#include <stdio.h>
#include "charset.h"

static int
add_unicode(char **d, size_t *len, uint16_t u)
{
	if (u < 0x80)
	{
		// 1 byte
		if (*len < 1) return 0;
		(*d)[0] = u;
		(*d)++, *len--;
		return 1;
	}
	if (u < 0x800)
	{
		// 2 bytes
		if (*len < 2) return 0;

		(*d)[0] = 0xc0 | ((u >> 6) & 0x1f);
		(*d)[1] = 0x80 | (u & 0x3f);
		*d += 2, *len -= 2;
		return 1;
	}
	if (u < 0x10000)
	{
		// 3 bytes
		if (*len < 3) return 0;

		(*d)[0] = 0xe0 | ((u >> 12) & 0xf);
		(*d)[1] = 0x80 | ((u >> 6) & 0x3f);
		(*d)[2] = 0x80 | (u & 0x3f);
		*d += 3, *len -= 3;
		return 1;
	}
	// 4 byte code point not supported.
	return 0;
}

int
xconv(char *src, char *dst, size_t dstlen)
{
	size_t len = dstlen;
	char *s, *d;
	int i;

	for (s = src, d = dst; *s && len > 0; s++)
	{
		// Check for combined character.
		if ((*s & 0xf0) == 0xc0 && s[1])
		{
			icc_t *p;
			int k = *s & 0xf;
			p = iso6937_combined[k];
			for (i = 0; p[i].c; i++)
			{
				if (p[i].c == (s[1] & 0xff))
				{
					add_unicode(&d, &len,
					    iso6937_combined[k][i].u);
					break;
				}
			}
			s++;
			continue;
		}

		add_unicode(&d, &len, iso6937_map[*s & 0xff]);
	}
	*d = '\0';
	return dstlen - len;
}