#include <stdbool.h>
#include <stdlib.h>
#include <curses.h>

#include "vis.h"
#include "util.h"

#ifdef NCURSES_VERSION
# ifndef NCURSES_EXT_COLORS
#  define NCURSES_EXT_COLORS 0
# endif
# if !NCURSES_EXT_COLORS
#  define MAX_COLOR_PAIRS 256
# endif
#endif
#ifndef MAX_COLOR_PAIRS
# define MAX_COLOR_PAIRS COLOR_PAIRS
#endif

static bool has_default_colors;
static short *color2palette, default_fg, default_bg;
static short color_pairs_reserved, color_pairs_max, color_pair_current;

static unsigned int color_hash(short fg, short bg)
{
	if (fg == -1)
		fg = COLORS;
	if (bg == -1)
		bg = COLORS + 1;
	return fg * (COLORS + 2) + bg;
}

short vis_color_get(short fg, short bg)
{
	if (fg >= COLORS)
		fg = default_fg;
	if (bg >= COLORS)
		bg = default_bg;

	if (!has_default_colors) {
		if (fg == -1)
			fg = default_fg;
		if (bg == -1)
			bg = default_bg;
	}

	if (!color2palette || (fg == -1 && bg == -1))
		return 0;
	unsigned int index = color_hash(fg, bg);
	if (color2palette[index] == 0) {
		short oldfg, oldbg;
		for (;;) {
			if (++color_pair_current >= color_pairs_max)
				color_pair_current = color_pairs_reserved + 1;
			pair_content(color_pair_current, &oldfg, &oldbg);
			unsigned int old_index = color_hash(oldfg, oldbg);
			if (color2palette[old_index] >= 0) {
				if (init_pair(color_pair_current, fg, bg) == OK) {
					color2palette[old_index] = 0;
					color2palette[index] = color_pair_current;
				}
				break;
			}
		}
	}

	short color_pair = color2palette[index];
	return color_pair >= 0 ? color_pair : -color_pair;
}

short vis_color_reserve(short fg, short bg)
{
	if (!color2palette)
		vis_init();
	if (!color2palette || fg >= COLORS || bg >= COLORS)
		return 0;
	if (!has_default_colors && fg == -1)
		fg = default_fg;
	if (!has_default_colors && bg == -1)
		bg = default_bg;
	if (fg == -1 && bg == -1)
		return 0;
	unsigned int index = color_hash(fg, bg);
	if (color2palette[index] >= 0) {
		if (init_pair(++color_pairs_reserved, fg, bg) == OK)
			color2palette[index] = -color_pairs_reserved;
	}
	short color_pair = color2palette[index];
	return color_pair >= 0 ? color_pair : -color_pair;
}

void vis_init(void)
{
	if (color2palette)
		return;
	pair_content(0, &default_fg, &default_bg);
	if (default_fg == -1)
		default_fg = COLOR_WHITE;
	if (default_bg == -1)
		default_bg = COLOR_BLACK;
	has_default_colors = (use_default_colors() == OK);
	color_pairs_max = MIN(COLOR_PAIRS, MAX_COLOR_PAIRS);
	if (COLORS)
		color2palette = calloc((COLORS + 2) * (COLORS + 2), sizeof(short));
	vis_color_reserve(COLOR_WHITE, COLOR_BLACK);
}