Rework MessageHandler to use associated types.

client/src/dispatcher.rs

@@ -35,15 +35,15 @@ impl From<ControlRequest> for Message {
 
 /// Pairs together a message and its handler as chosen by the dispatcher.
 /// Implements Job so as to be scheduled on an executor.
-struct DispatchedMessage<M, H> {
+struct DispatchedMessage<H, M> {
   message: M,
   handler: H,
 }
 
-impl<M, H> Job for DispatchedMessage<M, H>
+impl<H> Job for DispatchedMessage<H, <H as MessageHandler>::Message>
 where
-  M: Debug + Send,
-  H: MessageHandler<M> + Send,
+  H: MessageHandler + Send,
+  <H as MessageHandler>::Message: Debug + Send,
 {
   fn execute(self: Box<Self>, context: &Context) {
     if let Err(error) = self.handler.run(context, &self.message) {

client/src/handlers/room_list_request_handler.rs

@@ -1,5 +1,4 @@
-use std::io;
-
+use anyhow::Context as AnyhowContext;
 use solstice_proto::ServerRequest;
 
 use crate::context::Context;
@@ -8,12 +7,15 @@ use crate::message_handler::MessageHandler;
 #[derive(Debug, Default)]
 pub struct RoomListRequestHandler;
 
-impl MessageHandler<()> for RoomListRequestHandler {
-  fn run(self, context: &Context, message: &()) -> io::Result<()> {
+impl MessageHandler for RoomListRequestHandler {
+  type Message = ();
+
+  fn run(self, context: &Context, _message: &()) -> anyhow::Result<()> {
     // TODO: Send `RoomListResponse` back over socket.
     context
       .server_request_tx
-      .blocking_send(ServerRequest::RoomListRequest);
+      .blocking_send(ServerRequest::RoomListRequest)
+      .context("sending server request")?;
     Ok(())
   }
 

client/src/handlers/room_message_request_handler.rs

@@ -1,5 +1,4 @@
-use std::io;
-
+use anyhow::Context as AnyhowContext;
 use solstice_proto::server;
 use solstice_proto::ServerRequest;
 
@@ -10,12 +9,14 @@ use crate::message_handler::MessageHandler;
 #[derive(Debug, Default)]
 pub struct RoomMessageRequestHandler;
 
-impl MessageHandler<control::RoomMessageRequest> for RoomMessageRequestHandler {
+impl MessageHandler for RoomMessageRequestHandler {
+  type Message = control::RoomMessageRequest;
+
   fn run(
     self,
     context: &Context,
     message: &control::RoomMessageRequest,
-  ) -> io::Result<()> {
+  ) -> anyhow::Result<()> {
     context
       .server_request_tx
       .blocking_send(ServerRequest::RoomMessageRequest(
@@ -23,7 +24,8 @@ impl MessageHandler<control::RoomMessageRequest> for RoomMessageRequestHandler {
           room_name: message.room_name.clone(),
           message: message.message.clone(),
         },
-      ));
+      ))
+      .context("sending server request")?;
     Ok(())
   }
 

client/src/handlers/set_privileged_users_handler.rs

@@ -1,5 +1,3 @@
-use std::io;
-
 use solstice_proto::server::PrivilegedUsersResponse;
 
 use crate::context::Context;
@@ -8,12 +6,14 @@ use crate::message_handler::MessageHandler;
 #[derive(Debug, Default)]
 pub struct SetPrivilegedUsersHandler;
 
-impl MessageHandler<PrivilegedUsersResponse> for SetPrivilegedUsersHandler {
+impl MessageHandler for SetPrivilegedUsersHandler {
+  type Message = PrivilegedUsersResponse;
+
   fn run(
     self,
     context: &Context,
     message: &PrivilegedUsersResponse,
-  ) -> io::Result<()> {
+  ) -> anyhow::Result<()> {
     let users = message.users.clone();
     context.state.lock().users.set_all_privileged(users);
     Ok(())

client/src/handlers/set_room_list_handler.rs

@@ -1,5 +1,4 @@
-use std::io;
-
+use anyhow::Context as AnyhowContext;
 use solstice_proto::server::RoomListResponse;
 
 use crate::context::Context;
@@ -9,12 +8,14 @@ use crate::message_handler::MessageHandler;
 #[derive(Debug, Default)]
 pub struct SetRoomListHandler;
 
-impl MessageHandler<RoomListResponse> for SetRoomListHandler {
+impl MessageHandler for SetRoomListHandler {
+  type Message = RoomListResponse;
+
   fn run(
     self,
     context: &Context,
     message: &RoomListResponse,
-  ) -> io::Result<()> {
+  ) -> anyhow::Result<()> {
     let response = (*message).clone();
     {
       let mut guard = context.state.lock();
@@ -27,8 +28,10 @@ impl MessageHandler<RoomListResponse> for SetRoomListHandler {
           rooms,
         });
 
-      // TODO: decide what to do with errors here.
-      context.control_response_tx.blocking_send(control_response);
+      context
+        .control_response_tx
+        .blocking_send(control_response)
+        .context("sending control response")?;
     }
     Ok(())
   }

client/src/message_handler.rs

@@ -1,4 +1,4 @@
-use std::io;
+use std::fmt::Debug;
 
 use crate::context::Context;
 
@@ -6,9 +6,15 @@ use crate::context::Context;
 ///
 /// Message types are mapped to handler types by Dispatcher.
 /// This trait is intended to allow composing handler logic.
-pub trait MessageHandler<Message> {
+pub trait MessageHandler: Debug {
+  type Message;
+
   /// Attempts to handle the given message against the given context.
-  fn run(self, context: &Context, message: &Message) -> io::Result<()>;
+  fn run(
+    self,
+    context: &Context,
+    message: &Self::Message,
+  ) -> anyhow::Result<()>;
 
   /// Returns the name of this handler type.
   fn name() -> String;