From 56a4aa9d393bb418708511385f2a7d4838917767 Mon Sep 17 00:00:00 2001
From: herbglitch <herbglitch@github.com>
Date: Mon, 26 Jun 2023 01:27:30 -0600
Subject: [PATCH] collide and slide function for FRect

---
 include/arc/math/rectangle.h | 16 ++++++++++++++++
 src/math/rectangle.c         | 27 +++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/include/arc/math/rectangle.h b/include/arc/math/rectangle.h
index 183362b..7427579 100644
--- a/include/arc/math/rectangle.h
+++ b/include/arc/math/rectangle.h
@@ -3,6 +3,7 @@
 
 #include <stdint.h>
 #include "point.h"
+#include "vector2.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -118,6 +119,21 @@ int32_t ARC_FRect_IntersectsPoint(ARC_FRect *rect, ARC_Point *point);
  */
 int32_t ARC_Rect_LineIntersects(ARC_Rect *rect, int32_t *x1, int32_t *y1, int32_t *x2, int32_t *y2);
 
+/**
+ * @brief checks for a ARC_Rect on ARC_Rect collision and slides on collision
+ * 
+ * @note need to update this documenation to word it better
+ *
+ * @param rect     ARC_Rect that might collide with the wall
+ * @param velocity the ammount ARC_Rect will move
+ * @param wall     ARC_Rect that might have collision with rect
+ *
+ * @note velocity is updated based on colliding,
+ *       rect's values are not changed,
+ *       velocity should be applied after
+ */
+void ARC_FRect_CollideAndSlide(ARC_FRect *rect, ARC_Vector2 *velocity, ARC_FRect *wall);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/math/rectangle.c b/src/math/rectangle.c
index 42de8c2..ce1a3d4 100644
--- a/src/math/rectangle.c
+++ b/src/math/rectangle.c
@@ -69,3 +69,30 @@ int32_t ARC_Rect_LineIntersects(ARC_Rect *rect, int32_t *x1, int32_t *y1, int32_
     return 1;
 }
 
+//TODO: position 1px away from colliding, so if velocity is greater than 2px it doesn't have weird gap spacing
+//      might need to check diagnals as well, this is a rudamentry implementation
+void ARC_FRect_CollideAndSlide(ARC_FRect *rect, ARC_Vector2 *velocity, ARC_FRect *wall){
+    ARC_FRect nextRectPosition = {
+        .x = rect->x + velocity->x,
+        .y = rect->y + velocity->y,
+        .w = rect->w,
+        .h = rect->h
+    };
+
+    //there is no collision, return
+    if(!ARC_FRect_Intersects(&nextRectPosition, wall)){
+        return;
+    }
+
+    nextRectPosition.x = rect->x + velocity->x;
+    nextRectPosition.y = rect->y;
+    if(ARC_FRect_Intersects(&nextRectPosition, wall)){
+        velocity->x = 0;
+    }
+
+    nextRectPosition.x = rect->x;
+    nextRectPosition.y = rect->y + velocity->y;
+    if(ARC_FRect_Intersects(&nextRectPosition, wall)){
+        velocity->y = 0;
+    }
+}
\ No newline at end of file