From ed585355b1f78de15885e803138a98b75ca2b1e2 Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Mon, 20 Feb 2023 21:52:22 +0000
Subject: Split entities in modules.

---
 src/Game/Entities/Common.hs | 87 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)
 create mode 100644 src/Game/Entities/Common.hs

(limited to 'src/Game/Entities/Common.hs')

diff --git a/src/Game/Entities/Common.hs b/src/Game/Entities/Common.hs
new file mode 100644
index 0000000..b79c3db
--- /dev/null
+++ b/src/Game/Entities/Common.hs
@@ -0,0 +1,87 @@
+module Game.Entities.Common
+  ( toSpriteSet,
+    frameLimit,
+    collision,
+    hitPlayer,
+    collectedBattery,
+    updateFrame,
+    updateGravity,
+  )
+where
+
+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
+toSpriteSet DirRight = 0
+toSpriteSet DirLeft = 1
+
+-- | Return the number of frames available on the entity's sprite for current direction.
+frameLimit :: Entity -> Int
+frameLimit e = S.frameCount e.sprite (toSpriteSet e.dir)
+
+-- | Collision detection of player vs entity.
+--
+-- The player's head won't register, this is necessary to avoid hitting things on a platform above when jumping.
+collision :: IORef Entity -> Collision
+collision playerRef other = do
+  player <- readIORef playerRef
+  pure $
+    player.x + 4 < other.x + 12
+      && other.x + 4 < player.x + 12
+      && player.y + 12 < other.y + 16
+      && 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 = 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
+  | isGravityOn = e
+  | e.delay > 0 = e {delay = e.delay - 1}
+  | e.frame + 1 < frameLimit e = e {delay = frameDelay, frame = if updated then e.frame + 1 else 0}
+  | otherwise = e {delay = frameDelay, frame = 0}
+  where
+    isGravityOn = e.gravity > gravityOff
+
+applyGravity :: IsBlocked -> Int -> Entity -> Entity
+applyGravity isBlocked v e
+  | v == 0 = e
+  -- hit the floor
+  | isGoingDown
+      && (isBlocked (e.x + 4) (e.y + 24) || isBlocked (e.x + 10) (e.y + 24))
+      && not (isBlocked (e.x + 4) (e.y + 23))
+      && not (isBlocked (e.x + 10) (e.y + 23)) =
+      e {jumping = False, gravity = gravityOff, delay = 0}
+  | otherwise = applyGravity isBlocked (v - 1) e {y = e.y + change}
+  where
+    isGoingDown = e.gravity >= gravityDown
+    change = if isGoingDown then 1 else -1
+
+-- | Update gravity.
+--
+-- XXX: hardcoded to 16x24 pixels sprite.
+updateGravity :: IsBlocked -> Entity -> Entity
+updateGravity isBlocked e
+  | current > gravityOff = applyGravity isBlocked (gravityTable !! current) e {gravity = new}
+  | not (isBlocked (e.x + 4) (e.y + 24) || isBlocked (e.x + 10) (e.y + 24)) = e {gravity = gravityDown, frame = jumpFrame}
+  | otherwise = e
+  where
+    current = e.gravity
+    new = if current > gravityOff && current < length gravityTable - 1 then current + 1 else current
-- 
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