/**
 * @file _httppolicy.cpp
 * @brief Internal definitions of the Http policy thread
 *
 * $LicenseInfo:firstyear=2012&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2012-2014, Linden Research, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#include "linden_common.h"

#include "_httppolicy.h"

#include "_httpoprequest.h"
#include "_httpservice.h"
#include "_httplibcurl.h"
#include "_httppolicyclass.h"

#include "lltimer.h"
#include "httpstats.h"

namespace
{

static const char * const LOG_CORE("CoreHttp");

} // end anonymous namespace


namespace LLCore
{


// Per-policy-class data for a running system.
// Collection of queues, options and other data
// for a single policy class.
//
// Threading:  accessed only by worker thread
struct HttpPolicy::ClassState
{
public:
    ClassState()
        : mThrottleEnd(0),
          mThrottleLeft(0L),
          mRequestCount(0L),
          mStallStaging(false)
        {}

    HttpReadyQueue      mReadyQueue;
    HttpRetryQueue      mRetryQueue;

    HttpPolicyClass     mOptions;
    HttpTime            mThrottleEnd;
    long                mThrottleLeft;
    long                mRequestCount;
    bool                mStallStaging;
};


HttpPolicy::HttpPolicy(HttpService * service)
    : mService(service)
{
    // Create default class
    mClasses.push_back(new ClassState());
}


HttpPolicy::~HttpPolicy()
{
    shutdown();

    for (class_list_t::iterator it(mClasses.begin()); it != mClasses.end(); ++it)
    {
        delete (*it);
    }
    mClasses.clear();

    mService = NULL;
}


HttpRequest::policy_t HttpPolicy::createPolicyClass()
{
    const HttpRequest::policy_t policy_class(static_cast<HttpRequest::policy_t>(mClasses.size()));
    if (policy_class >= HTTP_POLICY_CLASS_LIMIT)
    {
        return HttpRequest::INVALID_POLICY_ID;
    }
    mClasses.push_back(new ClassState());
    return policy_class;
}


void HttpPolicy::shutdown()
{
    for (int policy_class(0); policy_class < mClasses.size(); ++policy_class)
    {
        ClassState & state(*mClasses[policy_class]);

        HttpRetryQueue & retryq(state.mRetryQueue);
        while (! retryq.empty())
        {
            HttpOpRequest::ptr_t op(retryq.top());
            retryq.pop();

            op->cancel();
        }

        HttpReadyQueue & readyq(state.mReadyQueue);
        while (! readyq.empty())
        {
            HttpOpRequest::ptr_t op(readyq.top());
            readyq.pop();

            op->cancel();
        }
    }
}


void HttpPolicy::start()
{
}


void HttpPolicy::addOp(const HttpOpRequest::ptr_t &op)
{
    const int policy_class(op->mReqPolicy);

    op->mPolicyRetries = 0;
    op->mPolicy503Retries = 0;
    mClasses[policy_class]->mReadyQueue.push(op);
}


void HttpPolicy::retryOp(const HttpOpRequest::ptr_t &op)
{
    static const HttpStatus error_503(503);

    const HttpTime now(totalTime());
    const int policy_class(op->mReqPolicy);

    HttpTime delta_min = op->mPolicyMinRetryBackoff;
    HttpTime delta_max = op->mPolicyMaxRetryBackoff;
    // mPolicyRetries limited to 100
    U32 delta_factor = op->mPolicyRetries <= 10 ? 1 << op->mPolicyRetries : 1024;
    HttpTime delta = llmin(delta_min * delta_factor, delta_max);
    bool external_delta(false);

    if (op->mReplyRetryAfter > 0 && op->mReplyRetryAfter < 30)
    {
        delta = op->mReplyRetryAfter * U64L(1000000);
        external_delta = true;
    }
    op->mPolicyRetryAt = now + delta;
    ++op->mPolicyRetries;
    if (error_503 == op->mStatus)
    {
        ++op->mPolicy503Retries;
    }
    LL_DEBUGS(LOG_CORE) << "HTTP request " << op->getHandle()
                        << " retry " << op->mPolicyRetries
                        << " scheduled in " << (delta / HttpTime(1000))
                        << " mS (" << (external_delta ? "external" : "internal")
                        << ").  Status:  " << op->mStatus.toTerseString()
                        << LL_ENDL;
    if (op->mTracing > HTTP_TRACE_OFF)
    {
        LL_INFOS(LOG_CORE) << "TRACE, ToRetryQueue, Handle:  "
                            << op->getHandle()
                            << ", Delta:  " << (delta / HttpTime(1000))
                            << ", Retries:  " << op->mPolicyRetries
                            << LL_ENDL;
    }
    mClasses[policy_class]->mRetryQueue.push(op);
}


// Attempt to deliver requests to the transport layer.
//
// Tries to find HTTP requests for each policy class with
// available capacity.  Starts with the retry queue first
// looking for requests that have waited long enough then
// moves on to the ready queue.
//
// If all queues are empty, will return an indication that
// the worker thread may sleep hard otherwise will ask for
// normal polling frequency.
//
// Implements a client-side request rate throttle as well.
// This is intended to mimic and predict throttling behavior
// of grid services but that is difficult to do with different
// time bases.  This also represents a rigid coupling between
// viewer and server that makes it hard to change parameters
// and I hope we can make this go away with pipelining.
//
HttpService::ELoopSpeed HttpPolicy::processReadyQueue()
{
    const HttpTime now(totalTime());
    HttpService::ELoopSpeed result(HttpService::REQUEST_SLEEP);
    HttpLibcurl & transport(mService->getTransport());

    for (int policy_class(0); policy_class < mClasses.size(); ++policy_class)
    {
        ClassState & state(*mClasses[policy_class]);
        HttpRetryQueue & retryq(state.mRetryQueue);
        HttpReadyQueue & readyq(state.mReadyQueue);

        if (state.mStallStaging)
        {
            // Stalling but don't sleep.  Need to complete operations
            // and get back to servicing queues.  Do this test before
            // the retryq/readyq test or you'll get stalls until you
            // click a setting or an asset request comes in.
            result = HttpService::NORMAL;
            continue;
        }
        if (retryq.empty() && readyq.empty())
        {
            continue;
        }

        const bool throttle_enabled(state.mOptions.mThrottleRate > 0L);
        const bool throttle_current(throttle_enabled && now < state.mThrottleEnd);

        if (throttle_current && state.mThrottleLeft <= 0)
        {
            // Throttled condition, don't serve this class but don't sleep hard.
            result = HttpService::NORMAL;
            continue;
        }

        int active(transport.getActiveCountInClass(policy_class));
        int active_limit(state.mOptions.mPipelining > 1L
                         ? (state.mOptions.mPerHostConnectionLimit
                            * state.mOptions.mPipelining)
                         : state.mOptions.mConnectionLimit);
        int needed(active_limit - active);      // Expect negatives here

        if (needed > 0)
        {
            // First see if we have any retries...
            while (needed > 0 && ! retryq.empty())
            {
                HttpOpRequest::ptr_t op(retryq.top());
                if (op->mPolicyRetryAt > now)
                    break;

                retryq.pop();

                op->stageFromReady(mService);
                op.reset();

                ++state.mRequestCount;
                --needed;
                if (throttle_enabled)
                {
                    if (now >= state.mThrottleEnd)
                    {
                        // Throttle expired, move to next window
                        LL_DEBUGS(LOG_CORE) << "Throttle expired with " << state.mThrottleLeft
                                            << " requests to go and " << state.mRequestCount
                                            << " requests issued." << LL_ENDL;
                        state.mThrottleLeft = state.mOptions.mThrottleRate;
                        state.mThrottleEnd = now + HttpTime(1000000);
                    }
                    if (--state.mThrottleLeft <= 0)
                    {
                        goto throttle_on;
                    }
                }
            }

            // Now go on to the new requests...
            while (needed > 0 && ! readyq.empty())
            {
                HttpOpRequest::ptr_t op(readyq.top());
                readyq.pop();

                op->stageFromReady(mService);
                op.reset();

                ++state.mRequestCount;
                --needed;
                if (throttle_enabled)
                {
                    if (now >= state.mThrottleEnd)
                    {
                        // Throttle expired, move to next window
                        LL_DEBUGS(LOG_CORE) << "Throttle expired with " << state.mThrottleLeft
                                            << " requests to go and " << state.mRequestCount
                                            << " requests issued." << LL_ENDL;
                        state.mThrottleLeft = state.mOptions.mThrottleRate;
                        state.mThrottleEnd = now + HttpTime(1000000);
                    }
                    if (--state.mThrottleLeft <= 0)
                    {
                        goto throttle_on;
                    }
                }
            }
        }

    throttle_on:

        if (! readyq.empty() || ! retryq.empty())
        {
            // If anything is ready, continue looping...
            result = HttpService::NORMAL;
        }
    } // end foreach policy_class

    return result;
}

bool HttpPolicy::cancel(HttpHandle handle)
{
    for (int policy_class(0); policy_class < mClasses.size(); ++policy_class)
    {
        ClassState & state(*mClasses[policy_class]);

        // Scan retry queue
        HttpRetryQueue::container_type & c1(state.mRetryQueue.get_container());
        for (HttpRetryQueue::container_type::iterator iter(c1.begin()); c1.end() != iter;)
        {
            HttpRetryQueue::container_type::iterator cur(iter++);

            if ((*cur)->getHandle() == handle)
            {
                HttpOpRequest::ptr_t op(*cur);
                c1.erase(cur);                                  // All iterators are now invalidated
                op->cancel();
                return true;
            }
        }

        // Scan ready queue
        HttpReadyQueue::container_type & c2(state.mReadyQueue.get_container());
        for (HttpReadyQueue::container_type::iterator iter(c2.begin()); c2.end() != iter;)
        {
            HttpReadyQueue::container_type::iterator cur(iter++);

            if ((*cur)->getHandle() == handle)
            {
                HttpOpRequest::ptr_t op(*cur);
                c2.erase(cur);                                  // All iterators are now invalidated
                op->cancel();
                return true;
            }
        }
    }

    return false;
}


bool HttpPolicy::stageAfterCompletion(const HttpOpRequest::ptr_t &op)
{
    // Retry or finalize
    if (! op->mStatus)
    {
        // *DEBUG:  For "[curl:bugs] #1420" tests.  This will interfere
        // with unit tests due to allocation retention by logging code.
        // But you won't be checking this in enabled.
#if 0
        if (op->mStatus == HttpStatus(HttpStatus::EXT_CURL_EASY, CURLE_OPERATION_TIMEDOUT))
        {
            LL_WARNS(LOG_CORE) << "HTTP request " << op->getHandle()
                               << " timed out."
                               << LL_ENDL;
        }
#endif

        // If this failed, we might want to retry.
        if (op->mPolicyRetries < op->mPolicyRetryLimit && op->mStatus.isRetryable())
        {
            // Okay, worth a retry.
            retryOp(op);
            return true;                // still active/ready
        }
    }

    // This op is done, finalize it delivering it to the reply queue...
    if (! op->mStatus)
    {
        LL_WARNS(LOG_CORE) << "HTTP request " << op->getHandle()
                           << " failed after " << op->mPolicyRetries
                           << " retries.  Reason:  " << op->mStatus.toString()
                           << " (" << op->mStatus.toTerseString() << ")"
                           << LL_ENDL;
    }
    else if (op->mPolicyRetries)
    {
        LL_DEBUGS(LOG_CORE) << "HTTP request " << op->getHandle()
                            << " succeeded on retry " << op->mPolicyRetries << "."
                            << LL_ENDL;
    }

    op->stageFromActive(mService);

    HTTPStats::instance().recordResultCode(op->mStatus.getType());
    return false;                       // not active
}


HttpPolicyClass & HttpPolicy::getClassOptions(HttpRequest::policy_t pclass)
{
    llassert_always(pclass >= 0 && pclass < mClasses.size());

    return mClasses[pclass]->mOptions;
}


int HttpPolicy::getReadyCount(HttpRequest::policy_t policy_class) const
{
    if (policy_class < mClasses.size())
    {
        return static_cast<int>((mClasses[policy_class]->mReadyQueue.size()
            + mClasses[policy_class]->mRetryQueue.size()));
    }
    return 0;
}


bool HttpPolicy::stallPolicy(HttpRequest::policy_t policy_class, bool stall)
{
    bool ret(false);

    if (policy_class < mClasses.size())
    {
        ret = mClasses[policy_class]->mStallStaging;
        mClasses[policy_class]->mStallStaging = stall;
    }
    return ret;
}


}  // end namespace LLCore