From edf7d4c8dc9c294b0caf76dbd998a58648c26e34 Mon Sep 17 00:00:00 2001
From: Humza Shahid <humzasaur@gmail.com>
Date: Sat, 18 Jan 2025 22:13:16 +0000
Subject: [PATCH] fix bug in physics.sml where player/enemy would drop below
 continuously past multiple platforms even if they intended to drop below
 platforms only once (fixed by setting yAxis to 'FALLING' if there are no
 collisions at all and player is in DROP_BELOW_PLATFORMS state)

---
 fcore/enemy-behaviour.sml | 18 +++++++++++++++++-
 fcore/physics.sml         | 16 ++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/fcore/enemy-behaviour.sml b/fcore/enemy-behaviour.sml
index 1d7649e..f4d01d9 100644
--- a/fcore/enemy-behaviour.sml
+++ b/fcore/enemy-behaviour.sml
@@ -1,4 +1,4 @@
-structure EnemyBehaviour =
+1tructure EnemyBehaviour =
 struct
   open GameType
 
@@ -143,6 +143,22 @@ struct
   fun hasVisted (find, visited) =
     helpHasVisited (0, Char.chr find, visited)
 
+  fun isBetween (p1, check, p2) = check >= p1 andalso check <= p2
+
+  fun isReachableFromBottom (prevPlat: platform, currentPlat: platform) =
+    let
+      val {x = prevX, y = prevY, width = prevWidth, ...} = prevPlat
+      val {x = curX, y = curY, width = curWidth, ...} = currentPlat
+
+      val prevFinishX = prevX + prevWidth
+      val curFinishX = curX + curWidth
+    in
+      (isBetween (prevX, curX, prevFinishX)
+       orelse
+       isBetween (prevX, curFinishX, prevFinishX)
+       andalso prevY + Constants.jumpLimit >= curY)
+    end
+
   fun isReachableFromLeft (prevPlat, currentPlat) =
     (* prev = right/from, current = left/to *)
     let
diff --git a/fcore/physics.sml b/fcore/physics.sml
index a17b532..2a78f5b 100644
--- a/fcore/physics.sml
+++ b/fcore/physics.sml
@@ -153,6 +153,22 @@ struct
         (x, y, size, size, 0, 0, ww, wh, 0, platformTree)
       val acc = getPlatformPatches (yAxis, platforms, platCollisions, [])
 
+      val acc = 
+        case yAxis of
+          DROP_BELOW_PLATFORM =>
+            (* if we dropped below platform before 
+            * but we have fully passed the platform now 
+            * such that there are no platform collisions
+            * then set new yAxis to FALLING
+            * so we do not drop below any platforms again
+            * *)
+            if QuadTree.hasCollisionAt (x, y, size, size, 0, 0, ww, wh, ~1,
+            platformTree)
+            then
+              Fn.W_Y_AXIS FALLING :: acc
+            else acc
+        | _ => acc
+
       val wallCollisions = QuadTree.getCollisionSides
         (x, y, size, size, 0, 0, ww, wh, 0, wallTree)
     in