Predict Flashes (#37640)

Co-authored-by: ScarKy0 <scarky0@onet.eu>

Content.Shared/Flash/FlashEvents.cs

@@ -0,0 +1,21 @@
+using Content.Shared.Inventory;
+
+namespace Content.Shared.Flash;
+
+/// <summary>
+/// Called before a flash is used to check if the attempt is cancelled by blindness, items or FlashImmunityComponent.
+/// Raised on the target hit by the flash and their inventory items.
+/// </summary>
+[ByRefEvent]
+public record struct FlashAttemptEvent(EntityUid Target, EntityUid? User, EntityUid? Used, bool Cancelled = false) : IInventoryRelayEvent
+{
+    SlotFlags IInventoryRelayEvent.TargetSlots => SlotFlags.HEAD | SlotFlags.EYES | SlotFlags.MASK;
+}
+
+/// <summary>
+/// Called when a player is successfully flashed.
+/// Raised on the target hit by the flash, the user of the flash and the flash used.
+/// The Melee parameter is used to check for rev conversion.
+/// </summary>
+[ByRefEvent]
+public record struct AfterFlashedEvent(EntityUid Target, EntityUid? User, EntityUid? Used, bool Melee);