From 5b7b4f1e12c0c9d8e2c555822d91d3301a4366ff Mon Sep 17 00:00:00 2001
From: Daniel Griffen <daniel@griffen.io>
Date: Sun, 28 Oct 2018 19:32:00 -0700
Subject: [PATCH] make cancellation a type property

---
 src/lib.rs          | 55 ++++++++++++++++++++++++++++++++-------
 tests/dyn_events.rs | 63 +++++++++++++++++++++++++--------------------
 2 files changed, 80 insertions(+), 38 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 105b7ef..58d854c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -56,14 +56,6 @@ macro_rules! post_event {
             // event setup, this may evaluate to any type.
             let event: &mut _ = $e;
             {
-                // it is a logic error for an event's cancellability to change based on its value.
-                static CANCELLABLE: ::std::sync::atomic::AtomicBool = ::std::sync::atomic::ATOMIC_BOOL_INIT;
-                static CANCELLABLE_INIT: ::std::sync::Once = ::std::sync::ONCE_INIT;
-                CANCELLABLE_INIT.call_once(|| {
-                    CANCELLABLE.store(<$crate::Event>::cancellable(event), std::sync::atomic::Ordering::Relaxed);
-                });
-                let cancellable = CANCELLABLE.load(std::sync::atomic::Ordering::Relaxed);
-
                 // event type setup
                 static EVENT_ID: ::std::sync::atomic::AtomicUsize = ::std::sync::atomic::ATOMIC_USIZE_INIT;
                 static EVENT_ID_INIT: ::std::sync::Once = ::std::sync::ONCE_INIT;
@@ -79,11 +71,50 @@ macro_rules! post_event {
                 let handlers = $crate::get_post_targets::<$t>(bus, event, id);
                 for (_pri, fun) in handlers.iter() {
                     fun(event);
-                    if cancellable && <$t as $crate::Event>::cancelled(event) {
+                }
+            }
+        }
+    }
+}
+
+/// Posts an event.
+///
+/// Usage: `post_event!(bus, type, event)`
+#[macro_export]
+macro_rules! post_event_cancellable {
+    // TODO allow multiple $t:ty at once and re-#[doc(hidden)] the low-level get_post_targets and
+    // get_event_id
+    ($b:expr, $t:ty, $e:expr) => {
+        {
+            // hygiene
+            let bus: &$crate::EventBus = $b;
+            // event setup, this may evaluate to any type.
+            let event: &mut _ = $e;
+            {
+                fn test<C: Cancellable>(e: &C) {
+
+                }
+
+                test(event);
+                // event type setup
+                static EVENT_ID: ::std::sync::atomic::AtomicUsize = ::std::sync::atomic::ATOMIC_USIZE_INIT;
+                static EVENT_ID_INIT: ::std::sync::Once = ::std::sync::ONCE_INIT;
+                // no generics allowed.
+                static DUMMY: ::std::marker::PhantomData<dyn Fn(&mut $t) + Send + Sync> = ::std::marker::PhantomData;
+                EVENT_ID_INIT.call_once(|| {
+                    EVENT_ID.store($crate::get_event_id::<$t>(), std::sync::atomic::Ordering::Relaxed);
+                });
+                let id = EVENT_ID.load(std::sync::atomic::Ordering::Relaxed);
+
+                // handler retrieval and invokation
+                let handlers = $crate::get_post_targets::<$t>(bus, event, id);
+                for (_pri, fun) in handlers.iter() {
+                    fun(event as &mut $t);
+                    if event.cancelled() {
                         break;
                     }
                 }
-                cancellable && <$t as $crate::Event>::cancelled(event)
+                event.cancelled()
             }
         }
     }
@@ -101,6 +132,10 @@ pub trait Event: 'static {
     fn cancellable(&self) -> bool {
         false
     }
+}
+
+/// Basic trait for defining an event.
+pub trait Cancellable: 'static {
 
     /// Returns whether this event has been cancelled.
     fn cancelled(&self) -> bool {
diff --git a/tests/dyn_events.rs b/tests/dyn_events.rs
index 0407f7f..8ea4599 100644
--- a/tests/dyn_events.rs
+++ b/tests/dyn_events.rs
@@ -1,53 +1,60 @@
 #[macro_use]
 extern crate eventbus;
 
-use eventbus::{Event, EventBus};
+use std::fmt::Debug;
+use eventbus::{Event, EventBus, Cancellable};
 
-trait MyEvent : Event {
-    fn get_i(&self) -> i32;
-    fn set_i(&mut self, i32);
+trait MyEvent : Event + Debug {
 }
 
+trait MyExtraEvent : MyEvent + Cancellable {
+}
+
+#[derive(Debug)]
 struct MyEventImpl {
     i: i32
 }
 
+#[derive(Debug)]
+struct MyExtraEventImpl {
+    i: i32
+}
+
 impl Event for MyEventImpl {
 }
+
 impl MyEvent for MyEventImpl {
-    fn get_i(&self) -> i32 {
-        self.i
-    }
-    fn set_i(&mut self, i: i32) {
-        self.i = i;
-    }
 }
 
-fn add_handler(e: &mut MyEvent) {
-    /* adds 1 */
-    let i = e.get_i();
-    e.set_i(i+1);
+impl Event for MyExtraEventImpl {
 }
 
-fn no_handler(e: &mut MyEvent) {
-    /* does nothing */
-    let i = e.get_i();
-    e.set_i(i);
+impl MyEvent for MyExtraEventImpl {
+}
+
+impl MyExtraEvent for MyExtraEventImpl {
+}
+
+impl Cancellable for MyExtraEventImpl {
+    
+}
+
+fn on_myevent(evt: &mut dyn MyEvent) {
+    println!("Got event for inspection and manipulation: {:?}", evt);
+}
+
+fn on_myextraevent(evt: &mut dyn MyExtraEvent) {
+    println!("Got event for inspection, manipulation, and cancellation: {:?}", evt);
 }
 
 #[test]
 fn test_dyn_usage() {
     let event_bus = EventBus::new();
-    //let handler_id = event_bus.register(add_handler, 0);
-    register_hook!(&event_bus, 0, dyn MyEvent, add_handler);
     let mut event = MyEventImpl { i: 3 };
-    assert_eq!(event.i, 3);
+    let mut extraEvent = MyExtraEventImpl { i: 4 };
+    //let handler_id = event_bus.register(add_handler, 0);
+    register_hook!(&event_bus, 0, dyn MyEvent, on_myevent);
+    register_hook!(&event_bus, 1, dyn MyExtraEvent, on_myextraevent);
     post_event!(&event_bus, dyn MyEvent, &mut event);
-    assert_eq!(event.i, 4);
-    register_hook!(&event_bus, 1, dyn MyEvent, no_handler);
-    post_event!(&event_bus, dyn MyEvent, &mut event);
-    assert_eq!(event.i, 5);
-    //event_bus.unregister(handler_id);
-    post_event!(&event_bus, dyn MyEvent, &mut event);
-    //assert_eq!(event.i, 5);
+    post_event_cancellable!(&event_bus, dyn MyExtraEvent, &mut extraEvent);
 }