#include "pathexec.h"

#include <unistd.h>

#include "alloc.h"
#include "byte.h"
#include "env.h"
#include "error.h"
#include "str.h"
#include "stralloc.h"

/**
  @file pathexec.c
  @author djb
  @ref ucspi-tcp, ucspi-ssl
  @brief populate environment after fork
*/

static stralloc plus;
static stralloc tmp;

int pathexec_env(const char *s, const char *t)
{
  if (!s) return 1;
  if (!stralloc_copys(&tmp, s)) return 0;
  if (t) {
    if (!stralloc_cats(&tmp, "=")) return 0;
    if (!stralloc_cats(&tmp, t)) return 0;
  }
  if (!stralloc_0(&tmp)) return 0;
  return stralloc_cat(&plus, &tmp);
}

int pathexec_multienv(stralloc *sa)
{
  if (!sa) return 1;
  return stralloc_cat(&plus, sa);
}

void pathexec(char *const *argv)
{
  char **e;
  unsigned int elen;
  unsigned int i;
  unsigned int j;
  unsigned int split;
  unsigned int t;

  if (!stralloc_cats(&plus, "")) return;

  elen = 0;
  for (i = 0; environ[i]; ++i) ++elen;
  for (i = 0; i < plus.len; ++i)
    if (!plus.s[i]) ++elen;

  e = (char **)alloc((elen + 1) * sizeof(char *));
  if (!e) return;

  elen = 0;
  for (i = 0; environ[i]; ++i) e[elen++] = environ[i];

  j = 0;
  for (i = 0; i < plus.len; ++i)
    if (!plus.s[i]) {
      split = str_chr(plus.s + j, '=');
      for (t = 0; t < elen; ++t)
        if (byte_equal(plus.s + j, split, e[t]))
          if (e[t][split] == '=') {
            --elen;
            e[t] = e[elen];
            break;
          }
      if (plus.s[j + split]) e[elen++] = plus.s + j;
      j = i + 1;
    }
  e[elen] = 0;

  pathexec_run(*argv, argv, e);
  alloc_free(e);
}

void pathexec_run(const char *file, char *const *argv, char *const *envp)
{
  char *path;
  unsigned int split;
  int savederrno;

  if (file[str_chr(file, '/')]) {
    execve(file, argv, envp);
    return;
  }

  path = env_get("PATH");
  if (!path) path = "/bin:/usr/bin";

  savederrno = 0;
  for (;;) {
    split = str_chr(path, ':');
    if (!stralloc_copyb(&tmp, path, split)) return;
    if (!split)
      if (!stralloc_cats(&tmp, ".")) return;
    if (!stralloc_cats(&tmp, "/")) return;
    if (!stralloc_cats(&tmp, file)) return;
    if (!stralloc_0(&tmp)) return;

    execve(tmp.s, argv, envp);
    if (errno != ENOENT) {
      savederrno = errno;
      if ((errno != EACCES) && (errno != EPERM) && (errno != EISDIR)) return;
    }

    if (!path[split]) {
      if (savederrno) errno = savederrno;
      return;
    }
    path += split;
    path += 1;
  }
}