/*
 * Copyright (C) 2001-2019 Jacek Sieka, arnetheduck on gmail point com
 *
 * 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, see <https://www.gnu.org/licenses/>.
 */

#pragma once

#include "typedefs.h"

namespace dcpp {

template<size_t N>
class BloomFilter {
public:
    BloomFilter(size_t tableSize) { table.resize(tableSize); }
    ~BloomFilter() { }

    void add(const string& s) {xadd(s, N); }
    bool match(const StringList& s) const {
        for(auto& i: s) {
            if(!match(i))
                return false;
        }
        return true;
    }
    bool match(const string& s) const {
        if(s.length() >= N) {
            string::size_type l = s.length() - N;
            for(string::size_type i = 0; i <= l; ++i) {
                if(!table[getPos(s, i, N)]) {
                    return false;
                }
            }
        }
        return true;
    }
    void clear() {
        size_t s = table.size();
        table.clear();
        table.resize(s);
    }
#ifdef TESTER
    void print_table_status() {
        int tot = 0;
        for (unsigned int i = 0; i < table.size(); ++i) if (table[i] == true) ++tot;

        std::cout << "table status: " << tot << " of " << table.size()
                  << " filled, for an occupancy percentage of " << (100.*tot)/table.size()
                  << "%" << std::endl;
    }
#endif
private:
    void xadd(const string& s, size_t n) {
        if(s.length() >= n) {
            string::size_type l = s.length() - n;
            for(string::size_type i = 0; i <= l; ++i) {
                table[getPos(s, i, n)] = true;
            }
        }
    }

    /* This is roughly how boost::hash does it */
    size_t getPos(const string& s, size_t i, size_t l) const {
        size_t h = 0;
        const char* c = s.data() + i;
        const char* end = s.data() + i + l;
        for(; c < end; ++c) {
            h ^= *c + 0x9e3779b9 + (h<<6) + (h>>2);
        }
        return (h % table.size());
    }

    vector<bool> table;
};

} // namespace dcpp
