#ifndef URLADER
# define URLADER "urlader"
#endif
#define URLADER_VERSION "1.0" // a decimal number, not a version string

#define MAX_ARGC 32
#define MAX_ARGS 256

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <time.h>
#include <fcntl.h>

#include "liblzf/lzf_d.c"

#define TAIL_MAGIC "SCHMORPPACK0"

#ifdef _WIN32

  #include <windows.h>
  //#include <winbase.h>
  #include <shlobj.h>
  #include <shlwapi.h>
  #include <wininet.h>

  static DWORD dword;

  #define u_handle HANDLE
  #define u_invalid_handle 0
  #define u_valid(handle) (!!handle)

  #define u_setenv(name,value) SetEnvironmentVariable (name, value)
  #define u_mkdir(path) !CreateDirectory (path, NULL)
  #define u_chdir(path) !SetCurrentDirectory (path)
  #define u_rename(fr,to) !MoveFile (fr, to)
  #define u_open(path) CreateFile (path, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, NULL)
  #define u_creat(path,exec) CreateFile (path, GENERIC_WRITE, FILE_SHARE_WRITE, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, NULL)
  #define u_creat(path,exec) CreateFile (path, GENERIC_WRITE, FILE_SHARE_WRITE, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, NULL)
  #define u_close(handle) CloseHandle (handle)
  #define u_append(path,add) PathAppend (path, add)
  #define u_write(handle,data,len) (WriteFile (handle, data, len, &dword, 0) ? dword : -1)

  #define u_fsync(handle) FlushFileBuffers (handle)
  #define u_sync()

  #define u_lockfile(path) CreateFile (path, GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL)
  #define u_cloexec(handle)

#else

  #define _GNU_SOURCE 1
  #define _BSD_SOURCE 1
  // the above increases our chances of getting MAP_ANONYMOUS

  #include <sys/mman.h>
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <unistd.h>
  #include <pwd.h>

  #if defined (MAP_ANON) && !defined (MAP_ANONYMOUS)
    #define MAP_ANONYMOUS MAP_ANON
  #endif

  #ifdef PATH_MAX
    #define MAX_PATH (PATH_MAX < 4096 ? 4096 : PATH_MAX)
  #else
    #define MAX_PATH 4096
  #endif

  #define u_handle int
  #define u_invalid_handle -1
  #define u_valid(fd) ((fd) >= 0)

  #define u_setenv(name,value) setenv (name, value, 1)
  #define u_mkdir(path) mkdir (path, 0777)
  #define u_chdir(path) chdir (path)
  #define u_rename(fr,to) rename (fr, to)
  #define u_open(path) open (path, O_RDONLY)
  #define u_creat(path,exec) open (path, O_WRONLY | O_CREAT | O_TRUNC, (exec) ? 0777 : 0666)
  #define u_close(handle) close (handle)
  #define u_append(path,add) strcat (strcat (path, "/"), add)
  #define u_write(handle,data,len) write (handle, data, len)

  // on a mostly idle system, a sync at the end is certainly faster, hope for the best
  #define u_fsync(handle)
  #define u_sync() sync ()

  #define u_lockfile(path) open (path, O_RDWR | O_CREAT, 0666)
  #define u_cloexec(handle) fcntl (handle, F_SETFD, FD_CLOEXEC)

#endif

#define u_16(ptr) (((ptr)[0] << 8) | (ptr)[1])
#define u_32(ptr) (((ptr)[0] << 24) | ((ptr)[1] << 16) | ((ptr)[2] << 8) | (ptr)[3])

/* some simple? dynamic memory management for paths might save ltos of ram */
static u_handle pack_handle;
static u_handle lock_handle;
static char tmppath[MAX_PATH];
static char currdir[MAX_PATH];
static char datadir[MAX_PATH];  // %AppData%/urlader
static char exe_dir[MAX_PATH];  // %AppData%/urlader/EXE_ID
static char execdir[MAX_PATH];  // %AppData%/urlader/EXE_ID/EXE_VER
static char exe_id[MAX_PATH];
static char exe_ver[MAX_PATH];

static int exe_argc;
static const char *exe_argv[MAX_ARGC];
static char exe_args[MAX_ARGS]; /* actual arguments strings copied here */
static unsigned int exe_argo;

static void
fatal (const char *msg)
{
#ifdef _WIN32
  MessageBox (0, msg, URLADER, 0);
#else
  write (2, URLADER ": ", sizeof (URLADER ": ") - 1);
  write (2, msg, strlen (msg));
  write (2, "\n", 1);
#endif

  _exit (1);
}

static void *
u_malloc (unsigned int size)
{
  void *addr;

#ifdef _WIN32
  HANDLE handle = CreateFileMapping (0, 0, PAGE_READWRITE, 0, size, NULL);

  if (!handle)
    return 0;

  addr = MapViewOfFile (handle, FILE_MAP_WRITE, 0, 0, size);

  CloseHandle (handle);
#elif defined (MAP_ANONYMOUS)
  addr = mmap (0, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);

  if (addr == (void *)-1)
    addr = 0;
#else
  addr = malloc (size);
#endif

  return addr;
}

static void
u_free (void *addr, unsigned int size)
{
#ifdef _WIN32
  UnmapViewOfFile (addr);
#elif defined (MAP_ANONYMOUS)
  munmap (addr, size);
#else
  free (addr);
#endif
}

static void *
u_mmap (u_handle h, unsigned int size)
{
  void *addr;

#ifdef _WIN32
  HANDLE handle = CreateFileMapping (h, 0, PAGE_READONLY, 0, size, NULL);

  if (!handle)
    return 0;

  addr = MapViewOfFile (handle, FILE_MAP_READ, 0, 0, size);

  CloseHandle (handle);
#else
  addr = mmap (0, size, PROT_READ, MAP_SHARED, h, 0);

  if (addr == (void *)-1)
    addr = 0;
#endif

  return addr;
}

static void
u_munmap (void *addr, unsigned int len)
{
#ifdef _WIN32
  UnmapViewOfFile (addr);
#else
  munmap (addr, len);
#endif
}

static void
tmpdir (const char *dir)
{
  static int cnt;

  for (;;)
    {
//      #ifdef _WIN32
//        sprintf (tmppath, "%s/%x_%x.tmp", dir, (unsigned int)GetCurrentProcessId (), ++cnt);
//      #else
        sprintf (tmppath, "%s/t-%x_%x.tmp", dir, (unsigned int)getpid ()             , ++cnt);
//      #endif

      if (!u_mkdir (tmppath))
        return;
    }
}

static u_handle
u_lock (const char *path, int excl, int dowait)
{
  u_handle h;

  h = u_lockfile (path);
  if (!u_valid (h))
    return h;

  u_cloexec (h);

  for (;;)
    {
      int success;

      // acquire the lock
#ifdef _WIN32
      OVERLAPPED ov = { 0 };

      success = LockFileEx (h,
                            (excl ? LOCKFILE_EXCLUSIVE_LOCK : 0)
                            | (dowait ? 0 : LOCKFILE_FAIL_IMMEDIATELY),
                            0,
                            1, 0,
                            &ov);
#else
      struct flock lck = { 0 };

      lck.l_type   = excl ? F_WRLCK : F_RDLCK;
      lck.l_whence = SEEK_SET;
      lck.l_len    = 1;

      success = !fcntl (h, dowait ? F_SETLKW : F_SETLK, &lck);
#endif

      if (!success)
        break;

      // we have the lock, now verify that the lockfile still exists

#ifdef _WIN32
      // apparently, we have to open the file to get its info :(
      BY_HANDLE_FILE_INFORMATION s1, s2;
      u_handle h2 = u_lockfile (path);
      if (!u_valid (h))
        break;

      success = GetFileInformationByHandle (h, &s1)
                && GetFileInformationByHandle (h2, &s2);

      u_close (h2);

      if (!success)
        break;

      success = s1.dwVolumeSerialNumber == s2.dwVolumeSerialNumber
             && s1.nFileIndexHigh       == s2.nFileIndexHigh
             && s1.nFileIndexLow        == s2.nFileIndexLow;
#else
      struct stat s1, s2;

      if (fstat (h, &s1) || stat (path, &s2))
        break;

      success = s1.st_dev == s2.st_dev
             && s1.st_ino == s2.st_ino;
#endif

      if (success)
        return h; // lock successfully acquired

      // files differ, close and retry - should be very rare
      u_close (h);
    }

  // failure
  u_close (h);
  return u_invalid_handle;
}

static void
systemv (const char *const argv[])
{
#ifdef _WIN32
  _spawnv (P_WAIT, argv [0], argv);
#else
  pid_t pid = fork ();

  if (pid < 0)
    fatal ("fork failure");

  if (!pid)
    {
      execv (argv [0], (void *)argv);
      _exit (124);
    }

  int status;
  waitpid (pid, &status, 0);
#endif
}

static void
deltree (const char *path)
{
  #ifdef _WIN32
    char buf[MAX_PATH * 2 + 64];
    const char *argv[] = { getenv ("COMSPEC"), "/c", "rd", "/s", "/q", buf, 0 };
    sprintf (buf, "\"%s\"", path);
  #else
    const char *argv[] = { "/bin/rm", "-rf", path, 0 };
  #endif
  systemv (argv);
}

enum
{
  T_NULL, // 5
  T_META, // 1 : exe_id, exe_ver
  T_ENV,  // 2 : name, value
  T_ARG,  // 3 : arg
  T_DIR,  // 4+: path
  T_FILE, // 4+: path, data
  T_NUM
};

enum
{
  F_EXEC = 1,
  F_LZF  = 2,
  F_NULL = 0
};

struct hdr
{
  unsigned char type;
  unsigned char flags;
  unsigned char namelen[2];
  unsigned char datalen[4];
};

struct tail {
  unsigned char max_filesize[4];
  unsigned char size[4];
  char magic[12];
};

static char *pack_base, *pack_end;
static struct hdr *pack_cur;
static char *scratch;
static unsigned int scratch_size;

#define PACK_NAME ((char *)(pack_cur + 1))
#define PACK_DATA (PACK_NAME + u_16 (pack_cur->namelen) + 1)
#define PACK_VALID pack_cur->type

static void
pack_next (void)
{
  unsigned int d = u_32 (pack_cur->datalen);

  pack_cur = (struct hdr *)(PACK_DATA + d);
}

static void
pack_unmap (void)
{
  if (pack_base)
    {
      u_munmap (pack_base, pack_end - pack_base);
      pack_base = 0;
    }

  if (scratch)
    {
      u_free (scratch, scratch_size);
      scratch = 0;
    }
}

static int
pack_map (void)
{
  char *addr;
  unsigned int size;

#ifdef _WIN32
  BY_HANDLE_FILE_INFORMATION fi;

  if (!GetFileInformationByHandle (pack_handle, &fi))
    return 0;

  size = fi.nFileSizeLow;
#else
  size = lseek (pack_handle, 0, SEEK_END);
#endif

  addr = u_mmap (pack_handle, size);
  if (!addr)
    return 0;

  pack_unmap ();

  pack_base = addr;
  pack_end  = pack_base + size;

  struct tail *tail;

  tail = (void *)(pack_end - sizeof (*tail));

  if (memcmp (tail->magic, TAIL_MAGIC, sizeof (TAIL_MAGIC) - 1))
    return 0;

  pack_cur = (struct hdr *)(pack_end - u_32 (tail->size));

  scratch = u_malloc (scratch_size = u_32 (tail->max_filesize));
  if (!scratch)
    return 0;

  return 1;
}

static void
exe_info (void)
{
  if (!pack_map ())
    fatal ("unable to locate packfile in executable - executable corrupted?");

  if (pack_cur->type != T_META)
    fatal ("unable to locate executable metadata - executable corrupted?");

  strcpy (exe_id, PACK_NAME);
}

static void
load (void)
{
  u_mkdir (datadir);

  strcpy (exe_dir, datadir);
  u_append (exe_dir, exe_id);
  u_mkdir (exe_dir);

  if (u_chdir (exe_dir))
    fatal ("unable to change to application data directory");

  u_handle h = u_open ("override");
  if (u_valid (h))
    {
      u_handle oh = pack_handle;

      pack_handle = h;
      if (!pack_map ())
        {
          pack_handle = oh;
          oh = h;
        }

      u_close (oh);
    }

  if (pack_cur->type != T_META)
    fatal ("unable to locate override metadata");

  strcpy (exe_ver, PACK_DATA);
  pack_next ();

  for (;;)
    {
      if (pack_cur->type == T_ENV)
        u_setenv (PACK_NAME, PACK_DATA);
      else if (pack_cur->type == T_ARG)
        {
          int len = u_16 (pack_cur->namelen) + 1;
          exe_argv [exe_argc++] = exe_args + exe_argo;
          memcpy (exe_args + exe_argo, PACK_NAME, len);
          exe_argo += len;
        }
      else
        break;

      pack_next ();
    }
 
done_env_arg:
  strcpy (execdir, exe_dir);
  u_append (execdir, "i-");
  strcat (execdir, exe_ver);

  strcat (strcpy (tmppath, execdir), ".lck");
  lock_handle = u_lock (tmppath, 0, 1);
  if (!lock_handle)
    fatal ("unable to lock application instance");

  if (access (execdir, F_OK))
    {
      // does not exist yet, so unpack and move
      tmpdir (exe_dir);

      if (u_chdir (tmppath))
        fatal ("unable to change to new instance directory");

      for (;;)
        {
          switch (pack_cur->type)
            {
              case T_DIR:
                u_mkdir (PACK_NAME);
                break;

              case T_FILE:
                {
                  u_handle h = u_creat (PACK_NAME, pack_cur->flags & F_EXEC);
                  unsigned int dlen, len = u_32 (pack_cur->datalen);
                  char *data = PACK_DATA;

                  if (pack_cur->flags & F_LZF)
                    if (dlen = lzf_decompress (data, len, scratch, scratch_size))
                      {
                        data = scratch;
                        len  = dlen;
                      }
                    else
                      fatal ("unable to uncompress file data - pack corrupted?");

                  if (!u_valid (h))
                    fatal ("unable to unpack file from packfile - disk full?");

                  if (u_write (h, data, len) != len)
                    fatal ("unable to unpack file from packfile - disk full?");

                  u_fsync (h);
                  u_close (h);
                }
                break;

              case T_NULL:
                goto done;
            }

          pack_next ();
        }

done:
      if (u_chdir (datadir))
        fatal ("unable to change to data directory");

      u_sync ();

      if (u_rename (tmppath, execdir))
        deltree (tmppath); // if move fails, delete new, assume other process created it independently
    }

  pack_unmap ();
  u_close (pack_handle);

  if (u_chdir (execdir))
    fatal ("unable to change to application instance directory");

  u_setenv ("URLADER_VERSION", URLADER_VERSION);
  u_setenv ("URLADER_DATADIR", datadir);
  u_setenv ("URLADER_EXECDIR", execdir);
  u_setenv ("URLADER_EXE_ID" , exe_id);
  u_setenv ("URLADER_EXE_DIR", exe_dir);
  u_setenv ("URLADER_EXE_VER", exe_ver);

#if 0
  // yes, this is overkill
  u_setenv ("SHLIB_PATH"        , execdir); // hpux
  u_setenv ("LIBPATH"           , execdir); // aix
  u_setenv ("LD_LIBRARY_PATH"   , execdir); // most elf systems
  u_setenv ("LD_LIBRARY_PATH_32", execdir); // solaris
  u_setenv ("LD_LIBRARY_PATH_64", execdir); // solaris
  u_setenv ("LD_LIBRARYN32_PATH", execdir); // irix
  u_setenv ("LD_LIBRARY64_PATH" , execdir); // irix
  u_setenv ("DYLD_LIBRARY_PATH" , execdir); // os sucks from apple
#endif
}

static void
execute (void)
{
  exe_argv [exe_argc] = 0;
  systemv (exe_argv);
}

#ifdef _WIN32

int APIENTRY
WinMain (HINSTANCE hI, HINSTANCE hP, LPSTR argv, int command_show)
{
  if (!GetModuleFileName (hI, tmppath, sizeof (tmppath)))
    fatal ("unable to find executable pack");

  pack_handle = u_open (tmppath);
  if (!u_valid (pack_handle))
    fatal ("unable to open executable pack");

  exe_info ();

  if (!GetCurrentDirectory (sizeof (currdir), currdir))
    strcpy (currdir, ".");

  if (SHGetFolderPath (0, CSIDL_APPDATA | CSIDL_FLAG_CREATE, NULL, SHGFP_TYPE_CURRENT, datadir) != S_OK)
    fatal ("unable to find application data directory");

  u_mkdir (datadir);
  u_append (datadir, URLADER);

  load ();
  execute ();

  return 0;
}

#else

int
main (int argc, char *argv[])
{
  char *home = getenv ("HOME");

  pack_handle = u_open (argv [0]);
  if (!u_valid (pack_handle))
    fatal ("unable to open executable pack");

  exe_info ();

  if (!home)
    {
      struct passwd *pw;

      if ((pw = getpwuid (getuid ())))
        home = pw->pw_dir;
      else
        home = "/tmp";
    }

  if (!getcwd (currdir, sizeof (currdir)))
    strcpy (currdir, ".");

  u_mkdir (home);
  //strcat (strcat (strcpy (datadir, home), "/."), URLADER);
  sprintf (datadir, "%s/.%s", home, URLADER);
  u_mkdir (datadir);

#if 0
  if (gethostname (tmppath, sizeof (tmppath)))
    strcpy (tmppath, "default");

  u_append (datadir, tmppath);
#endif

  load ();
  execute ();

  return 0;
}

#endif