various: implement fog of war; make enemy AI slightly more intelligent

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I3e22dbc5e10690871255980c52a24c226a6a6964

src/map.c

@@ -1,6 +1,8 @@
 #include "map.h"
 #include "rng.h"
+#include "settings.h"
 #include "utils.h"
+#include <stdlib.h>
 #include <string.h>
 
 void map_init(Map *map) {
@@ -186,3 +188,67 @@ void dungeon_generate(Dungeon *d, Map *map, int floor_num) {
   d->room_count = map->room_count;
   memcpy(d->rooms, map->rooms, sizeof(Room) * map->room_count);
 }
+
+int is_in_view_range(int x, int y, int view_x, int view_y, int range) {
+  int dx = x - view_x;
+  int dy = y - view_y;
+  return (dx * dx + dy * dy) <= (range * range);
+}
+
+static int trace_line_of_sight(const Map *map, int x1, int y1, int x2, int y2) {
+  int dx = abs(x2 - x1);
+  int dy = abs(y2 - y1);
+  int sx = (x1 < x2) ? 1 : -1;
+  int sy = (y1 < y2) ? 1 : -1;
+  int err = dx - dy;
+  int x = x1;
+  int y = y1;
+
+  while (1) {
+    if (!in_bounds(x, y, MAP_WIDTH, MAP_HEIGHT))
+      return 0;
+
+    if (x == x2 && y == y2)
+      return 1;
+
+    if (map->tiles[y][x] == TILE_WALL && !(x == x1 && y == y1))
+      return 0;
+
+    int e2 = 2 * err;
+    if (e2 > -dy) {
+      err -= dy;
+      x += sx;
+    }
+    if (e2 < dx) {
+      err += dx;
+      y += sy;
+    }
+  }
+}
+
+int has_line_of_sight(const Map *map, int x1, int y1, int x2, int y2) {
+  if (!in_bounds(x1, y1, MAP_WIDTH, MAP_HEIGHT) || !in_bounds(x2, y2, MAP_WIDTH, MAP_HEIGHT))
+    return 0;
+  return trace_line_of_sight(map, x1, y1, x2, y2);
+}
+
+int can_see_entity(const Map *map, int from_x, int from_y, int to_x, int to_y, int range) {
+  if (!is_in_view_range(to_x, to_y, from_x, from_y, range))
+    return 0;
+  return has_line_of_sight(map, from_x, from_y, to_x, to_y);
+}
+
+void calculate_visibility(Map *map, int x, int y) {
+  memset(map->visible, 0, sizeof(map->visible));
+
+  for (int ty = 0; ty < MAP_HEIGHT; ty++) {
+    for (int tx = 0; tx < MAP_WIDTH; tx++) {
+      if (is_in_view_range(tx, ty, x, y, PLAYER_VIEW_RANGE)) {
+        if (has_line_of_sight(map, x, y, tx, ty)) {
+          map->visible[ty][tx] = 1;
+          map->remembered[ty][tx] = 1;
+        }
+      }
+    }
+  }
+}