feat(rx): add cond fabric

src/snakia/core/rx/__init__.py

@@ -4,6 +4,7 @@ from .bindable import Bindable
 from .chain import chain
 from .combine import combine
 from .concat import concat
+from .cond import cond
 from .const import const
 from .filter import filter  # noqa: W0622 # pylint: disable=W0622
 from .map import map  # noqa: W0622 # pylint: disable=W0622
@@ -18,6 +19,7 @@ __all__ = [
     "chain",
     "combine",
     "concat",
+    "cond",
     "const",
     "filter",
     "map",

src/snakia/core/rx/cond.py

@@ -0,0 +1,13 @@
+from typing import Callable
+
+
+def cond[**P, T, F](
+    condition: Callable[P, bool],
+    if_true: Callable[P, T],
+    if_false: Callable[P, F],
+) -> Callable[P, T | F]:
+    return lambda *args, **kw: (
+        if_true(*args, **kw)
+        if condition(*args, **kw)
+        else if_false(*args, **kw)
+    )