/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/bits/weaken.h"
#include "libc/dce.h"
#include "libc/mem/internal.h"
#include "libc/runtime/runtime.h"

#define ToUpper(c) \
  (IsWindows() && (c) >= 'a' && (c) <= 'z' ? (c) - 'a' + 'A' : (c))

/**
 * Removes environment variable.
 */
int unsetenv(const char *s) {
  char **p;
  size_t i, j, k;
  if (s && (p = environ)) {
    for (i = 0; p[i]; ++i) {
      for (j = 0;; ++j) {
        if (!s[j]) {
          if (p[i][j] == '=') {
            if (weaken(__freeenv)) {
              weaken(__freeenv)(p[i]);
            }
            k = i + 1;
            do {
              p[k - 1] = p[k];
            } while (p[k++]);
            return 0;
          }
          break;
        }
        if (ToUpper(s[j]) != ToUpper(p[i][j])) {
          break;
        }
      }
    }
  }
  return 0;
}