module refactoring

game/state.py

@@ -8,6 +8,8 @@ import attrs
 import tcod.console
 import tcod.event
 
+import g
+
 
 class State(Protocol):
     """An abstract game state."""
@@ -42,3 +44,56 @@ class Reset:
 
 StateResult: TypeAlias = "Push | Pop | Reset | None"
 """Union of state results."""
+
+
+def main_draw() -> None:
+    """Render and present the active state."""
+    if not g.states:
+        return
+    g.console.clear()
+    g.states[-1].on_draw(g.console)
+    g.context.present(g.console)
+
+
+def apply_state_result(result: StateResult) -> None:
+    """Apply a StateResult to `g.states`."""
+    match result:
+        case Push(state=state):
+            g.states.append(state)
+        case Pop():
+            g.states.pop()
+        case Reset(state=state):
+            while g.states:
+                apply_state_result(Pop())
+            apply_state_result(Push(state))
+        case None:
+            pass
+        case _:
+            raise TypeError(result)
+
+
+def main_loop() -> None:
+    """Run the active state forever."""
+    while g.states:
+        main_draw()
+        for event in tcod.event.wait():
+            tile_event = g.context.convert_event(event)
+            if g.states:
+                apply_state_result(g.states[-1].on_event(tile_event))
+
+
+def get_previous_state(state: State) -> State | None:
+    """Return the state before `state` in the stack if it exists."""
+    current_index = next(index for index, value in enumerate(g.states) if value is state)
+    return g.states[current_index - 1] if current_index > 0 else None
+
+
+def draw_previous_states(state: State, console: tcod.console.Console, dim: bool = True) -> None:
+    """Draw previous states, optionally dimming all but the active state."""
+    prev_state = get_previous_state(state)
+    if prev_state is None:
+        return
+    prev_state.on_draw(console)
+    if dim and state is g.states[-1]:
+        console.rgb["fg"] //= 4
+        console.rgb["bg"] //= 4