Add game loop skeleton for periodic tick processing

src/mudlib/server.py

@@ -15,12 +15,15 @@ import mudlib.commands.fly
 import mudlib.commands.look
 import mudlib.commands.movement
 import mudlib.commands.quit
+from mudlib.effects import clear_expired
 from mudlib.player import Player, players
 from mudlib.world.terrain import World
 
 log = logging.getLogger(__name__)
 
 PORT = 6789
+TICK_RATE = 10  # ticks per second
+TICK_INTERVAL = 1.0 / TICK_RATE
 
 # Module-level world instance, generated once at startup
 _world: World | None = None
@@ -34,6 +37,18 @@ def load_world_config(world_name: str = "earth") -> dict:
         return tomllib.load(f)
 
 
+async def game_loop() -> None:
+    """Run periodic game tasks at TICK_RATE ticks per second."""
+    log.info("game loop started (%d ticks/sec)", TICK_RATE)
+    while True:
+        t0 = asyncio.get_event_loop().time()
+        clear_expired()
+        elapsed = asyncio.get_event_loop().time() - t0
+        sleep_time = TICK_INTERVAL - elapsed
+        if sleep_time > 0:
+            await asyncio.sleep(sleep_time)
+
+
 def find_passable_start(world: World, start_x: int, start_y: int) -> tuple[int, int]:
     """Find a passable tile starting from (start_x, start_y) and searching outward.
 
@@ -183,10 +198,13 @@ async def run_server() -> None:
     )
     log.info("listening on 127.0.0.1:%d", PORT)
 
+    loop_task = asyncio.create_task(game_loop())
+
     try:
         while True:
             await asyncio.sleep(3600)
     except KeyboardInterrupt:
         log.info("shutting down...")
+        loop_task.cancel()
         server.close()
         await server.wait_closed()

tests/test_server.py

@@ -103,3 +103,30 @@ def test_load_world_config_missing():
     """Config loader raises FileNotFoundError for nonexistent world."""
     with pytest.raises(FileNotFoundError):
         server.load_world_config("nonexistent")
+
+
+def test_tick_constants():
+    """Tick rate and interval are configured correctly."""
+    assert server.TICK_RATE == 10
+    assert server.TICK_INTERVAL == pytest.approx(0.1)
+
+
+def test_game_loop_exists():
+    """Game loop is an async callable."""
+    assert callable(server.game_loop)
+    assert asyncio.iscoroutinefunction(server.game_loop)
+
+
+@pytest.mark.asyncio
+async def test_game_loop_calls_clear_expired():
+    """Game loop calls clear_expired each tick."""
+    with patch("mudlib.server.clear_expired") as mock_clear:
+        task = asyncio.create_task(server.game_loop())
+        await asyncio.sleep(0.25)
+        task.cancel()
+        try:
+            await task
+        except asyncio.CancelledError:
+            pass
+
+        assert mock_clear.call_count >= 1