/* filesys.c -- filesystem specific functions.
   $Id: filesys.c 5337 2013-08-22 17:54:06Z karl $

   Copyright 1993, 1997, 1998, 2000, 2002, 2003, 2004, 2007, 2008, 2009, 2011,
   2012, 2013 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.

   Originally written by Brian Fox. */

#include "info.h"

#include "tilde.h"
#include "filesys.h"
#include "tag.h"

/* Local to this file. */
static char *info_file_in_path (char *filename, char *path);
static char *lookup_info_filename (char *filename);
static char *info_absolute_file (char *fname);

static void remember_info_filename (char *filename, char *expansion);

typedef struct
{
  char *suffix;
  char *decompressor;
} COMPRESSION_ALIST;

static char *info_suffixes[] = {
  ".info",
  "-info",
  "/index",
  ".inf",       /* 8+3 file on filesystem which supports long file names */
#ifdef __MSDOS__
  /* 8+3 file names strike again...  */
  ".in",        /* for .inz, .igz etc. */
  ".i",
#endif
  "",
  NULL
};

static COMPRESSION_ALIST compress_suffixes[] = {
#if STRIP_DOT_EXE
  { ".gz", "gunzip" },
  { ".lz", "lunzip" },
#else
  { ".gz", "gzip -d" },
  { ".lz", "lzip -d" },
#endif
  { ".xz", "unxz" },
  { ".bz2", "bunzip2" },
  { ".z", "gunzip" },
  { ".lzma", "unlzma" },
  { ".Z", "uncompress" },
  { ".Y", "unyabba" },
#ifdef __MSDOS__
  { "gz", "gunzip" },
  { "z", "gunzip" },
#endif
  { NULL, NULL }
};

/* Expand the filename in PARTIAL to make a real name for this operating
   system.  This looks in INFO_PATHS in order to find the correct file.
   If it can't find the file, it returns NULL. */
static char *local_temp_filename = NULL;
static int local_temp_filename_size = 0;

char *
info_find_fullpath (char *partial)
{
  int initial_character;
  char *temp;

  debug(1, (_("looking for file \"%s\""), partial));

  filesys_error_number = 0;

  if (partial && (initial_character = *partial))
    {
      char *expansion;

      expansion = lookup_info_filename (partial);

      if (expansion)
        return expansion;

      /* If we have the full path to this file, we still may have to add
         various extensions to it.  I guess we have to stat this file
         after all. */
      if (IS_ABSOLUTE (partial))
	temp = info_absolute_file (partial);
      else if (initial_character == '~')
        {
          expansion = tilde_expand_word (partial);
          if (IS_ABSOLUTE (expansion))
            {
              temp = info_absolute_file (expansion);
              free (expansion);
            }
          else
            temp = expansion;
        }
      else if (initial_character == '.' &&
               (IS_SLASH (partial[1]) ||
		(partial[1] == '.' && IS_SLASH (partial[2]))))
        {
          if (local_temp_filename_size < 1024)
            local_temp_filename = xrealloc
              (local_temp_filename, (local_temp_filename_size = 1024));
#if defined (HAVE_GETCWD)
          if (!getcwd (local_temp_filename, local_temp_filename_size))
#else /*  !HAVE_GETCWD */
          if (!getwd (local_temp_filename))
#endif /* !HAVE_GETCWD */
            {
              filesys_error_number = errno;
              return partial;
            }

          strcat (local_temp_filename, "/");
          strcat (local_temp_filename, partial);
	  temp = info_absolute_file (local_temp_filename); /* try extensions */
	  if (!temp)
	    partial = local_temp_filename;
        }
      else
        temp = info_file_in_path (partial, infopath ());

      if (temp)
        {
          remember_info_filename (partial, temp);
          if (strlen (temp) > (unsigned int) local_temp_filename_size)
            local_temp_filename = xrealloc
              (local_temp_filename,
               (local_temp_filename_size = (50 + strlen (temp))));
          strcpy (local_temp_filename, temp);
          free (temp);
          return local_temp_filename;
        }
    }
  return partial;
}

/* Scan the list of directories in PATH looking for FILENAME.  If we find
   one that is a regular file, return it as a new string.  Otherwise, return
   a NULL pointer. */
char *
info_file_find_next_in_path (char *filename, char *path, int *diridx)
{
  struct stat finfo;
  char *temp_dirname;
  int statable;

  /* Reject ridiculous cases up front, to prevent infinite recursion
     later on.  E.g., someone might say "info '(.)foo'"...  */
  if (!*filename || STREQ (filename, ".") || STREQ (filename, ".."))
    return NULL;

  while ((temp_dirname = extract_colon_unit (path, diridx)))
    {
      register int i, pre_suffix_length;
      char *temp;

      debug(1, (_("looking for file %s in %s"), filename, temp_dirname));
      /* Expand a leading tilde if one is present. */
      if (*temp_dirname == '~')
        {
          char *expanded_dirname = tilde_expand_word (temp_dirname);
          free (temp_dirname);
          temp_dirname = expanded_dirname;
        }

      temp = xmalloc (30 + strlen (temp_dirname) + strlen (filename));
      strcpy (temp, temp_dirname);
      if (!IS_SLASH (temp[(strlen (temp)) - 1]))
        strcat (temp, "/");
      strcat (temp, filename);

      pre_suffix_length = strlen (temp);

      free (temp_dirname);

      for (i = 0; info_suffixes[i]; i++)
        {
          strcpy (temp + pre_suffix_length, info_suffixes[i]);

          statable = (stat (temp, &finfo) == 0);

          /* If we have found a regular file, then use that.  Else, if we
             have found a directory, look in that directory for this file. */
          if (statable)
            {
              if (S_ISREG (finfo.st_mode))
                {
		  debug(1, (_("found file %s"), temp));
                  return temp;
                }
              else if (S_ISDIR (finfo.st_mode))
                {
                  char *newpath, *filename_only, *newtemp;

                  newpath = xstrdup (temp);
                  filename_only = filename_non_directory (filename);
                  newtemp = info_file_in_path (filename_only, newpath);

                  free (newpath);
                  if (newtemp)
                    {
                      free (temp);
		      debug(1, (_("found file %s"), newtemp));
                      return newtemp;
                    }
                }
            }
          else
            {
              /* Add various compression suffixes to the name to see if
                 the file is present in compressed format. */
              register int j, pre_compress_suffix_length;

              pre_compress_suffix_length = strlen (temp);

              for (j = 0; compress_suffixes[j].suffix; j++)
                {
                  strcpy (temp + pre_compress_suffix_length,
                          compress_suffixes[j].suffix);

                  statable = (stat (temp, &finfo) == 0);
                  if (statable && (S_ISREG (finfo.st_mode)))
		    {
		      debug(1, (_("found file %s"), temp));
		      return temp;
		    }
                }
            }
        }
      free (temp);
    }
  return NULL;
}

static char *
info_file_in_path (char *filename, char *path)
{
  int i = 0;
  return info_file_find_next_in_path (filename, path, &i);
}

/* Assume FNAME is an absolute file name, and check whether it is
   a regular file.  If it is, return it as a new string; otherwise
   return a NULL pointer.  We do it by taking the file name apart
   into its directory and basename parts, and calling info_file_in_path.*/
static char *
info_absolute_file (char *fname)
{
  char *containing_dir = xstrdup (fname);
  char *base = filename_non_directory (containing_dir);

  if (base > containing_dir)
    base[-1] = '\0';

  return info_file_in_path (filename_non_directory (fname), containing_dir);
}


/* Given a string containing units of information separated by the
   PATH_SEP character, return the next one after IDX, or NULL if there
   are no more.  Advance IDX to the character after the colon. */

char *
extract_colon_unit (char *string, int *idx)
{
  unsigned int i = (unsigned int) *idx;
  unsigned int start = i;

  if (!string || i >= strlen (string))
    return NULL;

  if (!string[i]) /* end of string */
    return NULL;

  /* Advance to next PATH_SEP.  */
  while (string[i] && string[i] != PATH_SEP[0])
    i++;

  {
    char *value = xmalloc ((i - start) + 1);
    strncpy (value, &string[start], (i - start));
    value[i - start] = 0;

    i++; /* move past PATH_SEP */
    *idx = i;
    return value;
  }
}

/* A structure which associates a filename with its expansion. */
typedef struct
{
  char *filename;
  char *expansion;
} FILENAME_LIST;

/* An array of remembered arguments and results. */
static FILENAME_LIST **names_and_files = NULL;
static int names_and_files_index = 0;
static int names_and_files_slots = 0;

/* Find the result for having already called info_find_fullpath () with
   FILENAME. */
static char *
lookup_info_filename (char *filename)
{
  if (filename && names_and_files)
    {
      register int i;
      for (i = 0; names_and_files[i]; i++)
        {
          if (FILENAME_CMP (names_and_files[i]->filename, filename) == 0)
            return names_and_files[i]->expansion;
        }
    }
  return NULL;
}

/* Add a filename and its expansion to our list. */
static void
remember_info_filename (char *filename, char *expansion)
{
  FILENAME_LIST *new;

  if (names_and_files_index + 2 > names_and_files_slots)
    {
      int alloc_size;
      names_and_files_slots += 10;

      alloc_size = names_and_files_slots * sizeof (FILENAME_LIST *);

      names_and_files = xrealloc (names_and_files, alloc_size);
    }

  new = xmalloc (sizeof (FILENAME_LIST));
  new->filename = xstrdup (filename);
  new->expansion = expansion ? xstrdup (expansion) : NULL;

  names_and_files[names_and_files_index++] = new;
  names_and_files[names_and_files_index] = NULL;
}

void
forget_file_names (void)
{
  int i;

  for (i = 0; i < names_and_files_index; i++)
    {
      free (names_and_files[i]->filename);
      free (names_and_files[i]->expansion);
      free (names_and_files[i]);
      names_and_files[i] = NULL;
    }
  names_and_files_index = 0;
}

/* Given a chunk of text and its length, convert all CRLF pairs at every
   end-of-line into a single Newline character.  Return the length of
   produced text.

   This is required because the rest of code is too entrenched in having
   a single newline at each EOL; in particular, searching for various
   Info headers and cookies can become extremely tricky if that assumption
   breaks.

   FIXME: this could also support Mac-style text files with a single CR
   at the EOL, but what about random CR characters in non-Mac files?  Can
   we afford converting them into newlines as well?  Maybe implement some
   heuristics here, like in Emacs 20.

   FIXME: is it a good idea to show the EOL type on the modeline?  */
long
convert_eols (char *text, long int textlen)
{
  register char *s = text;
  register char *d = text;

  while (textlen--)
    {
      if (*s == '\r' && textlen && s[1] == '\n')
	{
	  s++;
	  textlen--;
	}
      *d++ = *s++;
    }

  return d - text;
}

/* Read the contents of PATHNAME, returning a buffer with the contents of
   that file in it, and returning the size of that buffer in FILESIZE.
   FINFO is a stat struct which has already been filled in by the caller.
   If the file turns out to be compressed, set IS_COMPRESSED to non-zero.
   If the file cannot be read, return a NULL pointer. */
char *
filesys_read_info_file (char *pathname, size_t *filesize,
			struct stat *finfo, int *is_compressed)
{
  size_t fsize;
  char *contents;

  fsize = filesys_error_number = 0;

  if (compressed_filename_p (pathname))
    {
      *is_compressed = 1;
      contents = filesys_read_compressed (pathname, &fsize);
    }
  else
    {
      int descriptor;

      *is_compressed = 0;
      descriptor = open (pathname, O_RDONLY | O_BINARY, 0666);

      /* If the file couldn't be opened, give up. */
      if (descriptor < 0)
        {
          filesys_error_number = errno;
          return NULL;
        }

      /* Try to read the contents of this file. */
      fsize = (long) finfo->st_size;
      contents = xmalloc (1 + fsize);
      if ((read (descriptor, contents, fsize)) != fsize)
        {
	  filesys_error_number = errno;
	  close (descriptor);
	  free (contents);
	  return NULL;
        }
      contents[fsize] = 0;
      close (descriptor);
    }

  /* Convert any DOS-style CRLF EOLs into Unix-style NL.
     Seems like a good idea to have even on Unix, in case the Info
     files are coming from some Windows system across a network.  */
  fsize = convert_eols (contents, fsize);

  /* EOL conversion can shrink the text quite a bit.  We don't
     want to waste storage.  */
  contents = xrealloc (contents, 1 + fsize);
  contents[fsize] = '\0';
  *filesize = fsize;
  return contents;
}

/* Typically, pipe buffers are 4k. */
#define BASIC_PIPE_BUFFER (4 * 1024)

/* We use some large multiple of that. */
#define FILESYS_PIPE_BUFFER_SIZE (16 * BASIC_PIPE_BUFFER)

char *
filesys_read_compressed (char *pathname, size_t *filesize)
{
  FILE *stream;
  char *command, *decompressor;
  char *contents = NULL;

  *filesize = filesys_error_number = 0;

  decompressor = filesys_decompressor_for_file (pathname);

  if (!decompressor)
    return NULL;

  command = xmalloc (15 + strlen (pathname) + strlen (decompressor));
  /* Explicit .exe suffix makes the diagnostics of `popen'
     better on systems where COMMAND.COM is the stock shell.  */
  sprintf (command, "%s%s < %s",
	   decompressor, STRIP_DOT_EXE ? ".exe" : "", pathname);

#if !defined (BUILDING_LIBRARY)
  if (info_windows_initialized_p)
    {
      char *temp;

      temp = xmalloc (5 + strlen (command));
      sprintf (temp, "%s...", command);
      message_in_echo_area ("%s", temp);
      free (temp);
    }
#endif /* !BUILDING_LIBRARY */

  stream = popen (command, FOPEN_RBIN);
  free (command);

  /* Read chunks from this file until there are none left to read. */
  if (stream)
    {
      size_t offset, size;
      char *chunk;
    
      offset = size = 0;
      chunk = xmalloc (FILESYS_PIPE_BUFFER_SIZE);

      while (1)
        {
          size_t bytes_read;

          bytes_read = fread (chunk, 1, FILESYS_PIPE_BUFFER_SIZE, stream);

          if (bytes_read + offset >= size)
            contents = xrealloc
              (contents, size += (2 * FILESYS_PIPE_BUFFER_SIZE));

          memcpy (contents + offset, chunk, bytes_read);
          offset += bytes_read;
          if (bytes_read != FILESYS_PIPE_BUFFER_SIZE)
            break;
        }

      free (chunk);
      if (pclose (stream) == -1)
	{
	  if (contents)
	    free (contents);
	  contents = NULL;
	  filesys_error_number = errno;
	}
      else
	{
	  contents = xrealloc (contents, 1 + offset);
	  contents[offset] = '\0';
	  *filesize = offset;
	}
    }
  else
    {
      filesys_error_number = errno;
    }

#if !defined (BUILDING_LIBARARY)
  if (info_windows_initialized_p)
    unmessage_in_echo_area ();
#endif /* !BUILDING_LIBRARY */
  return contents;
}

/* Return non-zero if FILENAME belongs to a compressed file. */
int
compressed_filename_p (char *filename)
{
  char *decompressor;

  /* Find the final extension of this filename, and see if it matches one
     of our known ones. */
  decompressor = filesys_decompressor_for_file (filename);

  if (decompressor)
    return 1;
  else
    return 0;
}

/* Return the command string that would be used to decompress FILENAME. */
char *
filesys_decompressor_for_file (char *filename)
{
  register int i;
  char *extension = NULL;

  /* Find the final extension of FILENAME, and see if it appears in our
     list of known compression extensions. */
  for (i = strlen (filename) - 1; i > 0; i--)
    if (filename[i] == '.')
      {
        extension = filename + i;
        break;
      }

  if (!extension)
    return NULL;

  for (i = 0; compress_suffixes[i].suffix; i++)
    if (FILENAME_CMP (extension, compress_suffixes[i].suffix) == 0)
      return compress_suffixes[i].decompressor;

#if defined (__MSDOS__)
  /* If no other suffix matched, allow any extension which ends
     with `z' to be decompressed by gunzip.  Due to limited 8+3 DOS
     file namespace, we can expect many such cases, and supporting
     every weird suffix thus produced would be a pain.  */
  if (extension[strlen (extension) - 1] == 'z' ||
      extension[strlen (extension) - 1] == 'Z')
    return "gunzip";
#endif

  return NULL;
}

/* The number of the most recent file system error. */
int filesys_error_number = 0;

/* A function which returns a pointer to a static buffer containing
   an error message for FILENAME and ERROR_NUM. */
static char *errmsg_buf = NULL;
static int errmsg_buf_size = 0;

char *
filesys_error_string (char *filename, int error_num)
{
  int len;
  char *result;

  if (error_num == 0)
    return NULL;

  result = strerror (error_num);

  len = 4 + strlen (filename) + strlen (result);
  if (len >= errmsg_buf_size)
    errmsg_buf = xrealloc (errmsg_buf, (errmsg_buf_size = 2 + len));

  sprintf (errmsg_buf, "%s: %s", filename, result);
  return errmsg_buf;
}


/* Check for "dir" with all the possible info and compression suffixes,
   in combination.  */

int
is_dir_name (char *filename)
{
  unsigned i;

  for (i = 0; info_suffixes[i]; i++)
    {
      unsigned c;
      char trydir[50];
      strcpy (trydir, "dir");
      strcat (trydir, info_suffixes[i]);
      
      if (mbscasecmp (filename, trydir) == 0)
        return 1;

      for (c = 0; compress_suffixes[c].suffix; c++)
        {
          char dir_compressed[50]; /* can be short */
          strcpy (dir_compressed, trydir); 
          strcat (dir_compressed, compress_suffixes[c].suffix);
          if (mbscasecmp (filename, dir_compressed) == 0)
            return 1;
        }
    }  

  return 0;
}