doc: add wrpc-transport docs

SPEC.md

@@ -2,7 +2,7 @@
 
 wRPC is a transport-agnostic protocol designed for asynchronous transmit of WIT function call invocations over network and other means of communication.
 
-wRPC follows client-server model, where peers may *serve* function (servers) and method calls invoked by the other peers (clients).
+wRPC follows client-server model, where peers (servers) may *serve* function and method calls invoked by the other peers (clients).
 
 wRPC relies on [component model value definition encoding] for data encoding on the wire.
 

crates/transport/src/frame/codec.rs

@@ -6,6 +6,7 @@ use wasm_tokio::{Leb128DecoderU32, Leb128DecoderU64, Leb128Encoder};
 
 use super::{Frame, FrameRef};
 
+/// [Frame] decoder
 pub struct Decoder {
     path: Option<Vec<usize>>,
     path_cap: usize,
@@ -15,6 +16,7 @@ pub struct Decoder {
 }
 
 impl Decoder {
+    /// Construct a new [Frame] decoder
     #[must_use]
     pub fn new(max_depth: u32, max_size: u64) -> Self {
         Self {
@@ -125,6 +127,7 @@ impl tokio_util::codec::Decoder for Decoder {
     }
 }
 
+/// [Frame] encoder
 pub struct Encoder;
 
 impl tokio_util::codec::Encoder<FrameRef<'_>> for Encoder {

crates/transport/src/frame/conn/accept.rs

@@ -3,6 +3,7 @@ use core::ops::{Deref, DerefMut};
 
 use tokio::io::{AsyncRead, AsyncWrite};
 
+/// Accepts connections on a transport
 pub trait Accept {
     /// Transport-specific invocation context
     type Context: Send + Sync + 'static;
@@ -13,11 +14,13 @@ pub trait Accept {
     /// Incoming byte stream
     type Incoming: AsyncRead + Send + Sync + Unpin + 'static;
 
+    /// Accept a connection returning a pair of streams and connection context
     fn accept(
         &self,
     ) -> impl Future<Output = std::io::Result<(Self::Context, Self::Outgoing, Self::Incoming)>>;
 }
 
+/// Wrapper returned by [`AcceptExt::map_context`]
 pub struct AcceptMapContext<T, F> {
     inner: T,
     f: F,
@@ -37,7 +40,9 @@ impl<T, F> DerefMut for AcceptMapContext<T, F> {
     }
 }
 
+/// Extension trait for [Accept]
 pub trait AcceptExt: Accept + Sized {
+    /// Maps [`Self::Context`](Accept::Context) to a type `T` using `F`
     fn map_context<T, F: Fn(Self::Context) -> T>(self, f: F) -> AcceptMapContext<Self, F> {
         AcceptMapContext { inner: self, f }
     }

crates/transport/src/frame/conn/client.rs

@@ -15,6 +15,7 @@ use wasm_tokio::{CoreNameEncoder, CoreVecEncoderBytes};
 use crate::frame::conn::{egress, ingress, Incoming, Outgoing};
 use crate::frame::PROTOCOL;
 
+/// Invoke function `func` on instance `instance`
 #[instrument(level = "trace", skip_all)]
 pub async fn invoke<P, I, O>(
     mut tx: O,

crates/transport/src/frame/conn/mod.rs

@@ -28,8 +28,9 @@ pub use accept::*;
 pub use client::*;
 pub use server::*;
 
+/// Index trie containing async stream subscriptions
 #[derive(Default)]
-pub enum IndexTrie {
+enum IndexTrie {
     #[default]
     Empty,
     Leaf {
@@ -123,6 +124,7 @@ impl<P: AsRef<[Option<usize>]>> FromIterator<P> for IndexTrie {
 }
 
 impl IndexTrie {
+    /// Takes the receiver
     #[instrument(level = "trace", skip(self), ret(level = "trace"))]
     fn take_rx(&mut self, path: &[usize]) -> Option<mpsc::Receiver<std::io::Result<Bytes>>> {
         let Some((i, path)) = path.split_first() else {
@@ -157,6 +159,7 @@ impl IndexTrie {
         }
     }
 
+    /// Gets a sender
     #[instrument(level = "trace", skip(self), ret(level = "trace"))]
     fn get_tx(&mut self, path: &[usize]) -> Option<mpsc::Sender<std::io::Result<Bytes>>> {
         let Some((i, path)) = path.split_first() else {
@@ -269,6 +272,7 @@ impl IndexTrie {
 }
 
 pin_project! {
+    /// Incoming framed stream
     #[project = IncomingProj]
     pub struct Incoming {
         #[pin]
@@ -332,6 +336,7 @@ impl AsyncRead for Incoming {
 }
 
 pin_project! {
+    /// Outgoing framed stream
     #[project = OutgoingProj]
     pub struct Outgoing {
         #[pin]

crates/transport/src/frame/conn/server.rs

@@ -19,6 +19,7 @@ use crate::frame::conn::{egress, ingress, Accept};
 use crate::frame::{Incoming, Outgoing};
 use crate::Serve;
 
+/// wRPC server for framed transports
 pub struct Server<C, I, O>(Mutex<HashMap<String, HashMap<String, mpsc::Sender<(C, I, O)>>>>);
 
 impl<C, I, O> Default for Server<C, I, O> {
@@ -27,10 +28,20 @@ impl<C, I, O> Default for Server<C, I, O> {
     }
 }
 
+/// Error returned by [`Server::accept`]
 pub enum AcceptError<C, I, O> {
+    /// I/O error
     IO(std::io::Error),
+    /// Protocol version is not supported
     UnsupportedVersion(u8),
-    UnhandledFunction { instance: String, name: String },
+    /// Function was not handled
+    UnhandledFunction {
+        /// Instance
+        instance: String,
+        /// Function name
+        name: String,
+    },
+    /// Message sending failed
     Send(mpsc::error::SendError<(C, I, O)>),
 }
 

crates/transport/src/frame/mod.rs

@@ -1,3 +1,5 @@
+//! wRPC transport stream framing
+
 use std::sync::Arc;
 
 use bytes::Bytes;
@@ -19,14 +21,18 @@ pub const PROTOCOL: u8 = 0;
 /// Owned wRPC frame
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub struct Frame {
+    /// Frame path
     pub path: Arc<[usize]>,
+    /// Frame data
     pub data: Bytes,
 }
 
 /// wRPC frame reference
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub struct FrameRef<'a> {
+    /// Frame path
     pub path: &'a [usize],
+    /// Frame data
     pub data: &'a [u8],
 }
 

crates/transport/src/frame/tcp.rs

@@ -1,3 +1,5 @@
+//! TCP transport
+
 use core::net::SocketAddr;
 
 use anyhow::{bail, Context as _};
@@ -9,8 +11,13 @@ use tracing::instrument;
 use crate::frame::{invoke, Accept, Incoming, Outgoing};
 use crate::Invoke;
 
+/// [Invoke] implementation in terms of a single [TcpStream]
+///
+/// [`Invoke::invoke`] can only be called once on [Invocation],
+/// repeated calls with return an error
 pub struct Invocation(std::sync::Mutex<Option<TcpStream>>);
 
+/// [Invoke] implementation of a TCP transport
 #[derive(Clone, Debug)]
 pub struct Client<T>(T);
 

crates/transport/src/frame/unix.rs

@@ -1,3 +1,5 @@
+//! Unix domain socket transport
+
 use std::path::{Path, PathBuf};
 
 use anyhow::{bail, Context as _};
@@ -9,8 +11,13 @@ use tracing::instrument;
 use crate::frame::{invoke, Accept, Incoming, Outgoing};
 use crate::Invoke;
 
+/// [Invoke] implementation in terms of a single [UnixStream]
+///
+/// [`Invoke::invoke`] can only be called once on [Invocation],
+/// repeated calls with return an error
 pub struct Invocation(std::sync::Mutex<Option<UnixStream>>);
 
+/// [Invoke] implementation of a Unix domain socket transport
 #[derive(Clone, Debug)]
 pub struct Client<T>(T);
 

crates/transport/src/invoke.rs

@@ -1,3 +1,5 @@
+//! wRPC transport client handle
+
 use core::future::Future;
 use core::mem;
 use core::pin::pin;
@@ -76,9 +78,12 @@ pub trait Invoke: Send + Sync {
         P: AsRef<[Option<usize>]> + Send + Sync;
 }
 
+/// Wrapper struct returned by [InvokeExt::timeout]
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub struct Timeout<'a, T: ?Sized> {
+    /// Inner [Invoke]
     pub inner: &'a T,
+    /// Invocation timeout
     pub timeout: Duration,
 }
 
@@ -108,9 +113,12 @@ impl<T: Invoke> Invoke for Timeout<'_, T> {
     }
 }
 
+/// Wrapper struct returned by [InvokeExt::timeout_owned]
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub struct TimeoutOwned<T> {
+    /// Inner [Invoke]
     pub inner: T,
+    /// Invocation timeout
     pub timeout: Duration,
 }
 
@@ -138,6 +146,7 @@ impl<T: Invoke> Invoke for TimeoutOwned<T> {
     }
 }
 
+/// Extension trait for [Invoke]
 pub trait InvokeExt: Invoke {
     /// Invoke function `func` on instance `instance` using typed `Params` and `Results`
     #[instrument(level = "trace", skip(self, cx, params, paths))]

crates/transport/src/lib.rs

@@ -1,4 +1,18 @@
 #![allow(clippy::type_complexity)]
+#![deny(missing_docs)]
+
+//! wRPC transport abstractions, codec and framing
+//!
+//! wRPC is an RPC framework based on [WIT](https://component-model.bytecodealliance.org/design/wit.html).
+//! It follows client-server model, where peers (servers) may serve function and method calls invoked by the other peers (clients).
+//!
+//! The two main abstractions on top of which wRPC is built are:
+//! - [Invoke] - the client-side handle to a wRPC transport, allowing clients to *invoke* WIT functions over wRPC transport
+//! - [Serve] - the server-side handle to a wRPC transport, allowing servers to *serve* WIT functions over wRPC transport
+//!
+//! Implementations of [Invoke] and [Serve] define transport-specific, multiplexed bidirectional byte stream types:
+//! - [`Invoke::Incoming`] and [`Serve::Incoming`] represent the stream *incoming* from a peer.
+//! - [`Invoke::Outgoing`] and [`Serve::Outgoing`] represent the stream *outgoing* to a peer.
 
 pub mod frame;
 pub mod invoke;
@@ -27,20 +41,25 @@ use bytes::BytesMut;
 use tokio::io::{AsyncRead, ReadBuf};
 use tracing::trace;
 
+/// Internal workaround trait
+///
+/// This is an internal trait used as a workaround for
+/// https://github.com/rust-lang/rust/issues/63033
 #[doc(hidden)]
-// This is an internal trait used as a workaround for
-// https://github.com/rust-lang/rust/issues/63033
 pub trait Captures<'a> {}
 
 impl<'a, T: ?Sized> Captures<'a> for T {}
 
-/// `Index` implementations are capable of multiplexing underlying connections using a particular
-/// structural `path`
+/// Multiplexes streams
+///
+/// Implementations of this trait define multiplexing for underlying connections
+/// using a particular structural `path`
 pub trait Index<T> {
     /// Index the entity using a structural `path`
     fn index(&self, path: &[usize]) -> anyhow::Result<T>;
 }
 
+/// Buffered incoming stream used for decoding values
 pub struct Incoming<T> {
     buffer: BytesMut,
     inner: T,

crates/transport/src/serve.rs

@@ -1,3 +1,5 @@
+//! wRPC transport server handle
+
 use core::future::Future;
 use core::mem;
 use core::pin::Pin;
@@ -38,6 +40,7 @@ pub trait Serve: Sync {
     > + Send;
 }
 
+/// Extension trait for [Serve]
 pub trait ServeExt: Serve {
     /// Serve function `func` from instance `instance` using typed `Params` and `Results`
     #[instrument(level = "trace", skip(self, paths))]