/* Handle configuration data.
   Copyright (C) 1997, 1998 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <search.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/param.h>

#include <gconv_int.h>


/* This is the default path where we look for module lists.  */
static const char default_gconv_path[] = GCONV_PATH;

/* Name of the file containing the module information in the directories
   along the path.  */
static const char gconv_conf_filename[] = "gconv-modules";

/* Filename extension for the modules.  */
#ifndef MODULE_EXT
# define MODULE_EXT ".so"
#endif
static const char gconv_module_ext[] = MODULE_EXT;

/* We have a few builtin transformations.  */
static struct gconv_module builtin_modules[] =
{
#define BUILTIN_TRANSFORMATION(From, ConstPfx, ConstLen, To, Cost, Name, \
			       Fct, Init, End, MinF, MaxF, MinT, MaxT) \
  {									      \
    from_pattern: From,							      \
    from_constpfx: ConstPfx,						      \
    from_constpfx_len: ConstLen,					      \
    from_regex: NULL,							      \
    to_string: To,							      \
    cost_hi: Cost,							      \
    cost_lo: INT_MAX,							      \
    module_name: Name							      \
  },
#define BUILTIN_ALIAS(From, To)

#include "gconv_builtin.h"
};

#undef BUILTIN_TRANSFORMATION
#undef BUILTIN_ALIAS

static const char *
builtin_aliases[] =
{
#define BUILTIN_TRANSFORMATION(From, ConstPfx, ConstLen, To, Cost, Name, \
			       Fct, Init, End, MinF, MaxF, MinT, MaxT)
#define BUILTIN_ALIAS(From, To) From " " To,

#include "gconv_builtin.h"
};

#ifdef USE_IN_LIBIO
# include <libio/libioP.h>
# define __getdelim(line, len, c, fp) _IO_getdelim (line, len, c, fp)
#endif


/* Function for searching module.  */
static int
module_compare (const void *p1, const void *p2)
{
  const struct gconv_module *s1 = (const struct gconv_module *) p1;
  const struct gconv_module *s2 = (const struct gconv_module *) p2;
  int result;

  if (s1->from_pattern == NULL)
    {
      if (s2->from_pattern == NULL)
	result = strcmp (s1->from_constpfx, s2->from_constpfx);
      else
	result = -1;
    }
  else if (s2->from_pattern == NULL)
    result = 1;
  else
    result = strcmp (s1->from_pattern, s2->from_pattern);

  if (result == 0)
    result = strcmp (s1->to_string, s2->to_string);

  return result;
}


/* This function is used to test for a conflict which could be introduced
   if adding a new alias.

   This function is a *very* ugly hack.  The action-function is not
   supposed to alter the parameter.  But we have to do this.   We will if
   necessary compile the regular expression  so that we can see whether it
   matches the alias name.  This is safe in this environment and for the
   sake of performance we do it this way.  The alternative would be to
   compile all regular expressions right from the start or to forget about
   the compilation though we might need it later.

   The second ugliness is that we have no possibility to pass parameters
   to the function.  Therefore we use a global variable.  This is no problem
   since we are for sure alone even in multi-threaded applications.  */

/* This is alias we want to check.  */
static const char *alias_to_test;

/* This variable is set to a nonzero value once we have found a matching
   entry.  */
static int abort_conflict_search;

static void
detect_conflict (const void *p, VISIT value, int level)
{
  struct gconv_module *s = *(struct gconv_module **) p;

  if ((value != endorder && value != leaf) || s->from_constpfx == NULL
      || abort_conflict_search)
    return;

  /* Before we test the whole expression (if this is a regular expression)
     make sure the constant prefix matches.  In case this is no regular
     expression this is the whole string.  */
  if (strcmp (alias_to_test, s->from_constpfx) == 0)
    {
      if (s->from_pattern == NULL)
	/* This is a simple string and therefore we have a conflict.  */
	abort_conflict_search = 1;
      else
	{
	  /* Make sure the regular expression is compiled (if possible).  */
	  if (s->from_regex == NULL)
	    {
	      /* Beware, this is what I warned you about in the comment
		 above.  We are modifying the object.  */
	      if (__regcomp (&s->from_regex_mem, s->from_pattern,
			     REG_EXTENDED | REG_ICASE) != 0)
		/* Something is wrong.  Remember this.  */
		s->from_regex = (regex_t *) -1L;
	      else
		s->from_regex = &s->from_regex_mem;
	    }

	  if (s->from_regex != (regex_t *) -1L)
	    {
	      regmatch_t match[1];

	      if (__regexec (s->from_regex, alias_to_test, 1, match, 0) == 0
		  && match[0].rm_so == 0
		  && alias_to_test[match[0].rm_eo] == '\0')
		/* The whole string matched.  This is also a conflict.  */
		abort_conflict_search = 1;
	    }
	}
    }
}


/* Add new alias.  */
static inline void
add_alias (char *rp, void *modules)
{
  /* We now expect two more string.  The strings are normalized
     (converted to UPPER case) and strored in the alias database.  */
  struct gconv_alias *new_alias;
  char *from, *to, *wp;

  while (isspace (*rp))
    ++rp;
  from = wp = rp;
  while (*rp != '\0' && !isspace (*rp))
    ++rp;
  if (*rp == '\0')
    /* There is no `to' string on the line.  Ignore it.  */
    return;
  *rp++ = '\0';
  to = wp = rp;
  while (isspace (*rp))
    ++rp;
  while (*rp != '\0' && !isspace (*rp))
    *wp++ = *rp++;
  if (to == wp)
    /* No `to' string, ignore the line.  */
    return;
  *wp++ = '\0';

  /* Test whether this alias conflicts with any available module.  See
     the comment before the function `detect_conflict' for a description
     of this ugly hack.  */
  alias_to_test = from;
  abort_conflict_search = 0;
  __twalk (modules, detect_conflict);
  if (abort_conflict_search)
    /* It does conflict, don't add the alias.  */
    return;

  new_alias = (struct gconv_alias *)
    malloc (sizeof (struct gconv_alias) + (wp - from));
  if (new_alias != NULL)
    {
      new_alias->fromname = memcpy ((char *) new_alias
				    + sizeof (struct gconv_alias),
				    from, wp - from);
      new_alias->toname = new_alias->fromname + (to - from);

      if (__tsearch (new_alias, &__gconv_alias_db, __gconv_alias_compare)
	  == NULL)
	/* Something went wrong, free this entry.  */
	free (new_alias);
    }
}


/* Add new module.  */
static inline void
add_module (char *rp, const char *directory, size_t dir_len, void **modules,
	    size_t *nmodules, int modcounter)
{
  /* We expect now
     1. `from' name
     2. `to' name
     3. filename of the module
     4. an optional cost value
  */
  struct gconv_module *new_module;
  char *from, *to, *module, *wp;
  size_t const_len;
  int from_is_regex;
  int need_ext;
  int cost_hi;

  while (isspace (*rp))
    ++rp;
  from = rp;
  from_is_regex = 0;
  while (*rp != '\0' && !isspace (*rp))
    {
      if (!isalnum (*rp) && *rp != '-' && *rp != '/' && *rp != '.'
	  && *rp != '_')
	from_is_regex = 1;
      ++rp;
    }
  if (*rp == '\0')
    return;
  *rp++ = '\0';
  to = wp = rp;
  while (isspace (*rp))
    ++rp;
  while (*rp != '\0' && !isspace (*rp))
    *wp++ = *rp++;
  if (*rp == '\0')
    return;
  *wp++ = '\0';
  do
    ++rp;
  while (isspace (*rp));
  module = wp;
  while (*rp != '\0' && !isspace (*rp))
    *wp++ = *rp++;
  if (*rp == '\0')
    {
      /* There is no cost, use one by default.  */
      *wp++ = '\0';
      cost_hi = 1;
    }
  else
    {
      /* There might be a cost value.  */
      char *endp;

      *wp++ = '\0';
      cost_hi = strtol (rp, &endp, 10);
      if (rp == endp)
	/* No useful information.  */
	cost_hi = 1;
    }

  if (module[0] == '\0')
    /* No module name given.  */
    return;
  if (module[0] == '/')
    dir_len = 0;
  else
    /* Increment by one for the slash.  */
    ++dir_len;

  /* See whether we must add the ending.  */
  need_ext = 0;
  if (wp - module < sizeof (gconv_module_ext)
      || memcmp (wp - sizeof (gconv_module_ext), gconv_module_ext,
		 sizeof (gconv_module_ext)) != 0)
    /* We must add the module extension.  */
    need_ext = sizeof (gconv_module_ext) - 1;

  /* We've collected all the information, now create an entry.  */

  if (from_is_regex)
    {
      const_len = 0;
      while (isalnum (from[const_len]) || from[const_len] == '-'
	     || from[const_len] == '/' || from[const_len] == '.'
	     || from[const_len] == '_')
	++const_len;
    }
  else
    const_len = to - from - 1;

  new_module = (struct gconv_module *) malloc (sizeof (struct gconv_module)
					       + (wp - from)
					       + dir_len + need_ext);
  if (new_module != NULL)
    {
      char *tmp;

      new_module->from_constpfx = memcpy ((char *) new_module
					  + sizeof (struct gconv_module),
					  from, to - from);
      if (from_is_regex)
	new_module->from_pattern = new_module->from_constpfx;
      else
	new_module->from_pattern = NULL;

      new_module->from_constpfx_len = const_len;

      new_module->from_regex = NULL;

      new_module->to_string = memcpy ((char *) new_module->from_constpfx
				      + (to - from), to, module - to);

      new_module->cost_hi = cost_hi;
      new_module->cost_lo = modcounter;

      new_module->module_name = (char *) new_module->to_string + (module - to);

      if (dir_len == 0)
	tmp = (char *) new_module->module_name;
      else
	{
	  tmp = __mempcpy ((char *) new_module->module_name,
			   directory, dir_len - 1);
	  *tmp++ = '/';
	}

      tmp = __mempcpy (tmp, module, wp - module);

      if (need_ext)
	memcpy (tmp - 1, gconv_module_ext, sizeof (gconv_module_ext));

      /* See whether we have already an alias with this name defined.
	 We do allow regular expressions matching this any alias since
	 this expression can also match other names and we test for aliases
	 before testing for modules.  */
      if (! from_is_regex)
	{
	  struct gconv_alias fake_alias;

	  fake_alias.fromname = new_module->from_constpfx;

	  if (__tfind (&fake_alias, &__gconv_alias_db, __gconv_alias_compare)
	      != NULL)
	    {
	      /* This module duplicates an alias.  */
	      free (new_module);
	      return;
	    }
	}

      if (__tfind (new_module, modules, module_compare) == NULL)
	{
	  if (__tsearch (new_module, modules, module_compare) == NULL)
	    /* Something went wrong while inserting the new module.  */
	    free (new_module);
	  else
	    ++*nmodules;
	}
    }
}


static void
insert_module (const void *nodep, VISIT value, int level)
{
  if (value == preorder || value == leaf)
    __gconv_modules_db[__gconv_nmodules++] = *(struct gconv_module **) nodep;
}

static void
nothing (void *unused __attribute__ ((unused)))
{
}


/* Read the next configuration file.  */
static void
internal_function
read_conf_file (const char *filename, const char *directory, size_t dir_len,
		void **modules, size_t *nmodules)
{
  FILE *fp = fopen (filename, "r");
  char *line = NULL;
  size_t line_len = 0;
  int modcounter = 0;

  /* Don't complain if a file is not present or readable, simply silently
     ignore it.  */
  if (fp == NULL)
    return;

  /* Process the known entries of the file.  Comments start with `#' and
     end with the end of the line.  Empty lines are ignored.  */
  while (!feof_unlocked (fp))
    {
      char *rp, *endp, *word;
      ssize_t n = __getdelim (&line, &line_len, '\n', fp);
      if (n < 0)
	/* An error occurred.  */
	break;

      rp = line;
      /* Terminate the line (excluding comments or newline) by an NUL byte
	 to simplify the following code.  */
      endp = strchr (rp, '#');
      if (endp != NULL)
	*endp = '\0';
      else
	if (rp[n - 1] == '\n')
	  rp[n - 1] = '\0';

      while (isspace (*rp))
	++rp;

      /* If this is an empty line go on with the next one.  */
      if (rp == endp)
	continue;

      word = rp;
      while (*rp != '\0' && !isspace (*rp))
	++rp;

      if (rp - word == sizeof ("alias") - 1
	  && memcmp (word, "alias", sizeof ("alias") - 1) == 0)
	add_alias (rp, *modules);
      else if (rp - word == sizeof ("module") - 1
	       && memcmp (word, "module", sizeof ("module") - 1) == 0)
	add_module (rp, directory, dir_len, modules, nmodules, modcounter++);
      /* else */
	/* Otherwise ignore the line.  */
    }

  if (line != NULL)
    free (line);
  fclose (fp);
}


/* Read all configuration files found in the user-specified and the default
   path.  */
void
__gconv_read_conf (void)
{
  const char *user_path = __secure_getenv ("GCONV_PATH");
  char *gconv_path, *elem;
  void *modules = NULL;
  size_t nmodules = 0;
  int save_errno = errno;
  size_t cnt;

  if (user_path == NULL)
    /* No user-defined path.  Make a modifiable copy of the default path.  */
    gconv_path = strdupa (default_gconv_path);
  else
    {
      /* Append the default path to the user-defined path.  */
      size_t user_len = strlen (user_path);
      char *tmp;

      gconv_path = alloca (user_len + 1 + sizeof (default_gconv_path));
      tmp = __mempcpy (gconv_path, user_path, user_len);
      *tmp++ = ':';
      __mempcpy (tmp, default_gconv_path, sizeof (default_gconv_path));
    }

  elem = strtok_r (gconv_path, ":", &gconv_path);
  while (elem != NULL)
    {
#ifndef MAXPATHLEN
      /* We define a reasonable limit.  */
# define MAXPATHLEN 4096
#endif
      char real_elem[MAXPATHLEN];

      if (__realpath (elem, real_elem) != NULL)
	{
	  size_t elem_len = strlen (real_elem);
	  char *filename, *tmp;

	  filename = alloca (elem_len + 1 + sizeof (gconv_conf_filename));
	  tmp = __mempcpy (filename, real_elem, elem_len);
	  *tmp++ = '/';
	  __mempcpy (tmp, gconv_conf_filename, sizeof (gconv_conf_filename));

	  /* Read the next configuration file.  */
	  read_conf_file (filename, real_elem, elem_len, &modules, &nmodules);
	}

      /* Get next element in the path.  */
      elem = strtok_r (NULL, ":", &gconv_path);
    }

  /* If the configuration files do not contain any valid module specification
     remember this by setting the pointer to the module array to NULL.  */
  nmodules += sizeof (builtin_modules) / sizeof (builtin_modules[0]);
  if (nmodules == 0)
    __gconv_modules_db = NULL;
  else
    {
      __gconv_modules_db =
	(struct gconv_module **) malloc (nmodules
					 * sizeof (struct gconv_module));
      if (__gconv_modules_db != NULL)
	{
	  size_t cnt;

	  /* Insert all module entries into the array.  */
	  __twalk (modules, insert_module);

	  /* Finally insert the builtin transformations.  */
	  for (cnt = 0; cnt < (sizeof (builtin_modules)
			       / sizeof (struct gconv_module)); ++cnt)
	    __gconv_modules_db[__gconv_nmodules++] = &builtin_modules[cnt];
	}
    }

  /* Add aliases for builtin conversions.  */
  cnt = sizeof (builtin_aliases) / sizeof (builtin_aliases[0]);
  while (cnt > 0)
    {
      char *copy = strdupa (builtin_aliases[--cnt]);
      add_alias (copy, modules);
    }
  
  if (nmodules != 0)
    /* Now remove the tree data structure.  */
    __tdestroy (modules, nothing);

  /* Restore the error number.  */
  __set_errno (save_errno);
}