From f022a77f97c169807ae098e101a29301c0d19fbd Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Mon, 12 Sep 2022 17:43:10 +0200
Subject: Add documentation

---
 src/message.rs | 52 +++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 49 insertions(+), 3 deletions(-)

(limited to 'src/message.rs')

diff --git a/src/message.rs b/src/message.rs
index ec9433a..2b2b75f 100644
--- a/src/message.rs
+++ b/src/message.rs
@@ -41,17 +41,31 @@ pub const PRIO_SECONDARY: RequestPriority = 0x01;
 
 // ----
 
-#[derive(Clone, Copy)]
-pub struct OrderTagStream(u64);
+/// An order tag can be added to a message or a response to indicate
+/// whether it should be sent after or before other messages with order tags
+/// referencing a same stream
 #[derive(Clone, Copy, Serialize, Deserialize, Debug)]
 pub struct OrderTag(pub(crate) u64, pub(crate) u64);
 
+/// A stream is an opaque identifier that defines a set of messages
+/// or responses that are ordered wrt one another using to order tags.
+#[derive(Clone, Copy)]
+pub struct OrderTagStream(u64);
+
+
 impl OrderTag {
+	/// Create a new stream from which to generate order tags. Example:
+	///	```
+	///	let stream = OrderTag.stream();
+	///	let tag_1 = stream.order(1);
+	///	let tag_2 = stream.order(2);
+	///	```
 	pub fn stream() -> OrderTagStream {
 		OrderTagStream(thread_rng().gen())
 	}
 }
 impl OrderTagStream {
+	/// Create the order tag for message `order` in this stream
 	pub fn order(&self, order: u64) -> OrderTag {
 		OrderTag(self.0, order)
 	}
@@ -60,8 +74,10 @@ impl OrderTagStream {
 // ----
 
 /// This trait should be implemented by all messages your application
-/// wants to handle
+/// wants to handle. It specifies which data type should be sent
+/// as a response to this message in the RPC protocol.
 pub trait Message: Serialize + for<'de> Deserialize<'de> + Send + Sync + 'static {
+	/// The type of the response that is sent in response to this message
 	type Response: Serialize + for<'de> Deserialize<'de> + Send + Sync + 'static;
 }
 
@@ -79,10 +95,13 @@ pub struct Req<M: Message> {
 }
 
 impl<M: Message> Req<M> {
+	/// Creates a new request from a base message `M`
 	pub fn new(v: M) -> Result<Self, Error> {
 		Ok(v.into_req()?)
 	}
 
+	/// Attach a stream to message in request, where the stream is streamed
+	/// from a fixed `Bytes` buffer
 	pub fn with_stream_from_buffer(self, b: Bytes) -> Self {
 		Self {
 			stream: AttachedStream::Fixed(b),
@@ -90,6 +109,10 @@ impl<M: Message> Req<M> {
 		}
 	}
 
+	/// Attach a stream to message in request, where the stream is
+	/// an instance of `ByteStream`. Note than when a `Req<M>` has an attached
+	/// stream which is a `ByteStream` instance, it can no longer be cloned
+	/// to be sent to different nodes (`.clone()` will panic)
 	pub fn with_stream(self, b: ByteStream) -> Self {
 		Self {
 			stream: AttachedStream::Stream(b),
@@ -97,6 +120,8 @@ impl<M: Message> Req<M> {
 		}
 	}
 
+	/// Add an order tag to this request to indicate in which order it should
+	/// be sent.
 	pub fn with_order_tag(self, order_tag: OrderTag) -> Self {
 		Self {
 			order_tag: Some(order_tag),
@@ -104,10 +129,12 @@ impl<M: Message> Req<M> {
 		}
 	}
 
+	/// Get a reference to the message `M` contained in this request
 	pub fn msg(&self) -> &M {
 		&self.msg
 	}
 
+	/// Takes out the stream attached to this request, if any
 	pub fn take_stream(&mut self) -> Option<ByteStream> {
 		std::mem::replace(&mut self.stream, AttachedStream::None).into_stream()
 	}
@@ -142,8 +169,14 @@ impl<M: Message> Req<M> {
 	}
 }
 
+/// `IntoReq<M>` represents any object that can be transformed into `Req<M>`
 pub trait IntoReq<M: Message> {
+	/// Transform the object into a `Req<M>`, serializing the message M
+	/// to be sent to remote nodes
 	fn into_req(self) -> Result<Req<M>, rmp_serde::encode::Error>;
+	/// Transform the object into a `Req<M>`, skipping the serialization
+	/// of message M, in the case we are not sending this RPC message to
+	/// a remote node
 	fn into_req_local(self) -> Req<M>;
 }
 
@@ -220,6 +253,7 @@ pub struct Resp<M: Message> {
 }
 
 impl<M: Message> Resp<M> {
+	/// Creates a new response from a base response message
 	pub fn new(v: M::Response) -> Self {
 		Resp {
 			_phantom: Default::default(),
@@ -229,6 +263,8 @@ impl<M: Message> Resp<M> {
 		}
 	}
 
+	/// Attach a stream to message in response, where the stream is streamed
+	/// from a fixed `Bytes` buffer
 	pub fn with_stream_from_buffer(self, b: Bytes) -> Self {
 		Self {
 			stream: AttachedStream::Fixed(b),
@@ -236,6 +272,8 @@ impl<M: Message> Resp<M> {
 		}
 	}
 
+	/// Attach a stream to message in response, where the stream is
+	/// an instance of `ByteStream`.
 	pub fn with_stream(self, b: ByteStream) -> Self {
 		Self {
 			stream: AttachedStream::Stream(b),
@@ -243,6 +281,8 @@ impl<M: Message> Resp<M> {
 		}
 	}
 
+	/// Add an order tag to this response to indicate in which order it should
+	/// be sent.
 	pub fn with_order_tag(self, order_tag: OrderTag) -> Self {
 		Self {
 			order_tag: Some(order_tag),
@@ -250,14 +290,20 @@ impl<M: Message> Resp<M> {
 		}
 	}
 
+	/// Get a reference to the response message contained in this request
 	pub fn msg(&self) -> &M::Response {
 		&self.msg
 	}
 
+	/// Transforms the `Resp<M>` into the response message it contains,
+	/// dropping everything else (including attached data stream)
 	pub fn into_msg(self) -> M::Response {
 		self.msg
 	}
 
+	/// Transforms the `Resp<M>` into, on the one side, the response message
+	/// it contains, and on the other side, the associated data stream
+	/// if it exists
 	pub fn into_parts(self) -> (M::Response, Option<ByteStream>) {
 		(self.msg, self.stream.into_stream())
 	}
-- 
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