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Sources/Internals.FallbackDiffableDataUIDispatcher.swift

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+//
+//  Internals.FallbackDiffableDataUIDispatcher.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(UIKit) || canImport(AppKit)
+
+import CoreData
+
+#if canImport(QuartzCore)
+import QuartzCore
+
+#endif
+
+
+// MARK: - Internals
+
+extension Internals {
+
+    // MARK: Internal
+
+//    // Implementation based on https://github.com/ra1028/DiffableDataSources
+//    internal final class FallbackDiffableDataUIDispatcher {
+//
+//        // MARK: Internal
+//
+//        internal func apply() {
+//
+//        }
+//
+//        func snapshot() -> DiffableDataSourceSnapshot<SectionIdentifierType, ItemIdentifierType> {
+//            var snapshot = DiffableDataSourceSnapshot<SectionIdentifierType, ItemIdentifierType>()
+//            snapshot.structure.sections = currentSnapshot.structure.sections
+//            return snapshot
+//        }
+//
+//        func itemIdentifier(for indexPath: IndexPath) -> ItemIdentifierType? {
+//            guard 0..<sections.endIndex ~= indexPath.section else {
+//                return nil
+//            }
+//
+//            let items = sections[indexPath.section].elements
+//
+//            guard 0..<items.endIndex ~= indexPath.item else {
+//                return nil
+//            }
+//
+//            return items[indexPath.item].differenceIdentifier
+//        }
+//
+//        func unsafeItemIdentifier(for indexPath: IndexPath, file: StaticString = #file, line: UInt = #line) -> ItemIdentifierType {
+//            guard let itemIdentifier = itemIdentifier(for: indexPath) else {
+//                universalError("Item not found at the specified index path(\(indexPath)).")
+//            }
+//
+//            return itemIdentifier
+//        }
+//
+//        func indexPath(for itemIdentifier: ItemIdentifierType) -> IndexPath? {
+//            let indexPathMap: [ItemIdentifierType: IndexPath] = sections.enumerated()
+//                .reduce(into: [:]) { result, section in
+//                    for (itemIndex, item) in section.element.elements.enumerated() {
+//                        result[item.differenceIdentifier] = IndexPath(
+//                            item: itemIndex,
+//                            section: section.offset
+//                        )
+//                    }
+//            }
+//            return indexPathMap[itemIdentifier]
+//        }
+//
+//        func numberOfSections() -> Int {
+//            return sections.count
+//        }
+//
+//        func numberOfItems(inSection section: Int) -> Int {
+//            return sections[section].elements.count
+//        }
+//
+//
+//
+//        // MARK: Private
+//
+//        private let dispatcher: MainThreadSerialDispatcher = .init()
+//
+//        private var currentSnapshot: Internals.DiffableDataSourceSnapshot = FallbackDiffableDataSourceSnapshot()
+//        private var sections: [FallbackDiffableDataSourceSnapshot.BackingStructure.Section] = []
+//
+//
+//        // MARK: - MainThreadSerialDispatcher
+//
+//        fileprivate final class MainThreadSerialDispatcher {
+//
+//            // MARK: FilePrivate
+//
+//            fileprivate init() {
+//
+//                self.executingCount.initialize(to: 0)
+//            }
+//
+//            deinit {
+//
+//                self.executingCount.deinitialize(count: 1)
+//                self.executingCount.deallocate()
+//            }
+//
+//            fileprivate func dispatch(_ action: @escaping () -> Void) {
+//
+//                let count = OSAtomicIncrement32(self.executingCount)
+//                if Thread.isMainThread && count == 1 {
+//
+//                    action()
+//                    OSAtomicDecrement32(executingCount)
+//                }
+//                else {
+//
+//                    DispatchQueue.main.async { [weak self] in
+//
+//                        guard let self = self else {
+//
+//                            return
+//                        }
+//                        action()
+//                        OSAtomicDecrement32(self.executingCount)
+//                    }
+//                }
+//            }
+//
+//
+//            // MARK: Private
+//
+//            private let executingCount: UnsafeMutablePointer<Int32> = .allocate(capacity: 1)
+//        }
+//    }
+}
+
+#endif