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// 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/timezone_utils.h"

#include <cctz/civil_time.h>

#include <cctz/time_zone.h>

#include <fcntl.h>

#include <glog/logging.h>

#include <re2/re2.h>

#include <re2/stringpiece.h>

#include <sys/mman.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <unistd.h>

#include <boost/algorithm/string.hpp>

#include <boost/algorithm/string/case_conv.hpp>

#include <cstdlib>

#include <filesystem>

#include <memory>

#include <string>

#include "common/exception.h"

#include "common/logging.h"

#include "common/status.h"

using boost::algorithm::to_lower_copy;

namespace fs = std::filesystem;

#include "common/compile_check_begin.h"

namespace doris {

using ZoneList = std::unordered_map<std::string, cctz::time_zone>;

RE2 time_zone_offset_format_reg(R"(^[+-]{1}\d{2}\:\d{2}$)"); // visiting is thread-safe

// for ut, make it never nullptr.

std::unique_ptr<ZoneList> lower_zone_cache_ = std::make_unique<ZoneList>();

const std::string TimezoneUtils::default_time_zone = "+08:00";

static const char* tzdir = "/usr/share/zoneinfo"; // default value, may change by TZDIR env var

void TimezoneUtils::clear_timezone_caches() {

    lower_zone_cache_->clear();

}

size_t TimezoneUtils::cache_size() {

    return lower_zone_cache_->size();

}

static bool parse_save_name_tz(const std::string& tz_name) {

    cctz::time_zone tz;

    PROPAGATE_FALSE(cctz::load_time_zone(tz_name, &tz));

    lower_zone_cache_->emplace(to_lower_copy(tz_name), tz);

    return true;

}

void TimezoneUtils::load_timezones_to_cache() {

    std::string base_str;

    // try get from system

    char* tzdir_env = std::getenv("TZDIR");

    if (tzdir_env && *tzdir_env) {

        tzdir = tzdir_env;

    }

    base_str = tzdir;

    base_str += '/';

    const auto root_path = fs::path {base_str};

    if (!exists(root_path)) {

        throw Exception(Status::FatalError("Cannot find system tzfile. Doris exiting!"));

    }

    std::set<std::string> ignore_paths = {"posix", "right"}; // duplications. ignore them.

    for (fs::recursive_directory_iterator it {base_str}; it != end(it); it++) {

        const auto& dir_entry = *it;

        try {

            if (dir_entry.is_regular_file() ||

                (dir_entry.is_symlink() && is_regular_file(read_symlink(dir_entry)))) {

                auto tz_name = dir_entry.path().string().substr(base_str.length());

                if (!parse_save_name_tz(tz_name)) {

                    LOG(WARNING) << "Meet illegal tzdata file: " << tz_name << ". skipped";

                }

            } else if (dir_entry.is_directory() &&

                       ignore_paths.contains(dir_entry.path().filename())) {

                it.disable_recursion_pending();

            }

        } catch (const fs::filesystem_error& e) {

            // maybe symlink loop or to nowhere...

            LOG(WARNING) << "filesystem error when loading timezone file from " << dir_entry.path()

                         << ": " << e.what();

        }

    }

    // some special cases. Z = Zulu. CST = Asia/Shanghai

    if (auto it = lower_zone_cache_->find("zulu"); it != lower_zone_cache_->end()) {

        lower_zone_cache_->emplace("z", it->second);

    }

    if (auto it = lower_zone_cache_->find("asia/shanghai"); it != lower_zone_cache_->end()) {

        lower_zone_cache_->emplace("cst", it->second);

    }

    lower_zone_cache_->erase("lmt"); // local mean time for every timezone

    load_offsets_to_cache();

    LOG(INFO) << "Preloaded" << lower_zone_cache_->size() << " timezones.";

}

static std::string to_hour_string(int arg) {

    if (arg < 0 && arg > -10) { // -9 to -1

        return std::string {"-0"} + std::to_string(std::abs(arg));

    } else if (arg >= 0 && arg < 10) { //0 to 9

        return std::string {"0"} + std::to_string(arg);

    }

    return std::to_string(arg);

}

void TimezoneUtils::load_offsets_to_cache() {

    for (int hour = -12; hour <= +14; hour++) {

        for (int minute = 0; minute <= 30; minute += 30) {

            std::string offset_str = (hour >= 0 ? "+" : "") + to_hour_string(hour) + ':' +

                                     (minute == 0 ? "00" : "30");

            cctz::time_zone result;

            parse_tz_offset_string(offset_str, result);

            lower_zone_cache_->emplace(offset_str, result);

        }

    }

    // -00 for hour is also valid

    std::string offset_str = "-00:00";

    cctz::time_zone result;

    parse_tz_offset_string(offset_str, result);

    lower_zone_cache_->emplace(offset_str, result);

    offset_str = "-00:30";

    parse_tz_offset_string(offset_str, result);

    lower_zone_cache_->emplace(offset_str, result);

}

bool TimezoneUtils::find_cctz_time_zone(const std::string& timezone, cctz::time_zone& ctz) {

    if (auto it = lower_zone_cache_->find(to_lower_copy(timezone)); it != lower_zone_cache_->end())

            [[likely]] {

        ctz = it->second;

        return true;

    }

    return false;

}

bool TimezoneUtils::parse_tz_offset_string(const std::string& timezone, cctz::time_zone& ctz) {

    // like +08:00, which not in timezone_names_map_

    re2::StringPiece value;

    if (time_zone_offset_format_reg.Match(timezone, 0, timezone.size(), RE2::UNANCHORED, &value, 1))

            [[likely]] {

        bool positive = value[0] != '-';

        //Regular expression guarantees hour and minute must be int

        int hour = std::stoi(value.substr(1, 2).as_string());

        int minute = std::stoi(value.substr(4, 2).as_string());

        // timezone offsets around the world extended from -12:00 to +14:00

        if (!positive && hour > 12) {

            return false;

        } else if (positive && hour > 14) {

            return false;

        }

        int offset = hour * 60 * 60 + minute * 60;

        offset *= positive ? 1 : -1;

        ctz = cctz::fixed_time_zone(cctz::seconds(offset));

        return true;

    }

    return false;

}

#include "common/compile_check_end.h"

} // namespace doris