/**
 * @file llattachmentsmgr.h
 * @brief Batches up attachment requests and sends them all
 * in one message.
 *
 * $LicenseInfo:firstyear=2004&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, 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
 * $/LicenseInfo$
 */

#ifndef LL_LLATTACHMENTSMGR_H
#define LL_LLATTACHMENTSMGR_H

#include "llsingleton.h"

//--------------------------------------------------------------------------------
// LLAttachmentsMgr
//
// This class manages batching up of requests at two stages of
// attachment rezzing.
//
// First, attachments requested to rez get saved in
// mPendingAttachments and sent as a single
// RezMultipleAttachmentsFromInv request. This batching is needed
// mainly because of weaknessing the UI element->inventory item
// handling, such that we don't always know when we are requesting
// multiple items. Now they just pile up and get swept into a single
// request during the idle loop.
//
// Second, after attachments arrive, we need to generate COF links for
// them. There are both efficiency and UI correctness reasons why it
// is better to request all the COF links at once and run a single
// callback after they all complete. Given the vagaries of the
// attachment system, there is no guarantee that we will get all the
// attachments we ask for, but we frequently do. So in the common case
// that all the desired attachments arrive fairly quickly, we generate
// a single batched request for COF links. If attachments arrive late
// or not at all, we will still issue COF link requests once a timeout
// value has been exceeded.
//
// To handle attachments that never arrive, we forget about requests
// that exceed a timeout value.
//--------------------------------------------------------------------------------
class LLAttachmentsMgr: public LLSingleton<LLAttachmentsMgr>
{
    LLSINGLETON(LLAttachmentsMgr);
    virtual ~LLAttachmentsMgr();

public:
    // Stores info for attachments that will be requested during idle.
    struct AttachmentsInfo
    {
        LLUUID mItemID;
        U8 mAttachmentPt;
        bool mAdd;
    };
    typedef std::deque<AttachmentsInfo> attachments_vec_t;

    void addAttachmentRequest(const LLUUID& item_id,
                              const U8 attachment_pt,
                              const bool add);
    void onAttachmentRequested(const LLUUID& item_id);
    void requestAttachments(attachments_vec_t& attachment_requests);
    static void onIdle(void *);

    void onAttachmentArrived(const LLUUID& inv_item_id);

    void onDetachRequested(const LLUUID& inv_item_id);
    void onDetachCompleted(const LLUUID& inv_item_id);

    bool isAttachmentStateComplete() const;

private:

    class LLItemRequestTimes: public std::map<LLUUID,LLTimer>
    {
    public:
        LLItemRequestTimes(const std::string& op_name, F32 timeout);
        void addTime(const LLUUID& inv_item_id);
        void removeTime(const LLUUID& inv_item_id);
        bool wasRequestedRecently(const LLUUID& item_id) const;
        bool getTime(const LLUUID& inv_item_id, LLTimer& timer) const;

    private:
        F32 mTimeout;
        std::string mOpName;
    };

    void removeAttachmentRequestTime(const LLUUID& inv_item_id);
    void onIdle();
    void requestPendingAttachments();
    void linkRecentlyArrivedAttachments();
    void expireOldAttachmentRequests();
    void expireOldDetachRequests();
    void checkInvalidCOFLinks();
    void spamStatusInfo();

    // Attachments that we are planning to rez but haven't requested from the server yet.
    attachments_vec_t mPendingAttachments;

    // Attachments that have been requested from server but have not arrived yet.
    LLItemRequestTimes mAttachmentRequests;

    // Attachments that have been requested to detach but have not gone away yet.
    LLItemRequestTimes mDetachRequests;

    // Attachments that have arrived but have not been linked in the COF yet.
    std::set<LLUUID> mRecentlyArrivedAttachments;
    LLTimer mCOFLinkBatchTimer;

    // Attachments that are linked in the COF but may be invalid.
    LLItemRequestTimes mQuestionableCOFLinks;
};

#endif