proxy_macro.rs

use std::marker::PhantomData;
use tokio::sync::mpsc;
use anyhow::Result;

// Define a trait for RPC methods
pub trait RpcMethod<C> {
    type Input;
    type Output;

    fn call(client: &C, input: Self::Input) -> Result<Self::Output>;
}

// Generic Proxy struct
pub struct Proxy<C> {
    sender: mpsc::UnboundedSender<Box<dyn FnOnce(&C) -> Result<()> + Send>>,
    _phantom: PhantomData<C>,
}

impl<C: 'static> Proxy<C> {
    pub fn new(client: C) -> Self {
        let (sender, mut receiver) = mpsc::unbounded_channel();

        tokio::spawn(async move {
            while let Some(task) = receiver.recv().await {
                task(&client)?;
            }
        });

        Self {
            sender,
            _phantom: PhantomData,
        }
    }

    pub async fn call<M: RpcMethod<C> + 'static>(&self, input: M::Input) -> Result<M::Output> {
        let (response_sender, response_receiver) = tokio::sync::oneshot::channel();

        self.sender.send(Box::new(move |client| {
            let result = M::call(client, input);
            response_sender.send(result).map_err(|_| anyhow::anyhow!("Failed to send response"))?;
            Ok(())
        }))?;

        response_receiver.await?
    }
}

// Macro to generate client implementations
macro_rules! impl_client {
    ($client:ident, $($method:ident($input:ty) -> $output:ty),*) => {
        $(
            pub struct $method;

            impl RpcMethod<$client> for $method {
                type Input = $input;
                type Output = $output;

                fn call(client: &$client, input: Self::Input) -> Result<Self::Output> {
                    client.$method(input)
                }
            }
        )*
    };
}

// EchoClient implementation
pub struct EchoClient {
    // Add any necessary fields
}

impl EchoClient {
    pub fn new() -> Self {
        Self {}
    }

    pub fn echo(&self, message: String) -> Result<String> {
        Ok(message)
    }
}

impl_client!(EchoClient, echo(String) -> String);

// Usage example
async fn example() -> Result<()> {
    let echo_client = EchoClient::new();
    let proxy = Proxy::new(echo_client);

    let result = proxy.call::<echo>(String::from("Hello, world!")).await?;
    println!("Echo result: {}", result);

    Ok(())
}