/*
 * This file is part of the TrinityCore Project. See AUTHORS file for Copyright information
 *
 * 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 <http://www.gnu.org/licenses/>.
 */

#include "Timezone.h"
#include "Hash.h"
#include "MapUtils.h"
#include "Util.h"
#include <boost/locale/date_time_facet.hpp>
#include <boost/locale/generator.hpp>
#include <chrono>
#include <unordered_map>

namespace
{
std::unordered_map<uint32, Minutes, std::identity> InitTimezoneHashDb()
{
#if TRINITY_PLATFORM == TRINITY_PLATFORM_WINDOWS

    // Generate our hash db to match values sent in client authentication packets
    std::unordered_map<uint32, Minutes, std::identity> hashToOffset;
    std::chrono::system_clock::time_point dummmy;
    for (std::chrono::time_zone const& zone : std::chrono::get_tzdb().zones)
    {
        std::chrono::sys_info sysInfo = zone.get_info(dummmy);
        Minutes offsetMinutes = std::chrono::duration_cast<Minutes>(sysInfo.offset);
        std::string offsetStr = Trinity::ToString(offsetMinutes.count());
        hashToOffset.emplace(Trinity::HashFnv1a(offsetStr), offsetMinutes);
    }

#else
    // Pre-generated list of timezone offsets and their hashes for compilers (and their stl implementations) that dont support timezone api yet
    std::unordered_map<uint32, Minutes, std::identity> hashToOffset =
    {
        { 0xAADC2D37u, -720min },
        { 0x362F107Bu, -690min },
        { 0x2C44C70Cu, -660min },
        { 0xB84A209Eu, -640min },
        { 0xBA3D57D1u, -630min },
        { 0x4040695Au, -600min },
        { 0xB65A75D0u, -570min },
        { 0xC8614DEBu, -540min },
        { 0x3A68BD26u, -510min },
        { 0x51E8096Cu, -480min },
        { 0x4DD8F896u, -420min },
        { 0x674B7C0Fu, -360min },
        { 0x633C6B39u, -300min },
        { 0x0BAD340Au, -240min },
        { 0x74B25683u, -225min },
        { 0x09B9FCD7u, -210min },
        { 0x150C169Bu, -180min },
        { 0x191B2771u, -120min },
        { 0xD7D3B14Eu, -60min },
        { 0x47CE5170u, -44min },
        { 0x350CA8AFu, 0min },
        { 0x15E8E23Bu, 60min },
        { 0x733864AEu, 120min },
        { 0xF71F9C94u, 180min },
        { 0xBDE50F54u, 210min },
        { 0x2BDD6DB9u, 240min },
        { 0xB1E07F42u, 270min },
        { 0x454FF132u, 300min },
        { 0x3F4DA929u, 330min },
        { 0xD1554AC4u, 360min },
        { 0xBB667143u, 390min },
        { 0x9E2B78C9u, 420min },
        { 0x1C377816u, 450min },
        { 0x1A4440E3u, 480min },
        { 0xB49DF789u, 525min },
        { 0xC3A28C54u, 540min },
        { 0x35A9FB8Fu, 570min },
        { 0x889BD751u, 600min },
        { 0x8CAAE827u, 660min },
        { 0x7285EE60u, 690min },
        { 0x1CC2DEF4u, 720min },
        { 0x89B8FD2Fu, 765min },
        { 0x98DBA70Eu, 780min },
        { 0xC59585BBu, 840min }
    };
#endif

    return hashToOffset;
}

std::unordered_map<uint32, Minutes, std::identity> const _timezoneOffsetsByHash = InitTimezoneHashDb();

using ClientSupportedTimezone = std::pair<Minutes, std::string>;
std::array<ClientSupportedTimezone, 11> const _clientSupportedTimezones =
{{
    { -480min, "America/Los_Angeles" },
    { -420min, "America/Denver" },
    { -360min, "America/Chicago" },
    { -300min, "America/New_York" },
    { -180min, "America/Sao_Paulo" },
    {    0min, "Etc/UTC" },
    {   60min, "Europe/Paris" },
    {  480min, "Asia/Shanghai" },
    {  480min, "Asia/Taipei" },
    {  540min, "Asia/Seoul" },
    {  600min, "Australia/Melbourne" },
}};
}

namespace Trinity::Timezone
{
Minutes GetOffsetByHash(uint32 hash)
{
    if (Minutes const* offset = Containers::MapGetValuePtr(_timezoneOffsetsByHash, hash))
        return *offset;

    return 0min;
}

Minutes GetSystemZoneOffsetAt(SystemTimePoint date)
{
    Seconds offset;
#if TRINITY_PLATFORM == TRINITY_PLATFORM_WINDOWS
    offset = std::chrono::current_zone()->get_info(date).offset;
#else
    tm buf = TimeBreakdown(std::chrono::system_clock::to_time_t(date));
    offset = Seconds(buf.tm_gmtoff);
#endif
    return std::chrono::duration_cast<Minutes>(offset);
}

Minutes GetSystemZoneOffset(bool applyDst /*= true*/)
{
    std::chrono::system_clock::time_point date = std::chrono::system_clock::from_time_t(std::time_t(0));
    if (applyDst)
        date = std::chrono::system_clock::now();

    return GetSystemZoneOffsetAt(date);
}

std::string GetSystemZoneName()
{
#if TRINITY_PLATFORM == TRINITY_PLATFORM_WINDOWS
    return std::string(std::chrono::current_zone()->name());
#else
    static std::locale calendarLocale = boost::locale::generator().generate("");
    std::unique_ptr<boost::locale::abstract_calendar> p(std::use_facet<class boost::locale::calendar_facet>(calendarLocale).create_calendar());
    return p->get_timezone();
#endif
}

std::string_view FindClosestClientSupportedTimezone(std::string_view currentTimezone, Minutes currentTimezoneOffset)
{
    // try exact match
    auto itr = std::find_if(_clientSupportedTimezones.begin(), _clientSupportedTimezones.end(), [currentTimezone](ClientSupportedTimezone const& tz)
    {
        return tz.second == currentTimezone;
    });
    if (itr != _clientSupportedTimezones.end())
        return itr->second;

    // try closest offset
    itr = std::min_element(_clientSupportedTimezones.begin(), _clientSupportedTimezones.end(), [currentTimezoneOffset](ClientSupportedTimezone const& left, ClientSupportedTimezone const& right)
    {
        Minutes leftDiff = left.first - currentTimezoneOffset;
        Minutes rightDiff = right.first - currentTimezoneOffset;
        return std::abs(leftDiff.count()) < std::abs(rightDiff.count());
    });

    return itr->second;
}
}