/* tinyproxy - A fast light-weight HTTP proxy
 * Copyright (C) 1999 George Talusan <gstalusan@uwaterloo.ca>
 * Copyright (C) 2002 James E. Flemer <jflemer@acm.jhu.edu>
 * Copyright (C) 2002 Robert James Kaes <rjkaes@users.sourceforge.net>
 *
 * 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 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, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

/* A substring of the domain to be filtered goes into the file
 * pointed at by DEFAULT_FILTER.
 */

#include "tinyproxy.h"

#include "filter.h"
#include "heap.h"
#include "log.h"
#include "reqs.h"

#define FILTER_BUFFER_LEN (512)

static int err;

struct filter_list
{
  struct filter_list *next;
  char *pat;
  regex_t *cpat;
};

static struct filter_list *fl = NULL;
static int already_init = 0;
static filter_policy_t default_policy = FILTER_DEFAULT_ALLOW;

/*
 * Initializes a linked list of strings containing hosts/urls to be filtered
 */
void
filter_init (void)
{
  FILE *fd;
  struct filter_list *p;
  char buf[FILTER_BUFFER_LEN];
  char *s;
  int cflags;

  if (!fl && !already_init)
    {
      fd = fopen (config.filter, "r");
      if (fd)
        {
          p = NULL;

          cflags = REG_NEWLINE | REG_NOSUB;
          if (config.filter_extended)
            cflags |= REG_EXTENDED;
          if (!config.filter_casesensitive)
            cflags |= REG_ICASE;

          while (fgets (buf, FILTER_BUFFER_LEN, fd))
            {
              /*
               * Remove any trailing white space and
               * comments.
               */
              s = buf;
              while (*s)
                {
                  if (isspace ((unsigned char) *s))
                    break;
                  if (*s == '#')
                    {
                      /*
                       * If the '#' char is preceeded by
                       * an escape, it's not a comment
                       * string.
                       */
                      if (s == buf || *(s - 1) != '\\')
                        break;
                    }
                  ++s;
                }
              *s = '\0';

              /* skip leading whitespace */
              s = buf;
              while (*s && isspace ((unsigned char) *s))
                s++;

              /* skip blank lines and comments */
              if (*s == '\0')
                continue;

              if (!p)           /* head of list */
                fl = p = safecalloc (1, sizeof (struct filter_list));
              else
                {               /* next entry */
                  p->next = safecalloc (1, sizeof (struct filter_list));
                  p = p->next;
                }

              p->pat = safestrdup (s);
              p->cpat = safemalloc (sizeof (regex_t));
              if ((err = regcomp (p->cpat, p->pat, cflags)) != 0)
                {
                  fprintf (stderr, "Bad regex in %s: %s\n",
                           config.filter, p->pat);
                  exit (EX_DATAERR);
                }
            }
          if (ferror (fd))
            {
              perror ("fgets");
              exit (EX_DATAERR);
            }
          fclose (fd);

          already_init = 1;
        }
    }
}

/* unlink the list */
void
filter_destroy (void)
{
  struct filter_list *p, *q;

  if (already_init)
    {
      for (p = q = fl; p; p = q)
        {
          regfree (p->cpat);
          safefree (p->cpat);
          safefree (p->pat);
          q = p->next;
          safefree (p);
        }
      fl = NULL;
      already_init = 0;
    }
}

/* Return 0 to allow, non-zero to block */
int
filter_domain (const char *host)
{
  struct filter_list *p;
  int result;

  if (!fl || !already_init)
    goto COMMON_EXIT;

  for (p = fl; p; p = p->next)
    {
      result = regexec (p->cpat, host, (size_t) 0, (regmatch_t *) 0, 0);

      if (result == 0)
        {
          if (default_policy == FILTER_DEFAULT_ALLOW)
            return 1;
          else
            return 0;
        }
    }

COMMON_EXIT:
  if (default_policy == FILTER_DEFAULT_ALLOW)
    return 0;
  else
    return 1;
}

/* returns 0 to allow, non-zero to block */
int
filter_url (const char *url)
{
  struct filter_list *p;
  int result;

  if (!fl || !already_init)
    goto COMMON_EXIT;

  for (p = fl; p; p = p->next)
    {
      result = regexec (p->cpat, url, (size_t) 0, (regmatch_t *) 0, 0);

      if (result == 0)
        {
          if (default_policy == FILTER_DEFAULT_ALLOW)
            return 1;
          else
            return 0;
        }
    }

COMMON_EXIT:
  if (default_policy == FILTER_DEFAULT_ALLOW)
    return 0;
  else
    return 1;
}

/*
 * Set the default filtering policy
 */
void
filter_set_default_policy (filter_policy_t policy)
{
  default_policy = policy;
}