#include <stdio.h>
#include <stdlib.h>

#include <X11/Xlib.h>

#include <grass/gis.h>
#include <grass/glocale.h>

extern Display *dpy;
extern int scrn;
extern Window grwin;
extern XWindowAttributes xwa;

static int NCOLORS;
static unsigned long *xpixels;

static int Red[256], Grn[256], Blu[256];
static int Gray[256];

static int r_pos, g_pos, b_pos;
static int r_size, g_size, b_size;
static int r_scale, g_scale, b_scale;


static void get_shifts(unsigned long mask, int *pos, int *size, int *scale)
{
    int i, j;

    for (i = 0; (mask & 1) == 0; i++)
	mask >>= 1;
    if (pos)
	*pos = i;

    for (j = i; (mask & 1) != 0; j++)
	mask >>= 1;
    if (size)
	*size = j - i;
    if (scale)
	*scale = 8 - (j - i);
}

static int get_rgb_shifts(void)
{
    get_shifts(xwa.visual->red_mask, &r_pos, &r_size, &r_scale);
    get_shifts(xwa.visual->green_mask, &g_pos, &g_size, &g_scale);
    get_shifts(xwa.visual->blue_mask, &b_pos, &b_size, &b_scale);

    return (1 << r_size) * (1 << g_size) * (1 << b_size);
}

static unsigned long
find_color_gray(unsigned int r, unsigned int g, unsigned int b)
{
    unsigned int y = (r + g + b) / 3;

    return xpixels[Gray[y]];
}

static unsigned long
find_color_indexed(unsigned int r, unsigned int g, unsigned int b)
{
    return xpixels[Red[r] + Grn[g] + Blu[b]];
}

static unsigned long
find_color_rgb(unsigned int r, unsigned int g, unsigned int b)
{
    unsigned int rr = r >> r_scale;
    unsigned int gg = g >> g_scale;
    unsigned int bb = b >> b_scale;

    return (rr << r_pos) + (gg << g_pos) + (bb << b_pos);
}

unsigned long find_color(unsigned int r, unsigned int g, unsigned int b)
{

    switch (xwa.visual->class) {
    case StaticGray:
    case GrayScale:
	return find_color_gray(r, g, b);
    case StaticColor:
    case PseudoColor:
	return find_color_indexed(r, g, b);
    case TrueColor:
    case DirectColor:
	return find_color_rgb(r, g, b);
    default:
	G_fatal_error(_("Unknown visual class [%d]."), xwa.visual->class);
	return 0;
    }
}

static void get_max_levels(int n_colors, int *rr, int *gg, int *bb)
{
    int r, g, b, i;

    for (i = 0; i * i * i < n_colors; i++) ;

    for (r = g = b = i;;) {
	if (r * g * b <= n_colors)
	    break;
	b--;
	if (r * g * b <= n_colors)
	    break;
	r--;
	if (r * g * b <= n_colors)
	    break;
	g--;
    }

    *rr = r;
    *gg = g;
    *bb = b;
}

static int get_fewer_levels(int *rr, int *gg, int *bb)
{
    int r = *rr;
    int g = *gg;
    int b = *bb;

    /* 888 -> 887 -> 787 -> 777 -> ... */

    if (r > b)			/* 887 -> 787 */
	r--;
    else if (g > b)		/* 787 -> 777 */
	g--;
    else			/* 888 -> 888 */
	b--;

    *rr = r;
    *gg = g;
    *bb = b;

    return r >= 2 && g >= 2 && b >= 2;
}

static int try_get_colors(Colormap cmap, int nr, int ng, int nb)
{
    XColor xcolor;
    int n_pixels;
    int r, g, b;

    xpixels = (unsigned long *)G_realloc(xpixels,
					 nr * ng * nb *
					 sizeof(unsigned long));
    n_pixels = 0;

    xcolor.flags = DoRed | DoGreen | DoBlue;

    for (r = 0; r < nr; r++) {
	for (g = 0; g < ng; g++) {
	    for (b = 0; b < nb; b++) {
		xcolor.red = (unsigned short)(r * 0xFFFF / (nr - 1));
		xcolor.green = (unsigned short)(g * 0xFFFF / (ng - 1));
		xcolor.blue = (unsigned short)(b * 0xFFFF / (nb - 1));
		if (!XAllocColor(dpy, cmap, &xcolor)) {
		    XFreeColors(dpy, cmap, xpixels, n_pixels,
				(unsigned long)0);
		    return 0;
		}

		xpixels[n_pixels++] = xcolor.pixel;
	    }
	}
    }

    return 1;
}

static int try_get_grays(Colormap cmap, int ny)
{
    XColor xcolor;
    int n_pixels;
    int y;

    xpixels = (unsigned long *)G_realloc(xpixels, ny * sizeof(unsigned long));
    n_pixels = 0;

    xcolor.flags = DoRed | DoGreen | DoBlue;

    for (y = 0; y < ny; y++) {
	unsigned short v = (unsigned short)(y * 0xFFFF / (ny - 1));

	xcolor.red = v;
	xcolor.green = v;
	xcolor.blue = v;

	if (!XAllocColor(dpy, cmap, &xcolor)) {
	    XFreeColors(dpy, cmap, xpixels, n_pixels, (unsigned long)0);
	    return y;
	}

	xpixels[n_pixels++] = xcolor.pixel;
    }

    return ny;
}

static Colormap ramp_colormap(void)
{
    int n_colors = xwa.visual->map_entries;
    Colormap cmap = XCreateColormap(dpy, RootWindow(dpy, scrn),
				    xwa.visual, AllocAll);
    int i;

    for (i = 0; i < n_colors; i++) {
	unsigned int k = i * 65535 / (n_colors - 1);
	unsigned int l = i * 255 / (n_colors - 1);
	XColor xcolor;

	xcolor.flags = DoRed | DoGreen | DoBlue;
	xcolor.blue = k;
	xcolor.green = k;
	xcolor.red = k;
	xcolor.pixel = find_color_rgb(l, l, l);

	XStoreColor(dpy, cmap, &xcolor);
    }

    return cmap;
}

Colormap InitColorTableFixed(Colormap cmap)
{
    int n_colors = xwa.visual->map_entries;
    int r, g, b, y, i;

    switch (xwa.visual->class) {
    case StaticGray:
    case GrayScale:
	/* determine how many levels of gray we can actually get */
	y = try_get_grays(cmap, n_colors);
	if (y > 2 && y < n_colors)
	    y = try_get_grays(cmap, y);
	if (y < 2)
	    G_fatal_error(_("Unable to get sufficient gray shades."));

	NCOLORS = y;

	for (i = 0; i < 256; i++)
	    Gray[i] = i * y / 256;

	break;

    case StaticColor:
    case PseudoColor:
	/* determine how many levels of r, g, and b are possible */
	get_max_levels(n_colors, &r, &g, &b);

	/* now see how many we can actually get */
	while (!try_get_colors(cmap, r, g, b))
	    if (!get_fewer_levels(&r, &g, &b))
		G_fatal_error(_("Unable to get sufficient colors."));

	NCOLORS = r * g * b;

	for (i = 0; i < 256; i++) {
	    Red[i] = (i * r / 256) * g * b;
	    Grn[i] = (i * g / 256) * b;
	    Blu[i] = (i * b / 256);
	}

	break;

    case DirectColor:
	G_warning(_("Using private colormap for DirectColor visual."));

	/* free any previously-allocated Colormap */
	if (cmap != DefaultColormap(dpy, scrn))
	    XFreeColormap(dpy, cmap);

	/* get shift factors for R,G,B masks */
	NCOLORS = get_rgb_shifts();

	/* create colormap (emulates TrueColor visual) */
	cmap = ramp_colormap();
	break;

    case TrueColor:
	/* get shift factors for R,G,B masks */
	NCOLORS = get_rgb_shifts();
	break;

    default:
	G_fatal_error(_("Unknown visual class [%d]."), xwa.visual->class);
	break;
    }

    return cmap;
}