@MainActor
class StringChannel {
    static let shared = StringChannel()

    static func setUp(
        binaryMessenger: FlutterBinaryMessenger,
        codec: NSObjectProtocol & FlutterMessageCodec
    ) {
        let channel = FlutterBasicMessageChannel(
            name: "com.example.TestApp/StringChannel",
            binaryMessenger: binaryMessenger,
            codec: codec
        )

        channel.setMessageHandler { (message, reply) in
            print("native: StringChannel received message: \(message ?? "nil")")
            DispatchQueue.global().asyncAfter(deadline: .now() + 1) { @Sendable in
                let message = "StringChannel reply message"
                print("native: StringChannel sending reply: \(message)")
                reply(message)  // <-- Warning: Capture of 'reply' with non-sendable type 'FlutterReply' in a `@Sendable` closure
                
                Task { @MainActor in
                    let message = "StringChannel message from background"
                    print("native: StringChannel sending message: \(message)")
                    // There are two versions of sendMessage in FlutterChannel.h. One does not 
                    // have a reply callback, while the other does. It seems that if a Swift 
                    // function is async or in an isolated context, Swift always chooses the 
                    // version with a reply callback and converts it to an async function. 
                    // That's why we need to await the result of sendMessage.
                    let reply = await channel.sendMessage(message)  
                    // <-- Warning: Capture of 'channel' with non-sendable type 'FlutterBasicMessageChannel' in a `@Sendable` closure
                    // <-- Warning: Non-sendable type 'Any?' returned by implicitly asynchronous call cannot cross actor boundary; this is an error in Swift 6 Language Mode
                    print("native: StringChannel received reply: \(reply ?? "nil")")
                }
            }
        }
    }
}