// 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/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 <algorithm>

#include <boost/algorithm/string.hpp>

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

#include <cctype>

#include <chrono>

#include <cstdlib>

#include <filesystem>

#include <memory>

#include <string>

#include <string_view>

#include "common/exception.h"

#include "common/logging.h"

#include "common/status.h"

using boost::algorithm::to_lower_copy;

namespace fs = std::filesystem;

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() {

    static constexpr int supported_minutes[] = {0, 30, 45};

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

        for (int minute : supported_minutes) {

            char min_str[3];

            snprintf(min_str, sizeof(min_str), "%02d", minute);

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

            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);

    offset_str = "-00:45";

    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;

    }

    std::string normalized;

    if (!normalize_timezone_name(timezone, &normalized)) {

        return false;

    }

    if (auto it = lower_zone_cache_->find(to_lower_copy(normalized));

        it != lower_zone_cache_->end()) [[likely]] {

        ctz = it->second;

        return true;

    }

    return parse_tz_offset_string(normalized, ctz);

}

bool TimezoneUtils::try_get_fixed_offset_seconds(const cctz::time_zone& timezone,

                                                 int32_t* offset_seconds) {

    const std::string& timezone_name = timezone.name();

    if (timezone_name == "UTC" || timezone_name == "Etc/UTC" || timezone_name == "Etc/GMT") {

        *offset_seconds = 0;

        return true;

    }

    // cctz names fixed_time_zone() instances with the "Fixed/" prefix. TZDB's Etc/GMT*

    // zones are fixed offsets too; cctz handles their POSIX-style reversed sign in lookup_offset().

    // If this naming convention changes, falling through to the generic path remains correct.

    static const auto epoch = std::chrono::time_point_cast<cctz::sys_seconds>(

            std::chrono::system_clock::from_time_t(0));

    if (timezone_name.compare(0, 6, "Fixed/") == 0 || timezone_name.compare(0, 7, "Etc/GMT") == 0) {

        *offset_seconds = timezone.lookup_offset(epoch).offset;

        return true;

    }

    return false;

}

static bool normalize_offset_string(const std::string& timezone, bool allow_hour_only,

                                    std::string* normalized) {

    if (timezone.size() < 2 || (timezone[0] != '+' && timezone[0] != '-')) {

        return false;

    }

    const bool positive = timezone[0] == '+';

    const std::string_view rest(timezone.data() + 1, timezone.size() - 1);

    int hour = 0;

    int minute = 0;

    const auto parse_digit = [](char c) -> int { return c - '0'; };

    const auto is_two_digits = [](std::string_view value) -> bool {

        return value.size() == 2 && std::isdigit(static_cast<unsigned char>(value[0])) &&

               std::isdigit(static_cast<unsigned char>(value[1]));

    };

    const auto is_one_or_two_digits = [](std::string_view value) -> bool {

        return (value.size() == 1 || value.size() == 2) &&

               std::all_of(value.begin(), value.end(),

                           [](char c) { return std::isdigit(static_cast<unsigned char>(c)); });

    };

    auto colon_pos = rest.find(':');

    if (colon_pos != std::string_view::npos) {

        std::string_view hour_part = rest.substr(0, colon_pos);

        std::string_view minute_part = rest.substr(colon_pos + 1);

        if (!is_one_or_two_digits(hour_part) || !is_two_digits(minute_part)) {

            return false;

        }

        hour = std::stoi(std::string(hour_part));

        minute = parse_digit(minute_part[0]) * 10 + parse_digit(minute_part[1]);

    } else {

        if (!allow_hour_only || !is_one_or_two_digits(rest)) {

            return false;

        }

        hour = std::stoi(std::string(rest));

        minute = 0;

    }

    if ((!positive && hour > 12) || (positive && hour > 14) || minute >= 60) {

        return false;

    }

    *normalized = std::string(1, positive ? '+' : '-') + (hour < 10 ? "0" : "") +

                  std::to_string(hour) + ":" + (minute < 10 ? "0" : "") + std::to_string(minute);

    return true;

}

bool TimezoneUtils::normalize_timezone_name(const std::string& timezone, std::string* normalized) {

    const std::string lower = to_lower_copy(timezone);

    if (lower == "utc" || lower == "etc/utc" || lower == "zulu") {

        *normalized = "UTC";

        return true;

    }

    if (lower.rfind("utc", 0) == 0 || lower.rfind("gmt", 0) == 0) {

        if (timezone.size() <= 3) {

            return false;

        }

        return normalize_offset_string(timezone.substr(3), true, normalized);

    }

    if (!timezone.empty() && (timezone[0] == '+' || timezone[0] == '-')) {

        return normalize_offset_string(timezone, false, normalized);

    }

    return false;

}

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

    std::string normalized;

    if (!normalize_timezone_name(timezone, &normalized)) {

        return false;

    }

    if (normalized == "UTC") {

        ctz = cctz::utc_time_zone();

        return true;

    }

    re2::StringPiece value;

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

                                          1)) [[likely]] {

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

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

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

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

        offset *= positive ? 1 : -1;

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

        return true;

    }

    return false;

}

} // namespace doris