#include <vhex/display/image.h>
#include <vhex/display/types.h>
#include <vhex/display/stack.h>
#include <vhex/display/shader.h>

//---
// Internal functions
//---

/* dimg_shadow_default_render() : add shadow on image with no alpha */
static void dimg_shadow_default_render(
	image_t *image,
	struct imgbox *box,
	int xoff,
	int yoff
) {
	(void)image;
	(void)box;
	(void)xoff;
	(void)yoff;
}



/* dimg_shadow_alpha_render() : add shadow on image with no alpha */
static void dimg_shadow_alpha_render(
	image_t *image,
	struct imgbox *box,
	int xoff,
	int yoff
) {
	uint16_t *vram;
	uint16_t *data;
	uint16_t pixel;
	uint16_t alpha;
	int voff;
	int xcnt;
	int ycnt;
	int c;
	int msk;
	int pxl;

	(void)xoff;
	(void)yoff;

	voff = box->surface.voff;
	vram = box->surface.vram;
	alpha = image_alpha(image->format);



	if (yoff < 0)
	{
		ycnt = 4;
		if (box->img.y.start <= 0)
			ycnt = 0;
		for (int iy = box->img.y.start; iy < box->img.y.end; ++iy) {
			data = vram;
			xcnt = 0;
			if (xoff < 0) {
				c = 0;
				for (int ix = box->img.x.start; ix < box->img.x.end; ++ix) {
					pixel = image_get_pixel(image, ix, iy);
					if (pixel != alpha) {
						if (xcnt < 4 || ycnt < 4) {
							pxl = data[c];
							msk = pxl;
							pxl  = ((msk & 0xF81F) >> 1) & 0xF81F;
							pxl |= ((msk & 0x07E0) >> 1) & 0x07E0;
							data[c] = pxl;
							xcnt += 1;
						}
					} else {
						xcnt = 0;
					}
					c += 1;
				}
			} else {
				c = box->img.x.end - box->img.x.start - 1;
				for (int ix = box->img.x.end - 1; ix >= box->img.x.start; --ix) {
					pixel = image_get_pixel(image, ix, iy);
					if (pixel != alpha) {
						if (xcnt < 4 || ycnt < 4) {
							pxl = data[c];
							msk = pxl;
							pxl  = ((msk & 0xF81F) >> 1) & 0xF81F;
							pxl |= ((msk & 0x07E0) >> 1) & 0x07E0;
							data[c] = pxl;
							xcnt += 1;
						}
					} else {
						xcnt = 0;
					}
					c -= 1;
				}
			}
			vram = &vram[voff];
			ycnt += 1;
		}
	} else {
		ycnt = 4;
		if (box->img.y.end >= image->height)
			ycnt = 0;
		vram = &vram[voff * (box->img.y.end - box->img.y.start - 1)];
		for (int iy = box->img.y.end - 1; iy >= box->img.y.start; --iy) {
			data = vram;
			xcnt = 0;
			if (xoff < 0) {
				c = 0;
				for (int ix = box->img.x.start; ix < box->img.x.end; ++ix) {
					pixel = image_get_pixel(image, ix, iy);
					if (pixel != alpha) {
						if (xcnt < 4 || ycnt < 4) {
							pxl = data[c];
							msk = pxl;
							pxl  = ((msk & 0xF81F) >> 1) & 0xF81F;
							pxl |= ((msk & 0x07E0) >> 1) & 0x07E0;
							data[c] = pxl;
							xcnt += 1;
						}
					} else {
						xcnt = 0;
					}
					c += 1;
				}
			} else {
				c = box->img.x.end - box->img.x.start - 1;
				for (int ix = box->img.x.end - 1; ix >= box->img.x.start; --ix) {
					pixel = image_get_pixel(image, ix, iy);
					if (pixel != alpha) {
						if (xcnt < 4 || ycnt < 4) {
							pxl = data[c];
							msk = pxl;
							pxl  = ((msk & 0xF81F) >> 1) & 0xF81F;
							pxl |= ((msk & 0x07E0) >> 1) & 0x07E0;
							data[c] = pxl;
							xcnt += 1;
						}
					} else {
						xcnt = 0;
					}
					c -= 1;
				}
			}
			vram = &vram[0 - voff];
			ycnt += 1;
		}
	}
}


//---
// Dstack-level API
//---

#include <vhex/display.h>

/* dimage_shader_shadow() : add shadows in any image rendered */
static void dimage_shader_shadow_dstack(
	dsurface_t *surface,
	uintptr_t *draw,
	uintptr_t *shader
) {
	struct imgbox imgbox;
	image_t *image;
	int xoff;
	int yoff;
	int ret;

	image = (image_t*)draw[0];
	xoff = (int)shader[0];
	yoff = (int)shader[1];

	ret = dsubimage_render_box(
		&imgbox,
		surface,
		image,
		(int)draw[1] + xoff,
		(int)draw[2] + yoff,
		(int)draw[3],
		(int)draw[4],
		(int)draw[5],
		(int)draw[6]
	);
	if (ret != 0)
		return;

#if 0
	static int test = 0;
	if (++test >= 2) {
		dclear(C_WHITE);
		dprint(0, 0, C_BLACK,
			"surface.x1 = %d\n"
			"surface.x2 = %d\n"
			"surface.y1 = %d\n"
			"surface.y2 = %d\n"
			"surface.width = %d\n"
			"surface.height = %d\n"
			"\n"
			"img.y.start = %d\n"
			"img.y.end   = %d\n"
			"img.x.start = %d\n"
			"img.x.end   = %d\n"
			"\n"
			"image.x = %d\n"
			"image.y = %d\n"
			"image.width = %d\n"
			"image.heigt = %d\n"
			"image.ptr = %p\n",
			surface->x1,
			surface->x2,
			surface->y1,
			surface->y2,
			surface->width,
			surface->height,
			imgbox.img.y.start,
			imgbox.img.y.end,
			imgbox.img.x.start,
			imgbox.img.x.end,
			xoff,
			yoff,
			(int)draw[3],
			(int)draw[4],
			(int)draw[5],
			(int)draw[6],
			(image_t*)(uintptr_t)draw[0]
		);
		dupdate();
		while(1) { __asm__ volatile ("sleep"); }
	} else {
		return;
	}
#endif

	/* send drawing request in the approriate optimized function */
	if (IMAGE_IS_ALPHA(image->format)) {
		dimg_shadow_alpha_render(image, &imgbox, xoff, yoff);
		return;
	}
	dimg_shadow_default_render(image, &imgbox, xoff, yoff);
}

//---
// User-level API
//---

/* dimage_shader_shadow() : add shadows in any image rendered */
int dimage_shader_shadow(did_t did, int xoff, int yoff)
{
	return dstack_add_shader(
		did,
		DSHADER(&dimage_shader_shadow_dstack, xoff, yoff)
	);
}