1 files changed, 61 insertions, 0 deletions
diff --git a/python/cru/_event.py b/python/cru/_event.py
new file mode 100644
index 0000000..51a794c
--- /dev/null
+++ b/python/cru/_event.py
@@ -0,0 +1,61 @@
+from __future__ import annotations
+
+from collections.abc import Callable
+from typing import Generic, ParamSpec, TypeVar
+
+from .list import CruList
+
+_P = ParamSpec("_P")
+_R = TypeVar("_R")
+
+
+class CruEventHandlerToken(Generic[_P, _R]):
+    def __init__(
+        self, event: CruEvent, handler: Callable[_P, _R], once: bool = False
+    ) -> None:
+        self._event = event
+        self._handler = handler
+        self._once = once
+
+    @property
+    def event(self) -> CruEvent:
+        return self._event
+
+    @property
+    def handler(self) -> Callable[_P, _R]:
+        return self._handler
+
+    @property
+    def once(self) -> bool:
+        return self._once
+
+
+class CruEvent(Generic[_P, _R]):
+    def __init__(self, name: str) -> None:
+        self._name = name
+        self._tokens: CruList[CruEventHandlerToken] = CruList()
+
+    def register(
+        self, handler: Callable[_P, _R], once: bool = False
+    ) -> CruEventHandlerToken:
+        token = CruEventHandlerToken(self, handler, once)
+        self._tokens.append(token)
+        return token
+
+    def unregister(self, *handlers: CruEventHandlerToken | Callable[_P, _R]) -> int:
+        old_length = len(self._tokens)
+        self._tokens.reset(
+            self._tokens.as_cru_iterator().filter(
+                (lambda t: t in handlers or t.handler in handlers)
+            )
+        )
+        return old_length - len(self._tokens)
+
+    def trigger(self, *args: _P.args, **kwargs: _P.kwargs) -> CruList[_R]:
+        results = CruList(
+            self._tokens.as_cru_iterator()
+            .transform(lambda t: t.handler(*args, **kwargs))
+            .to_list()
+        )
+        self._tokens.reset(self._tokens.as_cru_iterator().filter(lambda t: not t.once))
+        return results