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


static struct {
	uint_least32_t a;
	uint_least32_t b;
} pairs[] = {
	{UINT32_C(0x00A1), UINT32_C(0x0021)},
	{UINT32_C(0xA4EF), (uint_least32_t)'A'},
	{UINT32_C(0xA4D5), (uint_least32_t)'Y'}, /* the one in letterlike is sans-serif */
	{UINT32_C(0xA4F5), (uint_least32_t)'U'},
	{UINT32_C(0xA4E5), (uint_least32_t)'V'},
	{UINT32_C(0x1D5B8), UINT32_C(0x2144)}
};


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

		if (UINT32_C(0x1F063) <= c && c <= UINT32_C(0x1F093)) {
			c -= UINT32_C(0x1F063);
			c = c % 7u * 7u + c / 7u;
			c += UINT32_C(0x1F063);
			goto conv;
		} else {
			for (i = 0u; i < sizeof(pairs) / sizeof(*pairs); i++) {
				if (c == pairs[i].a) {
					c = pairs[i].b;
					goto conv;
				}
				if (c == pairs[i].b) {
					c = pairs[i].a;
					goto conv;
				}
			}
		}

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

conv:
	if (*n)
		goto no_conv;
	if (*ncp)
		*cp = c;
	*n += clen;
	*ncp = 1u;
	return LIBCHARCONV_CONVERTED;
}