Refactor event handling

color.py

@@ -20,3 +20,6 @@ health_recovered = (0x0, 0xFF, 0x0)
 bar_text = white
 bar_filled = (0x0, 0x60, 0x0)
 bar_empty = (0x40, 0x10, 0x10)
+
+menu_title = (255, 255, 63)
+menu_text = white

components/consumable.py

@@ -8,7 +8,11 @@ import components.ai
 import components.inventory
 from components.base_component import BaseComponent
 from exceptions import Impossible
-from input_handlers import AreaRangedAttackHandler, SingleRangedAttackHandler
+from input_handlers import (
+    ActionOrHandler,
+    AreaRangedAttackHandler,
+    SingleRangedAttackHandler
+)
 
 if TYPE_CHECKING:
     from entity import Actor, Item
@@ -17,7 +21,7 @@ if TYPE_CHECKING:
 class Consumable(BaseComponent):
     parent: Item
 
-    def get_action(self, consumer: Actor) -> Optional[actions.Action]:
+    def get_action(self, consumer: Actor) -> Optional[ActionOrHandler]:
         """Try to return the action for this item."""
         return actions.ItemAction(consumer, self.parent)
 
@@ -40,18 +44,17 @@ class ConfusionConsumable(Consumable):
     def __init__(self, number_of_turns: int):
         self.number_of_turns = number_of_turns
 
-    def get_action(self, consumer: Actor) -> Optional[actions.Action]:
+    def get_action(self, consumer: Actor) -> SingleRangedAttackHandler:
         self.engine.message_log.add_message(
             "Select a target location.",
             color.needs_target
         )
-        self.engine.event_handler = SingleRangedAttackHandler(
+
+        return SingleRangedAttackHandler(
             self.engine,
             callback=lambda xy: actions.ItemAction(consumer, self.parent, xy),
         )
 
-        return None
-
     def activate(self, action: actions.ItemAction) -> None:
         consumer = action.entity
         target = action.target_actor
@@ -99,19 +102,18 @@ class FireballDamageConsumable(Consumable):
         self.damage = damage
         self.radius = radius
 
-    def get_action(self, consumer: Actor) -> Optional[actions.Action]:
+    def get_action(self, consumer: Actor) -> AreaRangedAttackHandler:
         self.engine.message_log.add_message(
             "Select a target location.",
             color.needs_target
         )
-        self.engine.event_handler = AreaRangedAttackHandler(
+
+        return AreaRangedAttackHandler(
             self.engine,
             self.radius,
             lambda xy: actions.ItemAction(consumer, self.parent, xy),
         )
 
-        return None
-
     def activate(self, action: actions.ItemAction) -> None:
         target_xy = action.target_xy
 

components/fighter.py

@@ -4,7 +4,6 @@ from typing import TYPE_CHECKING
 
 import color
 from components.base_component import BaseComponent
-from input_handlers import GameOverEventHandler
 from render_order import RenderOrder
 
 if TYPE_CHECKING:
@@ -34,7 +33,6 @@ class Fighter(BaseComponent):
         if self.engine.player is self.parent:
             death_message = "You died!"
             death_message_color = color.player_die
-            self.engine.event_handler = GameOverEventHandler(self.engine)
         else:
             death_message = f"{self.parent.name} is dead!"
             death_message_color = color.enemy_die

engine.py

@@ -2,12 +2,10 @@ from __future__ import annotations
 
 from typing import TYPE_CHECKING
 
-from tcod.context import Context
 from tcod.console import Console
 from tcod.map import compute_fov
 
 import exceptions
-from input_handlers import MainGameEventHandler
 from message_log import MessageLog
 from render_functions import render_bar, render_names_at_mouse_location
 
@@ -20,7 +18,6 @@ class Engine:
     game_map: GameMap
 
     def __init__(self, player: Actor):
-        self.event_handler: EventHandler = MainGameEventHandler(self)
         self.message_log = MessageLog()
         self.mouse_location = (0, 0)
         self.player = player

exceptions.py

@@ -2,4 +2,8 @@ class Impossible(Exception):
     """Exception raised when an action is impossible to be performed.
 
     The reason is given as the exception message.
-    """
+    """
+
+
+class QuitWithoutSaving(SystemExit):
+    """Can be raised to exit the game without automatically saving."""

input_handlers.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from typing import overload, Callable, Optional, Tuple, TYPE_CHECKING
+from typing import overload, Callable, Optional, Tuple, TYPE_CHECKING, Union
 
 import tcod.event
 
@@ -61,13 +61,50 @@ CONFIRM_KEYS = {
     tcod.event.K_KP_ENTER,
 }
 
+ActionOrHandler = Union[Action, "BaseEventHandler"]
+"""
+An event handler return value which can trigger an action or switch active handlers.
 
-class EventHandler(tcod.event.EventDispatch[Action]):
+If a handler is returned than it will become the active handler for future events.
+if an action is returned it will be attempted and if it's valid then 
+MainGameEventHandler will become the active handler.
+"""
+
+
+class BaseEventHandler(tcod.event.EventDispatch[ActionOrHandler]):
+    def handle_events(self, event: tcod.event.Event) -> BaseEventHandler:
+        """Handle an event and return the next active event handler."""
+        state = self.dispatch(event)
+        if isinstance(state, BaseEventHandler):
+            return state
+        assert not isinstance(state, Action), f"{self!r} can not handle actions."
+
+        return self
+
+    @overload
+    def on_render(self, console: tcod.Console) -> None:
+        """Must be implemented"""
+
+    def ev_quit(self, event: tcod.event.Quit) -> Optional[Action]:
+        raise SystemExit()
+
+
+class EventHandler(BaseEventHandler):
     def __init__(self, engine: Engine):
         self.engine = engine
 
-    def handle_events(self, event: tcod.event.Event) -> None:
+    def handle_events(self, event: tcod.event.Event) -> BaseEventHandler:
-        self.handle_action(self.dispatch(event))
+        """Handle events for input handlers with an engine."""
+        action_or_state = self.dispatch(event)
+        if isinstance(action_or_state, BaseEventHandler):
+            return action_or_state
+        if self.handle_action(action_or_state):
+            # A valid action was performed.
+            if not self.engine.player.is_alive:
+                # The player was killed sometime during or after the action.
+                return GameOverEventHandler(self.engine)
+            return MainGameEventHandler(self.engine)  # Return to the main handler.
+        return self
 
     def handle_action(self, action: Optional[Action]) -> bool:
         """Handle actions returned from event methods.
@@ -93,9 +130,6 @@ class EventHandler(tcod.event.EventDispatch[Action]):
         if self.engine.game_map.in_bounds(event.tile.x, event.tile.y):
             self.engine.mouse_location = event.tile.x, event.tile.y
 
-    def ev_quit(self, event: tcod.event.Quit) -> Optional[Action]:
-        raise SystemExit()
-
     def on_render(self, console: tcod.Console) -> None:
         self.engine.render(console)
 
@@ -103,16 +137,7 @@ class EventHandler(tcod.event.EventDispatch[Action]):
 class AskUserEventHandler(EventHandler):
     """Handles user input for actions which require special input."""
 
-    def handle_action(self, action: Optional[Action]) -> bool:
+    def ev_keydown(self, event: tcod.event.KeyDown) -> Optional[ActionOrHandler]:
-        """Return to the main event handler when a valid action was performed."""
-        if super().handle_action(action):
-            self.engine.event_handler = MainGameEventHandler(self.engine)
-
-            return True
-
-        return False
-
-    def ev_keydown(self, event: tcod.event.KeyDown) -> Optional[Action]:
         """By default any key exits this input handler."""
         # Ignore modifier keys.
         if event.sym in {
@@ -127,18 +152,16 @@ class AskUserEventHandler(EventHandler):
 
         return self.on_exit()
 
-    def ev_mousebuttondown(self, event: tcod.event.MouseButtonDown) -> Optional[Action]:
+    def ev_mousebuttondown(self, event: tcod.event.MouseButtonDown) -> Optional[ActionOrHandler]:
         """By default any mouse click exits this input handler."""
         return self.on_exit()
 
-    def on_exit(self) -> Optional[Action]:
+    def on_exit(self) -> Optional[ActionOrHandler]:
         """Called when the user is trying to exit or cancel an action.
 
         By default this returns to the main event handler.
         """
-        self.engine.event_handler = MainGameEventHandler(self.engine)
+        return MainGameEventHandler(self.engine)
-
-        return None
 
 
 class InventoryEventHandler(AskUserEventHandler):
@@ -189,7 +212,7 @@ class InventoryEventHandler(AskUserEventHandler):
         else:
             console.print(x + 1, y + 1, "(Empty)")
 
-    def ev_keydown(self, event: tcod.event.KeyDown) -> Optional[Action]:
+    def ev_keydown(self, event: tcod.event.KeyDown) -> Optional[ActionOrHandler]:
         player = self.engine.player
         key = event.sym
         index = key - tcod.event.K_a
@@ -206,7 +229,7 @@ class InventoryEventHandler(AskUserEventHandler):
         return super().ev_keydown(event)
 
     @overload
-    def on_item_selected(self, item: Item) -> Optional[Action]:
+    def on_item_selected(self, item: Item) -> Optional[ActionOrHandler]:
         """Called when the user selects a valid item."""
 
 
@@ -215,7 +238,7 @@ class InventoryActivateHandler(InventoryEventHandler):
 
     TITLE = "Select an item to use"
 
-    def on_item_selected(self, item: Item) -> Optional[Action]:
+    def on_item_selected(self, item: Item) -> Optional[ActionOrHandler]:
         """Return the action for the selected item."""
         return item.consumable.get_action(self.engine.player)
 
@@ -225,7 +248,7 @@ class InventoryDropHandler(InventoryEventHandler):
 
     TITLE = "Select an item to drop"
 
-    def on_item_selected(self, item: Item) -> Optional[Action]:
+    def on_item_selected(self, item: Item) -> Optional[ActionOrHandler]:
         """Drop this item."""
         return actions.DropItem(self.engine.player, item)
 
@@ -246,7 +269,7 @@ class SelectIndexHandler(AskUserEventHandler):
         console.tiles_rgb["bg"][x, y] = color.white
         console.tiles_rgb["fg"][x, y] = color.black
 
-    def ev_keydown(self, event: tcod.event.KeyDown) -> Optional[Action]:
+    def ev_keydown(self, event: tcod.event.KeyDown) -> Optional[ActionOrHandler]:
         """Check for key movement or confirmation keys."""
         key = event.sym
         if key in MOVE_KEYS:
@@ -273,7 +296,7 @@ class SelectIndexHandler(AskUserEventHandler):
 
         return super().ev_keydown(event)
 
-    def ev_mousebuttondown(self, event: tcod.event.MouseButtonDown) -> Optional[Action]:
+    def ev_mousebuttondown(self, event: tcod.event.MouseButtonDown) -> Optional[ActionOrHandler]:
         """Left click confirms a selection."""
         if self.engine.game_map.in_bounds(*event.tile):
             if event.button == 1:
@@ -282,16 +305,16 @@ class SelectIndexHandler(AskUserEventHandler):
         return super().ev_mousebuttondown(event)
 
     @overload
-    def on_index_selected(self, x: int, y: int) -> Optional[Action]:
+    def on_index_selected(self, x: int, y: int) -> Optional[ActionOrHandler]:
         """Called when an index is selected."""
 
 
 class LookHandler(SelectIndexHandler):
     """Lets the player look around using the keyboard."""
 
-    def on_index_selected(self, x: int, y: int) -> None:
+    def on_index_selected(self, x: int, y: int) -> MainGameEventHandler:
         """Return to main handler."""
-        self.engine.event_handler = MainGameEventHandler(self.engine)
+        return MainGameEventHandler(self.engine)
 
 
 class SingleRangedAttackHandler(SelectIndexHandler):
@@ -300,13 +323,13 @@ class SingleRangedAttackHandler(SelectIndexHandler):
     def __init__(
             self,
             engine: Engine,
-            callback: Callable[[Tuple[int, int]], Optional[Action]]
+            callback: Callable[[Tuple[int, int]], Optional[ActionOrHandler]]
     ):
         super().__init__(engine)
 
         self.callback = callback
 
-    def on_index_selected(self, x: int, y: int) -> Optional[Action]:
+    def on_index_selected(self, x: int, y: int) -> Optional[ActionOrHandler]:
         return self.callback((x, y))
 
 
@@ -320,7 +343,7 @@ class AreaRangedAttackHandler(SelectIndexHandler):
             self,
             engine: Engine,
             radius: int,
-            callback: Callable[[Tuple[int, int]], Optional[Action]]
+            callback: Callable[[Tuple[int, int]], Optional[ActionOrHandler]]
     ):
         super().__init__(engine)
 
@@ -343,12 +366,12 @@ class AreaRangedAttackHandler(SelectIndexHandler):
             clear=False,
         )
 
-    def on_index_selected(self, x: int, y: int) -> Optional[Action]:
+    def on_index_selected(self, x: int, y: int) -> Optional[ActionOrHandler]:
         return self.callback((x, y))
 
 
 class MainGameEventHandler(EventHandler):
-    def ev_keydown(self, event: tcod.event.KeyDown) -> Optional[Action]:
+    def ev_keydown(self, event: tcod.event.KeyDown) -> Optional[ActionOrHandler]:
         action: Optional[Action] = None
 
         key = event.sym
@@ -365,17 +388,17 @@ class MainGameEventHandler(EventHandler):
             raise SystemExit()
 
         elif key == tcod.event.K_v:
-            self.engine.event_handler = HistoryViewer(self.engine)
+            return HistoryViewer(self.engine)
 
         elif key == tcod.event.K_g:
             action = PickupAction(player)
 
         elif key == tcod.event.K_i:
-            self.engine.event_handler = InventoryActivateHandler(self.engine)
+            return InventoryActivateHandler(self.engine)
         elif key == tcod.event.K_d:
-            self.engine.event_handler = InventoryDropHandler(self.engine)
+            return InventoryDropHandler(self.engine)
         elif key == tcod.event.K_SLASH:
-            self.engine.event_handler = LookHandler(self.engine)
+            return LookHandler(self.engine)
 
         # No valid key was pressed
         return action
@@ -430,7 +453,7 @@ class HistoryViewer(EventHandler):
         )
         log_console.blit(console, 3, 3)
 
-    def ev_keydown(self, event: tcod.event.KeyDown) -> None:
+    def ev_keydown(self, event: tcod.event.KeyDown) -> Optional[MainGameEventHandler]:
         # Fancy conditional movement to make it feel right.
         if event.sym in CURSOR_Y_KEYS:
             adjust = CURSOR_Y_KEYS[event.sym]
@@ -448,4 +471,6 @@ class HistoryViewer(EventHandler):
         elif event.sym == tcod.event.K_END:
             self.cursor = self.log_length - 1  # Move directly to the last message.
         else:  # Any other key moves back to the main game state.
-            self.engine.event_handler = MainGameEventHandler(self.engine)
+            return MainGameEventHandler(self.engine)
+
+        return None

main.py

@@ -7,6 +7,8 @@ import tcod
 import color
 from engine import Engine
 import entity_factories
+import exceptions
+import input_handlers
 from procgen import generate_dungeon
 
 
@@ -52,6 +54,8 @@ def main() -> None:
         color.welcome_text
     )
 
+    handler: input_handlers.BaseEventHandler = input_handlers.MainGameEventHandler(engine)
+
     with tcod.context.new_terminal(
             screen_width,
             screen_height,
@@ -60,19 +64,29 @@ def main() -> None:
             vsync=True,
     ) as context:
         root_console = tcod.Console(screen_width, screen_height, order="F")
-        while True:
+        try:
-            root_console.clear()
+            while True:
-            engine.event_handler.on_render(console=root_console)
+                root_console.clear()
-            context.present(root_console)
+                engine.event_handler.on_render(console=root_console)
+                context.present(root_console)
 
-            try:
+                try:
-                for event in tcod.event.wait():
+                    for event in tcod.event.wait():
-                    context.convert_event(event)
+                        context.convert_event(event)
-                    engine.event_handler.handle_events(event)
+                        engine.event_handler.handle_events(event)
-            except Exception:  # Handle exceptions in game.
+                except Exception:  # Handle exceptions in game.
-                traceback.print_exc()  # Print error to stderr.
+                    traceback.print_exc()  # Print error to stderr.
-                # Then print the error to the message log.
+                    # Then print the error to the message log.
-                engine.message_log.add_message(traceback.format_exc(), color.error)
+                    engine.message_log.add_message(traceback.format_exc(), color.error)
+
+        except exceptions.QuitWithoutSaving:
+            raise
+        except SystemExit:  # Save and quit.
+            # TODO: Add the save function here
+            raise
+        except BaseException:  # Save on any other unexpected exception.
+            # TODO: Add the save function here
+            raise
 
 
 if __name__ == "__main__":