From b01133aa41dd617c27be81eabe33f90b69cbf618 Mon Sep 17 00:00:00 2001
From: Daniel Liu <mr.picklepinosaur@gmail.com>
Date: Sat, 1 May 2021 14:32:50 -0400
Subject: [PATCH] basic water update

---
 Sim.hs | 41 ++++++++++++++++++++++++++++++-----------
 1 file changed, 30 insertions(+), 11 deletions(-)

diff --git a/Sim.hs b/Sim.hs
index 8dd5819..c48dbe4 100644
--- a/Sim.hs
+++ b/Sim.hs
@@ -1,18 +1,18 @@
-module Sim ( initSimSpace, testSim, physStep ) where
+module Sim ( initSimSpace, testSim, physStep, updateWaterChunk, validDirects ) where
 
+import Debug.Trace
 import           Data.Vector ((!), (//))
 import qualified Data.Vector as V
 
--- Simulation simSpace simW simH
 data Simulation = Simulation
     { simSpace          :: V.Vector ChunkData
     , simW              :: Int
     , simH              :: Int
     } deriving (Show)
 
-data ChunkType = Empty
+data ChunkType = Air
     | Water 
-    | Wall deriving (Show)
+    | Wall deriving (Show, Enum)
 
 data ChunkData = ChunkData 
     { chunkType         :: ChunkType
@@ -21,29 +21,48 @@ data ChunkData = ChunkData
 -- vec accessors
 simGet Simulation{simSpace=s,simW=w} x y = s ! (y*w+x)
 simSet sim@Simulation{simSpace=s,simW=w,simH=h} c x y = sim { simSpace = (s // [(y*w+x,c)]) }
+simGetChunkType sim x y = chunkType $ simGet sim x y
 
 initSimSpace x y = Simulation
-    { simSpace = V.replicate (y*x) ChunkData { chunkType=Empty }
+    { simSpace = V.replicate (y*x) ChunkData { chunkType=Air }
     , simW = x
     , simH = y
     }
 
-testSim = simSet (initSimSpace 10 10) (ChunkData Water) 5 0
+testSim = simSet (initSimSpace 3 3) (ChunkData Water) 1 1
 
-physStep sim@Simulation{simW=w,simH=h} = _physStep [(x, y) | x <- [0..w-1], y <- [0..h-1]] (initSimSpace w h) sim
+physStep sim@Simulation{simW=w,simH=h} = _physStep [(x, y) | x <- [0..w-1], y <- [0..h-1]] sim sim
+-- _physStep grid acc sim@Simulation{simSpace=s,simW=w,simH=h} | trace ("" ++ show acc) False = undefined
 _physStep grid acc sim@Simulation{simSpace=s,simW=w,simH=h} =
     if null grid then acc
     else _physStep (tail grid) next sim
     where x = fst $ head grid
           y = snd $ head grid
-          next = sim
+          valid = validDirects x y w h
+          next = case simGetChunkType sim x y of
+              Water -> updateWaterChunk x y valid acc
+              _ -> acc
 
 -- takes in list of valid chunks, as well as the sim to modify
--- updateWaterChunk valid sim =
-    
+updateWaterChunk x y valid sim =
+    -- if the chunk below is free, fall straight down
+    if elem (0,-1) valid && fromEnum (simGetChunkType sim x (y-1)) == fromEnum Air
+        then
+            let moved = simSet sim ChunkData { chunkType=Air } x y
+            in simSet moved ChunkData { chunkType=Water } x (y-1)
+    else if elem (-1,-1) valid && fromEnum (simGetChunkType sim (x-1) (y-1)) == fromEnum Air
+        then
+            let moved = simSet sim ChunkData { chunkType=Air } x y
+            in simSet moved ChunkData { chunkType=Water } (x-1) (y-1)
+    else if elem (1,-1) valid && fromEnum (simGetChunkType sim (x+1) (y-1)) == fromEnum Air
+        then
+            let moved = simSet sim ChunkData { chunkType=Air } x y
+            in simSet moved ChunkData { chunkType=Water } (x+1) (y-1)
+    -- stay put
+    else sim
 
 -- gets chunks around a given chunk that are inside grid
 validDirects x y w h = filter
     (\q -> 0 <= (fst q) && (fst q) < w && (snd q) <= 0 && (snd q) < h)
-    [(a,b) | a <- [x-1..x+1], b <- [y-1..y+1], not (a==x && b==y)]
+    [(a-x,b-y) | a <- [x-1..x+1], b <- [y-1..y+1], not (a==x && b==y)]
 
-- 
2.20.1