup.leave()
+            }
+            guard self.enabled else {
+
+                return
+            }
+
+            self.handler?.controllerDidChangeContent(controller)
+        }
+
+        @objc
+        dynamic func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
+
+            guard self.enabled else {
+
+                return
+            }
+
+            if #available(iOS 10.3, tvOS 10.3, watchOS 3.2, macOS 10.13, *) {
+
+                self.handler?.controller(
+                    controller,
+                    didChangeObject: anObject,
+                    atIndexPath: indexPath,
+                    forChangeType: type,
+                    newIndexPath: newIndexPath
+                )
+                return
+            }
+
+            guard var actualType = NSFetchedResultsChangeType(rawValue: type.rawValue) else {
+
+                // This fix is for a bug where iOS passes 0 for NSFetchedResultsChangeType, but this is not a valid enum case.
+                // Swift will then always execute the first case of the switch causing strange behaviour.
+                // https://forums.developer.apple.com/thread/12184#31850
+                return
+            }
+
+            // This whole dance is a workaround for a nasty bug introduced in XCode 7 targeted at iOS 8 devices
+            // http://stackoverflow.com/questions/31383760/ios-9-attempt-to-delete-and-reload-the-same-index-path/31384014#31384014
+            // https://forums.developer.apple.com/message/9998#9998
+            // https://forums.developer.apple.com/message/31849#31849
+
+            if case .update = actualType,
+                indexPath != nil,
+                newIndexPath != nil {
+
+                actualType = .move
+            }
+
+            switch actualType {
+
+            case .update:
+                guard let section = indexPath?[0] else {
+
+                    return
+                }
+                if self.deletedSections.contains(section)
+                    || self.insertedSections.contains(section) {
+
+                    return
+                }
+
+            case .move:
+                guard let indexPath = indexPath, let newIndexPath = newIndexPath else {
+
+                    return
+                }
+                guard indexPath == newIndexPath else {
+
+                    break
+                }
+                if self.insertedSections.contains(indexPath[0]) {
+
+                    // Observers that handle the .Move change are advised to delete then reinsert the object instead of just moving. This is especially true when indexPath and newIndexPath are equal. For example, calling tableView.moveRowAtIndexPath(_:toIndexPath) when both indexPaths are the same will crash the tableView.
+                    self.handler?.controller(
+                        controller,
+                        didChangeObject: anObject,
+                        atIndexPath: indexPath,
+                        forChangeType: .move,
+                        newIndexPath: newIndexPath
+                    )
+                    return
+                }
+                if self.deletedSections.contains(indexPath[0]) {
+
+                    self.handler?.controller(
+                        controller,
+                        didChangeObject: anObject,
+                        atIndexPath: nil,
+                        forChangeType: .insert,
+                        newIndexPath: indexPath
+                    )
+                    return
+                }
+                self.handler?.controller(
+                    controller,
+                    didChangeObject: anObject,
+                    atIndexPath: indexPath,
+                    forChangeType: .update,
+                    newIndexPath: nil
+                )
+                return
+
+            default:
+                break
+            }
+
+            self.handler?.controller(
+                controller,
+                didChangeObject: anObject,
+                atIndexPath: indexPath,
+                forChangeType: actualType,
+                newIndexPath: newIndexPath
+            )
+        }
+
+        @objc
+        dynamic func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange sectionInfo: NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType) {
+
+            guard self.enabled else {
+
+                return
+            }
+
+            if #available(iOS 10.3, tvOS 10.3, watchOS 3.2, macOS 10.13, *) {}
+            else {
+
+                switch type {
+
+                case .delete:   self.deletedSections.insert(sectionIndex)
+                case .insert:   self.insertedSections.insert(sectionIndex)
+                default: break
+                }
+            }
+
+            self.handler?.controller(
+                controller,
+                didChangeSection: sectionInfo,
+                atIndex: sectionIndex,
+                forChangeType: type
+            )
+        }
+
+        @objc
+        dynamic func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, sectionIndexTitleForSectionName sectionName: String) -> String? {
+
+            return self.handler?.controller(
+                controller,
+                sectionIndexTitleForSectionName: sectionName
+            )
+        }
+
+
+        // MARK: Private
+
+        @nonobjc
+        private var deletedSections = Set<Int>()
+
+        @nonobjc
+        private var insertedSections = Set<Int>()
+    }
+}

Sources/LiveList.swift

@@ -0,0 +1,130 @@
+//
+//  LiveList.swift
+//  CoreStore
+//
+//  Copyright © 2018 John Rommel Estropia
+//
+//  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.
+//
+
+#if canImport(Combine)
+
+import Combine
+import CoreData
+
+
+// MARK: - LiveList
+
+@available(iOS 13.0, *)
+public class LiveList<D: DynamicObject>: Hashable, ObservableObject {
+    
+    // MARK: Public (Accessors)
+    
+    /**
+     The type for the objects contained bye the `ListMonitor`
+     */
+    public typealias ObjectType = D
+    
+    public var snapshot: Snapshot = []
+    
+    
+    // MARK: ObservableObject
+    
+    public var objectWillChange: ObservableObjectPublisher {
+        
+        return self.cs_toRaw().objectWillChange
+    }
+    
+    
+    // MARK: Private
+    
+    private let observer: Internals.FetchedResultsControllerDelegate
+    
+    
+    // MARK: - Snapshot
+    
+    public struct Snapshot: RandomAccessCollection {
+
+        // MARK: RandomAccessCollection
+        
+        public var startIndex: Index {
+            
+        }
+
+        public var endIndex: Index {
+        
+        }
+
+        public subscript(position: Index) -> ObjectType {
+        
+        }
+        
+        
+        // MARK: Sequence
+
+        public typealias Element = ObjectType
+
+        public typealias Index = Int
+
+//        public typealias SubSequence = Slice<Snapshot<ObjectType>>
+//
+//        /// A type that represents the indices that are valid for subscripting the
+//        /// collection, in ascending order.
+//        public typealias Indices = Range<Int>
+//
+//        /// A type that provides the collection's iteration interface and
+//        /// encapsulates its iteration state.
+//        ///
+//        /// By default, a collection conforms to the `Sequence` protocol by
+//        /// supplying `IndexingIterator` as its associated `Iterator`
+//        /// type.
+//        public typealias Iterator = IndexingIterator<FetchedResults<Result>>
+        
+        private let diffableSource: NSDiffable
+    }
+}
+
+extension ListMonitor: ObservableObject {
+
+    public var objectWillChange: ObservableObjectPublisher {
+        
+        return withUnsafePointer(to: &Static.objectWillChange) {
+            self.userInfo[
+                $0,
+                lazyInit: ObservableObjectPublisher.init
+            ] as! ObservableObjectPublisher
+        }
+    }
+}
+
+@available(iOS 13.0, *)
+extension CoreStoreObject: ObservableObject {
+    
+    public var objectWillChange: ObservableObjectPublisher {
+        
+        return self.cs_toRaw().objectWillChange
+    }
+}
+
+fileprivate enum Static {
+    
+    static var objectWillChange: Void?
+}
+
+#endif