Cache packet map generation

mcproto/packets/packet_map.py

@@ -3,6 +3,7 @@
 import importlib
 import pkgutil
 from collections.abc import Iterator, Mapping, Sequence
+from functools import lru_cache
 from types import ModuleType
 from typing import Literal, NamedTuple, NoReturn, overload
 
@@ -93,12 +94,21 @@ def generate_packet_map(
     ...
 
 
+@lru_cache()
 def generate_packet_map(direction: PacketDirection, state: GameState) -> Mapping[int, type[Packet]]:
     """Dynamically generated a packet map for given ``direction`` and ``state``.
 
     This generation is done by dynamically importing all of the modules containing these packets,
     filtering them to only contain those pacekts with the specified parameters, and storing those
     into a dictionary, using the packet id as key, and the packet class itself being the value.
+
+    As this fucntion is likely to be called quite often, and it uses dynamic importing to obtain
+    the packet classes, this function is cached, which means the logic only actually runs once,
+    after which, for the same arguments, the same dict will be returned.
+
+    ..warning: As this function is cached, make sure to avoid modifying the returned dictionary,
+        as that will directly modify the stored version in the cache, leading to future calls
+        with the same arguments returning a wrong (modified) version of this dictionary.
     """
     module = importlib.import_module(MODULE_PATHS[state])