From 4efc467d8407e699676e7dde163cc18dbd31d95b Mon Sep 17 00:00:00 2001
From: Giacomo Pasini <Zeegomo@users.noreply.github.com>
Date: Tue, 17 Jan 2023 14:45:22 +0100
Subject: [PATCH] Relax type bounds (#17)

* relax type bounds

* remove Send bound on NoOperator

* fix tests

* remove bound on service message

* re-add type bound on Relay

* remove duplicate PhantomBound
---
 overwatch-rs/src/overwatch/handle.rs |  6 +++---
 overwatch-rs/src/services/handle.rs  | 12 ++++++------
 overwatch-rs/src/services/mod.rs     |  2 +-
 overwatch-rs/src/services/relay.rs   | 27 +++++++++++++++------------
 overwatch-rs/src/services/state.rs   | 15 ++++++++++++---
 5 files changed, 37 insertions(+), 25 deletions(-)

diff --git a/overwatch-rs/src/overwatch/handle.rs b/overwatch-rs/src/overwatch/handle.rs
index 1b52d82..fe64876 100644
--- a/overwatch-rs/src/overwatch/handle.rs
+++ b/overwatch-rs/src/overwatch/handle.rs
@@ -3,13 +3,13 @@
 // crates
 use crate::overwatch::commands::{OverwatchCommand, OverwatchLifeCycleCommand, SettingsCommand};
 use crate::overwatch::Services;
+use crate::services::ServiceData;
 use tokio::runtime::Handle;
 use tokio::sync::mpsc::Sender;
 use tracing::{error, info, instrument};
 
 // internal
 use crate::services::relay::Relay;
-use crate::services::ServiceCore;
 
 /// Handler object over the main Overwatch runner
 /// It handles communications to the main Overwatch runner.
@@ -28,8 +28,8 @@ impl OverwatchHandle {
         }
     }
 
-    /// Request for a relay to an specific service by type
-    pub fn relay<S: ServiceCore>(&self) -> Relay<S> {
+    /// Request for a relay
+    pub fn relay<S: ServiceData>(&self) -> Relay<S> {
         Relay::new(self.clone())
     }
 
diff --git a/overwatch-rs/src/services/handle.rs b/overwatch-rs/src/services/handle.rs
index af392ca..a5085dc 100644
--- a/overwatch-rs/src/services/handle.rs
+++ b/overwatch-rs/src/services/handle.rs
@@ -6,14 +6,14 @@ use crate::overwatch::handle::OverwatchHandle;
 use crate::services::relay::{relay, InboundRelay, OutboundRelay};
 use crate::services::settings::{SettingsNotifier, SettingsUpdater};
 use crate::services::state::{StateHandle, StateOperator, StateUpdater};
-use crate::services::{ServiceCore, ServiceId, ServiceState};
+use crate::services::{ServiceCore, ServiceData, ServiceId, ServiceState};
 
 // TODO: Abstract handle over state, to diferentiate when the service is running and when it is not
 // that way we can expose a better API depending on what is happenning. Would get rid of the probably
 // unnecessary Option and cloning.
 /// Service handle
 /// This is used to access different parts of the service
-pub struct ServiceHandle<S: ServiceCore> {
+pub struct ServiceHandle<S: ServiceData> {
     /// Message channel relay
     /// Would be None if service is not running
     /// Will contain the channel if service is running
@@ -26,7 +26,7 @@ pub struct ServiceHandle<S: ServiceCore> {
 
 /// Service core resources
 /// It contains whatever is necessary to start a new service runner
-pub struct ServiceStateHandle<S: ServiceCore> {
+pub struct ServiceStateHandle<S: ServiceData> {
     /// Relay channel to communicate with the service runner
     pub inbound_relay: InboundRelay<S::Message>,
     /// Overwatch handle
@@ -38,12 +38,12 @@ pub struct ServiceStateHandle<S: ServiceCore> {
 
 /// Main service executor
 /// It is the object that hold the necessary information for the service to run
-pub struct ServiceRunner<S: ServiceCore> {
+pub struct ServiceRunner<S: ServiceData> {
     service_state: ServiceStateHandle<S>,
     state_handle: StateHandle<S::State, S::StateOperator>,
 }
 
-impl<S: ServiceCore> ServiceHandle<S> {
+impl<S: ServiceData> ServiceHandle<S> {
     pub fn new(
         settings: S::Settings,
         overwatch_handle: OverwatchHandle,
@@ -109,7 +109,7 @@ impl<S: ServiceCore> ServiceHandle<S> {
     }
 }
 
-impl<S: ServiceCore> ServiceStateHandle<S> {
+impl<S: ServiceData> ServiceStateHandle<S> {
     pub fn id(&self) -> ServiceId {
         S::SERVICE_ID
     }
diff --git a/overwatch-rs/src/services/mod.rs b/overwatch-rs/src/services/mod.rs
index e107b38..5b21843 100644
--- a/overwatch-rs/src/services/mod.rs
+++ b/overwatch-rs/src/services/mod.rs
@@ -36,7 +36,7 @@ pub trait ServiceData {
     /// State operator
     type StateOperator: StateOperator<StateInput = Self::State> + Clone;
     /// Service messages that the service itself understands and can react to
-    type Message: RelayMessage + Debug + Send + Sync;
+    type Message: RelayMessage + Debug;
 }
 
 /// Main trait for Services initialization and main loop hook
diff --git a/overwatch-rs/src/services/relay.rs b/overwatch-rs/src/services/relay.rs
index 9f17fb4..f250472 100644
--- a/overwatch-rs/src/services/relay.rs
+++ b/overwatch-rs/src/services/relay.rs
@@ -14,7 +14,7 @@ use tracing::{error, instrument};
 // internal
 use crate::overwatch::commands::{OverwatchCommand, RelayCommand, ReplyChannel};
 use crate::overwatch::handle::OverwatchHandle;
-use crate::services::{ServiceCore, ServiceId};
+use crate::services::{ServiceData, ServiceId};
 
 #[derive(Error, Debug)]
 pub enum RelayError {
@@ -66,20 +66,21 @@ pub struct OutboundRelay<M> {
 }
 
 #[derive(Debug)]
-pub struct Relay<S: ServiceCore> {
-    _marker: PhantomData<S>,
+pub struct Relay<S> {
     overwatch_handle: OverwatchHandle,
+    _bound: PhantomBound<S>,
 }
 
-impl<S: ServiceCore> Clone for Relay<S> {
-    fn clone(&self) -> Self {
-        Self {
-            _marker: PhantomData,
-            overwatch_handle: self.overwatch_handle.clone(),
-        }
-    }
+// Like PhantomData<T> but without
+// ownership of T
+#[derive(Debug)]
+struct PhantomBound<T> {
+    _inner: PhantomData<*const T>,
 }
 
+unsafe impl<T> Send for PhantomBound<T> {}
+unsafe impl<T> Sync for PhantomBound<T> {}
+
 impl<M> Clone for OutboundRelay<M> {
     fn clone(&self) -> Self {
         Self {
@@ -142,11 +143,13 @@ impl<M: Send + 'static> OutboundRelay<M> {
     }
 }
 
-impl<S: ServiceCore> Relay<S> {
+impl<S: ServiceData> Relay<S> {
     pub fn new(overwatch_handle: OverwatchHandle) -> Self {
         Self {
             overwatch_handle,
-            _marker: PhantomData,
+            _bound: PhantomBound {
+                _inner: PhantomData,
+            },
         }
     }
 
diff --git a/overwatch-rs/src/services/state.rs b/overwatch-rs/src/services/state.rs
index 24ceefa..f591f61 100644
--- a/overwatch-rs/src/services/state.rs
+++ b/overwatch-rs/src/services/state.rs
@@ -1,7 +1,7 @@
 // std
 use std::marker::PhantomData;
+use std::pin::Pin;
 use std::sync::Arc;
-
 // crates
 use async_trait::async_trait;
 use futures::StreamExt;
@@ -54,14 +54,23 @@ impl<T> Clone for NoOperator<T> {
 }
 
 #[async_trait]
-impl<StateInput: ServiceState + Send> StateOperator for NoOperator<StateInput> {
+impl<StateInput: ServiceState> StateOperator for NoOperator<StateInput> {
     type StateInput = StateInput;
 
     fn from_settings<Settings>(_settings: Settings) -> Self {
         NoOperator(PhantomData::default())
     }
 
-    async fn run(&mut self, _state: Self::StateInput) {}
+    fn run<'borrow, 'fut>(
+        &'borrow mut self,
+        _state: Self::StateInput,
+    ) -> Pin<Box<dyn std::future::Future<Output = ()> + Send + 'fut>>
+    where
+        'borrow: 'fut,
+        Self: 'fut,
+    {
+        Box::pin(async {})
+    }
 }
 
 /// Empty state