/* filesys.c -- File system specific functions for hacking this system. */

/* This file is part of GNU Info, a program for reading online documentation
   stored in Info format.

   Copyright (C) 1993 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 2, 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, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

   Written by Brian Fox (bfox@ai.mit.edu). */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <sys/errno.h>
#include "general.h"
#include "tilde.h"
#include "filesys.h"

#if !defined (O_RDONLY)
#if defined (HAVE_SYS_FCNTL_H)
#include <sys/fcntl.h>
#else /* !HAVE_SYS_FCNTL_H */
#include <fcntl.h>
#endif /* !HAVE_SYS_FCNTL_H */
#endif /* !O_RDONLY */

#if !defined (errno)
extern int errno;
#endif /* !errno */

/* Found in info-utils.c. */
extern char *filename_non_directory ();

#if !defined (BUILDING_LIBRARY)
/* Found in session.c */
extern int info_windows_initialized_p;

/* Found in window.c. */
extern void message_in_echo_area (), unmessage_in_echo_area ();
#endif /* !BUILDING_LIBRARY */

/* Local to this file. */
static char *info_file_in_path (), *lookup_info_filename ();
static void remember_info_filename (), maybe_initialize_infopath ();

#if !defined (NULL)
#  define NULL 0x0
#endif /* !NULL */

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

static char *info_suffixes[] = {
  "",
  ".info",
  "-info",
  (char *)NULL
};

static COMPRESSION_ALIST compress_suffixes[] = {
  { ".Z", "uncompress" },
  { ".Y", "unyabba" },
  { ".z", "gunzip" },
  { ".gz", "gunzip" },
  { (char *)NULL, (char *)NULL }
};

/* The path on which we look for info files.  You can initialize this
   from the environment variable INFOPATH if there is one, or you can
   call info_add_path () to add paths to the beginning or end of it.
   You can call zap_infopath () to make the path go away. */
char *infopath = (char *)NULL;
static int infopath_size = 0;

/* 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 = (char *)NULL;
static int local_temp_filename_size = 0;

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

  filesys_error_number = 0;

  maybe_initialize_infopath ();

  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 (initial_character == '/')
	temp = info_file_in_path (partial + 1, "/");
      else if (initial_character == '~')
	{
	  expansion = tilde_expand_word (partial);
	  if (*expansion == '/')
	    {
	      temp = info_file_in_path (expansion + 1, "/");
	      free (expansion);
	    }
	  else
	    temp = expansion;
	}
      else if (initial_character == '.' &&
	       (partial[1] == '/' || (partial[1] == '.' && partial[2] == '/')))
	{
	  if (local_temp_filename_size < 1024)
	    local_temp_filename = (char *)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);
	  return (local_temp_filename);
	}
      else
	temp = info_file_in_path (partial, infopath);

      if (temp)
	{
	  remember_info_filename (partial, temp);
	  if (strlen (temp) > local_temp_filename_size)
	    local_temp_filename = (char *) 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. */
static char *
info_file_in_path (filename, path)
     char *filename, *path;
{
  struct stat finfo;
  char *temp_dirname;
  int statable, dirname_index;

  dirname_index = 0;

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

      /* Expand a leading tilde if one is present. */
      if (*temp_dirname == '~')
	{
	  char *expanded_dirname;

	  expanded_dirname = tilde_expand_word (temp_dirname);
	  free (temp_dirname);
	  temp_dirname = expanded_dirname;
	}

      temp = (char *)xmalloc (30 + strlen (temp_dirname) + strlen (filename));
      strcpy (temp, temp_dirname);
      if (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))
		{
		  return (temp);
		}
	      else if (S_ISDIR (finfo.st_mode))
		{
		  char *newpath, *filename_only, *newtemp;

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

		  free (newpath);
		  if (newtemp)
		    {
		      free (temp);
		      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)))
		    return (temp);
		}
	    }
	}
      free (temp);
    }
  return ((char *)NULL);
}

/* Given a string containing units of information separated by colons,
   return the next one pointed to by IDX, or NULL if there are no more.
   Advance IDX to the character after the colon. */
char *
extract_colon_unit (string, idx)
     char *string;
     int *idx;
{
  register int i, start;

  i = start = *idx;
  if ((i >= strlen (string)) || !string)
    return ((char *) NULL);

  while (string[i] && string[i] != ':')
    i++;
  if (i == start)
    {
      return ((char *) NULL);
    }
  else
    {
      char *value = (char *) xmalloc (1 + (i - start));
      strncpy (value, &string[start], (i - start));
      value[i - start] = '\0';
      if (string[i])
	++i;
      *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 = (FILENAME_LIST **)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 (filename)
     char *filename;
{
  if (filename && names_and_files)
    {
      register int i;
      for (i = 0; names_and_files[i]; i++)
	{
	  if (strcmp (names_and_files[i]->filename, filename) == 0)
	    return (names_and_files[i]->expansion);
	}
    }
  return (char *)NULL;;
}

/* Add a filename and its expansion to our list. */
static void
remember_info_filename (filename, expansion)
     char *filename, *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 =
	(FILENAME_LIST **) xrealloc (names_and_files, alloc_size);
    }

  new = (FILENAME_LIST *)xmalloc (sizeof (FILENAME_LIST));
  new->filename = savestring (filename);
  new->expansion = expansion ? savestring (expansion) : (char *)NULL;

  names_and_files[names_and_files_index++] = new;
  names_and_files[names_and_files_index] = (FILENAME_LIST *)NULL;
}

static void
maybe_initialize_infopath ()
{
  if (!infopath_size)
    {
      infopath = (char *)
	xmalloc (infopath_size = (1 + strlen (DEFAULT_INFOPATH)));

      strcpy (infopath, DEFAULT_INFOPATH);
    }
}

/* Add PATH to the list of paths found in INFOPATH.  2nd argument says
   whether to put PATH at the front or end of INFOPATH. */
void
info_add_path (path, where)
     char *path;
     int where;
{
  int len;

  if (!infopath)
    {
      infopath = (char *)xmalloc (infopath_size = 200 + strlen (path));
      infopath[0] = '\0';
    }

  len = strlen (path) + strlen (infopath);

  if (len + 2 >= infopath_size)
    infopath = (char *)xrealloc (infopath, (infopath_size += (2 * len) + 2));

  if (!*infopath)
    strcpy (infopath, path);
  else if (where == INFOPATH_APPEND)
    {
      strcat (infopath, ":");
      strcat (infopath, path);
    }
  else if (where == INFOPATH_PREPEND)
    {
      char *temp = savestring (infopath);
      strcpy (infopath, path);
      strcat (infopath, ":");
      strcat (infopath, temp);
      free (temp);
    }
}

/* Make INFOPATH have absolutely nothing in it. */
void
zap_infopath ()
{
  if (infopath)
    free (infopath);

  infopath = (char *)NULL;
  infopath_size = 0;
}

/* 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 cannot be read, return a NULL pointer. */
char *
filesys_read_info_file (pathname, filesize, finfo)
     char *pathname;
     long *filesize;
     struct stat *finfo;
{
  *filesize = filesys_error_number = 0;

  if (compressed_filename_p (pathname))
    return (filesys_read_compressed (pathname, filesize, finfo));
  else
    {
      int descriptor;
      char *contents;

      descriptor = open (pathname, O_RDONLY, 0666);

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

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

      close (descriptor);

      *filesize = finfo->st_size;
      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 (pathname, filesize, finfo)
     char *pathname;
     long *filesize;
     struct stat *finfo;
{
  FILE *stream;
  char *command, *decompressor;
  char *contents = (char *)NULL;

  *filesize = filesys_error_number = 0;

  decompressor = filesys_decompressor_for_file (pathname);

  if (!decompressor)
    return ((char *)NULL);

  command = (char *)xmalloc (10 + strlen (pathname) + strlen (decompressor));
  sprintf (command, "%s < %s", decompressor, pathname);

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

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

  stream = popen (command, "r");
  free (command);

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

      while (1)
	{
	  int bytes_read;

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

	  if (bytes_read + offset >= size)
	    contents = (char *)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);
      pclose (stream);
      contents = (char *)xrealloc (contents, offset + 1);
      *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 (filename)
     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 (filename)
     char *filename;
{
  register int i;
  char *extension = (char *)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 ((char *)NULL);

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

  return ((char *)NULL);
}

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

#if !defined (HAVE_STRERROR)
extern char *sys_errlist[];
extern int sys_nerr;

char *
strerror (num)
     int num;
{
  if (num >= sys_nerr)
    return ("");
  else
    return (sys_errlist[num]);
}
#endif /* !HAVE_STRERROR */

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

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

  if (error_num == 0)
    return ((char *)NULL);

  result = strerror (error_num);

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

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