Widen platform support for iOS 12 and tvOS 12

Author: dcaunt

Package.swift

@@ -6,9 +6,11 @@ import PackageDescription
 let package = Package(
     name: "UID2",
     defaultLocalization: "en",
+    // NB: The UID2 framework code only runs on iOS 13 & tvOS 13, however this allows
+    // integration in apps supporting iOS 12.
     platforms: [
-        .iOS(.v13),
-        .tvOS(.v13)
+        .iOS(.v12),
+        .tvOS(.v12)
     ],
     products: [
         .library(

Sources/UID2/CryptoUtil.swift

@@ -9,6 +9,7 @@ import CryptoKit
 import Foundation
 import SwiftASN1
 
+@available(iOS 13, tvOS 13, *)
 struct CryptoUtil: Sendable {
     // Parses a server's public key and returns a newly generated public key and symmetric key.
     var parseKey: @Sendable (_ string: String) throws -> (SymmetricKey, P256.KeyAgreement.PublicKey)
@@ -17,6 +18,7 @@ struct CryptoUtil: Sendable {
     var encrypt: @Sendable (_ data: Data, _ key: SymmetricKey, _ authenticatedData: Data) throws -> AES.GCM.SealedBox
 }
 
+@available(iOS 13, tvOS 13, *)
 extension CryptoUtil {
     private static let serverPublicKeyPrefixLength = 9
 

Sources/UID2/Extensions/PublicKey+Extensions.swift

@@ -9,6 +9,7 @@ import CryptoKit
 import Foundation
 import SwiftASN1
 
+@available(iOS 13, tvOS 13, *)
 extension P256.KeyAgreement.PublicKey {
     // CryptoKit's implementation is only available in iOS 14
     var derRepresentation: Data {

Sources/UID2/Extensions/URLSession+Extensions.swift

@@ -7,6 +7,7 @@
 
 import Foundation
 
+@available(iOS 13, tvOS 13, *)
 extension URLSession: NetworkSession {
 
     func loadData(for request: URLRequest) async throws -> (Data, HTTPURLResponse) {

Sources/UID2/Internal/Broadcaster.swift

@@ -1,6 +1,7 @@
 import Foundation
 
 /// Send a value to multiple observers
+@available(iOS 13, tvOS 13, *)
 actor Broadcaster<Element: Sendable> {
     typealias Identifier = UUID
     private var continuations: [Identifier: AsyncStream<Element>.Continuation] = [:]

Sources/UID2/Internal/Queue.swift

@@ -3,6 +3,7 @@ import Foundation
 /// When bridging from a sync to async context using multiple `Task`s, order of execution is not guaranteed.
 /// Using an `AsyncStream` we can bridge enqueued work to an async context within a single `Task`.
 /// https://forums.swift.org/t/a-pitfall-when-using-didset-and-task-together-order-cant-be-guaranteed/71311/6
+@available(iOS 13, tvOS 13, *)
 final class Queue {
     typealias Operation = @Sendable () async -> Void
     private let continuation: AsyncStream<Operation>.Continuation

Sources/UID2/KeychainManager.swift

@@ -5,6 +5,7 @@
 import Foundation
 import Security
 
+@available(iOS 13, tvOS 13, *)
 extension Storage {
     static func keychainStorage() -> Storage {
         let storage = KeychainManager()
@@ -17,6 +18,7 @@ extension Storage {
 }
 
 /// Securely manages data in the Keychain
+@available(iOS 13, tvOS 13, *)
 actor KeychainManager {
 
     private let attrAccount = "uid2"

Sources/UID2/Networking/ClientGenerate.swift

@@ -9,6 +9,8 @@ import CryptoKit
 import Foundation
 
 extension Request {
+
+    @available(iOS 13, tvOS 13, *)
     static func clientGenerate(
         payload: Data,
         initializationVector: Data,
@@ -54,6 +56,7 @@ struct ClientGeneratePayload: Encodable {
     }
 }
 
+@available(iOS 13, tvOS 13, *)
 extension ClientGeneratePayload {
     init(_ identity: IdentityType) {
         switch identity {
@@ -87,6 +90,7 @@ struct ClientGenerateRequestBody: Encodable {
     }
 }
 
+@available(iOS 13, tvOS 13, *)
 fileprivate extension String {
     func sha256hash() -> Data {
         let digest = SHA256.hash(data: Data(self.utf8))

Sources/UID2/Networking/DataEnvelope.swift

@@ -8,6 +8,7 @@
 import CryptoKit
 import Foundation
 
+@available(iOS 13, tvOS 13, *)
 internal enum DataEnvelope {
 
     /// Decrypts raw response envelope data, which is expected to be a base64 encoded string.

Sources/UID2/Networking/NetworkSession.swift

@@ -8,6 +8,7 @@
 import Foundation
 
 /// Common interface for networking and unit testing
+@available(iOS 13, tvOS 13, *)
 protocol NetworkSession: Sendable {
 
     func loadData(for request: URLRequest) async throws -> (Data, HTTPURLResponse)