/** 
 * @file llinventorymodelbackgroundfetch.cpp
 * @brief Implementation of background fetching of inventory.
 *
 * $LicenseInfo:firstyear=2002&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 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 "llviewerprecompiledheaders.h"
#include "llinventorymodelbackgroundfetch.h"

#include "llaisapi.h"
#include "llagent.h"
#include "llappviewer.h"
#include "llcallbacklist.h"
#include "llinventorymodel.h"
#include "llinventoryobserver.h"
#include "llinventorypanel.h"
#include "llstartup.h"
#include "llviewercontrol.h"
#include "llviewerinventory.h"
#include "llviewermessage.h"
#include "llviewerregion.h"
#include "llviewerwindow.h"
#include "llhttpconstants.h"
#include "bufferarray.h"
#include "bufferstream.h"
#include "llcorehttputil.h"

// History (may be apocryphal)
//
// Around V2, an HTTP inventory download mechanism was added
// along with inventory LINK items referencing other inventory
// items.  As part of this, at login, the entire inventory
// structure is downloaded 'in the background' using the
// backgroundFetch()/bulkFetch() methods.  The UDP path can
// still be used and is found in the 'DEPRECATED OLD CODE'
// section.
//
// The old UDP path implemented a throttle that adapted
// itself during running.  The mechanism survived info HTTP
// somewhat but was pinned to poll the HTTP plumbing at
// 0.5S intervals.  The reasons for this particular value
// have been lost.  It's possible to switch between UDP
// and HTTP while this is happening but there may be
// surprises in what happens in that case.
//
// Conversion to llcorehttp reduced the number of connections
// used but batches more data and queues more requests (but
// doesn't due pipelining due to libcurl restrictions).  The
// poll interval above was re-examined and reduced to get
// inventory into the viewer more quickly.
//
// Possible future work:
//
// * Don't download the entire heirarchy in one go (which
//   might have been how V1 worked).  Implications for
//   links (which may not have a valid target) and search
//   which would then be missing data.
//
// * Review the download rate throttling.  Slow then fast?
//   Detect bandwidth usage and speed up when it drops?
//
// * An error on a fetch could be due to one item in the batch.
//   If the batch were broken up, perhaps more of the inventory
//   would download.  (Handwave here, not certain this is an
//   issue in practice.)
//
// * Conversion to AISv3.
//


namespace
{

///----------------------------------------------------------------------------
/// Class <anonymous>::BGItemHttpHandler
///----------------------------------------------------------------------------

//
// Http request handler class for single inventory item requests.
//
// We'll use a handler-per-request pattern here rather than
// a shared handler.  Mainly convenient as this was converted
// from a Responder class model.
//
// Derives from and is identical to the normal FetchItemHttpHandler
// except that:  1) it uses the background request object which is
// updated more slowly than the foreground and 2) keeps a count of
// active requests on the LLInventoryModelBackgroundFetch object
// to indicate outstanding operations are in-flight.
//
class BGItemHttpHandler : public LLInventoryModel::FetchItemHttpHandler
{
	LOG_CLASS(BGItemHttpHandler);
	
public:
	BGItemHttpHandler(const LLSD & request_sd)
		: LLInventoryModel::FetchItemHttpHandler(request_sd)
		{
			LLInventoryModelBackgroundFetch::instance().incrFetchCount(1);
		}

	virtual ~BGItemHttpHandler()
		{
			LLInventoryModelBackgroundFetch::instance().incrFetchCount(-1);
		}

protected:
	BGItemHttpHandler(const BGItemHttpHandler &);				// Not defined
	void operator=(const BGItemHttpHandler &);					// Not defined
};


///----------------------------------------------------------------------------
/// Class <anonymous>::BGFolderHttpHandler
///----------------------------------------------------------------------------

// Http request handler class for folders.
//
// Handler for FetchInventoryDescendents2 and FetchLibDescendents2
// caps requests for folders.
//
class BGFolderHttpHandler : public LLCore::HttpHandler
{
	LOG_CLASS(BGFolderHttpHandler);
	
public:
	BGFolderHttpHandler(const LLSD & request_sd, const uuid_vec_t & recursive_cats)
		: LLCore::HttpHandler(),
		  mRequestSD(request_sd),
		  mRecursiveCatUUIDs(recursive_cats)
		{
			LLInventoryModelBackgroundFetch::instance().incrFetchCount(1);
		}

	virtual ~BGFolderHttpHandler()
		{
			LLInventoryModelBackgroundFetch::instance().incrFetchCount(-1);
		}
	
protected:
	BGFolderHttpHandler(const BGFolderHttpHandler &);			// Not defined
	void operator=(const BGFolderHttpHandler &);				// Not defined

public:
	virtual void onCompleted(LLCore::HttpHandle handle, LLCore::HttpResponse * response);

	bool getIsRecursive(const LLUUID & cat_id) const;

private:
	void processData(LLSD & body, LLCore::HttpResponse * response);
	void processFailure(LLCore::HttpStatus status, LLCore::HttpResponse * response);
	void processFailure(const char * const reason, LLCore::HttpResponse * response);

private:
	LLSD mRequestSD;
	const uuid_vec_t mRecursiveCatUUIDs; // hack for storing away which cat fetches are recursive
};


const char * const LOG_INV("Inventory");

} // end of namespace anonymous


///----------------------------------------------------------------------------
/// Class LLInventoryModelBackgroundFetch
///----------------------------------------------------------------------------

LLInventoryModelBackgroundFetch::LLInventoryModelBackgroundFetch():
	mBackgroundFetchActive(false),
	mFolderFetchActive(false),
	mFetchCount(0),
    mLastFetchCount(0),
    mFetchFolderCount(0),
    mAllRecursiveFoldersFetched(false),
	mRecursiveInventoryFetchStarted(false),
	mRecursiveLibraryFetchStarted(false),
	mMinTimeBetweenFetches(0.3f)
{}

LLInventoryModelBackgroundFetch::~LLInventoryModelBackgroundFetch()
{}

bool LLInventoryModelBackgroundFetch::isBulkFetchProcessingComplete() const
{
	return mFetchFolderQueue.empty() && mFetchItemQueue.empty() && mFetchCount <= 0;
}

bool LLInventoryModelBackgroundFetch::isFolderFetchProcessingComplete() const
{
    return mFetchFolderQueue.empty() && mFetchFolderCount <= 0;
}

bool LLInventoryModelBackgroundFetch::libraryFetchStarted() const
{
	return mRecursiveLibraryFetchStarted;
}

bool LLInventoryModelBackgroundFetch::libraryFetchCompleted() const
{
	return libraryFetchStarted() && fetchQueueContainsNoDescendentsOf(gInventory.getLibraryRootFolderID());
}

bool LLInventoryModelBackgroundFetch::libraryFetchInProgress() const
{
	return libraryFetchStarted() && !libraryFetchCompleted();
}
	
bool LLInventoryModelBackgroundFetch::inventoryFetchStarted() const
{
	return mRecursiveInventoryFetchStarted;
}

bool LLInventoryModelBackgroundFetch::inventoryFetchCompleted() const
{
	return inventoryFetchStarted() && fetchQueueContainsNoDescendentsOf(gInventory.getRootFolderID());
}

bool LLInventoryModelBackgroundFetch::inventoryFetchInProgress() const
{
	return inventoryFetchStarted() && ! inventoryFetchCompleted();
}

bool LLInventoryModelBackgroundFetch::isEverythingFetched() const
{
	return mAllRecursiveFoldersFetched;
}

BOOL LLInventoryModelBackgroundFetch::folderFetchActive() const
{
	return mFolderFetchActive;
}

void LLInventoryModelBackgroundFetch::addRequestAtFront(const LLUUID & id, bool recursive, bool is_category)
{
    EFetchType recursion_type = recursive ? FT_RECURSIVE : FT_DEFAULT;
    if (is_category)
    {
        mFetchFolderQueue.push_front(FetchQueueInfo(id, recursion_type, is_category));
    }
    else
    {
        mFetchItemQueue.push_front(FetchQueueInfo(id, recursion_type, is_category));
    }
}

void LLInventoryModelBackgroundFetch::addRequestAtBack(const LLUUID & id, bool recursive, bool is_category)
{
    EFetchType recursion_type = recursive ? FT_RECURSIVE : FT_DEFAULT;
    if (is_category)
    {
        mFetchFolderQueue.push_back(FetchQueueInfo(id, recursion_type, is_category));
    }
    else
    {
        mFetchItemQueue.push_back(FetchQueueInfo(id, recursion_type, is_category));
    }
}

void LLInventoryModelBackgroundFetch::start(const LLUUID& id, bool recursive)
{
	LLViewerInventoryCategory * cat(gInventory.getCategory(id));

	if (cat || (id.isNull() && ! isEverythingFetched()))
	{
		// it's a folder, do a bulk fetch
		LL_DEBUGS(LOG_INV) << "Start fetching category: " << id << ", recursive: " << recursive << LL_ENDL;

		mBackgroundFetchActive = true;
		mFolderFetchActive = true;
        EFetchType recursion_type = recursive ? FT_RECURSIVE : FT_DEFAULT;
		if (id.isNull())
		{
			if (! mRecursiveInventoryFetchStarted)
			{
				mRecursiveInventoryFetchStarted |= recursive;
                if (recursive && AISAPI::isAvailable())
                {
                    // Not only root folder can be massive, but
                    // most system folders will be requested independently
                    // so request root folder and content separately
                    mFetchFolderQueue.push_front(FetchQueueInfo(gInventory.getRootFolderID(), FT_CONTENT_RECURSIVE));
                }
                else
                {
                    mFetchFolderQueue.push_back(FetchQueueInfo(gInventory.getRootFolderID(), recursion_type));
                }
				gIdleCallbacks.addFunction(&LLInventoryModelBackgroundFetch::backgroundFetchCB, NULL);
			}
			if (! mRecursiveLibraryFetchStarted)
			{
				mRecursiveLibraryFetchStarted |= recursive;
                mFetchFolderQueue.push_back(FetchQueueInfo(gInventory.getLibraryRootFolderID(), recursion_type));
				gIdleCallbacks.addFunction(&LLInventoryModelBackgroundFetch::backgroundFetchCB, NULL);
			}
		}
		else
		{
            if (AISAPI::isAvailable())
            {
                if (mFetchFolderQueue.empty() || mFetchFolderQueue.back().mUUID != id)
                {
                    // On AIS make sure root goes to the top and follow up recursive
                    // fetches, not individual requests
                    mFetchFolderQueue.push_back(FetchQueueInfo(id, recursion_type));
                    gIdleCallbacks.addFunction(&LLInventoryModelBackgroundFetch::backgroundFetchCB, NULL);
                }
            }
            else if (mFetchFolderQueue.empty() || mFetchFolderQueue.front().mUUID != id)
            {
                    // Specific folder requests go to front of queue.
                    mFetchFolderQueue.push_front(FetchQueueInfo(id, recursion_type));
                    gIdleCallbacks.addFunction(&LLInventoryModelBackgroundFetch::backgroundFetchCB, NULL);
            }

			if (id == gInventory.getLibraryRootFolderID())
			{
				mRecursiveLibraryFetchStarted |= recursive;
			}
			if (id == gInventory.getRootFolderID())
			{
				mRecursiveInventoryFetchStarted |= recursive;
			}
		}
	}
	else if (LLViewerInventoryItem * itemp = gInventory.getItem(id))
	{
		if (! itemp->mIsComplete)
		{
            scheduleItemFetch(id);
		}
	}
}

void LLInventoryModelBackgroundFetch::scheduleFolderFetch(const LLUUID& cat_id, bool forced)
{
    if (AISAPI::isAvailable())
    {
        if (mFetchFolderQueue.empty() || mFetchFolderQueue.back().mUUID != cat_id)
        {
            // On AIS make sure root goes to the top and follow up recursive
            // fetches, not individual requests
            mFetchFolderQueue.push_back(FetchQueueInfo(cat_id, forced ? FT_FORCED : FT_DEFAULT));
            gIdleCallbacks.addFunction(&LLInventoryModelBackgroundFetch::backgroundFetchCB, NULL);
        }
    }
    else if (mFetchFolderQueue.empty() || mFetchFolderQueue.front().mUUID != cat_id)
    {
        // Specific folder requests go to front of queue.
        mFetchFolderQueue.push_front(FetchQueueInfo(cat_id, forced ? FT_FORCED : FT_DEFAULT));
        gIdleCallbacks.addFunction(&LLInventoryModelBackgroundFetch::backgroundFetchCB, NULL);
    }
}

void LLInventoryModelBackgroundFetch::scheduleItemFetch(const LLUUID& item_id, bool forced)
{
    if (mFetchItemQueue.empty() || mFetchItemQueue.front().mUUID != item_id)
    {
        mBackgroundFetchActive = true;

        mFetchItemQueue.push_front(FetchQueueInfo(item_id, forced ? FT_FORCED : FT_DEFAULT, false));
        gIdleCallbacks.addFunction(&LLInventoryModelBackgroundFetch::backgroundFetchCB, NULL);
    }
}

void LLInventoryModelBackgroundFetch::findLostItems()
{
    mBackgroundFetchActive = true;
    mFolderFetchActive = true;
    mFetchFolderQueue.push_back(FetchQueueInfo(LLUUID::null, FT_RECURSIVE));
    gIdleCallbacks.addFunction(&LLInventoryModelBackgroundFetch::backgroundFetchCB, NULL);
}

void LLInventoryModelBackgroundFetch::fetchCOF()
{
    // Will get COF folder, links in it and items those links point to
    AISAPI::FetchCOF();
}

void LLInventoryModelBackgroundFetch::setAllFoldersFetched()
{
	if (mRecursiveInventoryFetchStarted &&
		mRecursiveLibraryFetchStarted)
	{
        mAllRecursiveFoldersFetched = true;
		//LL_INFOS(LOG_INV) << "All folders fetched, validating" << LL_ENDL;
		//gInventory.validate();
	}

	mFolderFetchActive = false;
    if (isBulkFetchProcessingComplete())
    {
        mBackgroundFetchActive = false;
    }

    // For now only informs about initial fetch being done
    mFoldersFetchedSignal();

	LL_INFOS(LOG_INV) << "Inventory background fetch completed" << LL_ENDL;
}

boost::signals2::connection LLInventoryModelBackgroundFetch::setFetchCompletionCallback(folders_fetched_callback_t cb)
{
    return mFoldersFetchedSignal.connect(cb);
}

void LLInventoryModelBackgroundFetch::backgroundFetchCB(void *)
{
	LLInventoryModelBackgroundFetch::instance().backgroundFetch();
}

void LLInventoryModelBackgroundFetch::backgroundFetch()
{
	if (mBackgroundFetchActive)
	{
        if (AISAPI::isAvailable())
        {
            bulkFetchViaAis();
        }
        else if (gAgent.getRegion() && gAgent.getRegion()->capabilitiesReceived())
        {
            // If we'll be using the capability, we'll be sending batches and the background thing isn't as important.
            bulkFetch();
        }
	}
}

void LLInventoryModelBackgroundFetch::incrFetchCount(S32 fetching) 
{  
	mFetchCount += fetching; 
	if (mFetchCount < 0)
	{
		LL_WARNS_ONCE(LOG_INV) << "Inventory fetch count fell below zero (0)." << LL_ENDL;
		mFetchCount = 0; 
	}
}
void LLInventoryModelBackgroundFetch::incrFetchFolderCount(S32 fetching)
{
    incrFetchCount(fetching);
    mFetchFolderCount += fetching;
    if (mFetchCount < 0)
    {
        LL_WARNS_ONCE(LOG_INV) << "Inventory fetch count fell below zero (0)." << LL_ENDL;
        mFetchFolderCount = 0;
    }
}

void ais_simple_item_callback(const LLUUID& inv_id)
{
    LL_DEBUGS(LOG_INV , "AIS3") << "Response for " << inv_id << LL_ENDL;
    LLInventoryModelBackgroundFetch::instance().incrFetchCount(-1);
}

void LLInventoryModelBackgroundFetch::onAISFolderCalback(const LLUUID &request_id, const LLUUID &response_id, EFetchType recursion)
{
    incrFetchFolderCount(-1);
    std::list<LLUUID>::const_iterator found = std::find(mExpectedFolderIds.begin() , mExpectedFolderIds.end(), request_id);
    if (found != mExpectedFolderIds.end())
    {
        mExpectedFolderIds.erase(found);
    }
    else
    {
        // ais shouldn't respond twice
        llassert(false);
        LL_WARNS() << "Unexpected folder response for " << request_id << LL_ENDL;
    }

    if (request_id.isNull())
    {
        // orhans, no other actions needed
        return;
    }

    bool request_descendants = false;
    if (response_id.isNull()) // Failure
    {
        LL_DEBUGS(LOG_INV , "AIS3") << "Failure response for folder " << request_id << LL_ENDL;
        if (recursion == FT_RECURSIVE)
        {
            // A full recursive request failed.
            // Try requesting folder and nested content separately
            mBackgroundFetchActive = true;
            mFolderFetchActive = true;
            mFetchFolderQueue.push_front(FetchQueueInfo(request_id, FT_CONTENT_RECURSIVE));
            gIdleCallbacks.addFunction(&LLInventoryModelBackgroundFetch::backgroundFetchCB, NULL);
        }
        else if (recursion == FT_CONTENT_RECURSIVE)
        {
            LL_WARNS() << "Failed to download folder: " << request_id << " Requesting known content separately" << LL_ENDL;
            request_descendants = true;
        }
    }
    else
    {
        if (recursion == FT_CONTENT_RECURSIVE || recursion == FT_RECURSIVE)
        {
            // Got the folder, now recursively request content
            // Request content even for FT_RECURSIVE in case of changes, failures
            // or if depth limit gets imlemented.
            // This shouldn't redownload folders if they already have version
            request_descendants = true;
            LL_DEBUGS(LOG_INV, "AIS3") << "Got folder " << request_id << ". Requesting content" << LL_ENDL;
        }
        else
        {
            LL_DEBUGS(LOG_INV, "AIS3") << "Got folder " << request_id << "." << LL_ENDL;
        }

    }

    if (request_descendants)
    {
        LLInventoryModel::cat_array_t* categories(NULL);
        LLInventoryModel::item_array_t* items(NULL);
        gInventory.getDirectDescendentsOf(request_id, categories, items);
        if (categories)
        {
            for (LLInventoryModel::cat_array_t::const_iterator it = categories->begin();
                 it != categories->end();
                 ++it)
            {
                mFetchFolderQueue.push_front(FetchQueueInfo((*it)->getUUID(), FT_RECURSIVE));
            }
            if (!mFetchFolderQueue.empty())
            {
                mBackgroundFetchActive = true;
                mFolderFetchActive = true;
                gIdleCallbacks.addFunction(&LLInventoryModelBackgroundFetch::backgroundFetchCB, NULL);
            }
        }
    }

    // done
    LLViewerInventoryCategory * cat(gInventory.getCategory(request_id));
    if (cat)
    {
        cat->setFetching(LLViewerInventoryCategory::FETCH_NONE);
    }
}

static LLTrace::BlockTimerStatHandle FTM_BULK_FETCH("Bulk Fetch");

void LLInventoryModelBackgroundFetch::bulkFetchViaAis()
{
    LL_RECORD_BLOCK_TIME(FTM_BULK_FETCH);
    //Background fetch is called from gIdleCallbacks in a loop until background fetch is stopped.
    if (gDisconnected)
    {
        return;
    }

    static LLCachedControl<U32> ais_pool(gSavedSettings, "PoolSizeAIS", 20);
    const U32 max_concurrent_fetches = llmax(1, ais_pool - 1);

    if (mFetchCount >= max_concurrent_fetches)
    {
        return;
    }

    // Don't loop for too long (in case of large, fully loaded inventory)
    F64 curent_time = LLTimer::getTotalSeconds();
    const F64 max_time = LLStartUp::getStartupState() > STATE_WEARABLES_WAIT
        ? 0.006f // 6 ms
        : 1.f; 
    const F64 end_time = curent_time + max_time;
    S32 last_fetch_count = mFetchCount;

    while (!mFetchFolderQueue.empty() && mFetchCount < max_concurrent_fetches && curent_time < end_time)
    {
        const FetchQueueInfo & fetch_info(mFetchFolderQueue.front());
        bulkFetchViaAis(fetch_info);
        mFetchFolderQueue.pop_front();
        curent_time = LLTimer::getTotalSeconds();
    }

    // Ideally we shouldn't fetch items if recursive fetch isn't done,
    // but there is a chance some request will start timeouting and recursive
    // fetch will get stuck on a signle folder, don't block item fetch in such case
    while (!mFetchItemQueue.empty() && mFetchCount < max_concurrent_fetches && curent_time < end_time)
    {
        const FetchQueueInfo& fetch_info(mFetchItemQueue.front());
        bulkFetchViaAis(fetch_info);
        mFetchItemQueue.pop_front();
        curent_time = LLTimer::getTotalSeconds();
    }

    if (last_fetch_count != mFetchCount // if anything was added
        || mLastFetchCount != mFetchCount) // if anything was substracted
    {
        LL_DEBUGS(LOG_INV , "AIS3") << "Total active fetches: " << mLastFetchCount << "->" << last_fetch_count << "->" << mFetchCount
            << ", scheduled fodler fetches: " << (S32)mFetchFolderQueue.size()
            << ", scheduled item fetches: " << (S32)mFetchItemQueue.size()
            << LL_ENDL;
        mLastFetchCount = mFetchCount;

        if (!mExpectedFolderIds.empty())
        {
            // A folder seem to be stack fetching on QA account, print oldest folder out
            LL_DEBUGS(LOG_INV , "AIS3") << "Oldest expected folder: ";
            std::list<LLUUID>::const_iterator iter = mExpectedFolderIds.begin();
            LL_CONT << *iter;
            if ((*iter).notNull())
            {
                LLViewerInventoryCategory* cat(gInventory.getCategory(*iter));
                if (cat)
                {
                    LL_CONT << " Folder name: " << cat->getName() << " Parent: " << cat->getParentUUID();
                }
                else
                {
                    LL_CONT << " This folder doesn't exist";
                }
            }
            else
            {
                LL_CONT << " Orphans request";
            }
            LL_CONT << LL_ENDL;
        }
    }
    
    if (isFolderFetchProcessingComplete() && mFolderFetchActive)
    {
        setAllFoldersFetched();
    }

    if (isBulkFetchProcessingComplete())
    {
        mBackgroundFetchActive = false;
    }
}

void LLInventoryModelBackgroundFetch::bulkFetchViaAis(const FetchQueueInfo& fetch_info)
{
    if (fetch_info.mIsCategory)
    {
        const LLUUID & cat_id(fetch_info.mUUID);
        if (cat_id.isNull())
        {
            incrFetchFolderCount(1);
            mExpectedFolderIds.push_back(cat_id);
            // Lost and found
            // Should it actually be recursive?
            AISAPI::FetchOrphans([](const LLUUID& response_id)
                                 {
                                     LLInventoryModelBackgroundFetch::instance().onAISFolderCalback(LLUUID::null,
                                         response_id,
                                         FT_DEFAULT);
                                 });
        }
        else
        {
            LLViewerInventoryCategory * cat(gInventory.getCategory(cat_id));
            if (cat)
            {
                if (LLViewerInventoryCategory::VERSION_UNKNOWN == cat->getVersion() || fetch_info.mFetchType == FT_FORCED)
                {
                    LLViewerInventoryCategory::EFetchType target_state =
                        fetch_info.mFetchType >= FT_CONTENT_RECURSIVE
                        ? LLViewerInventoryCategory::FETCH_RECURSIVE
                        : LLViewerInventoryCategory::FETCH_NORMAL;
                    // start again if we did a non-recursive fetch before
                    // to get all children in a single request
                    if (cat->getFetching() < target_state)
                    {
                        // increment before call in case of immediate callback
                        incrFetchFolderCount(1);
                        cat->setFetching(target_state);
                        mExpectedFolderIds.push_back(cat_id);

                        EFetchType type = fetch_info.mFetchType;
                        LLUUID cat_id = cat->getUUID();
                        AISAPI::completion_t cb = [cat_id , type](const LLUUID& response_id)
                        {
                            LLInventoryModelBackgroundFetch::instance().onAISFolderCalback(cat_id , response_id , type);
                        };

                        AISAPI::ITEM_TYPE item_type = AISAPI::INVENTORY;
                        if (ALEXANDRIA_LINDEN_ID == cat->getOwnerID())
                        {
                            item_type = AISAPI::LIBRARY;
                        }

                        AISAPI::FetchCategoryChildren(cat_id , item_type , type == FT_RECURSIVE , cb, 0);
                    }
                }
                else
                {
                    // Already fetched, check if anything inside needs fetching
                    if (fetch_info.mFetchType >= FT_CONTENT_RECURSIVE)
                    {
                        LLInventoryModel::cat_array_t * categories(NULL);
                        LLInventoryModel::item_array_t * items(NULL);
                        gInventory.getDirectDescendentsOf(cat_id, categories, items);
                        for (LLInventoryModel::cat_array_t::const_iterator it = categories->begin();
                            it != categories->end();
                            ++it)
                        {
                            // not push_front to not cause an infinite loop
                            mFetchFolderQueue.push_back(FetchQueueInfo((*it)->getUUID(), FT_RECURSIVE));
                        }
                    }
                }
            } // else?
        }
    }
    else
    {
        LLViewerInventoryItem * itemp(gInventory.getItem(fetch_info.mUUID));

        if (itemp)
        {
            if (!itemp->isFinished() || fetch_info.mFetchType == FT_FORCED)
            {
                mFetchCount++;
                if (itemp->getPermissions().getOwner() == gAgent.getID())
                {
                    AISAPI::FetchItem(fetch_info.mUUID, AISAPI::INVENTORY, ais_simple_item_callback);
                }
                else
                {
                    AISAPI::FetchItem(fetch_info.mUUID, AISAPI::LIBRARY, ais_simple_item_callback);
                }
            }
        }
        else // We don't know it, assume incomplete
        {
            // Assume agent's inventory, library wouldn't have gotten here
            mFetchCount++;
            AISAPI::FetchItem(fetch_info.mUUID, AISAPI::INVENTORY, ais_simple_item_callback);
        }
    }
}

// Bundle up a bunch of requests to send all at once.
void LLInventoryModelBackgroundFetch::bulkFetch()
{
	LL_RECORD_BLOCK_TIME(FTM_BULK_FETCH);
	//Background fetch is called from gIdleCallbacks in a loop until background fetch is stopped.
	//If there are items in mFetchQueue, we want to check the time since the last bulkFetch was 
	//sent.  If it exceeds our retry time, go ahead and fire off another batch.  
	LLViewerRegion * region(gAgent.getRegion());
	if (! region || gDisconnected || LLApp::isExiting())
	{
		return;
	}

	// *TODO:  These values could be tweaked at runtime to effect
	// a fast/slow fetch throttle.  Once login is complete and the scene
	// is mostly loaded, we could turn up the throttle and fill missing
	// inventory more quickly.
	static const U32 max_batch_size(10);
	static const S32 max_concurrent_fetches(12);		// Outstanding requests, not connections

	if (mFetchCount)
	{
		// Process completed background HTTP requests
		gInventory.handleResponses(false);
		// Just processed a bunch of items.
		// Note: do we really need notifyObservers() here?
		// OnIdle it will be called anyway due to Add flag for processed item.
		// It seems like in some cases we are updaiting on fail (no flag),
		// but is there anything to update?
		gInventory.notifyObservers();
	}
	
	if (mFetchCount > max_concurrent_fetches)
	{
		return;
	}

	U32 item_count(0);
	U32 folder_count(0);

	const U32 sort_order(gSavedSettings.getU32(LLInventoryPanel::DEFAULT_SORT_ORDER) & 0x1);

	// *TODO:  Think I'd like to get a shared pointer to this and share it
	// among all the folder requests.
	uuid_vec_t recursive_cats;

	LLSD folder_request_body;
	LLSD folder_request_body_lib;
	LLSD item_request_body;
	LLSD item_request_body_lib;

	while (! mFetchFolderQueue.empty() 
			&& (item_count + folder_count) < max_batch_size)
	{
		const FetchQueueInfo & fetch_info(mFetchFolderQueue.front());
		if (fetch_info.mIsCategory)
		{
			const LLUUID & cat_id(fetch_info.mUUID);
			if (cat_id.isNull()) //DEV-17797 Lost and found
			{
				LLSD folder_sd;
				folder_sd["folder_id"]		= LLUUID::null.asString();
				folder_sd["owner_id"]		= gAgent.getID();
				folder_sd["sort_order"]		= LLSD::Integer(sort_order);
				folder_sd["fetch_folders"]	= LLSD::Boolean(false);
				folder_sd["fetch_items"]	= LLSD::Boolean(true);
				folder_request_body["folders"].append(folder_sd);
				folder_count++;
			}
			else
			{
                const LLViewerInventoryCategory * cat(gInventory.getCategory(cat_id));
                if (cat)
                {
                    if (LLViewerInventoryCategory::VERSION_UNKNOWN == cat->getVersion())
                    {
                        LLSD folder_sd;
                        folder_sd["folder_id"] = cat->getUUID();
                        folder_sd["owner_id"] = cat->getOwnerID();
                        folder_sd["sort_order"] = LLSD::Integer(sort_order);
                        folder_sd["fetch_folders"] = LLSD::Boolean(true); //(LLSD::Boolean)sFullFetchStarted;
                        folder_sd["fetch_items"] = LLSD::Boolean(true);

                        if (ALEXANDRIA_LINDEN_ID == cat->getOwnerID())
                        {
                            folder_request_body_lib["folders"].append(folder_sd);
                        }
                        else
                        {
                            folder_request_body["folders"].append(folder_sd);
                        }
                        folder_count++;
                    }
                    else
                    {
                        // May already have this folder, but append child folders to list.
                        if (fetch_info.mFetchType >= FT_CONTENT_RECURSIVE)
                        {
                            LLInventoryModel::cat_array_t * categories(NULL);
                            LLInventoryModel::item_array_t * items(NULL);
                            gInventory.getDirectDescendentsOf(cat_id, categories, items);
                            for (LLInventoryModel::cat_array_t::const_iterator it = categories->begin();
                                it != categories->end();
                                ++it)
                            {
                                mFetchFolderQueue.push_back(FetchQueueInfo((*it)->getUUID(), fetch_info.mFetchType));
                            }
                        }
                    }
                }
			}
			if (fetch_info.mFetchType >= FT_CONTENT_RECURSIVE)
			{
				recursive_cats.push_back(cat_id);
			}
		}

        mFetchFolderQueue.pop_front();
    }


    while (!mFetchItemQueue.empty()
        && (item_count + folder_count) < max_batch_size)
    {
        const FetchQueueInfo & fetch_info(mFetchItemQueue.front());

        LLViewerInventoryItem * itemp(gInventory.getItem(fetch_info.mUUID));

        if (itemp)
        {
            LLSD item_sd;
            item_sd["owner_id"] = itemp->getPermissions().getOwner();
            item_sd["item_id"] = itemp->getUUID();
            if (itemp->getPermissions().getOwner() == gAgent.getID())
            {
                item_request_body.append(item_sd);
            }
            else
            {
                item_request_body_lib.append(item_sd);
            }
            //itemp->fetchFromServer();
            item_count++;
        }

        mFetchItemQueue.pop_front();
	}

	// Issue HTTP POST requests to fetch folders and items
	
	if (item_count + folder_count > 0)
	{
		if (folder_count)
		{
			if (folder_request_body["folders"].size())
			{
				const std::string url(region->getCapability("FetchInventoryDescendents2"));

				if (! url.empty())
				{
                    LLCore::HttpHandler::ptr_t  handler(new BGFolderHttpHandler(folder_request_body, recursive_cats));
					gInventory.requestPost(false, url, folder_request_body, handler, "Inventory Folder");
				}
			}
			
			if (folder_request_body_lib["folders"].size())
			{
				const std::string url(region->getCapability("FetchLibDescendents2"));

				if (! url.empty())
				{
                    LLCore::HttpHandler::ptr_t  handler(new BGFolderHttpHandler(folder_request_body_lib, recursive_cats));
					gInventory.requestPost(false, url, folder_request_body_lib, handler, "Library Folder");
				}
			}
		} // if (folder_count)

		if (item_count)
		{
			if (item_request_body.size())
			{
				const std::string url(region->getCapability("FetchInventory2"));

				if (! url.empty())
				{
					LLSD body;
					body["items"] = item_request_body;
                    LLCore::HttpHandler::ptr_t  handler(new BGItemHttpHandler(body));
					gInventory.requestPost(false, url, body, handler, "Inventory Item");
				}
			}

			if (item_request_body_lib.size())
			{
				const std::string url(region->getCapability("FetchLib2"));

				if (! url.empty())
				{
					LLSD body;
					body["items"] = item_request_body_lib;
                    LLCore::HttpHandler::ptr_t handler(new BGItemHttpHandler(body));
					gInventory.requestPost(false, url, body, handler, "Library Item");
				}
			}
		} // if (item_count)
		
		mFetchTimer.reset();
	}
	else if (isBulkFetchProcessingComplete())
	{
		setAllFoldersFetched();
	}
}

bool LLInventoryModelBackgroundFetch::fetchQueueContainsNoDescendentsOf(const LLUUID & cat_id) const
{
	for (fetch_queue_t::const_iterator it = mFetchFolderQueue.begin();
		 it != mFetchFolderQueue.end();
		 ++it)
	{
		const LLUUID & fetch_id = (*it).mUUID;
		if (gInventory.isObjectDescendentOf(fetch_id, cat_id))
			return false;
	}
    for (fetch_queue_t::const_iterator it = mFetchItemQueue.begin();
        it != mFetchItemQueue.end();
        ++it)
    {
        const LLUUID & fetch_id = (*it).mUUID;
        if (gInventory.isObjectDescendentOf(fetch_id, cat_id))
            return false;
    }
	return true;
}


namespace
{

///----------------------------------------------------------------------------
/// Class <anonymous>::BGFolderHttpHandler
///----------------------------------------------------------------------------

void BGFolderHttpHandler::onCompleted(LLCore::HttpHandle handle, LLCore::HttpResponse * response)
{
	do  	// Single-pass do-while used for common exit handling
	{
		LLCore::HttpStatus status(response->getStatus());
		// status = LLCore::HttpStatus(404);				// Dev tool to force error handling
		if (! status)
		{
			processFailure(status, response);
			break;			// Goto common exit
		}

		// Response body should be present.
		LLCore::BufferArray * body(response->getBody());
		// body = NULL;									// Dev tool to force error handling
		if (! body || ! body->size())
		{
			LL_WARNS(LOG_INV) << "Missing data in inventory folder query." << LL_ENDL;
			processFailure("HTTP response missing expected body", response);
			break;			// Goto common exit
		}

		// Could test 'Content-Type' header but probably unreliable.

		// Convert response to LLSD
		// body->write(0, "Garbage Response", 16);		// Dev tool to force error handling
		LLSD body_llsd;
		if (! LLCoreHttpUtil::responseToLLSD(response, true, body_llsd))
		{
			// INFOS-level logging will occur on the parsed failure
			processFailure("HTTP response contained malformed LLSD", response);
			break;			// goto common exit
		}

		// Expect top-level structure to be a map
		// body_llsd = LLSD::emptyArray();				// Dev tool to force error handling
		if (! body_llsd.isMap())
		{
			processFailure("LLSD response not a map", response);
			break;			// goto common exit
		}

		// Check for 200-with-error failures
		//
		// See comments in llinventorymodel.cpp about this mode of error.
		//
		// body_llsd["error"] = LLSD::emptyMap();		// Dev tool to force error handling
		// body_llsd["error"]["identifier"] = "Development";
		// body_llsd["error"]["message"] = "You left development code in the viewer";
		if (body_llsd.has("error"))
		{
			processFailure("Inventory application error (200-with-error)", response);
			break;			// goto common exit
		}

		// Okay, process data if possible
		processData(body_llsd, response);
	}
	while (false);
}


void BGFolderHttpHandler::processData(LLSD & content, LLCore::HttpResponse * response)
{
	LLInventoryModelBackgroundFetch * fetcher(LLInventoryModelBackgroundFetch::getInstance());

	// API V2 and earlier should probably be testing for "error" map
	// in response as an application-level error.

	// Instead, we assume success and attempt to extract information.
	if (content.has("folders"))	
	{
		LLSD folders(content["folders"]);
		
		for (LLSD::array_const_iterator folder_it = folders.beginArray();
			folder_it != folders.endArray();
			++folder_it)
		{	
			LLSD folder_sd(*folder_it);

			//LLUUID agent_id = folder_sd["agent_id"];

			//if(agent_id != gAgent.getID())	//This should never happen.
			//{
			//	LL_WARNS(LOG_INV) << "Got a UpdateInventoryItem for the wrong agent."
			//			<< LL_ENDL;
			//	break;
			//}

			LLUUID parent_id(folder_sd["folder_id"].asUUID());
			LLUUID owner_id(folder_sd["owner_id"].asUUID());
			S32    version(folder_sd["version"].asInteger());
			S32    descendents(folder_sd["descendents"].asInteger());
			LLPointer<LLViewerInventoryCategory> tcategory = new LLViewerInventoryCategory(owner_id);

            if (parent_id.isNull())
            {
				LLSD items(folder_sd["items"]);
			    LLPointer<LLViewerInventoryItem> titem = new LLViewerInventoryItem;
				
			    for (LLSD::array_const_iterator item_it = items.beginArray();
				    item_it != items.endArray();
				    ++item_it)
			    {	
                    const LLUUID lost_uuid(gInventory.findCategoryUUIDForType(LLFolderType::FT_LOST_AND_FOUND));

                    if (lost_uuid.notNull())
                    {
				        LLSD item(*item_it);

				        titem->unpackMessage(item);
				
                        LLInventoryModel::update_list_t update;
                        LLInventoryModel::LLCategoryUpdate new_folder(lost_uuid, 1);
                        update.push_back(new_folder);
                        gInventory.accountForUpdate(update);

                        titem->setParent(lost_uuid);
                        titem->updateParentOnServer(FALSE);
                        gInventory.updateItem(titem);
                    }
                }
            }

	        LLViewerInventoryCategory * pcat(gInventory.getCategory(parent_id));
			if (! pcat)
			{
				continue;
			}

			LLSD categories(folder_sd["categories"]);
			for (LLSD::array_const_iterator category_it = categories.beginArray();
				category_it != categories.endArray();
				++category_it)
			{	
				LLSD category(*category_it);
				tcategory->fromLLSD(category); 
				
				const bool recursive(getIsRecursive(tcategory->getUUID()));
				if (recursive)
				{
					fetcher->addRequestAtBack(tcategory->getUUID(), recursive, true);
				}
				else if (! gInventory.isCategoryComplete(tcategory->getUUID()))
				{
					gInventory.updateCategory(tcategory);
				}
			}

			LLSD items(folder_sd["items"]);
			LLPointer<LLViewerInventoryItem> titem = new LLViewerInventoryItem;
			for (LLSD::array_const_iterator item_it = items.beginArray();
				 item_it != items.endArray();
				 ++item_it)
			{	
				LLSD item(*item_it);
				titem->unpackMessage(item);
				
				gInventory.updateItem(titem);
			}

			// Set version and descendentcount according to message.
			LLViewerInventoryCategory * cat(gInventory.getCategory(parent_id));
			if (cat)
			{
				cat->setVersion(version);
				cat->setDescendentCount(descendents);
				cat->determineFolderType();
			}
		}
	}
		
	if (content.has("bad_folders"))
	{
		LLSD bad_folders(content["bad_folders"]);
		for (LLSD::array_const_iterator folder_it = bad_folders.beginArray();
			 folder_it != bad_folders.endArray();
			 ++folder_it)
		{
			// *TODO: Stop copying data [ed:  this isn't copying data]
			LLSD folder_sd(*folder_it);
			
			// These folders failed on the dataserver.  We probably don't want to retry them.
			LL_WARNS(LOG_INV) << "Folder " << folder_sd["folder_id"].asString() 
							  << "Error: " << folder_sd["error"].asString() << LL_ENDL;
		}
	}
	
	if (fetcher->isBulkFetchProcessingComplete())
	{
		fetcher->setAllFoldersFetched();
	}
}


void BGFolderHttpHandler::processFailure(LLCore::HttpStatus status, LLCore::HttpResponse * response)
{
	const std::string & ct(response->getContentType());
	LL_WARNS(LOG_INV) << "Inventory folder fetch failure\n"
					  << "[Status: " << status.toTerseString() << "]\n"
					  << "[Reason: " << status.toString() << "]\n"
					  << "[Content-type: " << ct << "]\n"
					  << "[Content (abridged): "
					  << LLCoreHttpUtil::responseToString(response) << "]" << LL_ENDL;

	// Could use a 404 test here to try to detect revoked caps...
	
	// This was originally the request retry logic for the inventory
	// request which tested on HTTP_INTERNAL_ERROR status.  This
	// retry logic was unbounded and lacked discrimination as to the
	// cause of the retry.  The new http library should be doing
	// adquately on retries but I want to keep the structure of a
	// retry for reference.
	LLInventoryModelBackgroundFetch *fetcher = LLInventoryModelBackgroundFetch::getInstance();
	if (false)
	{
		// timed out or curl failure
		for (LLSD::array_const_iterator folder_it = mRequestSD["folders"].beginArray();
			 folder_it != mRequestSD["folders"].endArray();
			 ++folder_it)
		{
			LLSD folder_sd(*folder_it);
			LLUUID folder_id(folder_sd["folder_id"].asUUID());
			const BOOL recursive = getIsRecursive(folder_id);
			fetcher->addRequestAtFront(folder_id, recursive, true);
		}
	}
	else
	{
		if (fetcher->isBulkFetchProcessingComplete())
		{
			fetcher->setAllFoldersFetched();
		}
	}
}


void BGFolderHttpHandler::processFailure(const char * const reason, LLCore::HttpResponse * response)
{
	LL_WARNS(LOG_INV) << "Inventory folder fetch failure\n"
					  << "[Status: internal error]\n"
					  << "[Reason: " << reason << "]\n"
					  << "[Content (abridged): "
					  << LLCoreHttpUtil::responseToString(response) << "]" << LL_ENDL;

	// Reverse of previous processFailure() method, this is invoked
	// when response structure is found to be invalid.  Original
	// always re-issued the request (without limit).  This does
	// the same but be aware that this may be a source of problems.
	// Philosophy is that inventory folders are so essential to
	// operation that this is a reasonable action.
	LLInventoryModelBackgroundFetch *fetcher = LLInventoryModelBackgroundFetch::getInstance();
	if (true)
	{
		for (LLSD::array_const_iterator folder_it = mRequestSD["folders"].beginArray();
			 folder_it != mRequestSD["folders"].endArray();
			 ++folder_it)
		{
			LLSD folder_sd(*folder_it);
			LLUUID folder_id(folder_sd["folder_id"].asUUID());
			const BOOL recursive = getIsRecursive(folder_id);
			fetcher->addRequestAtFront(folder_id, recursive, true);
		}
	}
	else
	{
		if (fetcher->isBulkFetchProcessingComplete())
		{
			fetcher->setAllFoldersFetched();
		}
	}
}


bool BGFolderHttpHandler::getIsRecursive(const LLUUID & cat_id) const
{
	return std::find(mRecursiveCatUUIDs.begin(), mRecursiveCatUUIDs.end(), cat_id) != mRecursiveCatUUIDs.end();
}

///----------------------------------------------------------------------------
/// Class <anonymous>::BGItemHttpHandler
///----------------------------------------------------------------------------

// Nothing to implement here.  All ctor/dtor changes.

} // end namespace anonymous