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

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

struct imgbox {
	struct {
		struct {
			int start;
			int end;
		} y;
		struct {
			int start;
			int end;
		} x;
	} img;
	struct {
		uint16_t *vram;
		int voff;
	} surface;
};

/* dsubimage_default_render() : raw-format image render */
static void dsubimage_default_render(image_t const *image, struct imgbox *box)
{
	(void)image;
	(void)box;
#if 0
	uint16_t *vram;
	uint16_t *vidxs;
	uint16_t *vidx;
	int voff;

	vram = surface->draw;
	voff = box->surface.idx.offset;
	vidxs = &vram[box->surface.idx.start];

	for (int iy = box->img.y.start; iy < box->img.y.end; ++iy) {
		vidx = vidxs;
		for (int ix = box->img.x.start; ix < box->img.x.end; ++ix) {
			*(vidx++) = image_decode_pixel(
				image,
				image_get_pixel(image, ix, iy)
			);
		}
		vidxs = &vidxs[voff];
	}
#endif
}

/* dsubimage_alpha_render() : alpha-format image render */
static void dsubimage_alpha_render(image_t const *image, struct imgbox *box)
{
	uint16_t *vram;
	uint16_t *data;
	uint16_t pixel;
	uint16_t alpha;
	int voff;
	int c;

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

	for (int iy = box->img.y.start; iy < box->img.y.end; ++iy) {
		data = vram;
		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)
				data[c] = image_decode_pixel(image, pixel);
			c += 1;
		}
		vram = &vram[voff];
	}
}


//---
// Kernel-level API
//---

void dsubimage_render(
	dsurface_t *surface,
	int x, int y,
	image_t const *image,
	int left, int top, int width, int height
) {
	uint16_t *vram;
	int vxs;
	int vys;

	/* precalculate culling information */
	if (x < 0) {
		left  -= x;
		width += x;
		x = 0;
	}
	if (y < 0) {
		top    -= y;
		height += y;
		y = 0;
	}

	/* check error */
	if (top < 0 || left < 0 || width < 0 || height < 0)
		return;

	/* check culling */
	if (y >= surface->y2
		|| y + height < surface->y1
		|| x >= surface->x2
		|| x + width < surface->x1) {
		return;
	}

	/* precalculate geometry information (both image and vram) */
	vxs = x - surface->x1;
	vys = y - surface->y1;
	if (vxs < 0) {
		vxs    = 0;
		left  += (surface->x1 - x);
		width -= (surface->x1 - x);
	}
	if (vys < 0) {
		vys     = 0;
		top    += (surface->y1 - y);
		height -= (surface->y1 + y);
	}
	if ((size_t)(vxs + width)  > surface->width)
		width  = surface->width - vxs;
	if ((size_t)(vys + height) > surface->height)
		height = surface->height - vys;
	vram = surface->frag;


	/* prepare box request */
	struct imgbox imgbox = {
		.img = {
			.y = {
				.start = top,
				.end   = top + height
			},
			.x = {
				.start = left,
				.end   = left + width
			}
		},
		.surface = {
			.vram = &vram[(surface->width * vys) + vxs],
			.voff = surface->width
		}
	};

#if 0
	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",
		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,
		x,
		y,
		width,
		height
	);
	dupdate();
	while(1) { __asm__ volatile ("sleep"); }
#endif

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

/* dimage_render(): Render a full image */
void dimage_render(dsurface_t *surface, int x, int y, image_t const *img)
{
	dsubimage_render(surface, x, y, img, 0, 0, img->width, img->height);
}



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

/* dimage_dstack(): dstack wrapper primitive */
void dimage_dstack(dsurface_t *surface, uint32_t *args)
{
	dimage_render(
		surface,
		(int)args[0],
		(int)args[1],
		(image_t*)(uintptr_t)args[2]
	);
}

/* dsubimage_dstack(): dstack wrapper primitive */
void dsubimage_dstack(dsurface_t *surface, uint32_t *args)
{
	dsubimage_render(
		surface,
		(int)args[0],
		(int)args[1],
		(image_t*)(uintptr_t)args[2],
		(int)args[3],
		(int)args[4],
		(int)args[5],
		(int)args[6]
	);
}



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

/* dimage(): Render a full image */
void dimage(image_t const *image, int x, int y, int mode)
{
	if (mode & DIMAGE_CENTER) { x -= image->width >> 1; }
	if (mode & DIMAGE_RIGHT)  { x -= image->width; }
	if (mode & DIMAGE_MIDDLE) { y -= image->height >> 1; }
	if (mode & DIMAGE_BOTTOM) { y -= image->height; }
	dstack_add_action(
		&DSTACK_CALL(&dimage_dstack, x, y, (uintptr_t)image),
		NULL,
		NULL
	);
}

/* dsubimage(): Render a section of an image */
void dsubimage(
	int x, int y,
	image_t const *image,
	int left, int top, int width, int height
) {
	dstack_add_action(
		&DSTACK_CALL(
			&dsubimage_dstack,
			x, y,
			(uintptr_t)image,
			left, top, width, height
		),
		NULL,
		NULL
	);
}