/*
 * Copyright (C) 2009-2012 Jacek Sieka, arnetheduck on gmail point com
 *
 * 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 <https://www.gnu.org/licenses/>.
 */

#include "stdinc.h"

#include "ThrottleManager.h"

#include "DownloadManager.h"
#include "Singleton.h"
#include "Socket.h"
#include "Thread.h"
#include "TimerManager.h"
#include "UploadManager.h"
#include "ClientManager.h"

namespace dcpp {
/**
 * Manager for throttling traffic flow.
 * Inspired by Token Bucket algorithm: https://en.wikipedia.org/wiki/Token_bucket
 */

/*
 * Throttles traffic and reads a packet from the network
 */
int ThrottleManager::read(Socket* sock, void* buffer, size_t len)
{
    int64_t readSize = -1;
    size_t downs = DownloadManager::getInstance()->getDownloadCount();
    auto downLimit = getDownLimit(); // avoid even intra-function races
    if(!BOOLSETTING(THROTTLE_ENABLE) || !getCurThrottling() || downLimit == 0 || downs == 0)
        return sock->read(buffer, len);

    {
        Lock l(downCS);

        if(downTokens > 0)
        {
            int64_t slice = (downLimit * 1024) / downs;
            readSize = min(slice, min(static_cast<int64_t>(len), downTokens));

            // read from socket
            readSize = sock->read(buffer, static_cast<size_t>(readSize));

            if(readSize > 0)
                downTokens -= readSize;
        }
    }

    if(readSize != -1)
    {
        Thread::yield(); // give a chance to other transfers to get a token
        return readSize;
    }

    waitToken();
    return -1;  // from BufferedSocket: -1 = retry, 0 = connection close
}

/*
 * Throttles traffic and writes a packet to the network
 * Handle this a little bit differently than downloads due to OpenSSL stupidity
 */
int ThrottleManager::write(Socket* sock, void* buffer, size_t& len)
{
    bool gotToken = false;
    size_t ups = UploadManager::getInstance()->getUploadCount();
    auto upLimit = getUpLimit(); // avoid even intra-function races
    if(!BOOLSETTING(THROTTLE_ENABLE) || !getCurThrottling() || upLimit == 0 || ups == 0)
        return sock->write(buffer, len);

    {
        Lock l(upCS);

        if(upTokens > 0)
        {
            size_t slice = (upLimit * 1024) / ups;
            len = min(slice, min(len, static_cast<size_t>(upTokens)));
            upTokens -= len;

            gotToken = true; // token successfuly assigned
        }
    }

    if(gotToken)
    {
        // write to socket
        int sent = sock->write(buffer, len);

        Thread::yield(); // give a chance to other transfers get a token
        return sent;
    }

    waitToken();
    return 0;   // from BufferedSocket: -1 = failed, 0 = retry
}

SettingsManager::IntSetting ThrottleManager::getCurSetting(SettingsManager::IntSetting setting) {
    SettingsManager::IntSetting upLimit   = SettingsManager::MAX_UPLOAD_SPEED_MAIN;
    SettingsManager::IntSetting downLimit = SettingsManager::MAX_DOWNLOAD_SPEED_MAIN;
    SettingsManager::IntSetting slots     = SettingsManager::SLOTS_PRIMARY;

    if(BOOLSETTING(TIME_DEPENDENT_THROTTLE)) {
        time_t currentTime;
        time(&currentTime);
        int currentHour = localtime(&currentTime)->tm_hour;
        if((SETTING(BANDWIDTH_LIMIT_START) < SETTING(BANDWIDTH_LIMIT_END) &&
            currentHour >= SETTING(BANDWIDTH_LIMIT_START) && currentHour < SETTING(BANDWIDTH_LIMIT_END)) ||
                (SETTING(BANDWIDTH_LIMIT_START) > SETTING(BANDWIDTH_LIMIT_END) &&
                 (currentHour >= SETTING(BANDWIDTH_LIMIT_START) || currentHour < SETTING(BANDWIDTH_LIMIT_END))))
        {
            upLimit   = SettingsManager::MAX_UPLOAD_SPEED_ALTERNATE;
            downLimit = SettingsManager::MAX_DOWNLOAD_SPEED_ALTERNATE;
            slots     = SettingsManager::SLOTS_ALTERNATE_LIMITING;
        }
    }

    switch (setting) {
    case SettingsManager::MAX_UPLOAD_SPEED_MAIN:
        return upLimit;
    case SettingsManager::MAX_DOWNLOAD_SPEED_MAIN:
        return downLimit;
    case SettingsManager::SLOTS:
        return slots;
    default:
        return setting;
    }
}

int ThrottleManager::getUpLimit() {
    return SettingsManager::getInstance()->get(getCurSetting(SettingsManager::MAX_UPLOAD_SPEED_MAIN));
}

int ThrottleManager::getDownLimit() {
    return SettingsManager::getInstance()->get(getCurSetting(SettingsManager::MAX_DOWNLOAD_SPEED_MAIN));
}

void ThrottleManager::setSetting(SettingsManager::IntSetting setting, int value) {
    SettingsManager::getInstance()->set(setting, value);
    ClientManager::getInstance()->infoUpdated();
}

bool ThrottleManager::getCurThrottling() {
    Lock l(stateCS);
    return activeWaiter != -1;
}

void ThrottleManager::waitToken() {
    // no tokens, wait for them, so long as throttling still active
    // avoid keeping stateCS lock on whole function
    CriticalSection *curCS = 0;
    {
        Lock l(stateCS);
        if (activeWaiter != -1)
            curCS = &waitCS[activeWaiter];
    }
    // possible post-CS aW shifts: 0->1/1->0: lock lands in wrong place, will
    // either fall through immediately or wait depending on whether in
    // stateCS-protected transition elsewhere; 0/1-> -1: falls through. Both harmless.
    if (curCS)
        Lock l(*curCS);
}

ThrottleManager::~ThrottleManager()
{
    shutdown();
    TimerManager::getInstance()->removeListener(this);
}

#ifdef _WIN32

void ThrottleManager::shutdown() {
    Lock l(stateCS);
    if (activeWaiter != -1) {
        waitCS[activeWaiter].unlock();
        activeWaiter = -1;
    }
}
#else //*nix

void ThrottleManager::shutdown()
{
    bool wait = false;
    {
        Lock l(stateCS);
        if (activeWaiter != -1)
        {
            n_lock = activeWaiter;
            activeWaiter = -1;
            halt = 1;
            wait = true;
        }
    }

    // wait shutdown...
    if (wait)
    {
        Lock l(shutdownCS);
    }
}
#endif //*nix

// TimerManagerListener
void ThrottleManager::on(TimerManagerListener::Second, uint64_t /* aTick */) noexcept
{
    int newSlots = SettingsManager::getInstance()->get(getCurSetting(SettingsManager::SLOTS));
    if(newSlots != SETTING(SLOTS)) {
        setSetting(SettingsManager::SLOTS, newSlots);
    }

    {
        Lock l(stateCS);

#ifndef _WIN32 //*nix

        if (halt == 1)
        {
            halt = -1;

            // unlock shutdown and token wait
            dcassert(n_lock == 0 || n_lock == 1);
            waitCS[n_lock].unlock();
            shutdownCS.unlock();

            return;
        }
        else if (halt == -1)
        {
            return;
        }
#endif
        if (activeWaiter == -1)
        {
            // This will create slight weirdness for the read/write calls between
            // here and the first activeWaiter-toggle below.
            waitCS[activeWaiter = 0].lock();

        #ifndef _WIN32 //*nix

                    // lock shutdown
                    shutdownCS.lock();
        #endif
        }
        }

                    int downLimit = getDownLimit();
                    int upLimit   = getUpLimit();

                    // readd tokens
            {
                Lock l(downCS);
                downTokens = downLimit * 1024;
            }

            {
                Lock l(upCS);
                upTokens = upLimit * 1024;
            }

            // let existing events drain out (fairness).
            // www.cse.wustl.edu/~schmidt/win32-cv-1.html documents various
            // fairer strategies, but when only broadcasting, irrelevant
            {
                Lock l(stateCS);

                dcassert(activeWaiter == 0 || activeWaiter == 1);
                waitCS[1-activeWaiter].lock();
                activeWaiter = 1-activeWaiter;
                waitCS[1-activeWaiter].unlock();
            }
        }

    }   // namespace dcpp
