/* See LICENSE file for copyright and license details. */
#include "lib-common.h"


static struct {
	uint_least32_t a;
	uint_least32_t b;
	uint_least32_t to;
} pairs[] = {
	{(uint_least32_t)'?', (uint_least32_t)'!', UINT32_C(0x2048)},
	{(uint_least32_t)'?', (uint_least32_t)'?', UINT32_C(0x2047)},
	{(uint_least32_t)'!', (uint_least32_t)'!', UINT32_C(0x203C)},
	{(uint_least32_t)'!', (uint_least32_t)'?', UINT32_C(0x2049)},
	{UINT32_C(0x23CB), UINT32_C(0x23BE), UINT32_C(0x23C9)},
	{UINT32_C(0x23CC), UINT32_C(0x23BF), UINT32_C(0x23CA)}
};


enum libcharconv_result
libcharconv_joined(const char *s, size_t slen, size_t *n, uint_least32_t *cp, size_t *ncp)
{
	uint_least32_t a, b;
	size_t i, alen, blen;
	*n = 0;
	while (slen) {
		alen = libcharconv_decode_utf8_(s, slen, &a);
		if (alen > slen) {
			if (*n)
				goto no_conv;
			return LIBCHARCONV_INDETERMINATE;
		}
		if (!alen) {
			*n += 1u;
			slen -= 1u;
			s = &s[1];
			continue;
		}

		for (i = 0u; i < sizeof(pairs) / sizeof(*pairs); i++) {
			if (a != pairs[i].a)
				continue;
			if (*n)
				goto no_conv;
			if (slen == alen)
				return LIBCHARCONV_INDETERMINATE;
			blen = libcharconv_decode_utf8_(&s[alen], slen - alen, &b);
			if (blen > slen)
				return LIBCHARCONV_INDETERMINATE;
			if (!blen)
				goto no_conv;
			if (b == pairs[i].b)
				goto conv;
		}

		*n += alen;
		s = &s[alen];
		slen -= alen;
	}
no_conv:
	return LIBCHARCONV_NO_CONVERT;

conv:
	if (*n)
		goto no_conv;
	if (*ncp)
		*cp = pairs[i].to;
	*n += alen + blen;
	*ncp = 1u;
	return LIBCHARCONV_CONVERTED;
}