#include "asset.h"
#include "config.h"
#include "map.h"
#include "maths.h"
#include "physics.h"
#include "rect.h"
#include "render.h"

int test_bit(
	unsigned* data,
	int x,
	int y,
	int w
) {
	int idx = x + y * w;
	return data[idx >> 5] & (1 << (idx & 0x1f));
}

static int solve_mask(
	unsigned char t,
	int* y,
	int* vy,
	const Rect* col,
	const Rect* r,
	const Rect* tr,
	int* od
) {
	int n, d = 0;
	const Bitmap* b = get_bitmap(asset_id_mask_img);
	unsigned* mp;
	int xoff = 0;
	int mx = r->x + r->w / 2;
	int my = (r->y + r->h) - f1;
	mx -= tr->x;
	my -= tr->y;
	mx >>= fbits;
	my >>= fbits;
	if (mx < 0 || mx >= map_tile_size)
		return 0;
	if ((n = my - map_tile_size) >= 0 && n < 4)
		my = map_tile_size - 1;
	mp = (unsigned*)&b[1];
	xoff = (t & 0xf) * map_tile_size;
	if (my >= map_tile_size) return 0;
	if (my < 0 || *vy < 0) goto up;
	if (test_bit(mp, mx + xoff, my, b->w)) {
		d = -1;
		my = map_tile_size - 1;
	} else {
up:
		my = (r->y - tr->y) >> fbits;
		if (my < 0) {
			if (my >= -4) my = 0;
			else          return 0;
		}
		if (my >= map_tile_size) return 0;
		if (test_bit(mp, mx + xoff, my, b->w)) d = 1;
		my = 0;
	}
	if (!d)                return 0;
	if (d < 0 && *vy <= 0) return 0;
	if (d > 0 && *vy >= 0) return 0;
	for (
		;
			test_bit(mp, mx + xoff, my, b->w) &&
			my >= 0 &&
			my < map_tile_size;
		my += d
	);
	if (d < 0) {
		*y = (tr->y - (col->y + col->h));
		*y += (my << fbits) + f1 * 2;
	} else {
		*y = (tr->y + tr->h) - col->y;
		*y -= ((map_tile_size - my) << fbits);
	}
	*vy = 0;
	*od = d;
	return 1;
}

void update_body(
	const struct Map* map,
	int* x,
	int* y,
	int* vx,
	int* vy,
	int* grounded,
	int* headbutted,
	int* on_ramp,
	const Rect* r
) {
	Rect rect = { 0 };
	int ramp = 0, d;
	rect.w = r->w;
	rect.h = r->h;
	if (grounded[0] < 3) {
		*vx = (*vx << fbits) / (f1 + player_friction);
	}
	grounded[0]++;
	headbutted[0] = 0;
#define ittiles(expr) { \
	int sx, sy, ex, ey, tx, ty; \
	Rect tr; \
	rect.x = *x + r->x; \
	rect.y = *y + r->y; \
	sx = (rect.x >> fbits) / map_tile_size; \
	sy = (rect.y >> fbits) / map_tile_size; \
	ex = ((rect.x + rect.w) >> fbits) / map_tile_size; \
	ey = ((rect.y + rect.h) >> fbits) / map_tile_size; \
	tr.w = map_tile_size << fbits; \
	tr.h = map_tile_size << fbits; \
	for (ty = sy; ty <= ey && ty < map_h; ty++) { \
		for (tx = sx; tx <= ex && tx < map_w; tx++) { \
			int tc = map->collision[tx + ty * map_w]; \
			tr.x = (tx * map_tile_size) << fbits; \
			tr.y = (ty * map_tile_size) << fbits; \
			if (rects_overlap(&tr, &rect)) \
				expr \
		} \
	}}
	/* increase the gravity if i'm on a ramp, to
	 * smoothly slide down instead of skipping */
	*vy += main_gravity + main_gravity_ramp * (*on_ramp && *grounded < 3);
	if (*vy) {
		*y += *vy;
		ittiles({
			if (tc > 1) {
				int id = tc - 2;
				if (solve_mask(
					id,
					y,
					vy,
					r,
					&rect,
					&tr,
					&d
				)) {
					if (d < 0)
						*grounded = 0;
					else {
						*headbutted = 1;
					}
					ramp = 1;
				}
			}
		});
		if (ramp) goto do_x;
		ittiles({
			if (tc == 1) {
				if (*vy > 0) {
					*y = tr.y - (r->y + r->h);
					*vy = 0;
					*grounded = 0;
				} else if (*vy < 0) {
					*y = (tr.y + tr.h) - r->y;
					*vy = 0;
					*headbutted = 1;
				}
			}
		});
	}
do_x:
	*on_ramp = ramp;
	if (*vx) {
		*x += *vx;
		if (ramp) {
			/* Handle the case where the body is at the top
			 * of a ramp hitting into a block. */
			ittiles({
				if (tc == 1) {
					int cy;
					if (d < 0) cy = rect.y;
					else cy = rect.y + rect.h;
					if (*vx < 0 && point_rect_overlap(
						&tr,
						rect.x,
						cy
					)) *x = (tr.x + tr.w) - r->x;
					if (*vx > 0 && point_rect_overlap(
						&tr,
						rect.x + rect.w,
						cy
					)) *x = tr.x - (r->x + r->w);
				}
			});
			return;
		}
		ittiles({
			if (tc == 1) {
				if (*vx > 0) {
					*x = tr.x - (r->x + r->w);
					*vx = 0;
				} else if (*vx < 0) {
					*x = (tr.x + tr.w) - r->x;
					*vx = 0;
				}
			}
		});
	}
}