/**
 * @file  cfgpath.h
 * @brief Cross platform methods for obtaining paths to configuration files.
 *
 * Copyright (C) 2013 Adam Nielsen <malvineous@shikadi.net>
 *
 * This code is placed in the public domain.  You are free to use it for any
 * purpose.  If you add new platform support, please contribute a patch!
 *
 * Example use:
 *
 * char cfgdir[256];
 * get_user_config_file(cfgdir, sizeof(cfgdir), "myapp");
 * if (cfgdir[0] == 0) {
 *     printf("Unable to find home directory.\n");
 *     return 1;
 * }
 * printf("Saving configuration file to %s\n", cfgdir);
 *
 * A number of constants are also defined:
 *
 *  - MAX_PATH: Maximum length of a path, in characters.  Used to allocate a
 *      char array large enough to hold the returned path.
 *
 *  - PATH_SEPARATOR_CHAR: The separator between folders.  This will be either a
 *      forward slash or a backslash depending on the platform.  This is a
 *      character constant.
 *
 *  - PATH_SEPARATOR_STRING: The same as PATH_SEPARATOR_CHAR but as a C string,
 *      to make it easier to append to other string constants.
 */

#ifndef CFGPATH_H_
#define CFGPATH_H_

#ifdef _MSC_VER
#define inline __inline
#include <direct.h>
#define mkdir _mkdir
#endif

#if defined(__linux__) || defined(__APPLE__)
#include <string.h>
#include <stdlib.h>
#include <sys/stat.h>
#define MAX_PATH 260  /* matches windows */
#define PATH_SEPARATOR_CHAR '/'
#define PATH_SEPARATOR_STRING "/"
#elif defined(WIN32)
#include <shlobj.h>
/* MAX_PATH is defined by the Windows API */
#define PATH_SEPARATOR_CHAR '\\'
#define PATH_SEPARATOR_STRING "\\"
#else
#error cfgpath.h functions have not been implemented for your platform!  Please send patches.
#endif

namespace cfgpath {

/** Get an absolute path to a single configuration file, specific to this user.
 *
 * This function is useful for programs that need only a single configuration
 * file.  The file is unique to the user account currently logged in.
 *
 * Output is typically:
 *
 *   Windows: C:\Users\jcitizen\AppData\Roaming\appname.ini
 *   Linux: /home/jcitizen/.config/appname.conf
 *   Mac: /Users/jcitizen/Library/Application Support/appname.conf
 *
 * @param out
 *   Buffer to write the path.  On return will contain the path, or an empty
 *   string on error.
 *
 * @param maxlen
 *   Length of out.  Must be >= MAX_PATH.
 *
 * @param appname
 *   Short name of the application.  Avoid using spaces or version numbers, and
 *   use lowercase if possible.
 *
 * @post The file may or may not exist.
 * @post The folder holding the file is created if needed.
 */
static inline void get_user_config_file(char *out, unsigned int maxlen, const char *appname)
{
#if defined(__APPLE__) || defined(__linux__)
  const char *out_orig = out;
  char *home = getenv("XDG_CONFIG_HOME");
  unsigned int config_len = 0;
  if (!home) {
    home = getenv("HOME");
    if (!home) {
      // Can't find home directory
      out[0] = 0;
      return;
    }
    config_len = strlen(".config/");
  }

  unsigned int home_len = strlen(home);
  unsigned int appname_len = strlen(appname);
  const int ext_len = strlen(".conf");

  /* first +1 is "/", second is terminating null */
  if (home_len + 1 + config_len + appname_len + ext_len + 1 > maxlen) {
    out[0] = 0;
    return;
  }

  memcpy(out, home, home_len);
  out += home_len;
  *out = '/';
  out++;
  if (config_len) {
    memcpy(out, ".config/", config_len);
    out += config_len;
    /* Make the .config folder if it doesn't already exist */
    mkdir(out_orig, 0755);
  }
  memcpy(out, appname, appname_len);
  out += appname_len;
  memcpy(out, ".conf", ext_len);
  out += ext_len;
  *out = 0;
#elif defined(WIN32)
  if (!SUCCEEDED(SHGetFolderPath(NULL, CSIDL_APPDATA, NULL, 0, out))) {
    out[0] = 0;
    return;
  }
  /* We don't try to create the AppData folder as it always exists already */
  unsigned int appname_len = strlen(appname);
  if (strlen(out) + 1 + appname_len + strlen(".ini") + 1 > maxlen) {
    out[0] = 0;
    return;
  }
  strcat(out, "\\");
  strcat(out, appname);
  strcat(out, ".ini");
#endif
}

}

#endif /* CFGPATH_H_ */