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use crate::frame::{FrameDecodeError, FrameEncodeError};
use crate::rpc::rpc_internals::{
RpcHeader, RpcSession, RpcStreamEncoder, RpcStreamEvent,
rpc_trait::{RpcEmit, RpcResponseHandler, RpcStreamMethodRouter},
};
use std::collections::HashMap;
impl<'a> Default for RpcRespondableSession<'a> {
fn default() -> Self {
Self::new()
}
}
/// Lightweight wrapper over `RpcSession` that tracks response handlers.
///
/// This struct allows the caller to associate a response callback per
/// outgoing request. It also supports an optional global fallback handler
/// for unmatched or unsolicited events.
///
/// Suitable for simple scenarios where dispatch logic is externally managed.
pub struct RpcRespondableSession<'a> {
rpc_session: RpcSession,
// TODO: Make these names less vague
pub(crate) response_handlers: HashMap<u32, Box<dyn FnMut(RpcStreamEvent) + Send + 'a>>,
catch_all_response_handler: Option<Box<dyn FnMut(RpcStreamEvent) + Send + 'a>>,
prebuffered_responses: HashMap<u32, Vec<u8>>, // Track buffered responses by request ID
prebuffering_flags: HashMap<u32, bool>, // Track whether pre-buffering is enabled for each request
/// Optional router that maps (method_id, request_id) to a per-request handler.
/// When set, it is consulted on each `Header` event. If it returns a handler,
/// the handler is registered for that stream, bypassing the catch-all accumulator.
/// This enables streaming handler dispatch on the endpoint side.
stream_method_router: Option<RpcStreamMethodRouter<'a>>,
}
impl<'a> RpcRespondableSession<'a> {
pub fn new() -> Self {
Self {
rpc_session: RpcSession::new(),
response_handlers: HashMap::new(),
catch_all_response_handler: None,
prebuffered_responses: HashMap::new(),
prebuffering_flags: HashMap::new(),
stream_method_router: None,
}
}
// TODO: Document that prebuffering buffers the entire response payload into a single chunk
pub fn init_respondable_request<E, R>(
&mut self,
hdr: RpcHeader,
max_chunk_size: usize,
on_emit: E,
on_response: Option<R>,
prebuffer_response: bool,
) -> Result<RpcStreamEncoder<E>, FrameEncodeError>
where
E: RpcEmit,
R: RpcResponseHandler + 'a,
{
let rpc_request_id = hdr.rpc_request_id;
// Set pre-buffering flag for this specific request
self.prebuffering_flags
.insert(rpc_request_id, prebuffer_response);
if let Some(on_response) = on_response {
self.response_handlers
.insert(rpc_request_id, Box::new(on_response));
}
self.rpc_session
.init_request(hdr, max_chunk_size, on_emit)
.map_err(|_| FrameEncodeError::CorruptFrame)
}
pub fn start_reply_stream<E>(
&mut self,
hdr: RpcHeader,
max_chunk_size: usize,
on_emit: E,
) -> Result<RpcStreamEncoder<E>, FrameEncodeError>
where
E: RpcEmit,
{
self.rpc_session
.init_request(hdr, max_chunk_size, on_emit)
.map_err(|_| FrameEncodeError::CorruptFrame)
}
/// Sets a router function for streaming method dispatch.
///
/// When a `Header` event arrives and no per-request handler exists yet,
/// the router is called with `(method_id, request_id)`. If it returns a
/// handler, that handler is registered for the stream's lifetime.
/// Subsequent events (`PayloadChunk`, `End`) are routed to the per-request
/// handler instead of the catch-all accumulator.
pub fn set_stream_method_router<R>(&mut self, router: R)
where
R: FnMut(u64, u32) -> Option<Box<dyn FnMut(RpcStreamEvent) + Send + 'a>> + Send + 'a,
{
self.stream_method_router = Some(Box::new(router));
}
// TODO: Document
// Invoked on the remote in response to `init_respondable_request` from the local client
pub fn set_catch_all_response_handler<R>(&mut self, handler: R)
where
R: RpcResponseHandler + 'a,
{
self.catch_all_response_handler = Some(Box::new(handler));
}
pub fn read_bytes(&mut self, bytes: &[u8]) -> Result<(), FrameDecodeError> {
self.rpc_session.read_bytes(bytes, |evt| {
// --- Streaming method routing ---
// If a Header event arrives for a streaming method, register a
// per-request handler BEFORE the normal routing so subsequent
// events bypass the catch-all accumulator.
if let RpcStreamEvent::Header {
rpc_request_id,
rpc_method_id,
..
} = &evt
&& let Some(ref mut router) = self.stream_method_router
&& let Some(handler) = router(*rpc_method_id, *rpc_request_id)
{
self.response_handlers.insert(*rpc_request_id, handler);
}
let id = match &evt {
RpcStreamEvent::Header { rpc_request_id, .. } => Some(*rpc_request_id),
RpcStreamEvent::PayloadChunk { rpc_request_id, .. } => Some(*rpc_request_id),
RpcStreamEvent::End { rpc_request_id, .. } => Some(*rpc_request_id),
RpcStreamEvent::Error { rpc_request_id, .. } => *rpc_request_id,
};
let method_id = match &evt {
RpcStreamEvent::Header { rpc_method_id, .. } => Some(*rpc_method_id),
RpcStreamEvent::PayloadChunk { rpc_method_id, .. } => Some(*rpc_method_id),
RpcStreamEvent::End { rpc_method_id, .. } => Some(*rpc_method_id),
RpcStreamEvent::Error { rpc_method_id, .. } => *rpc_method_id,
};
let mut handled = false;
if let Some(rpc_id) = id {
let is_prebuffering_response =
self.prebuffering_flags.get(&rpc_id).unwrap_or(&false);
if *is_prebuffering_response {
// Accumulate the bytes into the buffer for this request ID
let buffer = self.prebuffered_responses.entry(rpc_id).or_default();
match &evt {
RpcStreamEvent::Header { .. } => {
if let Some(cb) = self.response_handlers.get_mut(&rpc_id) {
cb(evt.clone());
}
}
RpcStreamEvent::PayloadChunk { bytes, .. } => {
buffer.extend_from_slice(bytes);
}
RpcStreamEvent::End { rpc_header, .. } => {
// When the end of the stream is reached, call the response handler
if let Some(cb) = self.response_handlers.get_mut(&rpc_id) {
let rpc_method_id =
method_id.ok_or(FrameDecodeError::CorruptFrame)?;
let rpc_payload_event = RpcStreamEvent::PayloadChunk {
rpc_request_id: rpc_id,
rpc_method_id,
bytes: buffer.clone(),
rpc_header: rpc_header.clone(),
};
cb(rpc_payload_event);
cb(evt.clone());
self.prebuffered_responses.remove(&rpc_id); // Clear the buffer after calling
}
}
_ => {
tracing::error!("Unknown `RpcStreamEvent`");
}
};
} else if let Some(cb) = self.response_handlers.get_mut(&rpc_id) {
cb(evt.clone());
handled = true;
}
if matches!(
evt,
RpcStreamEvent::End { .. } | RpcStreamEvent::Error { .. }
) {
self.response_handlers.remove(&rpc_id);
}
}
if !handled && let Some(cb) = self.catch_all_response_handler.as_mut() {
cb(evt);
}
Ok(())
})?;
Ok(())
}
pub fn get_remaining_response_handlers(&self) -> usize {
self.response_handlers.len()
}
}