Untangle state changes into actions

WIP: still unclear if we really need the IORefs!

8 files changed, 59 insertions, 62 deletions

diff --git a/src/Game/Entities.hs b/src/Game/Entities.hs
index 4e5a686..4d8b12b 100644
--- a/src/Game/Entities.hs
+++ b/src/Game/Entities.hs
@@ -17,6 +17,7 @@ import Game.Entities.Types
 import qualified Game.Map as M
 import qualified Game.Sprites as S
 import qualified Game.State as GS
+import SDL (($~))
 import qualified SDL
 
 mkEntities :: S.SpriteSheet -> M.Map -> IORef C.Controls -> IORef GS.State -> IO Entities
@@ -30,9 +31,9 @@ mkEntities sprites m controls stateRef = do
   pure $ Entities sprites playerRef stateRef (player : entities)
   where
     toEntity :: IORef Entity -> M.Object -> IO Entity
-    toEntity playerRef (M.SlimeEntity x y) = mkSlime sprites x y (collision playerRef 16) (M.isBlocked m) (hitPlayer stateRef)
-    toEntity playerRef (M.RobotEntity x y) = mkRobot sprites x y (collision playerRef 24) (M.isBlocked m) (hitPlayer stateRef)
-    toEntity playerRef (M.BatteryEntity x y) = mkBattery sprites x y (collision playerRef 16) (collectedBattery stateRef)
+    toEntity playerRef (M.SlimeEntity x y) = mkSlime sprites x y (collision playerRef 16) (M.isBlocked m)
+    toEntity playerRef (M.RobotEntity x y) = mkRobot sprites x y (collision playerRef 24) (M.isBlocked m)
+    toEntity playerRef (M.BatteryEntity x y) = mkBattery sprites x y (collision playerRef 16)
     toEntity _ (M.PlayerEntity _ _) = error "Player already processed"
 
 -- | Return the player's entity position (x, y).
@@ -42,32 +43,48 @@ playerPosition (Entities _ _ _ entities) =
   where
     player = head entities
 
-processSpawn :: S.SpriteSheet -> Spawn -> IO Entity
-processSpawn sprites (DustEffectSpawn x y) = mkEffect sprites x y "dust"
-
 updateAll :: Entities -> IO Entities
 updateAll es = do
   -- update the player first (including the reference)
   updatedPlayer <- player.update player
   void $ writeIORef es.player updatedPlayer
-  state <- readIORef es.state
+  state <- readIORef stateRef
   -- update hit delay if the player was hit
   let playerWasHit = state.hitDelay > 0
-  when playerWasHit (writeIORef es.state state {GS.hitDelay = state.hitDelay - 1})
+  when playerWasHit (writeIORef stateRef state {GS.hitDelay = state.hitDelay - 1})
   -- then the other entities
   updated <- (updatedPlayer :) <$> traverse (updateFilter playerWasHit) others
-  -- collect new entities
-  new <- traverse (processSpawn es.sprites) (concatMap (\e -> e.spawns) updated)
-  -- is the player dead?
-  updated' <- do
-    s <- readIORef es.state
-    pure $ if s.lives == 0 && updatedPlayer.dir /= Dying then (head updated) {dir = Dying, gravity = gravityUp, frame = 0} : tail updated else updated
+  -- process actions
+  updated' <- processActions updated (concatMap (\e -> e.actions) updated)
   -- clear spawns (new entities), filter out destroyed entities, and add the new ones
-  pure es {entities = map (\e -> e {spawns = []}) (filter (\e -> not e.destroy) updated') ++ new}
+  pure es {entities = map (\e -> e {actions = []}) (filter (\e -> not e.destroy) updated')}
   where
+    stateRef = es.state
     player = head es.entities
     others = tail es.entities
 
+    processActions :: [Entity] -> [Action] -> IO [Entity]
+    processActions ents (a : t) =
+      case a of
+        ActionAddDustEffect x y -> do
+          effect <- mkEffect es.sprites x y "dust"
+          processActions (ents ++ [effect]) t
+        ActionAddBattery -> do
+          stateRef $~ (\s -> s {GS.batteries = s.batteries + 1})
+          processActions ents t
+        ActionHitPlayer -> do
+          s <- readIORef stateRef
+          ents' <-
+            if s.lives == 1
+              then do
+                writeIORef stateRef s {GS.lives = 0, GS.gameOverDelay = gameOverDelay}
+                pure $ (head ents) {dir = Dying, gravity = gravityUp, frame = 0} : tail ents
+              else do
+                writeIORef stateRef s {GS.lives = s.lives - 1, GS.hitDelay = hitDelay}
+                pure ents
+          processActions ents' t
+    processActions ents [] = pure ents
+
     -- Update entities skipping enemies if the player was hit.
     updateFilter :: Bool -> Entity -> IO Entity
     updateFilter False e = e.update e
diff --git a/src/Game/Entities/Common.hs b/src/Game/Entities/Common.hs
index ca5eb78..2e447f5 100644
--- a/src/Game/Entities/Common.hs
+++ b/src/Game/Entities/Common.hs
@@ -2,8 +2,6 @@ module Game.Entities.Common
   ( toSpriteSet,
     frameLimit,
     collision,
-    hitPlayer,
-    collectedBattery,
     updateFrame,
     updateGravity,
   )
@@ -13,8 +11,6 @@ import Data.IORef
 import Game.Entities.Const
 import Game.Entities.Types
 import qualified Game.Sprites as S
-import qualified Game.State as GS
-import SDL (($~))
 
 -- | Convert direction into a sprite set.
 toSpriteSet :: Dir -> Int
@@ -40,22 +36,6 @@ collision playerRef otherHeight other = do
       && player.y + otherHeight - 4 < other.y + otherHeight
       && other.y + 4 < player.y + 24
 
--- | Update game state to reflect that the player was hit by an enemy.
-hitPlayer :: IORef GS.State -> IO ()
-hitPlayer stateRef =
-  stateRef $~ updatePlayerHit
-  where
-    updatePlayerHit :: GS.State -> GS.State
-    updatePlayerHit s
-      -- if we run out of lives, trigger the game over
-      | s.lives == 1 = s {GS.lives = 0, GS.gameOverDelay = gameOverDelay}
-      | otherwise = s {GS.lives = s.lives - 1, GS.hitDelay = hitDelay}
-
--- | Update game state to reflect that the player picked up a battery.
-collectedBattery :: IORef GS.State -> IO ()
-collectedBattery stateRef =
-  stateRef $~ (\s -> s {GS.batteries = s.batteries + 1})
-
 -- | Update frame animation for entities that have direction.
 updateFrame :: Bool -> Entity -> Entity
 updateFrame updated e
diff --git a/src/Game/Entities/Effect.hs b/src/Game/Entities/Effect.hs
index 0a20445..7a2b341 100644
--- a/src/Game/Entities/Effect.hs
+++ b/src/Game/Entities/Effect.hs
@@ -21,7 +21,7 @@ mkEffect sprites x y name = do
         sprite = s,
         update = pure . updateEffect,
         destroy = False,
-        spawns = []
+        actions = []
       }
 
 updateEffect :: Entity -> Entity
diff --git a/src/Game/Entities/Pickup.hs b/src/Game/Entities/Pickup.hs
index 4aa7326..7c1937c 100644
--- a/src/Game/Entities/Pickup.hs
+++ b/src/Game/Entities/Pickup.hs
@@ -5,8 +5,8 @@ import Game.Entities.Const
 import Game.Entities.Types
 import qualified Game.Sprites as S
 
-mkBattery :: S.SpriteSheet -> Int -> Int -> Collision -> IO () -> IO Entity
-mkBattery sprites x y playerCollision collectedBattery' = do
+mkBattery :: S.SpriteSheet -> Int -> Int -> Collision -> IO Entity
+mkBattery sprites x y playerCollision = do
   s <- S.get sprites "battery"
   pure
     Entity
@@ -19,15 +19,15 @@ mkBattery sprites x y playerCollision collectedBattery' = do
         gravity = gravityOff,
         dir = DirRight,
         sprite = s,
-        update = updateBattery playerCollision collectedBattery',
+        update = updateBattery playerCollision,
         destroy = False,
-        spawns = []
+        actions = []
       }
 
-updateBattery :: Collision -> IO () -> Entity -> IO Entity
-updateBattery touchedPlayer collectedBattery' e = do
+updateBattery :: Collision -> Entity -> IO Entity
+updateBattery touchedPlayer e = do
   touched <- touchedPlayer e
-  if touched then e {destroy = True} <$ collectedBattery' else pure updateBatteryFrame
+  pure $ if touched then e {destroy = True, actions = [ActionAddBattery]} else updateBatteryFrame
   where
     updateBatteryFrame :: Entity
     updateBatteryFrame
diff --git a/src/Game/Entities/Player.hs b/src/Game/Entities/Player.hs
index f0a526c..87e8a7a 100644
--- a/src/Game/Entities/Player.hs
+++ b/src/Game/Entities/Player.hs
@@ -23,7 +23,7 @@ mkPlayer sprites x y controls isBlocked = do
         sprite = s,
         update = updatePlayer controls isBlocked,
         destroy = False,
-        spawns = []
+        actions = []
       }
 
 updateHorizontal :: IsBlocked -> Bool -> Bool -> Entity -> Entity
@@ -48,7 +48,7 @@ updateVertical isBlocked jump down e
       -- make jumping easier with "Coyote time"
       || (e.gravity /= gravityOff && (e.gravity < gravityDown || e.gravity > jumpLimit)) =
       e
-  | not down = e {jumping = True, gravity = gravityUp, frame = jumpFrame, spawns = e.spawns ++ [DustEffectSpawn e.x (e.y + 8)]}
+  | not down = e {jumping = True, gravity = gravityUp, frame = jumpFrame, actions = [ActionAddDustEffect e.x (e.y + 8)]}
   -- go down a 8 pixel tall platform; not ideal to have these values hardcoded here
   -- but to be fair, the player height/width is hardcoded as well
   | down
diff --git a/src/Game/Entities/Robot.hs b/src/Game/Entities/Robot.hs
index 39b63aa..dd3404a 100644
--- a/src/Game/Entities/Robot.hs
+++ b/src/Game/Entities/Robot.hs
@@ -6,8 +6,8 @@ import Game.Entities.Const
 import Game.Entities.Types
 import qualified Game.Sprites as S
 
-mkRobot :: S.SpriteSheet -> Int -> Int -> Collision -> IsBlocked -> IO () -> IO Entity
-mkRobot sprites x y playerCollision isBlocked hitPlayer' = do
+mkRobot :: S.SpriteSheet -> Int -> Int -> Collision -> IsBlocked -> IO Entity
+mkRobot sprites x y playerCollision isBlocked = do
   s <- S.get sprites "robot"
   pure
     Entity
@@ -20,16 +20,16 @@ mkRobot sprites x y playerCollision isBlocked hitPlayer' = do
         gravity = gravityOff,
         dir = DirRight,
         sprite = s,
-        update = updateRobot playerCollision isBlocked hitPlayer',
+        update = updateRobot playerCollision isBlocked,
         destroy = False,
-        spawns = []
+        actions = []
       }
 
-updateRobot :: Collision -> IsBlocked -> IO () -> Entity -> IO Entity
-updateRobot touchedPlayer isBlocked hitPlayer' e = do
+updateRobot :: Collision -> IsBlocked -> Entity -> IO Entity
+updateRobot touchedPlayer isBlocked e = do
   touched <- touchedPlayer e
   let updated = updateFrame True e
-  if touched then fmap (const e) hitPlayer' else pure $ updateMovement updated
+  pure $ if touched then updated {actions = [ActionHitPlayer]} else updateMovement updated
   where
     updateMovement :: Entity -> Entity
     updateMovement ent
diff --git a/src/Game/Entities/Slime.hs b/src/Game/Entities/Slime.hs
index 5ca6fe7..1f50927 100644
--- a/src/Game/Entities/Slime.hs
+++ b/src/Game/Entities/Slime.hs
@@ -6,8 +6,8 @@ import Game.Entities.Const
 import Game.Entities.Types
 import qualified Game.Sprites as S
 
-mkSlime :: S.SpriteSheet -> Int -> Int -> Collision -> IsBlocked -> IO () -> IO Entity
-mkSlime sprites x y playerCollision isBlocked hitPlayer' = do
+mkSlime :: S.SpriteSheet -> Int -> Int -> Collision -> IsBlocked -> IO Entity
+mkSlime sprites x y playerCollision isBlocked = do
   s <- S.get sprites "slime"
   pure
     Entity
@@ -20,16 +20,16 @@ mkSlime sprites x y playerCollision isBlocked hitPlayer' = do
         gravity = gravityOff,
         dir = DirRight,
         sprite = s,
-        update = updateSlime playerCollision isBlocked hitPlayer',
+        update = updateSlime playerCollision isBlocked,
         destroy = False,
-        spawns = []
+        actions = []
       }
 
-updateSlime :: Collision -> IsBlocked -> IO () -> Entity -> IO Entity
-updateSlime touchedPlayer isBlocked hitPlayer' e = do
+updateSlime :: Collision -> IsBlocked -> Entity -> IO Entity
+updateSlime touchedPlayer isBlocked e = do
   touched <- touchedPlayer e
   let updated = updateSlimeFrame
-  if touched then fmap (const e) hitPlayer' else pure $ updateMovement updated
+  pure $ if touched then updated {actions = [ActionHitPlayer]} else updateMovement updated
   where
     updateMovement :: Entity -> Entity
     updateMovement ent
diff --git a/src/Game/Entities/Types.hs b/src/Game/Entities/Types.hs
index a50ab2d..e22032b 100644
--- a/src/Game/Entities/Types.hs
+++ b/src/Game/Entities/Types.hs
@@ -4,7 +4,7 @@ module Game.Entities.Types
     Collision,
     IsBlocked,
     Entities (..),
-    Spawn (..),
+    Action (..),
     Entity (..),
   )
 where
@@ -28,7 +28,7 @@ data Entities = Entities
     entities :: [Entity]
   }
 
-data Spawn = DustEffectSpawn Int Int
+data Action = ActionAddDustEffect Int Int | ActionAddBattery | ActionHitPlayer deriving (Show)
 
 data Entity = Entity
   { typ :: Type,
@@ -42,5 +42,5 @@ data Entity = Entity
     sprite :: S.Sprite,
     update :: Entity -> IO Entity,
     destroy :: Bool,
-    spawns :: [Spawn]
+    actions :: [Action]
   }