/**

 * WinPR: Windows Portable Runtime

 * Time Zone

 *

 * Copyright 2024 Armin Novak <anovak@thincast.com>

 * Copyright 2024 Thincast Technologies GmbH

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#include "TimeZoneIanaAbbrevMap.h"

#include <stdlib.h>

#include <dirent.h>

#include <time.h>

#include <sys/stat.h>

#include <unistd.h>

#include <winpr/string.h>

typedef struct

{

  const char* Iana;

  const char* Abbrev;

} TimeZoneInanaAbbrevMapEntry;

const static char* zonepath = "/usr/share/zoneinfo";

static TimeZoneInanaAbbrevMapEntry* TimeZoneIanaAbbrevMap = NULL;

static size_t TimeZoneIanaAbbrevMapSize = 0;

static void append(const char* iana, const char* sname)

{

  const size_t size = TimeZoneIanaAbbrevMapSize + 1;

  TimeZoneInanaAbbrevMapEntry* tmp =

      realloc(TimeZoneIanaAbbrevMap, size * sizeof(TimeZoneInanaAbbrevMapEntry));

  if (!tmp)

    return;

  TimeZoneIanaAbbrevMap = tmp;

  TimeZoneIanaAbbrevMapSize = size;

  TimeZoneInanaAbbrevMapEntry* cur = &TimeZoneIanaAbbrevMap[size - 1];

  cur->Abbrev = _strdup(sname);

  cur->Iana = _strdup(iana);

}

static void append_timezone(const char* dir, const char* name)

{

  char* tz = NULL;

  if (!dir && !name)

    return;

  if (!dir)

  {

    size_t len = 0;

    winpr_asprintf(&tz, &len, "%s", name);

  }

  else

  {

    size_t len = 0;

    winpr_asprintf(&tz, &len, "%s/%s", dir, name);

  }

  if (!tz)

    return;

  const char* otz = getenv("TZ");

  char* oldtz = NULL;

  if (otz)

    oldtz = _strdup(otz);

  setenv("TZ", tz, 1);

  tzset();

  const time_t t = time(NULL);

  struct tm lt = { 0 };

  localtime_r(&t, &lt);

  append(tz, lt.tm_zone);

  if (oldtz)

  {

    setenv("TZ", oldtz, 1);

    free(oldtz);

  }

  else

    unsetenv("TZ");

  free(tz);

}

static void handle_link(const char* base, const char* dir, const char* name);

static char* topath(const char* base, const char* bname, const char* name)

{

  size_t plen = 0;

  char* path = NULL;

  if (!base && !bname && !name)

    return NULL;

  if (!base && !name)

    return _strdup(bname);

  if (!bname && !name)

    return _strdup(base);

  if (!base && !bname)

    return _strdup(name);

  if (!base)

    winpr_asprintf(&path, &plen, "%s/%s", bname, name);

  else if (!bname)

    winpr_asprintf(&path, &plen, "%s/%s", base, name);

  else if (!name)

    winpr_asprintf(&path, &plen, "%s/%s", base, bname);

  else

    winpr_asprintf(&path, &plen, "%s/%s/%s", base, bname, name);

  return path;

}

static void iterate_subdir_recursive(const char* base, const char* bname, const char* name)

{

  char* path = topath(base, bname, name);

  if (!path)

    return;

  DIR* d = opendir(path);

  if (d)

  {

    struct dirent* dp = NULL;

    while ((dp = readdir(d)) != NULL)

    {

      switch (dp->d_type)

      {

        case DT_DIR:

        {

          if (strcmp(dp->d_name, ".") == 0)

            continue;

          if (strcmp(dp->d_name, "..") == 0)

            continue;

          iterate_subdir_recursive(path, dp->d_name, NULL);

        }

        break;

        case DT_LNK:

          handle_link(base, bname, dp->d_name);

          break;

        case DT_REG:

          append_timezone(bname, dp->d_name);

          break;

        default:

          break;

      }

    }

    closedir(d);

  }

  free(path);

}

static char* get_link_target(const char* base, const char* dir, const char* name)

{

  char* apath = NULL;

  char* path = topath(base, dir, name);

  if (!path)

    return NULL;

  SSIZE_T rc = -1;

  size_t size = 0;

  char* target = NULL;

  do

  {

    size += 64;

    char* tmp = realloc(target, size + 1);

    if (!tmp)

      goto fail;

    target = tmp;

    memset(target, 0, size + 1);

    rc = readlink(path, target, size);

    if (rc < 0)

      goto fail;

  } while (rc >= size);

  apath = topath(base, dir, target);

fail:

  free(target);

  free(path);

  return apath;

}

void handle_link(const char* base, const char* dir, const char* name)

{

  int isDir = -1;

  char* target = get_link_target(base, dir, name);

  if (target)

  {

    struct stat s = { 0 };

    const int rc3 = stat(target, &s);

    if (rc3 == 0)

      isDir = S_ISDIR(s.st_mode);

    free(target);

  }

  switch (isDir)

  {

    case 1:

      iterate_subdir_recursive(base, dir, name);

      break;

    case 0:

      append_timezone(dir, name);

      break;

    default:

      break;

  }

}

static void TimeZoneIanaAbbrevCleanup(void)

{

  if (!TimeZoneIanaAbbrevMap)

    return;

  for (size_t x = 0; x < TimeZoneIanaAbbrevMapSize; x++)

  {

    TimeZoneInanaAbbrevMapEntry* entry = &TimeZoneIanaAbbrevMap[x];

    free(entry->Iana);

    free(entry->Abbrev);

  }

  free(TimeZoneIanaAbbrevMap);

  TimeZoneIanaAbbrevMap = NULL;

  TimeZoneIanaAbbrevMapSize = 0;

}

static void TimeZoneIanaAbbrevInitialize(void)

{

  static BOOL initialized = FALSE;

  if (initialized)

    return;

  iterate_subdir_recursive(zonepath, NULL, NULL);

  (void)atexit(TimeZoneIanaAbbrevCleanup);

  initialized = TRUE;

}

size_t TimeZoneIanaAbbrevGet(const char* abbrev, const char** list, size_t listsize)

{

  TimeZoneIanaAbbrevInitialize();

  size_t rc = 0;

  for (size_t x = 0; x < TimeZoneIanaAbbrevMapSize; x++)

  {

    const TimeZoneInanaAbbrevMapEntry* entry = &TimeZoneIanaAbbrevMap[x];

    if (strcmp(abbrev, entry->Abbrev) == 0)

    {

      if (listsize > rc)

        list[rc] = entry->Iana;

      rc++;

    }

  }

  return rc;

}