//

// tempdir.c

//

// Copyright (c) 2014 Stephen Mathieson

// MIT licensed

//

#include <stdlib.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <unistd.h>

#include "strdup/strdup.h"

#include "tempdir.h"

// 1. The directory named by the TMPDIR environment variable.

// 2. The directory named by the TEMP environment variable.

// 3. The directory named by the TMP environment variable.

// 4. A platform-specific location:

//   4.1 On RiscOS, the directory named by the Wimp$ScrapDir

//       environment variable.

//   4.2 On Windows, the directories C:\TEMP, C:\TMP, \TEMP,

//       and \TMP, in that order.

//   4.3 On all other platforms, the directories /tmp,

//       /var/tmp, and /usr/tmp, in that order.

// 5. As a last resort, the current working directory.

static const char *env_vars[] = {

  "TMPDIR",

  "TEMP",

  "TMP",

  // RiscOS (4.1)

  "Wimp$ScrapDir",

  NULL,

};

#ifdef _WIN32

  // 4.2

  static const char *platform_dirs[] = {

    "C:\\TEMP",

    "C:\\TMP",

    "\\TEMP",

    "\\TMP",

    NULL,

  };

#else

  // 4.3

  static const char *platform_dirs[] = {

    "/tmp",

    "/var/tmp",

    "/usr/tmp",

    NULL,

  };

#endif

/**

 * Check if the file at `path` exists and is a directory.

 *

 * Returns `0` if both checks pass, and `-1` if either fail.

 */

static int

is_directory(const char *path) {

  struct stat s;

  if (-1 == stat(path, &s)) return -1;

  return 1 == S_ISDIR(s.st_mode) ? 0 : -1;

}

char *

gettempdir(void) {

  // check ENV vars (1, 2, 3)

  for (int i = 0; env_vars[i]; i++) {

    char *dir = getenv(env_vars[i]);

    if (dir && 0 == is_directory(dir)) {

      return strdup(dir);

    }

  }

  // platform-specific checks (4)

  for (int i = 0; platform_dirs[i]; i++) {

    if (0 == is_directory(platform_dirs[i])) {

      return strdup(platform_dirs[i]);

    }

  }

  // fallback to cwd (5)

  char cwd[256];

  if (NULL != getcwd(cwd, sizeof(cwd))) {

    return strdup(cwd);

  }

  return NULL;

}