/* man.c: How to read and format man files.
   $Id: man.c 6877 2015-12-19 16:42:47Z gavin $

   Copyright 1995, 1997, 1998, 1999, 2000, 2002, 2003, 2004, 2005, 2007, 2008, 
   2009, 2011, 2012, 2013, 2014, 2015 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 Thu May  4 09:17:52 1995. */

#include "info.h"
#include "signals.h"
#if defined (HAVE_SYS_TIME_H)
#include <sys/time.h>
#endif
#if defined (HAVE_SYS_WAIT_H)
#include <sys/wait.h>
#endif

#include "tilde.h"
#include "nodes.h"
#include "man.h"
#include "variables.h"

#if !defined (_POSIX_VERSION)
#define pid_t int
#endif

#if defined (FD_SET)
#  if defined (hpux)
#    define fd_set_cast(x) (int *)(x)
#  else
#    define fd_set_cast(x) (fd_set *)(x)
#  endif /* !hpux */
#endif /* FD_SET */

#if STRIP_DOT_EXE
static char const * const exec_extensions[] = {
  ".exe", ".com", ".bat", ".btm", ".sh", ".ksh", ".pl", ".sed", "", NULL
};
#else
static char const * const exec_extensions[] = { "", NULL };
#endif

static REFERENCE **xrefs_of_manpage (NODE *node);
static char *read_from_fd (int fd);
static char *get_manpage_contents (char *pagename);

/* We store the contents of retrieved man pages in here. */
static NODE **manpage_nodes = 0;
size_t manpage_node_index = 0;
size_t manpage_node_slots = 0;

NODE *
get_manpage_node (char *pagename)
{
  NODE *node = 0, **n, *node2 = 0;
  char *page;

  if (manpage_node_index > 0)
    for (n = manpage_nodes; (node = *n); n++)
      if (!strcmp (node->nodename, pagename))
        break;

  /* Node was not found, so we have to create it. */
  if (!node)
    {
      node = info_create_node ();
      node->fullpath = MANPAGE_FILE_BUFFER_NAME;
      node->nodename = xstrdup (pagename);
      node->flags |= N_HasTagsTable | N_IsManPage;

      /* Save this node. */
      add_pointer_to_array (node, manpage_node_index,
                            manpage_nodes,
                            manpage_node_slots, 100);
    } 

  /* Node wasn't found, or its contents were freed since last time. */
  if (!node->contents)
    {
      int plen;

      page = get_manpage_contents (pagename);
      if (!page)
        return 0;
      plen = strlen (page);

      node->contents = page;
      node->nodelen = plen;

      node->body_start = 0;
      node->references = xrefs_of_manpage (node);
      node->up = "(dir)";
    }

  node2 = xmalloc (sizeof (NODE));
  *node2 = *node;
  return node2;
}

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

  dirname_index = 0;

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

      /* 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 = xmalloc (34 + strlen (temp_dirname) + strlen (filename));
      strcpy (temp, temp_dirname);
      if (!IS_SLASH (temp[(strlen (temp)) - 1]))
        strcat (temp, "/");
      strcat (temp, filename);
      temp_end = temp + strlen (temp);

      free (temp_dirname);

      /* Look for FILENAME, possibly with any of the extensions
	 in EXEC_EXTENSIONS[].  */
      for (i = 0; exec_extensions[i]; i++)
	{
	  if (exec_extensions[i][0])
	    strcpy (temp_end, exec_extensions[i]);
	  statable = (stat (temp, &finfo) == 0);

	  /* If we have found a regular executable file, then use it. */
	  if ((statable) && (S_ISREG (finfo.st_mode)) &&
	      (access (temp, X_OK) == 0))
	    return temp;
	}

      free (temp);
    }
  return NULL;
}

/* Return the full pathname of the system man page formatter. */
static char *
find_man_formatter (void)
{
  char *man_command = getenv ("INFO_MAN_COMMAND");
  return man_command ? man_command :
                       executable_file_in_path ("man", getenv ("PATH"));
}

static char *manpage_pagename = NULL;
static char *manpage_section  = NULL;

static void
get_page_and_section (char *pagename)
{
  register int i;

  if (manpage_pagename)
    free (manpage_pagename);

  if (manpage_section)
    free (manpage_section);

  manpage_pagename = NULL;
  manpage_section  = NULL;

  for (i = 0; pagename[i] != '\0' && pagename[i] != '('; i++);

  manpage_pagename = xmalloc (1 + i);
  strncpy (manpage_pagename, pagename, i);
  manpage_pagename[i] = '\0';

  if (pagename[i] == '(')
    {
      int start;

      start = i + 1;

      for (i = start; pagename[i] != '\0' && pagename[i] != ')'; i++);

      manpage_section = xmalloc (1 + (i - start));
      strncpy (manpage_section, pagename + start, (i - start));
      manpage_section[i - start] = '\0';
    }
}

void
clean_manpage (char *manpage)
{
  mbi_iterator_t iter;
  size_t len = strlen (manpage);
  char *newpage = xmalloc (len + 1);
  char *np = newpage;
  int prev_len = 0;
  
  for (mbi_init (iter, manpage, len);
       mbi_avail (iter);
       mbi_advance (iter))
    {
      const char *cur_ptr = mbi_cur_ptr (iter);
      size_t cur_len = mb_len (mbi_cur (iter));

      if (cur_len == 1)
	{
	  if (*cur_ptr == '\b' || *cur_ptr == '\f')
	    {
	      if (np >= newpage + prev_len)
		np -= prev_len;
	    }
	  else if (ansi_escape (iter, &cur_len))
	    {
	      memcpy (np, cur_ptr, cur_len);
	      np += cur_len;
	      ITER_SETBYTES (iter, cur_len);
	    }
	  else if (show_malformed_multibyte_p || mbi_cur (iter).wc_valid)
	    *np++ = *cur_ptr;
	}
      else
	{
	  memcpy (np, cur_ptr, cur_len);
	  np += cur_len;
	}
      prev_len = cur_len;
    }
  *np = 0;
  
  strcpy (manpage, newpage);
  free (newpage);
}

static char *get_manpage_from_formatter (char *formatter_args[]);

static char *
get_manpage_contents (char *pagename)
{
  static char *formatter_args[4] = { NULL };
  char *formatted_page;

  if (formatter_args[0] == NULL)
    formatter_args[0] = find_man_formatter ();

  if (formatter_args[0] == NULL)
    return NULL;

  get_page_and_section (pagename);

  if (manpage_section)
    formatter_args[1] = manpage_section;
  else
    formatter_args[1] = "-a";

  formatter_args[2] = manpage_pagename;
  formatter_args[3] = NULL;

  formatted_page = get_manpage_from_formatter (formatter_args);

  /* If there was a section and the page wasn't found, try again
     without the section (e.g. "man 3X curses" versus "man -a curses"). */
  if (!formatted_page && manpage_section)
    {
      formatter_args[1] = "-a";
      formatted_page = get_manpage_from_formatter (formatter_args);
    }

  return formatted_page;
}

static char *
get_manpage_from_formatter (char *formatter_args[])
{
  char *formatted_page = NULL;
  int pipes[2];
  pid_t child;
  int formatter_status = 0;

  /* Open a pipe to this program, read the output, and save it away
     in FORMATTED_PAGE.  The reader end of the pipe is pipes[0]; the
     writer end is pipes[1]. */
#if PIPE_USE_FORK
  pipe (pipes);

  child = fork ();
  if (child == -1)
    return NULL;

  if (child != 0)
    {
      /* In the parent, close the writing end of the pipe, and read from
         the exec'd child. */
      close (pipes[1]);
      formatted_page = read_from_fd (pipes[0]);
      close (pipes[0]);
      wait (&formatter_status); /* Wait for child process to exit. */
    }
  else
    { /* In the child, close the read end of the pipe, make the write end
         of the pipe be stdout, and execute the man page formatter. */
      close (pipes[0]);
      freopen (NULL_DEVICE, "w", stderr);
      freopen (NULL_DEVICE, "r", stdin);
      dup2 (pipes[1], fileno (stdout));

      execv (formatter_args[0], formatter_args);

      /* If we get here, we couldn't exec, so close out the pipe and
         exit. */
      close (pipes[1]);
      exit (EXIT_SUCCESS);
    }
#else  /* !PIPE_USE_FORK */
  /* Cannot fork/exec, but can popen/pclose.  */
  {
    FILE *fpipe;
    char *cmdline;
    size_t cmdlen = 0;
    int save_stderr = dup (fileno (stderr));
    int fd_err = open (NULL_DEVICE, O_WRONLY, 0666);
    int i;

    for (i = 0; formatter_args[i]; i++)
      cmdlen += strlen (formatter_args[i]);
    /* Add-ons: 2 blanks, 2 quotes for the formatter program, 1
       terminating null character.  */
    cmdlen += 2 + 2 + 1;
    cmdline = xmalloc (cmdlen);

    if (fd_err > 2)
      dup2 (fd_err, fileno (stderr)); /* Don't print errors. */
    sprintf (cmdline, "\"%s\" %s %s",
	     formatter_args[0], formatter_args[1], formatter_args[2]);
    fpipe = popen (cmdline, "r");
    free (cmdline);
    if (fd_err > 2)
      close (fd_err);
    dup2 (save_stderr, fileno (stderr));
    if (fpipe == 0)
      return NULL;
    formatted_page = read_from_fd (fileno (fpipe));
    formatter_status = pclose (fpipe);
  }
#endif /* !PIPE_USE_FORK */

  if (!formatted_page)
    return 0;

  /* We could check the exit status of "man -a" to see if it successfully
     output a man page  However:
      * It is possible for "man -a" to output a man page and still to exit with
        a non-zero status.  This was found to happen when duplicate man pages 
        were found.
      * "man" was found to exit with a zero status on Solaris 10 even when
        it found nothing.
     Hence, treat it as a success if more than three lines were output.  (A 
     small amount of output could be error messages that were sent to standard 
     output.) */
  {
    int i;
    char *p;
    p = formatted_page;
    for (i = 0; i < 3; i++)
      {
        p = strchr (p, '\n');
        if (!p)
          {
            free (formatted_page);
            return NULL;
          }
        p++;
      }
  }

  /* If we have the page, then clean it up. */
  clean_manpage (formatted_page);

  return formatted_page;
}

/* Return pointer to bytes read from file descriptor FD.  Return value to be
   freed by caller. */
static char *
read_from_fd (int fd)
{
  struct timeval timeout;
  char *buffer = NULL;
  int bsize = 0;
  int bindex = 0;
  int select_result;
#if defined (FD_SET)
  fd_set read_fds;

  timeout.tv_sec = 15;
  timeout.tv_usec = 0;

  FD_ZERO (&read_fds);
  FD_SET (fd, &read_fds);

  select_result = select (fd + 1, fd_set_cast (&read_fds), 0, 0, &timeout);
#else /* !FD_SET */
  select_result = 1;
#endif /* !FD_SET */

  switch (select_result)
    {
    case 0:
    case -1:
      break;

    default:
      {
        int amount_read;
        int done = 0;

        while (!done)
          {
            while ((bindex + 1024) > (bsize))
              buffer = xrealloc (buffer, (bsize += 1024));
            buffer[bindex] = '\0';

            amount_read = read (fd, buffer + bindex, 1023);

            if (amount_read < 0)
              {
                done = 1;
              }
            else
              {
                bindex += amount_read;
                buffer[bindex] = '\0';
                if (amount_read == 0)
                  done = 1;
              }
          }
      }
    }

  if ((buffer != NULL) && (*buffer == '\0'))
    {
      free (buffer);
      buffer = NULL;
    }

  return buffer;
}

/* Search in the whole man page for references now. */
#if 0
static char *reference_section_starters[] =
{
  "\nRELATED INFORMATION",
  "\nRELATED\tINFORMATION",
  "RELATED INFORMATION\n",
  "RELATED\tINFORMATION\n",
  "\nSEE ALSO",
  "\nSEE\tALSO",
  "SEE ALSO\n",
  "SEE\tALSO\n",
  NULL
};

static SEARCH_BINDING frs_binding;

static SEARCH_BINDING *
find_reference_section (NODE *node)
{
  register int i;
  long position = -1;

  frs_binding.buffer = node->contents;
  frs_binding.start = 0;
  frs_binding.end = node->nodelen;
  frs_binding.flags = S_SkipDest;

  for (i = 0; reference_section_starters[i] != NULL; i++)
    {
      if (search_forward (reference_section_starters[i], &frs_binding,
			  &position) == search_success)
        break;
    }

  if (position == -1)
    return NULL;

  /* We found the start of the reference section, and point is right after
     the string which starts it.  The text from here to the next header
     (or end of buffer) contains the only references in this manpage. */
  frs_binding.start = position;

  for (i = frs_binding.start; i < frs_binding.end - 2; i++)
    {
      if ((frs_binding.buffer[i] == '\n') &&
          (!whitespace (frs_binding.buffer[i + 1])))
        {
          frs_binding.end = i;
          break;
        }
    }

  return &frs_binding;
}

#endif

static REFERENCE **
xrefs_of_manpage (NODE *node)
{
  SEARCH_BINDING s;

  REFERENCE **refs = NULL;
  size_t refs_index = 0;
  size_t refs_slots = 0;
  long position;

  /* Initialize reference list to have a single null entry. */
  refs = calloc(1, sizeof (REFERENCE *));
  refs_slots = 1;

  s.buffer = node->contents;
  s.start = 0;
  s.flags = 0;
  s.end = node->nodelen;

  /* Exclude first line, which often looks like:
CAT(1)                           User Commands                          CAT(1)
  */
  s.start = strcspn (node->contents, "\n");

  /* Build a list of references.  A reference is alphabetic characters
     followed by non-whitespace text within parenthesis leading with a digit. */
  while (search_forward ("(", &s, &position) == search_success)
    {
      register int name, name_end;
      int section, section_end;

      for (name = position; name > 0; name--)
        if (whitespace_or_newline (s.buffer[name]))
          break;

      if (name == 0)
        goto skip;
      name++;

      if (name == position)
        goto skip; /* Whitespace immediately before '('. */

      /* If we are on an ECMA-48 SGR escape sequence, skip past it. */
      if (s.buffer[name] == '\033' && s.buffer[name + 1] == '[')
        {
          name += 2;
          name += strspn (s.buffer + name, "0123456789;");
          if (s.buffer[name] == 'm')
            name++;
          else
            goto skip;
        }

      for (name_end = name; name_end < position; name_end++)
        if (!isalnum (s.buffer[name_end])
            && s.buffer[name_end] != '_'
            && s.buffer[name_end] != '.'
            && s.buffer[name_end] != '-')
          break;

      section = position;
      if (!isdigit (s.buffer[section + 1]))
        goto skip; /* Could be ordinary text in parentheses. */

      for (section_end = section + 1; section_end < s.end; section_end++)
        {
          if (whitespace (s.buffer[section_end]))
            {
              continue;
              break;
            }

          if (s.buffer[section_end] == ')')
            {
              section_end++;
              break;
            }
        }

      {
        REFERENCE *entry;
        int len = name_end - name + section_end - section;

        entry = xmalloc (sizeof (REFERENCE));
        entry->label = xcalloc (1, 1 + len);
        strncpy (entry->label, s.buffer + name, name_end - name);
        strncpy (entry->label + strlen (entry->label),
                 s.buffer + section,
                 section_end - section);

        entry->filename = xstrdup (MANPAGE_FILE_BUFFER_NAME);
        entry->nodename = xstrdup (entry->label);
        entry->line_number = 0;
        entry->start = name;
        entry->end = section_end;
        entry->type = REFERENCE_XREF;

        add_pointer_to_array (entry, refs_index, refs, refs_slots, 10);
      }

skip:
      s.start = position + 1;
    }

  return refs;
}
