/*
 * Copyright(c) 2014 Tim Ruehsen
 *
 * This file is part of MGet.
 *
 * Mget 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.
 *
 * Mget 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 Mget.  If not, see <http://www.gnu.org/licenses/>.
 *
 *
 * Public Suffix List routines (right now experimental)
 *
 * Changelog
 * 19.03.2014  Tim Ruehsen  created from libmget/cookie.c
 *
 */

// need _GNU_SOURCE for qsort_r()
#ifndef _GNU_SOURCE
#	define _GNU_SOURCE
#endif

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

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#include <libpsl.h>

#define countof(a) (sizeof(a)/sizeof(*(a)))

typedef struct {
	char
		label_buf[48];
	const char *
		label;
	unsigned short
		length;
	unsigned char
		nlabels, // number of labels
		wildcard; // this is a wildcard rule (e.g. *.sapporo.jp)
} _psl_entry_t;

// stripped down version libmget vector routines
typedef struct {
	int
		(*cmp)(const _psl_entry_t *, const _psl_entry_t *); // comparison function
	_psl_entry_t
		**entry; // pointer to array of pointers to elements
	int
		max,     // allocated elements
		cur;     // number of elements in use
} _psl_vector_t;

struct _psl_ctx_st {
	_psl_vector_t
		*suffixes,
		*suffix_exceptions;
};

static _psl_vector_t *_vector_alloc(int max, int (*cmp)(const _psl_entry_t *, const _psl_entry_t *))
{
	_psl_vector_t *v;
	
	if (!(v = calloc(1, sizeof(_psl_vector_t))))
		return NULL;

	if (!(v->entry = malloc(max * sizeof(_psl_entry_t *)))) {
		free(v);
		return NULL;
	}

	v->max = max;
	v->cmp = cmp;
	return v;
}

static void _vector_free(_psl_vector_t **v)
{
	if (v && *v) {
		if ((*v)->entry) {
			int it;

			for (it = 0; it < (*v)->cur; it++)
				free((*v)->entry[it]);

			free((*v)->entry);
		}
		free(*v);
	}
}

static _psl_entry_t *_vector_get(const _psl_vector_t *v, int pos)
{
	if (pos < 0 || !v || pos >= v->cur) return NULL;

	return v->entry[pos];
}

// the entries must be sorted by
static int _vector_find(const _psl_vector_t *v, const _psl_entry_t *elem)
{
	if (v) {
		int l, r, m;
		int res;

		// binary search for element (exact match)
		for (l = 0, r = v->cur - 1; l <= r;) {
			m = (l + r) / 2;
			if ((res = v->cmp(elem, v->entry[m])) > 0) l = m + 1;
			else if (res < 0) r = m - 1;
			else return m;
		}
	}

	return -1; // not found
}

static int _vector_add(_psl_vector_t *v, const _psl_entry_t *elem)
{
	if (v) {
		void *elemp;

		elemp = malloc(sizeof(_psl_entry_t));
		memcpy(elemp, elem, sizeof(_psl_entry_t));

		if (v->max == v->cur)
			v->entry = realloc(v->entry, (v->max *= 2) * sizeof(_psl_entry_t *));

		v->entry[v->cur++] = elemp;
		return v->cur - 1;
	}

	return -1;
}

static int _compare(const void *p1, const void *p2, void *v)
{
	return ((_psl_vector_t *)v)->cmp(*((_psl_entry_t **)p1), *((_psl_entry_t **)p2));
}

static void _vector_sort(_psl_vector_t *v)
{
	if (v && v->cmp)
		qsort_r(v->entry, v->cur, sizeof(_psl_vector_t *), _compare, v);
}

static inline int _vector_size(_psl_vector_t *v)
{
	return v ? v->cur : 0;
}

// by this kind of sorting, we can easily see if a domain matches or not (match = supercookie !)

static int _suffix_compare(const _psl_entry_t *s1, const _psl_entry_t *s2)
{
	int n;

	if ((n = s2->nlabels - s1->nlabels))
		return n; // most labels first

	if ((n = s1->length - s2->length))
		return n;  // shorter rules first

	return strcmp(s1->label, s2->label);
}

static void _suffix_init(_psl_entry_t *suffix, const char *rule, size_t length)
{
	const char *src;
	char *dst;

	suffix->label = suffix->label_buf;

	if (length >= sizeof(suffix->label_buf) - 1) {
		suffix->nlabels = 0;
		fprintf(stderr, _("Suffix rule too long (%zd, ignored): %s\n"), length, rule);
		return;
	}

	if (*rule == '*') {
		if (*++rule != '.') {
			suffix->nlabels = 0;
			fprintf(stderr, _("Unsupported kind of rule (ignored): %s\n"), rule);
			return;
		}
		rule++;
		suffix->wildcard = 1;
		suffix->length = (unsigned char)length - 2;
	} else {
		suffix->wildcard = 0;
		suffix->length = (unsigned char)length;
	}

	suffix->nlabels = 1;

	for (dst = suffix->label_buf, src = rule; *src;) {
		if (*src == '.')
			suffix->nlabels++;
		*dst++ = tolower(*src++);
	}
	*dst = 0;
}

int psl_is_public(const psl_ctx_t *psl, const char *domain)
{
	_psl_entry_t suffix, *rule;
	const char *p, *label_bak;
	unsigned short length_bak;

	// this function should be called without leading dots, just make sure
	suffix.label = domain + (*domain == '.');
	suffix.length = strlen(suffix.label);
	suffix.wildcard = 0;
	suffix.nlabels = 1;

	for (p = suffix.label; *p; p++)
		if (*p == '.')
			suffix.nlabels++;

	// if domain has enough labels, it is public
	rule = _vector_get(psl->suffixes, 0);
	if (!rule || rule->nlabels < suffix.nlabels - 1)
		return 1;

	rule = _vector_get(psl->suffixes, _vector_find(psl->suffixes, &suffix));
	if (rule) {
		// definitely a match, no matter if the found rule is a wildcard or not
		return 0;
	}

	label_bak = suffix.label;
	length_bak = suffix.length;

	if ((suffix.label = strchr(suffix.label, '.'))) {
		suffix.label++;
		suffix.length = strlen(suffix.label);
		suffix.nlabels--;

		rule = _vector_get(psl->suffixes, _vector_find(psl->suffixes, &suffix));
		if (rule) {
			if (rule->wildcard) {
				// now that we matched a wildcard, we have to check for an exception
				suffix.label = label_bak;
				suffix.length = length_bak;
				suffix.nlabels++;

				if (_vector_get(psl->suffix_exceptions, _vector_find(psl->suffix_exceptions, &suffix)) != 0)
					return 1; // found an exception, so 'domain' is public

				return 0;
			}
		}
	}

	return 1;
}

psl_ctx_t *psl_load_file(const char *fname)
{
	FILE *fp;
	psl_ctx_t *psl = NULL;

	if ((fp = fopen(fname, "r"))) {
		psl = psl_load_fp(fp);
		fclose(fp);
	}

	return psl;
}

psl_ctx_t *psl_load_fp(FILE *fp)
{
	psl_ctx_t *psl;
	_psl_entry_t suffix, *suffixp;
	int nsuffixes = 0;
	char buf[256], *linep, *p;

	if (!fp)
		return NULL;

	if (!(psl = calloc(1, sizeof(psl_ctx_t))))
		return NULL;

	// as of 02.11.2012, the list at http://publicsuffix.org/list/ contains ~6000 rules and 40 exceptions.
	// as of 19.02.2014, the list at http://publicsuffix.org/list/ contains ~6500 rules and 19 exceptions.
	psl->suffixes = _vector_alloc(8*1024, _suffix_compare);
	psl->suffix_exceptions = _vector_alloc(64, _suffix_compare);

	while ((linep = fgets(buf, sizeof(buf), fp))) {
		while (isspace(*linep)) linep++; // ignore leading whitespace
		if (!*linep) continue; // skip empty lines

		if (*linep == '/' && linep[1] == '/')
			continue; // skip comments

		// parse suffix rule
		for (p = linep; *linep && !isspace(*linep);) linep++;
		*linep = 0;

		if (*p == '!') {
			// add to exceptions
			_suffix_init(&suffix, p + 1, linep - p - 1);
			suffixp = _vector_get(psl->suffix_exceptions, _vector_add(psl->suffix_exceptions, &suffix));
		} else {
			_suffix_init(&suffix, p, linep - p);
			suffixp = _vector_get(psl->suffixes, _vector_add(psl->suffixes, &suffix));
		}

		if (suffixp)
			suffixp->label = suffixp->label_buf; // set label to changed address

		nsuffixes++;;
	}

	_vector_sort(psl->suffix_exceptions);
	_vector_sort(psl->suffixes);

	return psl;
}

/* does not include exceptions */
int psl_suffix_count(const psl_ctx_t *psl)
{
	return _vector_size(psl->suffixes);
}

/* just counts exceptions */
int psl_suffix_exception_count(const psl_ctx_t *psl)
{
	return _vector_size(psl->suffix_exceptions);
}

void psl_free(psl_ctx_t **psl)
{
	if (psl && *psl) {
		_vector_free(&(*psl)->suffixes);
		_vector_free(&(*psl)->suffix_exceptions);
		free(*psl);
		*psl = NULL;
	}
}