#include <stdio.h>
#include <uniconv.h>
#include <uninorm.h>
#include <unistr.h>
#include <unicase.h>
#include <string.h>

struct titlecase_context {
  casing_prefix_context_t ctx;
};

int titlecase_partial(struct titlecase_context *ctx,
    const void **_start, size_t *len,
    unsigned char *result_r, size_t *result_len)
{
  const uint8_t *ptr;
  const uint8_t *start = *_start;

  if ((ptr = u8_check(start, *len)) != NULL) {
    /* not fully good, so use only parts of it */
    *len = ptr-start;
  }

  casing_prefix_context_t case_ctx = ctx->ctx;
  ctx->ctx = u8_casing_prefixes_context(start, *len, case_ctx);

  if (u8_ct_totitle(start, *len, case_ctx, unicase_empty_suffix_context,
         "fr", UNINORM_NFC, result_r, result_len) == NULL) {
    return -1;
  }

  *_start = start + *len;

  return 0;
}

int main(void) {
  FILE *f = fopen("udhr-fra.txt", "r");
  if (f == NULL) {
    perror("fopen: ");
    return 1;
  }
  unsigned char buf[32];
  size_t r = 0, off = 0;

  struct titlecase_context ctx = {
    .ctx = unicase_empty_prefix_context,
  };

  while((r = fread(buf+off, 1, sizeof(buf)-off, f)) > 0) {
    const void *bufptr = buf;
    unsigned char newbuf[64] = {0};
    size_t len = sizeof(newbuf);
    size_t foo = r+off;
    r += off;

    if (titlecase_partial(&ctx, &bufptr, &r, newbuf, &len) < 0)
      return 1;

    fwrite(newbuf, len, 1, stdout);

    if (r == foo) {
      off = 0;
    } else {
      memmove(buf, buf+r, sizeof(buf) - r);
      off = sizeof(buf) - r;
    }
  }

  return 0;
}