From 0a11e8d322c27c53ee94945fe737530dc13c5159 Mon Sep 17 00:00:00 2001
From: Hazel Atkinson <yellowsink@riseup.net>
Date: Sun, 21 Apr 2024 18:57:36 +0100
Subject: [PATCH] [sync] fix TEvent (see
 https://github.com/vibe-d/eventcore/issues/238#issuecomment-2068148847)

---
 source/rockhopper/sync.d | 32 ++++++++++++++++++++++++++------
 testscript.d             | 33 +++++++++++++++++++++++++++------
 2 files changed, 53 insertions(+), 12 deletions(-)

diff --git a/source/rockhopper/sync.d b/source/rockhopper/sync.d
index 13dd8c2..991fdf3 100644
--- a/source/rockhopper/sync.d
+++ b/source/rockhopper/sync.d
@@ -50,9 +50,11 @@ shared class TEvent
 	import std.typecons : Tuple, tuple;
 	import core.thread.osthread : Thread;
 
+	alias ThreadEventsTy = Tuple!(shared(EventDriver), EventID)[typeof(Thread.getThis.id)];
+
 	shared bool triggered;
 	// you may only await an event from the thread that created it, so we need one event per thread
-	shared Tuple!(shared(EventDriver), EventID)[typeof(Thread.getThis.id)] threadEvents;
+	shared ThreadEventsTy threadEvents;
 
 	import std.stdio;
 
@@ -63,7 +65,7 @@ shared class TEvent
 		foreach (_, tup; threadEvents)
 			tup[0].events.trigger(tup[1], true);
 
-		threadEvents = typeof(threadEvents).init;
+		threadEvents = ThreadEventsTy.init;
 	}
 
 	synchronized void reset()
@@ -71,7 +73,7 @@ shared class TEvent
 		if (triggered)
 		{
 			triggered = false;
-			threadEvents = typeof(threadEvents).init;
+			threadEvents = ThreadEventsTy.init;
 		}
 		else
 		{
@@ -86,9 +88,27 @@ shared class TEvent
 
 		auto tid = Thread.getThis.id;
 
-		auto ev = eventDriver.events.create();
-		// TODO: this does not compile?
-		threadEvents[tid] = tuple(cast(shared) eventDriver, ev);
+		EventID ev = void; // always assigned
+
+		synchronized(this)
+		{
+			// while in a synchronized, you can cast away a `shared`
+			// -- technically you can cast shared away any time, but its safe here :)
+			// use a pointer else this causes a copy and that screws stuff up.
+			// we still have to make sure the contents of the AA are shared due to transititivy,
+			// but this fixes it not liking us trying to do the assignment *at all*
+			auto tEvs = cast(ThreadEventsTy*) &threadEvents;
+
+			if (tid in *tEvs)
+			{
+				ev = (*tEvs)[tid][1];
+			}
+			else
+			{
+				ev = eventDriver.events.create();
+				(*tEvs)[tid] = tuple(cast(shared) eventDriver, ev);
+			}
+		}
 
 		waitThreadEvent(ev);
 
diff --git a/testscript.d b/testscript.d
index 79d1657..8e62801 100755
--- a/testscript.d
+++ b/testscript.d
@@ -22,11 +22,32 @@ import core.thread.osthread : Thread;
 void main()
 {
 	entrypoint({
-		auto eepyTask = taskify!sleep(dur!"seconds"(5));
-		auto tBefore = MonoTime.currTime;
-
-		eepyTask.waitRes(); // void
-
-		writeln("eeped for ", MonoTime.currTime - tBefore);
+		auto ev = new TEvent;
+
+		auto thread2 = new Thread({
+			entrypoint({
+				ev.wait();
+				writeln("yay 2!");
+			});
+		}).start();
+
+		auto thread3 = new Thread({
+			entrypoint({
+				ev.wait();
+				writeln("yay 3!");
+			});
+		}).start();
+
+		auto thread4 = new Thread({
+			entrypoint({
+				writeln("helo");
+				Thread.sleep(dur!"seconds"(2));
+				ev.notify();
+			});
+		}).start();
+
+		thread2.join();
+		thread3.join();
+		thread4.join();
 	});
 }