#include "fitz-base.h"
#include "fitz-world.h"
#include "fitz-draw.h"

/*
 * Global Edge List -- list of straight path segments for scan conversion
 *
 * Stepping along the edges is with bresenham's line algorithm.
 *
 * See Mike Abrash -- Graphics Programming Black Book (notably chapter 40)
 */

fz_error *
fz_newgel(fz_gel **gelp)
{
	fz_gel *gel;

	gel = *gelp = fz_malloc(sizeof(fz_gel));
	if (!gel)
		return fz_outofmem;

	gel->edges = nil;

	gel->cap = 512;
	gel->len = 0;
	gel->edges = fz_malloc(sizeof(fz_edge) * gel->cap);
	if (!gel->edges) {
		fz_free(gel);
		return fz_outofmem;
	}

	gel->xmin = gel->ymin = INT_MAX;
	gel->xmax = gel->ymax = INT_MIN;
	gel->hs = 1;
	gel->vs = 1;

	return nil;
}

void
fz_resetgel(fz_gel *gel, int hs, int vs)
{
	gel->xmin = gel->ymin = INT_MAX;
	gel->xmax = gel->ymax = INT_MIN;
	gel->hs = hs;
	gel->vs = vs;
	gel->len = 0;
}

void
fz_dropgel(fz_gel *gel)
{
	fz_free(gel->edges);
	fz_free(gel);
}

fz_irect
fz_boundgel(fz_gel *gel)
{
	fz_irect bbox;
	bbox.x0 = fz_idiv(gel->xmin, gel->hs);
	bbox.y0 = fz_idiv(gel->ymin, gel->vs);
	bbox.x1 = fz_idiv(gel->xmax, gel->hs) + 1;
	bbox.y1 = fz_idiv(gel->ymax, gel->vs) + 1;
	return bbox;
}

fz_error *
fz_insertgel(fz_gel *gel, float fx0, float fy0, float fx1, float fy1)
{
	fz_edge *edge;
	int x0, y0, x1, y1;
	int dx, dy;
	int winding;
	int width;
	int tmp;

	fx0 *= gel->hs;
	fy0 *= gel->vs;
	fx1 *= gel->hs;
	fy1 *= gel->vs;

	/* TODO: should we round or truncate? */
	x0 = fx0 < 0 ? fx0 - 0.5 : fx0 + 0.5;
	y0 = fy0 < 0 ? fy0 - 0.5 : fy0 + 0.5;
	x1 = fx1 < 0 ? fx1 - 0.5 : fx1 + 0.5;
	y1 = fy1 < 0 ? fy1 - 0.5 : fy1 + 0.5;

	if (y0 == y1)
		return nil;

	if (y0 > y1) {
		winding = -1;
		tmp = x0; x0 = x1; x1 = tmp;
		tmp = y0; y0 = y1; y1 = tmp;
	}
	else
		winding = 1;

	if (x0 < gel->xmin) gel->xmin = x0;
	if (x0 > gel->xmax) gel->xmax = x0;
	if (x1 < gel->xmin) gel->xmin = x1;
	if (x1 > gel->xmax) gel->xmax = x1;

	if (y0 < gel->ymin) gel->ymin = y0;
	if (y1 > gel->ymax) gel->ymax = y1;

	if (gel->len + 1 == gel->cap) {
		int newcap = gel->cap + 512;
		fz_edge *newedges = fz_realloc(gel->edges, sizeof(fz_edge) * newcap);
		if (!newedges)
			return fz_outofmem;
		gel->cap = newcap;
		gel->edges = newedges;
	}

	edge = &gel->edges[gel->len++];

	dy = y1 - y0;
	dx = x1 - x0;
	width = dx < 0 ? -dx : dx;

	edge->xdir = dx > 0 ? 1 : -1;
	edge->ydir = winding;
	edge->x = x0;
	edge->y = y0;
	edge->h = dy;
	edge->adjdown = dy;

	/* initial error term going l->r and r->l */
	if (dx >= 0)
		edge->e = 0;
	else
		edge->e = -dy + 1;

	/* y-major edge */
	if (dy >= width) {
		edge->xmove = 0;
		edge->adjup = width;
	}

	/* x-major edge */
	else {
		edge->xmove = (width / dy) * edge->xdir;
		edge->adjup = width % dy;
	}

	return nil;
}

void
fz_sortgel(fz_gel *gel)
{
	fz_edge *a = gel->edges;
	int n = gel->len;

	int h, i, k;
	fz_edge t;

	h = 1;
	if (n < 14) {
		h = 1;
	}
	else {
		while (h < n)
			h = 3 * h + 1;
		h /= 3;
		h /= 3;
	}

	while (h > 0)
	{
		for (i = 0; i < n; i++) {
			t = a[i];
			k = i - h;
			/* TODO: sort on y major, x minor */
			while (k >= 0 && a[k].y > t.y) {
				a[k + h] = a[k];
				k -= h;
			}
			a[k + h] = t;
		}

		h /= 3;
	}
}

/*
 * Active Edge List -- keep track of active edges while sweeping
 */

fz_error *
fz_newael(fz_ael **aelp)
{
	fz_ael *ael;

	ael = *aelp = fz_malloc(sizeof(fz_ael));
	if (!ael)
		return fz_outofmem;

	ael->cap = 64;
	ael->len = 0;
	ael->edges = fz_malloc(sizeof(fz_edge*) * ael->cap);
	if (!ael->edges) {
		fz_free(ael);
		return fz_outofmem;
	}

	return nil;
}

void
fz_dropael(fz_ael *ael)
{
	fz_free(ael->edges);
	fz_free(ael);
}

static inline void
sortael(fz_edge **a, int n)
{
	int h, i, k;
	fz_edge *t;

	h = 1;
	if (n < 14) {
		h = 1;
	}
	else {
		while (h < n)
			h = 3 * h + 1;
		h /= 3;
		h /= 3;
	}

	while (h > 0)
	{
		for (i = 0; i < n; i++) {
			t = a[i];
			k = i - h;
			while (k >= 0 && a[k]->x > t->x) {
				a[k + h] = a[k];
				k -= h;
			}
			a[k + h] = t;
		}

		h /= 3;
	}
}

static fz_error *
insertael(fz_ael *ael, fz_gel *gel, int y, int *e)
{
	/* insert edges that start here */
	int e2 = *e;
	while (e2 < gel->len && gel->edges[e2].y == y) {
		if (ael->len + 1 == ael->cap) {
			int newcap = ael->cap + 256;
			fz_edge **newedges = fz_realloc(ael->edges, sizeof(fz_edge*) * newcap);
			if (!newedges)
				return fz_outofmem;
			ael->edges = newedges;
			ael->cap = newcap;
		}
		ael->edges[ael->len++] = &gel->edges[e2++];
	}
	*e = e2;
	/* shell-sort the edges by increasing x */
	sortael(ael->edges, ael->len);

	return nil;
}

static void
advanceael(fz_ael *ael)
{
	fz_edge *edge;
	int i = 0;

	while (i < ael->len)
	{
		edge = ael->edges[i];

		edge->h --;

		/* terminator! */
		if (edge->h == 0) {
			ael->edges[i] = ael->edges[--ael->len];
		}

		else {
			edge->x += edge->xmove;
			edge->e += edge->adjup;
			if (edge->e > 0) {
				edge->x += edge->xdir;
				edge->e -= edge->adjdown;
			}
			i ++;
		}
	}
}

/*
 * Scan convert
 */

static inline void
addspan(unsigned char *list, int x0, int x1, int xofs, int hs)
{
	int x0pix, x0sub;
	int x1pix, x1sub;

	if (x0 == x1)
		return;

	/* x between 0 and width of bbox */
	x0 -= xofs;
	x1 -= xofs;

	x0pix = x0 / hs;
	x0sub = x0 % hs;
	x1pix = x1 / hs;
	x1sub = x1 % hs;

	if (x0pix == x1pix)
	{
		list[x0pix] += x1sub - x0sub;
		list[x0pix+1] += x0sub - x1sub;
	}

	else
	{
		list[x0pix] += hs - x0sub;
		list[x0pix+1] += x0sub;
		list[x1pix] += x1sub - hs;
		list[x1pix+1] += -x1sub;
	}
}

static inline void
nonzerowinding(fz_ael *ael, unsigned char *list, int xofs, int hs)
{
	int winding = 0;
	int x = 0;
	int i;
	for (i = 0; i < ael->len; i++)
	{
		if (!winding && (winding + ael->edges[i]->ydir))
			x = ael->edges[i]->x;
		if (winding && !(winding + ael->edges[i]->ydir))
			addspan(list, x, ael->edges[i]->x, xofs, hs);
		winding += ael->edges[i]->ydir;
	}
}

static inline void
evenodd(fz_ael *ael, unsigned char *list, int xofs, int hs)
{
	int even = 0;
	int x = 0;
	int i;
	for (i = 0; i < ael->len; i++)
	{
		if (!even)
			x = ael->edges[i]->x;
		else
			addspan(list, x, ael->edges[i]->x, xofs, hs);
		even = !even;
	}
}

static inline void toalpha(unsigned char *list, int n)
{
	int d = 0;
	while (n--)
	{
		d += *list;
		*list++ = d;
	}
}

static inline void blit(fz_pixmap *pix, int x, int y,
						unsigned char *list, int skipx, int len,
						unsigned char *rgb, int over)
{
	unsigned char *dst;
	int cov;

	dst = pix->samples + ( (y - pix->y) * pix->w + (x - pix->x) ) * pix->n;
	cov = 0;

	while (skipx--)
	{
		cov += *list;
		*list = 0;
		++list;
	}

	if (rgb)
		fz_path_w3i1o4(rgb, list, cov, len, dst);
	else if (over)
		fz_path_1o1(list, cov, len, dst);
	else
		fz_path_1c1(list, cov, len, dst);
}

fz_error *
fz_scanconvert(fz_gel *gel, fz_ael *ael, int eofill, fz_irect clip,
	fz_pixmap *pix, unsigned char *rgb, int over)
{
	fz_error *error;
	unsigned char *deltas;
	int y, e;
	int yd, yc;

	int xmin = fz_idiv(gel->xmin, gel->hs);
	int xmax = fz_idiv(gel->xmax, gel->hs) + 1;

	int xofs = xmin * gel->hs;
	int hs = gel->hs;
	int vs = gel->vs;

	int skipx = clip.x0 - xmin;
	int clipn = clip.x1 - clip.x0;

	assert(clip.x0 >= xmin);
	assert(clip.x1 <= xmax);

	if (gel->len == 0)
		return nil;

	deltas = fz_malloc(xmax - xmin + 1);
	if (!deltas)
		return fz_outofmem;

	memset(deltas, 0, xmax - xmin + 1);

	e = 0;
	y = gel->edges[0].y;
	yc = fz_idiv(y, vs);
	yd = yc;

	while (ael->len > 0 || e < gel->len)
	{
		yc = fz_idiv(y, vs);
		if (yc != yd)
		{
			if (yd >= clip.y0 && yd < clip.y1)
			{
				blit(pix, xmin + skipx, yd, deltas, skipx, clipn, rgb, over);
			}
		}
		yd = yc;

		error = insertael(ael, gel, y, &e);
		if (error) {
			fz_free(deltas);
			return error;
		}

		if (yd >= clip.y0 && yd < clip.y1)
		{
			if (eofill)
				evenodd(ael, deltas, xofs, hs);
			else
				nonzerowinding(ael, deltas, xofs, hs);
		}

		advanceael(ael);

		if (ael->len > 0)
			y ++;
		else if (e < gel->len)
			y = gel->edges[e].y;
	}

	if (yd >= clip.y0 && yd < clip.y1)
	{
		blit(pix, xmin + skipx, yd, deltas, skipx, clipn, rgb, over);
	}

	fz_free(deltas);
	return nil;
}