Implement Locale.Region category filtering methods

Sources/FoundationInternationalization/Locale/Locale+Components_ICU.swift

@@ -290,7 +290,7 @@ extension Locale.Region {
 
     internal static let _isoRegionCodes: [String] = {
         var status = U_ZERO_ERROR
-        let types = [URGN_WORLD, URGN_CONTINENT, URGN_SUBCONTINENT, URGN_TERRITORY]
+        let types = [URGN_WORLD, URGN_CONTINENT, URGN_SUBCONTINENT, URGN_TERRITORY, URGN_GROUPING]
         var codes: [String] = []
         for t in types {
             status = U_ZERO_ERROR
@@ -302,6 +302,182 @@ extension Locale.Region {
         }
         return codes
     }()
+
+    /// Categories of a region. See https://www.unicode.org/reports/tr35/tr35-35/tr35-info.html#Territory_Data
+    @available(FoundationPreview 6.2, *)
+    public struct Category: Codable, Sendable, Hashable, CustomDebugStringConvertible {
+        public var debugDescription: String {
+            switch inner {
+            case .world:
+                return "world"
+            case .continent:
+                return "continent"
+            case .subcontinent:
+                return "subcontinent"
+            case .territory:
+                return "territory"
+            case .grouping:
+                return "grouping"
+            }
+        }
+
+        enum Inner {
+            case world
+            case continent
+            case subcontinent
+            case territory
+            case grouping
+        }
+
+        var inner: Inner
+        fileprivate init(_ inner: Inner) {
+            self.inner = inner
+        }
+
+        var uregionType: URegionType {
+            switch inner {
+            case .world:
+                return URGN_WORLD
+            case .continent:
+                return URGN_CONTINENT
+            case .subcontinent:
+                return URGN_SUBCONTINENT
+            case .territory:
+                return URGN_TERRITORY
+            case .grouping:
+                return URGN_GROUPING
+            }
+        }
+
+        fileprivate init?(uregionType: URegionType) {
+            switch uregionType {
+            case URGN_CONTINENT:
+                self = .init(.continent)
+            case URGN_WORLD:
+                self = .init(.world)
+            case URGN_SUBCONTINENT:
+                self = .init(.subcontinent)
+            case URGN_TERRITORY:
+                self = .init(.territory)
+            case URGN_GROUPING:
+                self = .init(.grouping)
+            default:
+                return nil
+            }
+        }
+
+        /// Category representing the whold world.
+        public static let world: Category = Category(.world)
+
+        /// Category representing a continent, regions contained directly by world.
+        public static let continent: Category = Category(.continent)
+
+        /// Category representing a sub-continent, regions contained directly by a continent.
+        public static let subcontinent: Category = Category(.subcontinent)
+
+        /// Category representing a territory.
+        public static let territory: Category = Category(.territory)
+
+        /// Category representing a grouping, regions that has a well defined membership.
+        public static let grouping: Category = Category(.grouping)
+
+        public init(from decoder: Decoder) throws {
+            let container = try decoder.singleValueContainer()
+            let inner: Inner
+            switch try container.decode(Int.self) {
+            case 0:
+                inner = .world
+            case 1:
+                inner = .continent
+            case 2:
+                inner = .subcontinent
+            case 3:
+                inner = .territory
+            case 4:
+                inner = .grouping
+            default:
+                throw DecodingError.dataCorrupted(.init(codingPath: decoder.codingPath, debugDescription: "Unknown Category"))
+            }
+            self = .init(inner)
+        }
+
+        public func encode(to encoder: Encoder) throws {
+            var container = encoder.singleValueContainer()
+            switch inner {
+            case .world:
+                try container.encode(0)
+            case .continent:
+                try container.encode(1)
+            case .subcontinent:
+                try container.encode(2)
+            case .territory:
+                try container.encode(3)
+            case .grouping:
+                try container.encode(4)
+
+            }
+        }
+    }
+
+    /// An array of regions matching the specified categories.
+    @available(FoundationPreview 6.2, *)
+    public static func isoRegions(ofCategory category: Category) -> [Locale.Region] {
+        var status = U_ZERO_ERROR
+        let values = uregion_getAvailable(category.uregionType, &status)
+        guard let values, status.isSuccess else {
+            return []
+        }
+        return ICU.Enumerator(enumerator: values).elements.map { Locale.Region($0) }
+    }
+
+    /// The category of the region.
+    @available(FoundationPreview 6.2, *)
+    public var category: Category? {
+        var status = U_ZERO_ERROR
+        let icuRegion = uregion_getRegionFromCode(identifier, &status)
+        guard status.isSuccess, let icuRegion else {
+            return nil
+        }
+        let type = uregion_getType(icuRegion)
+        return Category(uregionType: type)
+    }
+
+    /// An array of the sub-regions, matching the specified category of the region.
+    @available(FoundationPreview 6.2, *)
+    public func subRegions(ofCategoy category: Category) -> [Locale.Region] {
+        var status = U_ZERO_ERROR
+        let icuRegion = uregion_getRegionFromCode(identifier, &status)
+        guard let icuRegion, status.isSuccess else {
+            return []
+        }
+
+        status = U_ZERO_ERROR
+        let enumerator = uregion_getContainedRegionsOfType(icuRegion, category.uregionType, &status)
+        guard let enumerator, status.isSuccess else {
+            return []
+        }
+        return ICU.Enumerator(enumerator: enumerator).elements.map { Locale.Region($0) }
+    }
+
+    /// The subcontinent that contains this region, if any.
+    @available(FoundationPreview 6.2, *)
+    public var subcontinent: Locale.Region? {
+        var status = U_ZERO_ERROR
+        let icuRegion = uregion_getRegionFromCode(identifier, &status)
+        guard let icuRegion, status.isSuccess else {
+            return nil
+        }
+
+        guard let containing = uregion_getContainingRegionOfType(icuRegion, URGN_SUBCONTINENT) else {
+            return nil
+        }
+
+        guard let code = String(validatingCString: uregion_getRegionCode(containing)) else {
+            return nil
+        }
+
+        return Locale.Region(code)
+    }
 }
 
 @available(macOS 13, iOS 16, tvOS 16, watchOS 9, *)

Tests/FoundationInternationalizationTests/LocaleRegionTests.swift

@@ -0,0 +1,56 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 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
+//
+//===----------------------------------------------------------------------===//
+
+import Testing
+
+#if FOUNDATION_FRAMEWORK
+import Foundation
+#else
+import FoundationEssentials
+import FoundationInternationalization
+#endif
+
+@Suite("Locale.Region Tests")
+struct LocaleRegionTests {
+    @Test func regionCategory() async throws {
+        #expect(Locale.Region.unknown.category == nil)
+        #expect(Locale.Region.world.category == .world)
+        #expect(Locale.Region.unitedStates.category == .territory)
+        #expect(Locale.Region("EU").category == .grouping)
+        #expect(Locale.Region("not a region").category == nil)
+
+        let africa = Locale.Region("002")
+        #expect(africa.category == .continent)
+
+        let continentOfSpain = try #require(Locale.Region.spain.continent)
+        #expect(continentOfSpain.category == .continent)
+    }
+
+    @Test func subcontinent() async throws {
+        #expect(Locale.Region.unknown.subcontinent == nil)
+        #expect(Locale.Region.world.subcontinent == nil)
+        #expect(Locale.Region("not a region").subcontinent == nil)
+        #expect(Locale.Region.argentina.subcontinent == Locale.Region("005"))
+    }
+
+    @Test func subRegionOfCategory() async throws {
+        #expect(Locale.Region.unknown.subRegions(ofCategoy: .world) == [])
+        #expect(Locale.Region.unknown.subRegions(ofCategoy: .territory) == [])
+
+        #expect(Set(Locale.Region.world.subRegions(ofCategoy: .continent)) == Set(Locale.Region.isoRegions(ofCategory: .continent)))
+
+        #expect(Locale.Region.argentina.subRegions(ofCategoy: .continent) == [])
+        #expect(Locale.Region.argentina.subRegions(ofCategoy: .territory) == Locale.Region.argentina.subRegions)
+
+        #expect(Locale.Region("not a region").subRegions(ofCategoy: .territory) == [])
+    }
+}