Merge pull request #25345 from lorentey/foundation-diff-apis

[Foundation] Bridge difference APIs between Foundation and swift stdlib

Author: lorentey

Darwin/Foundation-swiftoverlay/NSOrderedCollectionDifference.swift

@@ -0,0 +1,106 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+@_exported import Foundation // Clang module
+
+// CollectionDifference<ChangeElement>.Change is conditionally bridged to NSOrderedCollectionChange
+@available(iOS 9999, macOS 9999, tvOS 9999, watchOS 9999, *) // FIXME(availability-5.1)
+extension CollectionDifference.Change : _ObjectiveCBridgeable {
+  @_semantics("convertToObjectiveC")
+  public func _bridgeToObjectiveC() -> NSOrderedCollectionChange {
+    switch self {
+    case .insert(offset: let o, element: let e, associatedWith: let a):
+      return NSOrderedCollectionChange(object: e, type: .insert, index: o, associatedIndex: a ?? NSNotFound)
+    case .remove(offset: let o, element: let e, associatedWith: let a):
+      return NSOrderedCollectionChange(object: e, type: .remove, index: o, associatedIndex: a ?? NSNotFound)
+    }
+  }
+  
+  public static func _forceBridgeFromObjectiveC(_ input: NSOrderedCollectionChange, result: inout CollectionDifference.Change?) {
+    let _ = input.object as! ChangeElement
+
+    if !_conditionallyBridgeFromObjectiveC(input, result: &result) {
+      fatalError("Unable to bridge \(_ObjectiveCType.self) to \(self)")
+    }
+  }
+  
+  public static func _conditionallyBridgeFromObjectiveC(
+    _ x: NSOrderedCollectionChange, result: inout CollectionDifference.Change?
+  ) -> Bool {
+    guard let element = x.object as? ChangeElement else { return false }
+
+    let a: Int?
+    if x.associatedIndex == NSNotFound {
+      a = nil
+    } else {
+      a = x.associatedIndex
+    }
+
+    switch x.changeType {
+    case .insert:
+      result = .insert(offset: x.index, element: element, associatedWith: a)
+    case .remove:
+      result = .remove(offset: x.index, element: element, associatedWith: a)
+    default:
+      return false
+    }
+
+    return true
+  }
+  
+  @_effects(readonly)
+  public static func _unconditionallyBridgeFromObjectiveC(_ s: NSOrderedCollectionChange?) -> CollectionDifference.Change {
+    var result: CollectionDifference<ChangeElement>.Change? = nil
+    CollectionDifference<ChangeElement>.Change._forceBridgeFromObjectiveC(s!, result: &result)
+    return result!
+  }
+}
+
+// CollectionDifference<ChangeElement> is conditionally bridged to NSOrderedCollectionDifference
+@available(iOS 9999, macOS 9999, tvOS 9999, watchOS 9999, *) // FIXME(availability-5.1)
+extension CollectionDifference : _ObjectiveCBridgeable {
+  @_semantics("convertToObjectiveC")
+  public func _bridgeToObjectiveC() -> NSOrderedCollectionDifference {
+    return NSOrderedCollectionDifference(changes: self.map({ $0 as NSOrderedCollectionChange }))
+  }
+  
+  public static func _forceBridgeFromObjectiveC(_ input: NSOrderedCollectionDifference, result: inout CollectionDifference?) {
+    if !_conditionallyBridgeFromObjectiveC(input, result: &result) {
+      fatalError("Unable to bridge \(_ObjectiveCType.self) to \(self)")
+    }
+  }
+
+  private static func _formDifference(
+    from input: NSOrderedCollectionDifference,
+    _ changeConverter: (Any) -> CollectionDifference<ChangeElement>.Change?
+  ) -> CollectionDifference<ChangeElement>? {
+    var changes = Array<Change>()
+    let iteratorSeq = IteratorSequence(NSFastEnumerationIterator(input))
+    for objc_change in iteratorSeq {
+      guard let swift_change = changeConverter(objc_change) else { return nil }
+      changes.append(swift_change)
+    }
+    return CollectionDifference(changes)
+  }
+
+  public static func _conditionallyBridgeFromObjectiveC(
+    _ input: NSOrderedCollectionDifference, result: inout CollectionDifference?
+  ) -> Bool {
+    result = _formDifference(from: input) { $0 as? Change }
+    return result != nil
+  }
+  
+  @_effects(readonly)
+  public static func _unconditionallyBridgeFromObjectiveC(_ s: NSOrderedCollectionDifference?) -> CollectionDifference {
+    return _formDifference(from: s!) { $0 as! Change }!
+  }
+}