/*
* Copyright (c) 2013-2022, The PurpleI2P Project
*
* This file is part of Purple i2pd project and licensed under BSD3
*
* See full license text in LICENSE file at top of project tree
*/

#include <time.h>
#include <stdio.h>
#include <inttypes.h>
#include <string.h>
#include <chrono>
#include <future>
#include <boost/asio.hpp>
#include <boost/algorithm/string.hpp>
#include "Config.h"
#include "Log.h"
#include "RouterContext.h"
#include "I2PEndian.h"
#include "Timestamp.h"
#include "util.h"

#ifdef _WIN32
#ifndef _WIN64
#define _USE_32BIT_TIME_T
#endif
#endif

namespace i2p {
    namespace util {
        static uint64_t GetLocalMillisecondsSinceEpoch() {
            return std::chrono::duration_cast<std::chrono::milliseconds>(
                    std::chrono::system_clock::now().time_since_epoch()).count();
        }

        static uint64_t GetLocalSecondsSinceEpoch() {
            return std::chrono::duration_cast<std::chrono::seconds>(
                    std::chrono::system_clock::now().time_since_epoch()).count();
        }

        static uint32_t GetLocalMinutesSinceEpoch() {
            return std::chrono::duration_cast<std::chrono::minutes>(
                    std::chrono::system_clock::now().time_since_epoch()).count();
        }

        static uint32_t GetLocalHoursSinceEpoch() {
            return std::chrono::duration_cast<std::chrono::hours>(
                    std::chrono::system_clock::now().time_since_epoch()).count();
        }

        static int64_t g_TimeOffset = 0; // in seconds

        static void SyncTimeWithNTP(const std::string &address) {
            LogPrint(eLogInfo, "Timestamp: NTP request to ", address);
            boost::asio::io_service service;
            boost::system::error_code ec;
            auto it = boost::asio::ip::udp::resolver(service).resolve(
                    boost::asio::ip::udp::resolver::query(address, "ntp"), ec);
            if (!ec) {
                bool found = false;
                boost::asio::ip::udp::resolver::iterator end;
                boost::asio::ip::udp::endpoint ep;
                while (it != end) {
                    ep = *it;
                    if (!ep.address().is_unspecified()) {
                        if (ep.address().is_v4()) {
                            if (i2p::context.SupportsV4()) found = true;
                        } else if (ep.address().is_v6()) {
                            if (i2p::util::net::IsYggdrasilAddress(ep.address())) {
                                if (i2p::context.SupportsMesh()) found = true;
                            } else if (i2p::context.SupportsV6()) found = true;
                        }
                    }
                    if (found) break;
                    it++;
                }
                if (!found) {
                    LogPrint(eLogError, "Timestamp: can't find compatible address for ", address);
                    return;
                }

                boost::asio::ip::udp::socket socket(service);
                socket.open(ep.protocol(), ec);
                if (!ec) {
                    uint8_t buf[48];// 48 bytes NTP request/response
                    memset(buf, 0, 48);
                    htobe32buf(buf, (3 << 27) | (3 << 24)); // RFC 4330
                    size_t len = 0;
                    try {
                        socket.send_to(boost::asio::buffer(buf, 48), ep);
                        int i = 0;
                        while (!socket.available() && i < 10) // 10 seconds max
                        {
                            std::this_thread::sleep_for(std::chrono::seconds(1));
                            i++;
                        }
                        if (socket.available())
                            len = socket.receive_from(boost::asio::buffer(buf, 48), ep);
                    }
                    catch (std::exception &e) {
                        LogPrint(eLogError, "Timestamp: NTP error: ", e.what());
                    }
                    if (len >= 8) {
                        auto ourTs = GetLocalSecondsSinceEpoch();
                        uint32_t ts = bufbe32toh(buf + 32);
                        if (ts > 2208988800U) ts -= 2208988800U; // 1/1/1970 from 1/1/1900
                        g_TimeOffset = ts - ourTs;
                        LogPrint(eLogInfo, "Timestamp: ", address, " time offset from system time is ", g_TimeOffset,
                                 " seconds");
                    }
                } else
                    LogPrint(eLogError, "Timestamp: Couldn't open UDP socket");
            } else
                LogPrint(eLogError, "Timestamp: Couldn't resolve address ", address);
        }

        NTPTimeSync::NTPTimeSync() : m_IsRunning(false), m_Timer(m_Service) {
            i2p::config::GetOption("nettime.ntpsyncinterval", m_SyncInterval);
            std::string ntpservers;
            i2p::config::GetOption("nettime.ntpservers", ntpservers);
            boost::split(m_NTPServersList, ntpservers, boost::is_any_of(","), boost::token_compress_on);
        }

        NTPTimeSync::~NTPTimeSync() {
            Stop();
        }

        void NTPTimeSync::Start() {
            if (m_NTPServersList.size() > 0) {
                m_IsRunning = true;
                LogPrint(eLogInfo, "Timestamp: NTP time sync starting");
                m_Service.post(std::bind(&NTPTimeSync::Sync, this));
                m_Thread.reset(new std::thread(std::bind(&NTPTimeSync::Run, this)));
            } else
                LogPrint(eLogWarning, "Timestamp: No NTP server found");
        }

        void NTPTimeSync::Stop() {
            if (m_IsRunning) {
                LogPrint(eLogInfo, "Timestamp: NTP time sync stopping");
                m_IsRunning = false;
                m_Timer.cancel();
                m_Service.stop();
                if (m_Thread) {
                    m_Thread->join();
                    m_Thread.reset(nullptr);
                }
            }
        }

        void NTPTimeSync::Run() {
            i2p::util::SetThreadName("Timesync");

            while (m_IsRunning) {
                try {
                    m_Service.run();
                }
                catch (std::exception &ex) {
                    LogPrint(eLogError, "Timestamp: NTP time sync exception: ", ex.what());
                }
            }
        }

        void NTPTimeSync::Sync() {
            if (m_NTPServersList.size() > 0)
                SyncTimeWithNTP(m_NTPServersList[rand() % m_NTPServersList.size()]);
            else
                m_IsRunning = false;

            if (m_IsRunning) {
                m_Timer.expires_from_now(boost::posix_time::hours(m_SyncInterval));
                m_Timer.async_wait([this](const boost::system::error_code &ecode) {
                    if (ecode != boost::asio::error::operation_aborted)
                        Sync();
                });
            }
        }

        uint64_t GetMillisecondsSinceEpoch() {
            return GetLocalMillisecondsSinceEpoch() + g_TimeOffset * 1000;
        }

        uint64_t GetSecondsSinceEpoch() {
            return GetLocalSecondsSinceEpoch() + g_TimeOffset;
        }

        uint32_t GetMinutesSinceEpoch() {
            return GetLocalMinutesSinceEpoch() + g_TimeOffset / 60;
        }

        uint32_t GetHoursSinceEpoch() {
            return GetLocalHoursSinceEpoch() + g_TimeOffset / 3600;
        }

        void GetCurrentDate(char *date) {
            GetDateString(GetSecondsSinceEpoch(), date);
        }

        void GetDateString(uint64_t timestamp, char *date) {
            using clock = std::chrono::system_clock;
            auto t = clock::to_time_t(clock::time_point(std::chrono::seconds(timestamp)));
            struct tm tm;
#ifdef _WIN32
            gmtime_s(&tm, &t);
            sprintf_s(date, 9, "%04i%02i%02i", tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
#else
            gmtime_r(&t, &tm);
            sprintf(date, "%04i%02i%02i", tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
#endif
        }

        void AdjustTimeOffset(int64_t offset) {
            g_TimeOffset += offset;
        }
    }
}