futures-jsonrpc

Futures + JSON-RPC

A lightweight remote procedure call protocol. It is designed to be simple! And, with futures, even more flexible!

This crate will associate Futures with method signatures via registermethod, and parse/handle JSON-RPC messages via handlemessage.

It is fully compliant with JSON-RPC 2.0 Specification.

Contributing

The crate is not test covered yet! Any PR with a test coverage will be much appreciated :)

Installation

Add this to your Cargo.toml:

toml [dependencies] futures_jsonrpc = "0.1"

Examples

```rust use futuresjsonrpc::futures::prelude::*; use futuresjsonrpc::*; use serde_json::Number;

// JrpcHandler use foreign structures as controllers

[derive(Debug, Clone)]

struct SomeNotification { request: Option, }

// Here is some boilerplate to instantiate a new Notification, and handle the received request impl SomeNotification { pub fn new() -> Result { let request = None; let somenotification = SomeNotification { request }; Ok(somenotification) }

pub fn get_request(&self) -> Result<JrpcRequest, ErrorVariant> {
    let request = self.request.clone();
    request
        .map(|r| Ok(r.clone()))
        .unwrap_or(Err(ErrorVariant::NoRequestProvided))
}

pub fn set_request(mut self, request: JrpcRequest) -> Result<Self, ErrorVariant> {
    self.request = Some(request);
    Ok(self)
}

pub fn clone_with_request(&self, request: JrpcRequest) -> Result<Self, ErrorVariant> {
    self.clone().set_request(request)
}

}

// JrpcHandler will just return a pollable associated future. // // The main implementation will go here // // Tokio provides very good documentation on futures. Check it: https://tokio.rs/ impl Future for SomeNotification { // Optimally, we want to use JrpcResponse, for it is guaranteed to respect the JSON-RPC // specification. But, we can change the response here to something else, if required. type Item = Option; type Error = ErrorVariant;

fn poll(&mut self) -> Result<Async<Self::Item>, Self::Error> {
    // We fetch the provided request to copy the data
    let request = self.get_request()?;

    // The params, in this case, will be only a reflection on what was sent
    let params = request.get_params().clone().unwrap_or(JsonValue::Null);

    // `generate_response` will receive an enum `JrpcResponseParam` and reply
    // with either an error or success.
    let message = JrpcResponseParam::generate_result(params)
        .and_then(|result| request.generate_response(result))?;

    // Then, our reply is ready
    Ok(Async::Ready(Some(message)))
}

}

// The handler will call this trait to spawn a new future and process it when a registered method // is requested. impl JrpcMethodTrait for SomeNotification { // generate_future can generate any Future that respects the trait signature. This can be a // foreign structure, or just a copy of self, in case it implements Future. This can also // be a decision based on the received JrpcRequest. // // Since its not a reference, there are no restrictions. fn generatefuture<'a>( &self, request: JrpcRequest, ) -> Result, Error = ErrorVariant>>, ErrorVariant> { Ok(Box::new(self.clonewith_request(request)?)) } }

// Or, alternitavely, we can use the generate_method_with_future macro to only implement the // Future generatemethodwith_future!(InitializeRequest, impl Future for InitializeRequest { type Item = Option; type Error = ErrorVariant;

fn poll(&mut self) -> Result<Async<Self::Item>, Self::Error> {
    let request = self.get_request()?;

    let params = request.get_params().clone().unwrap_or(JsonValue::Null);

    let message = JrpcResponseParam::generate_result(params)
        .and_then(|result| request.generate_response(result))?;

    Ok(Async::Ready(Some(message)))
}

});

fn main() { // JrpcHanlder instance is responsible for registering the JSON-RPC methods and receiving the // requests. // // This is full Arc/RwLock protected. Therefore, it can be freely copied/sent among // threads. let handler = JrpcHandler::new().unwrap();

handler
    // `register_method` will tie the method signature to an instance, not a generic. This
    // means we can freely mutate this instance across different signatures.
    .register_method("some/copyParams", SomeNotification::new().unwrap())
    .and_then(|h| h.register_method("initialize", InitializeRequest::new().unwrap()))
    .and_then(|h| {
        // `handle_message` will receive a raw implementation of `ToString` and return the
        // associated future. If no future is found, an instance of
        // `Err(ErrorVariant::MethodSignatureNotFound(String))` is returned
        h.handle_message(
            r#"
            {
                "jsonrpc": "2.0",
                "method": "some/copyParams",
                "params": [42, 23],
                "id": 531
            }"#,
        )
    })
    // Just waiting for the poll of future. Check futures documentation.
    .and_then(|future| future.wait())
    .and_then(|result| {
        // The result is an instance of `JrpcResponse`
        let result = result.unwrap();
        assert_eq!(result.get_jsonrpc(), "2.0");
        assert_eq!(
            result.get_result(),
            &Some(JsonValue::Array(vec![
                JsonValue::Number(Number::from(42)),
                JsonValue::Number(Number::from(23)),
            ]))
        );
        assert!(result.get_error().is_none());
        assert_eq!(result.get_id(), &JsonValue::Number(Number::from(531)));
        Ok(())
    })
    .unwrap();

} ```