// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements.  See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership.  The ASF licenses this file

// to you under the Apache License, Version 2.0 (the

// "License"); you may not use this file except in compliance

// with the License.  You may obtain a copy of the License at

//

//   http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing,

// software distributed under the License is distributed on an

// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

// KIND, either express or implied.  See the License for the

// specific language governing permissions and limitations

// under the License.

#include "util/hyperscan_util.h"

#include <re2/re2.h>

#include <re2/stringpiece.h>

#include <charconv>

namespace doris {

namespace {

bool is_larger_than_fifty(std::string_view str) {

    int number = 0;

    auto [_, error] = std::from_chars(str.data(), str.data() + str.size(), number);

    return error == std::errc() && number > 50;

}

class SlowWithHyperscanChecker {

public:

    SlowWithHyperscanChecker()

            : _searcher_one_repeat(R"(\{\s*([\d]+)\s*,?\s*})"),

              _searcher_two_repeats(R"(\{\s*([\d]+)\s*,\s*([\d]+)\s*\})") {}

    bool is_slow(std::string_view regexp) const {

        return is_slow_one_repeat(regexp) || is_slow_two_repeats(regexp);

    }

private:

    bool is_slow_one_repeat(std::string_view regexp) const {

        re2::StringPiece haystack(regexp.data(), regexp.size());

        re2::StringPiece matches[2];

        size_t start_pos = 0;

        while (start_pos < haystack.size()) {

            if (!_searcher_one_repeat.Match(haystack, start_pos, haystack.size(),

                                            re2::RE2::Anchor::UNANCHORED, matches, 2)) {

                break;

            }

            start_pos = matches[0].data() - haystack.data() + matches[0].size();

            if (is_larger_than_fifty({matches[1].data(), matches[1].size()})) {

                return true;

            }

        }

        return false;

    }

    bool is_slow_two_repeats(std::string_view regexp) const {

        re2::StringPiece haystack(regexp.data(), regexp.size());

        re2::StringPiece matches[3];

        size_t start_pos = 0;

        while (start_pos < haystack.size()) {

            if (!_searcher_two_repeats.Match(haystack, start_pos, haystack.size(),

                                             re2::RE2::Anchor::UNANCHORED, matches, 3)) {

                break;

            }

            start_pos = matches[0].data() - haystack.data() + matches[0].size();

            if (is_larger_than_fifty({matches[1].data(), matches[1].size()}) ||

                is_larger_than_fifty({matches[2].data(), matches[2].size()})) {

                return true;

            }

        }

        return false;

    }

    re2::RE2 _searcher_one_repeat;

    re2::RE2 _searcher_two_repeats;

};

} // namespace

bool is_hyperscan_regexp_expensive(std::string_view regexp) {

    static const SlowWithHyperscanChecker slow_with_hyperscan_checker;

    return slow_with_hyperscan_checker.is_slow(regexp);

}

} // namespace doris