From d19748f3d18c739a469e68f6c381bf7917acccd5 Mon Sep 17 00:00:00 2001
From: Tait Hoyem <tait@tait.tech>
Date: Thu, 21 Mar 2024 10:37:20 -0600
Subject: [PATCH] Implement generic first parameters for Handler

Combined with the new atspi_event_handler function, automatically
convert a HandlerService for a specific event type, into a generic event
handler, which checks if the event type matches before passing it into
the inner event handler.

It will either: transform the event into its specific type, or abort
the calling of the service with an
`OdiliaError::AtspiError(AtspiError::Conversion(...))`

Clipppy and fmt
---
 odilia/Cargo.toml   |  2 +-
 odilia/src/tower.rs | 22 +++++++++++++++++++---
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/odilia/Cargo.toml b/odilia/Cargo.toml
index 9f0e8e60..f864bba4 100644
--- a/odilia/Cargo.toml
+++ b/odilia/Cargo.toml
@@ -56,7 +56,7 @@ zbus.workspace = true
 odilia-notify = { version = "0.1.0", path = "../odilia-notify" }
 clap = { version = "4.5.1", features = ["derive"] }
 tokio-util.workspace=true
-tower = { version = "0.4.13", features = ["util"] }
+tower = { version = "0.4.13", features = ["util", "filter"] }
 
 [dev-dependencies]
 lazy_static = "1.4.0"
diff --git a/odilia/src/tower.rs b/odilia/src/tower.rs
index 7a77762c..064a8c89 100644
--- a/odilia/src/tower.rs
+++ b/odilia/src/tower.rs
@@ -1,3 +1,5 @@
+#![allow(dead_code)]
+
 use odilia_common::errors::OdiliaError;
 use std::future::Future;
 use std::marker::PhantomData;
@@ -5,6 +7,7 @@ use std::marker::PhantomData;
 use std::task::Context;
 use std::task::Poll;
 
+use tower::filter::Filter;
 use tower::Service;
 
 type Response = ();
@@ -19,6 +22,19 @@ pub trait Handler<T, S, E>: Clone {
 	fn call(self, req: E, state: S) -> Self::Future;
 }
 
+fn is_right_type<E: TryFrom<Request, Error = Error>>(req: Request) -> Result<E, Error> {
+	req.try_into()
+}
+
+fn atspi_event_handler<H, T, S, E>(h: HandlerService<H, T, S, E>) -> impl Service<Request>
+where
+	S: Clone,
+	E: TryFrom<Request, Error = Error>,
+	H: Handler<T, S, E>,
+{
+	Filter::new(h, is_right_type::<E>)
+}
+
 impl<F, Fut, S, E> Handler<((),), S, E> for F
 where
 	F: FnOnce() -> Fut + Clone + Send + 'static,
@@ -81,7 +97,7 @@ pub struct HandlerService<H, T, S, E> {
 	_marker: PhantomData<fn(E) -> T>,
 }
 
-impl<H, T, S, E> Service<Request> for HandlerService<H, T, S, E>
+impl<H, T, S, E> Service<E> for HandlerService<H, T, S, E>
 where
 	H: Handler<T, S, E>,
 	S: Clone,
@@ -95,9 +111,9 @@ where
 	fn poll_ready(&mut self, _ctx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
 		Poll::Ready(Ok(()))
 	}
-	fn call(&mut self, req: Request) -> Self::Future {
+	fn call(&mut self, req: E) -> Self::Future {
 		let handler = self.handler.clone();
 		let state = self.state.clone();
-		handler.call(req.try_into().expect("Must be converted from a certain type"), state)
+		handler.call(req, state)
 	}
 }