#include <string>
#include <iostream>
#include <irrlicht.h>
#include <assert.h>

using namespace irr;
#define errorstream std::cerr

static inline bool hex_digit_decode(char hexdigit, unsigned char &value)
{
	if(hexdigit >= '0' && hexdigit <= '9')
		value = hexdigit - '0';
	else if(hexdigit >= 'A' && hexdigit <= 'F')
		value = hexdigit - 'A' + 10;
	else if(hexdigit >= 'a' && hexdigit <= 'f')
		value = hexdigit - 'a' + 10;
	else
		return false;
	return true;
}

bool parseColor(const std::string &value, video::SColor &color, bool quiet)
{
	const char *hexpattern = NULL;
	if (value[0] == '#') {
		if (value.size() == 9)
			hexpattern = "#RRGGBBAA";
		else if (value.size() == 7)
			hexpattern = "#RRGGBB";
		else if (value.size() == 5)
			hexpattern = "#RGBA";
		else if (value.size() == 4)
			hexpattern = "#RGB";
	}

	if (hexpattern) {
		assert(strlen(hexpattern) == value.size());
		video::SColor outcolor(255, 255, 255, 255);
		for (size_t pos = 0; pos < value.size(); ++pos) {
			// '#' in the pattern means skip that character
			if (hexpattern[pos] == '#')
				continue;

			// Else assume hexpattern[pos] is one of 'R' 'G' 'B' 'A'
			// Read one or two digits, depending on hexpattern
			unsigned char c1, c2;
			if (hexpattern[pos+1] == hexpattern[pos]) {
				// Two digits, e.g. hexpattern == "#RRGGBB"
				if (!hex_digit_decode(value[pos], c1) ||
				    !hex_digit_decode(value[pos+1], c2))
					goto fail;
				++pos;
			}
			else {
				// One digit, e.g. hexpattern == "#RGB"
				if (!hex_digit_decode(value[pos], c1))
					goto fail;
				c2 = c1;
			}
			u32 colorpart = ((c1 & 0x0f) << 4) | (c2 & 0x0f);

			// Update outcolor with newly read color part
			if (hexpattern[pos] == 'R')
				outcolor.setRed(colorpart);
			else if (hexpattern[pos] == 'G')
				outcolor.setGreen(colorpart);
			else if (hexpattern[pos] == 'B')
				outcolor.setBlue(colorpart);
			else if (hexpattern[pos] == 'A')
				outcolor.setAlpha(colorpart);
		}

		color = outcolor;
		return true;
	}

	// Optionally, named colors could be implemented here

fail:
	if (!quiet)
		errorstream<<"Invalid color: \""<<value<<"\""<<std::endl;
	return false;
}

void dumpColor(video::SColor color)
{
	std::cout<<"R="<<color.getRed()<<" G="<<color.getGreen()
		<<" B="<<color.getBlue()<<" A="<<color.getAlpha()<<std::endl;
}

int main(void)
{
	video::SColor color(1, 2, 3, 4);
	parseColor("#c0ffee", color, false);
	dumpColor(color);
	parseColor("#406082a0", color, false);
	dumpColor(color);
	parseColor("#0dd", color, false);
	dumpColor(color);
	parseColor("#affe", color, false);
	dumpColor(color);
	return 0;
}