[package]
name = "ump-server"
version = "0.2.0"
edition = "2021"
license = "0BSD"
categories = [ "concurrency", "asynchronous" ]
keywords = [ "channel", "threads", "sync", "message-passing" ]
repository = "https://repos.qrnch.tech/pub/ump-server"
description = "Server message dispatch loop for ump."
rust-version = "1.56"
exclude = [
  ".fossil-settings",
  ".efiles",
  ".fslckout",
  "www",
  "rustfmt.toml"
]

[features]
default = ["tokio"]
tokio = ["dep:tokio", "dep:async-trait"]

[dependencies]
async-trait = { version = "0.1.77", optional = true }
# ToDo: Shouldn't need "net", but without it the docs will not build.
#       Once this is fixed in tokio, remove "net".
tokio = { version = "1.35.1", features = ["net", "rt"], optional = true }
ump = { version = "0.12.1" }

[dev-dependencies]
tokio-test = { version = "0.4.3" }

[package.metadata.docs.rs]
all-features = true
rustdoc-args = ["--cfg", "docsrs", "--generate-link-to-definition"]

# Server message dispatch loop for ump

The _ump-server_ crate is a server message dispatch abstraction for
[ump](https://crates.io/crates/ump).

//! ump server running in an async task.
//!
//! ```
//! # tokio_test::block_on(async {
//! use std::ops::ControlFlow;
//! use ump_server::{
//!   async_trait,
//!   task::{Handler, spawn},
//!   ump::ReplyContext
//! };
//! enum Request {
//!   Add(usize, usize)
//! }
//! enum Reply {
//!   Sum(usize)
//! }
//! enum MyError { }
//! struct MyHandler {};
//! #[async_trait]
//! impl Handler<Request, Reply, MyError, ()> for MyHandler {
//!   async fn proc_req(
//!     &mut self,
//!     msg: Request,
//!     rctx: ReplyContext<Reply, MyError>
//!   ) -> ControlFlow<(), ()> {
//!     match msg {
//!       Request::Add(a, b) => {
//!         rctx.reply(Reply::Sum(a + b));
//!         ControlFlow::Continue(())
//!       }
//!     }
//!   }
//! }
//!
//! let (clnt, jh) = spawn(|clnt| {
//!   MyHandler { }
//! });
//!
//! let Ok(Reply::Sum(sum)) = clnt.areq(Request::Add(3, 7)).await else {
//!   panic!("Unexpected reply");
//! };
//! assert_eq!(sum, 10);
//!
//! // Dropping the only client will terminate the dispatch loop
//! drop(clnt);
//!
//! let _ = jh.await;
//! # });
//! ```

use std::ops::ControlFlow;

use tokio::task::{self, JoinHandle};

use async_trait::async_trait;

}

/// Run a task which will process incoming messages from an ump server
/// end-point.
///
/// See top module's documentation for an overview of the [dispatch
/// loop](crate#dispatch-loop).
pub fn spawn<S, R, E, RV, F>(
  hbldr: impl FnOnce(&Client<S, R, E>) -> F
) -> (Client<S, R, E>, JoinHandle<Option<RV>>)
where
  S: 'static + Send,
  R: 'static + Send,
  E: 'static + Send,
  RV: 'static + Send,
  F: Handler<S, R, E, RV> + Send + 'static
{
  let (server, client) = channel();

  let mut handler = hbldr(&client);

  let weak_client = client.weak();
  let jh = task::spawn(async move {
    handler.init(weak_client);
    let ret = loop {
      let (msg, rctx) = match server.async_wait().await {
        Ok(d) => d,
        Err(_) => break None

//! ump server running on a thread.
//!
//! ```
//! use std::ops::ControlFlow;
//! use ump_server::{
//!   thread::{Handler, spawn},
//!   ump::ReplyContext
//! };
//! enum Request {
//!   Add(usize, usize)
//! }
//! enum Reply {
//!   Sum(usize)
//! }
//! enum MyError { }
//! struct MyHandler {};
//! impl Handler<Request, Reply, MyError, ()> for MyHandler {
//!   fn proc_req(
//!     &mut self,
//!     msg: Request,
//!     rctx: ReplyContext<Reply, MyError>
//!   ) -> ControlFlow<(), ()> {
//!     match msg {
//!       Request::Add(a, b) => {
//!         rctx.reply(Reply::Sum(a + b));
//!         ControlFlow::Continue(())
//!       }
//!     }
//!   }
//! }
//!
//! let (clnt, jh) = spawn(|clnt| {
//!   MyHandler { }
//! });
//!
//! let Ok(Reply::Sum(sum)) = clnt.req(Request::Add(3, 7)) else {
//!   panic!("Unexpected reply");
//! };
//! assert_eq!(sum, 10);
//!
//! // Dropping the only client will terminate the dispatch loop
//! drop(clnt);
//!
//! let _ = jh.join();
//! ```

use std::{ops::ControlFlow, thread};

use super::{channel, Client, ReplyContext};

/// Message processing trait for a threaded handler.
pub trait Handler<S, R, E, RV> {

}

/// Run a thread which will process incoming messages from an ump server
/// end-point.
///
/// See top module's documentation for an overview of the [dispatch
/// loop](crate#dispatch-loop).
pub fn spawn<S, R, E, RV, F>(
  hbldr: impl FnOnce(&Client<S, R, E>) -> F
) -> (Client<S, R, E>, thread::JoinHandle<Option<RV>>)
where
  S: 'static + Send,
  R: 'static + Send,
  E: 'static + Send,
  RV: 'static + Send,
  F: Handler<S, R, E, RV> + Send + 'static
{
  let (server, client) = channel();

  let mut handler = hbldr(&client);

  let weak_client = client.weak();
  let jh = thread::spawn(move || {
    handler.init(weak_client);
    let ret = loop {
      let (msg, rctx) = match server.wait() {
        Ok(d) => d,
        Err(_) => break None

mod common;

use common::{Reply, Request, ThreadedServer};

// Terminate the dispatcher loop by dropping the only client.
#[test]
fn no_clients() {

  let (clnt, jh) = ump_server::spawn_thread(|_clnt| ThreadedServer {});

  // Drop the (only) client, which should cause dispatch loop to terminate.
  drop(clnt);

  // Termination by clients disappearing should return None
  assert_eq!(jh.join().unwrap(), None);
}

// Terminate the dispatcher loop by explicitly requesting it to terminate from
// its handler.
#[test]
fn handler_req_term() {

  let (clnt, jh) = ump_server::spawn_thread(|_clnt| ThreadedServer {});

  assert_eq!(clnt.req(Request::Add(2, 4)).unwrap(), Reply::Sum(6));
  assert_eq!(clnt.req(Request::Croak).unwrap(), Reply::OkIWillCroak);

  assert_eq!(jh.join().unwrap(), Some(42));
}

# Change Log

## [Unreleased]

[Details](/vdiff?from=ump-server-0.2.0&to=trunk)

### Added

### Changed

### Removed

---

## [0.2.0] - 2024-01-28

[Details](/vdiff?from=ump-server-0.1.0&to=ump-server-0.2.0)

### Added

- Add `net` feature to `tokio` dependency to work around what appears to be a
  bug in tokio which prohibits doc generation without it.

### Changed

- Instead of taking in an `impl Handler` into the `{thread,task}::spawn()`
  function, take in a closure that returns the handler.  A reference to the
  handler channel's client endpoint is passed to the closure, which makes it
  possible to store `Client`/`WeakClient` in the handler, without involving an
  `Option` (or similar).

---

## [0.1.0] - 2023-10-03

Initial release.

# ump-server

The _ump-server_ crate is a server message dispatch abstraction for
[ump](https://repos.qrnch.tech/pub/ump).


## Feature labels in documentation

The crate's documentation uses automatically generated feature labels, which
currently requires nightly featuers.  To build the documentation locally use:

```
RUSTFLAGS="--cfg docsrs" RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc --all-features
```


## Change log

The details of changes can always be found in the timeline, but for a
high-level view of changes between released versions there's a manually
maintained [Change Log](./changelog.md).