Channel-based event API (v2)

[Axionize]

Picks up where #19 left off. Each event gets its own EventChannel
subclass that exposes a typed fire(user, check, verbose, ...) — the
hot path is a volatile read + direct method invoke, no per-fire
allocation, no reflection. The legacy bus.post(...) /
bus.subscribe(Class, listener) / @GrimEventHandler paths all keep
working as @Deprecated shims that route through each channel's legacy
slot.

Usage

GrimAbstractAPI api = GrimAPIProvider.get();
EventBus bus = api.getEventBus();
GrimPlugin grim = api.getGrimPlugin(this);   // resolve once at plugin enable

bus.get(FlagEvent.class).onFlag(grim, (user, check, verbose, cancelled) -> {
    if (shouldSuppress(user, check)) return true;   // cancel
    return cancelled;
});

Every typed subscribe takes a GrimPlugin so bus.unregisterAllListeners(grim)
sweeps it on disable, same shape as Bukkit's HandlerList. Plugin
authors that want to pass a platform-specific context (Bukkit
JavaPlugin, Fabric ModContainer, a Class) can use the
@Deprecated onX(Object ctx, Handler) overload that resolves through
the bus's extension manager — the warning is there to nudge toward
api.getGrimPlugin(this)-once-and-cache.

Hot path / caching

private static final FlagEvent.Channel FLAG =
    GrimAPIProvider.get().getEventBus().get(FlagEvent.class);

// later, on the netty thread:
FLAG.fire(user, check, verbose);

static final so the JIT folds the getfield. Check.flag() uses a
volatile lazy-init pattern instead to sidestep class-load-order worries
across check subclasses.

Priority ordering flips

Lower number fires first, higher gets the final say — Bukkit
EventPriority convention (LOWEST → LOW → NORMAL → HIGH → HIGHEST → MONITOR). Pre-1.3 Grim sorted highest-first. Plugins using default
priority (0) are unaffected; anyone with explicit numbers on
@GrimEventHandler / bus.subscribe(...) needs to re-evaluate.

No reflection on the dispatch path

OptimizedEventBus constructor news each channel explicitly:

installChannel(FlagEvent.class, new FlagEvent.Channel());
installChannel(CommandExecuteEvent.class, new CommandExecuteEvent.Channel());
// ... 9 more

So renaming FlagEvent.Channel breaks at compile time, not at runtime,
and ProGuard/tree-shakers keep everything reachable from the
constructor. bus.get(E.class) is a ConcurrentHashMap lookup keyed on
the Class identity. The only getDeclaredMethods / MethodHandle.invoke
live in the @Deprecated registerAnnotatedListeners path — opt-in, for
back-compat with plugins using @GrimEventHandler.

JMH

Benchmark                    (mode)  (subscribers)  Mode  Cnt    Score  Units
EventDispatchBenchmark.fire   typed              0  avgt    3    2.17  ns/op
EventDispatchBenchmark.fire   typed              1  avgt    3    7.19  ns/op
EventDispatchBenchmark.fire   typed              3  avgt    3   13.51  ns/op
EventDispatchBenchmark.fire  legacy              1  avgt    3   15.05  ns/op
EventDispatchBenchmark.fire  legacy              3  avgt    3   21.99  ns/op
EventDispatchBenchmark.fire   mixed              3  avgt    3   18.39  ns/op

With -prof gc: gc.count ≈ 0, gc.alloc.rate.norm ≈ 10⁻⁵ B/op — the
residual is JMH infrastructure noise, not dispatch overhead. Zero-alloc
fire confirmed across typed / legacy / mixed configurations.

Tests

25 unit tests in grim-internal/src/test:

• priority ordering + typed/legacy mixed dispatch (11)
• bus routing + reflective @GrimEventHandler + plugin-disable sweep (13)
• 8 threads × 2000 fires per-thread legacy pool isolation (1)

Related

Grim-side migration PR: GrimAnticheat/Grim#