1 files changed, 159 insertions, 13 deletions

diff --git a/collision_system.c b/collision_system.c
index 68e3b09..2a1ac03 100644
--- a/collision_system.c
+++ b/collision_system.c
@@ -1,11 +1,43 @@
 #ifndef systems_h
 #define systems_h
 
+#include <stdint.h>
+
+#include "components.h"
 #include "config.h"
 #include "fx.h"
 #include "rect.h"
+#include "standard.h"
 #include "world.h"
 
+#ifdef DEBUG
+#include "error.h"
+#include "platform.h"
+#endif
+
+typedef enum {
+	collision_side_left = 0,
+	collision_side_right,
+	collision_side_top,
+	collision_side_bottom
+} Collision_Side;
+
+static Collision_Side invert_side(Collision_Side side) {
+	switch (side) {
+		case collision_side_left:   return collision_side_right;
+		case collision_side_right:  return collision_side_left;
+		case collision_side_bottom: return collision_side_top;
+		case collision_side_top:    return collision_side_bottom;
+	}
+
+#if DEBUG
+	platform_err("Invalid collision side.\n");
+	platform_abort(error_gameplay_error);
+#endif
+
+	return -1;
+}
+
 static void handle_bullet_vs_player(
 	World* world,
 	Entity bullet,
@@ -32,7 +64,66 @@ static void handle_bullet_vs_enemy(
 	destroy_entity(world, bullet);
 }
 
-static void handle(World* world, Entity a, Entity b) {
+static void handle_bullet_vs_solid(
+	World* world,
+	Entity bullet,
+	Entity solid
+) {
+	const CPosition* pos;
+	unsigned bbits;
+
+	bbits = world->bitmask[bullet];
+
+	if (bbits & ctype_enemy_bullet) {
+		pos = &world->positions[bullet];
+		new_enemy_bullet_explosion(world, pos->x, pos->y);
+	}
+
+	destroy_entity(world, bullet);
+}
+
+static void handle_moveable_vs_solid(
+	World* world,
+	Entity moveable,
+	Entity solid,
+	Collision_Side side
+) {
+	const CCollider* scol, * mcol;
+	const CPosition* spos;
+	CPosition* mpos;
+
+	scol = &world->colliders[solid];
+	mcol = &world->colliders[moveable];
+	spos = &world->positions[solid];
+	mpos = &world->positions[moveable];
+
+	switch (side) {
+		case collision_side_top:
+			mpos->y = spos->y + scol->y + scol->h - mcol->y;
+			return;
+		case collision_side_bottom:
+			mpos->y = (spos->y + scol->y) - (mcol->y + mcol->h);
+			return;
+		case collision_side_left:
+			mpos->x = spos->x + scol->x + scol->w - mcol->x;
+			return;
+		case collision_side_right:
+			mpos->x = (spos->x + scol->x) - (mcol->x + mcol->w);
+			return;
+	}
+
+#if DEBUG
+	platform_err("Invalid collision side.\n");
+	platform_abort(error_gameplay_error);
+#endif
+}
+
+static void handle(
+	World* world,
+	Entity a,
+	Entity b,
+	Collision_Side side
+) {
 	unsigned ab, bb;
 
 	ab = world->bitmask[a];
@@ -42,7 +133,6 @@ static void handle(World* world, Entity a, Entity b) {
 		handle_bullet_vs_player(world, a, b);
 		return;
 	}
-
 	if ((ab & ctype_player) && (bb & ctype_enemy_bullet)) {
 		handle_bullet_vs_player(world, b, a);
 		return;
@@ -52,18 +142,39 @@ static void handle(World* world, Entity a, Entity b) {
 		handle_bullet_vs_enemy(world, a, b);
 		return;
 	}
-
 	if ((ab & ctype_enemy) && (bb & ctype_player_bullet)) {
 		handle_bullet_vs_enemy(world, b, a);
 		return;
 	}
+
+	if ((ab & ctype_bullet) && (bb & ctype_solid)) {
+		handle_bullet_vs_solid(world, a, b);
+		return;
+	}
+	if ((ab & ctype_solid) && (bb & ctype_bullet)) {
+		handle_bullet_vs_solid(world, b, a);
+		return;
+	}
+
+	if ((ab & ctype_moveable) && (bb & ctype_solid)) {
+		handle_moveable_vs_solid(world, a, b, side);
+		return;
+	}
+	if ((ab & ctype_solid) && (bb & ctype_moveable)) {
+		side = invert_side(side);
+		handle_moveable_vs_solid(world, b, a, side);
+		return;
+	}
 }
 
 void collision_system(World* world) {
-	int i, j, p0x, p0y;
+	int i, j, k, s, s2, p0x, p0y, r, l, t, b;
+	int ax, ay, aw, ah, bx, by, bw, bh;
+	int overlap[4];
 	unsigned bits;
 	const CPosition* pos0, * pos1;
 	const CCollider* col0, * col1;
+	Collision_Side side;
 
 	for (i = 0; i < world->entity_count; i++) {
 		bits = world->bitmask[i];
@@ -87,17 +198,52 @@ void collision_system(World* world) {
 			pos1 = &world->positions[j];
 			col1 = &world->colliders[j];
 
+			ax = p0x;
+			ay = p0y;
+			aw = col0->w;
+			ah = col0->h;
+			bx = pos1->x + col1->x;
+			by = pos1->y + col1->y;
+			bw = col1->w;
+			bh = col1->h;
+
+			/* Can you tell I made this while I had a migraine? */
 			if (rects_overlap2(
-				p0x,
-				p0y,
-				col0->w,
-				col0->h,
-				pos1->x + col1->x,
-				pos1->y + col1->y,
-				col1->w,
-				col1->h
+				ax,
+				ay,
+				aw,
+				ah,
+				bx,
+				by,
+				bw,
+				bh
 			)) {
-				handle(world, i, j);
+				r = (ax + aw) - bx;
+				l = (bx + bw) - ax;
+				t = (by + bh) - ay;
+				b = (ay + ah) - by;
+
+				overlap[0] = r;
+				overlap[1] = l;
+				overlap[2] = t;
+				overlap[3] = b;
+				s = INT32_MAX;
+				for (k = 0; k < 4; k++) {
+					s2 = overlap[k];
+					if (s2 < s) { s = s2; }
+				}
+
+				if (s == absolute(r)) {
+					side = collision_side_right;
+				} else if (s == absolute(l)) {
+					side = collision_side_left;
+				} else if (s == absolute(b)) {
+					side = collision_side_bottom;
+				} else if (s == absolute(t)) {
+					side = collision_side_top;
+				}
+
+				handle(world, i, j, side);
 			}
 		}
 	}