/* 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 "main.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) {
                return;
        }

        fd = fopen (config.filter, "r");
        if (!fd) {
                return;
        }

        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 =
                            (struct filter_list *)
                            safecalloc (1, sizeof (struct filter_list));
                else {  /* next entry */
                        p->next =
                            (struct filter_list *)
                            safecalloc (1, sizeof (struct filter_list));
                        p = p->next;
                }

                p->pat = safestrdup (s);
                p->cpat = (regex_t *) safemalloc (sizeof (regex_t));
                err = regcomp (p->cpat, p->pat, cflags);
                if (err != 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;
        }
}

/**
 * reload the filter file if filtering is enabled
 */
void filter_reload (void)
{
        if (config.filter) {
                log_message (LOG_NOTICE, "Re-reading filter file.");
                filter_destroy ();
                filter_init ();
        }
}

/* 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;
}