/** 
 * @file llavatarnamecache.cpp
 * @brief Provides lookup of avatar SLIDs ("bobsmith123") and display names
 * ("James Cook") from avatar UUIDs.
 *
 * $LicenseInfo:firstyear=2010&license=viewergpl$
 * 
 * Copyright (c) 2010, Linden Research, Inc.
 * 
 * Second Life Viewer Source Code
 * The source code in this file ("Source Code") is provided by Linden Lab
 * to you under the terms of the GNU General Public License, version 2.0
 * ("GPL"), unless you have obtained a separate licensing agreement
 * ("Other License"), formally executed by you and Linden Lab.  Terms of
 * the GPL can be found in doc/GPL-license.txt in this distribution, or
 * online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
 * 
 * There are special exceptions to the terms and conditions of the GPL as
 * it is applied to this Source Code. View the full text of the exception
 * in the file doc/FLOSS-exception.txt in this software distribution, or
 * online at
 * http://secondlifegrid.net/programs/open_source/licensing/flossexception
 * 
 * By copying, modifying or distributing this software, you acknowledge
 * that you have read and understood your obligations described above,
 * and agree to abide by those obligations.
 * 
 * ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
 * WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
 * COMPLETENESS OR PERFORMANCE.
 * $/LicenseInfo$
 */
#include "linden_common.h"

#include "llavatarnamecache.h"

#include "llframetimer.h"
#include "llhttpclient.h"
#include "llsd.h"
#include "llsdserialize.h"

#include <map>
#include <set>

namespace LLAvatarNameCache
{
	// Will be turned on and off based on service availability, sometimes
	// in the middle of a session.
	bool sUseDisplayNames = true;
	
	// Base lookup URL for name service.
	// On simulator, loaded from indra.xml
	// On viewer, usually a simulator capability (at People API team's request)
	// Includes the trailing slash, like "http://pdp60.lindenlab.com:8000/agents/"
	std::string sNameLookupURL;

	// accumulated agent IDs for next query against service
	typedef std::set<LLUUID> ask_queue_t;
	ask_queue_t sAskQueue;

	// agent IDs that have been requested, but with no reply
	// maps agent ID to frame time request was made
	typedef std::map<LLUUID, F64> pending_queue_t;
	pending_queue_t sPendingQueue;

	// Callbacks to fire when we received a name.
	// May have multiple callbacks for a single ID, which are
	// represented as multiple slots bound to the signal.
	// Avoid copying signals via pointers.
	typedef std::map<LLUUID, callback_signal_t*> signal_map_t;
	signal_map_t sSignalMap;

	// names we know about
	typedef std::map<LLUUID, LLAvatarName> cache_t;
	cache_t sCache;

	// Send bulk lookup requests a few times a second at most
	// only need per-frame timing resolution
	LLFrameTimer sRequestTimer;

	// Periodically clean out expired entries from the cache
	LLFrameTimer sEraseExpiredTimer;

	// Handle name response off network
	void processName(const LLUUID& agent_id, const LLAvatarName& av_name);

	void requestNamesViaCapability();
	void requestNamesViaLegacy();
	bool isRequestPending(const LLUUID& agent_id);

	// Erase expired names from cache
	void eraseExpired();
}

/* Sample response:
<?xml version="1.0"?>
<llsd>
  <map>
    <key>agents</key>
    <array>
      <map>
        <key>display_name_next_update</key>
        <date>2010-04-16T21:34:02+00:00Z</date>
        <key>display_name_expires</key>
        <date>2010-04-16T21:32:26.142178+00:00Z</date>
        <key>display_name</key>
        <string>MickBot390 LLQABot</string>
        <key>sl_id</key>
        <string>mickbot390.llqabot</string>
        <key>id</key>
        <string>0012809d-7d2d-4c24-9609-af1230a37715</string>
        <key>is_display_name_default</key>
        <boolean>false</boolean>
      </map>
      <map>
        <key>display_name_next_update</key>
        <date>2010-04-16T21:34:02+00:00Z</date>
        <key>display_name_expires</key>
        <date>2010-04-16T21:32:26.142178+00:00Z</date>
        <key>display_name</key>
        <string>Bjork Gudmundsdottir</string>
        <key>sl_id</key>
        <string>sardonyx.linden</string>
        <key>id</key>
        <string>3941037e-78ab-45f0-b421-bd6e77c1804d</string>
        <key>is_display_name_default</key>
        <boolean>true</boolean>
      </map>
    </array>
  </map>
</llsd>
*/

class LLAvatarNameResponder : public LLHTTPClient::Responder
{
private:
	// need to store agent ids that are part of this request in case of
	// an error, so we can flag them as unavailable
	std::vector<LLUUID> mAgentIDs;
	
public:
	LLAvatarNameResponder(const std::vector<LLUUID>& agent_ids)
	:	mAgentIDs(agent_ids)
	{ }
	
	/*virtual*/ void result(const LLSD& content)
	{
		LLSD agents = content["agents"];
		LLSD::array_const_iterator it = agents.beginArray();
		for ( ; it != agents.endArray(); ++it)
		{
			const LLSD& row = *it;
			LLUUID agent_id = row["id"].asUUID();

			LLAvatarName av_name;
			av_name.fromLLSD(row);

			// Some avatars don't have explicit display names set
			if (av_name.mDisplayName.empty())
			{
				av_name.mDisplayName = av_name.mSLID;
			}

			LLAvatarNameCache::processName(agent_id, av_name);
		}
	}

	// This is called for both successful and failed requests, and is
	// called _after_ result() above.
	/*virtual*/ void completedHeader(U32 status, const std::string& reason, 
		const LLSD& headers)
	{
		// Only care about headers when there is an error
		if (isGoodStatus(status)) return;

		// We're going to construct a dummy record and cache it for a while,
		// either briefly for a 503 Service Unavailable, or longer for other
		// errors.
		F64 retry_timestamp = errorRetryTimestamp(status, headers);

		// *NOTE: "??" starts trigraphs in C/C++, escape the question marks.
		const std::string DUMMY_NAME("\?\?\?");
		LLAvatarName av_name;
		av_name.mSLID = DUMMY_NAME;
		av_name.mDisplayName = DUMMY_NAME;
		av_name.mIsDisplayNameDefault = false;
		av_name.mExpires = retry_timestamp;

		// Add dummy records for all agent IDs in this request
		std::vector<LLUUID>::const_iterator it = mAgentIDs.begin();
		for ( ; it != mAgentIDs.end(); ++it)
		{
			const LLUUID& agent_id = *it;
			LLAvatarNameCache::processName(agent_id, av_name);
		}
	}

	// Return time to retry a request that generated an error, based on
	// error type and headers.  Return value is seconds-since-epoch.
	F64 errorRetryTimestamp(S32 status, const LLSD& headers)
	{
		LLSD expires = headers["expires"];
		if (expires.isDefined())
		{
			LLDate expires_date = expires.asDate();
			return expires_date.secondsSinceEpoch();
		}

		LLSD retry_after = headers["retry-after"];
		if (retry_after.isDefined())
		{
			// does the header use the delta-seconds type?
			S32 delta_seconds = retry_after.asInteger();
			if (delta_seconds > 0)
			{
				// ...valid delta-seconds
				F64 now = LLFrameTimer::getTotalSeconds();
				return now + F64(delta_seconds);
			}
			else
			{
				// ...it's a date
				LLDate expires_date = retry_after.asDate();
				return expires_date.secondsSinceEpoch();
			}
		}

		// No information in header, make a guess
		F64 now = LLFrameTimer::getTotalSeconds();
		if (status == 503)
		{
			// ...service unavailable, retry soon
			const F64 SERVICE_UNAVAILABLE_DELAY = 600.0; // 10 min
			return now + SERVICE_UNAVAILABLE_DELAY;
		}
		else
		{
			// ...other unexpected error
			const F64 DEFAULT_DELAY = 3600.0; // 1 hour
			return now + DEFAULT_DELAY;
		}
	}
};

void LLAvatarNameCache::processName(const LLUUID& agent_id,
									const LLAvatarName& av_name)
{
	sCache[agent_id] = av_name;

	sPendingQueue.erase(agent_id);

	// signal everyone waiting on this name
	signal_map_t::iterator sig_it =	sSignalMap.find(agent_id);
	if (sig_it != sSignalMap.end())
	{
		callback_signal_t* signal = sig_it->second;
		(*signal)(agent_id, av_name);

		sSignalMap.erase(agent_id);

		delete signal;
		signal = NULL;
	}
}

void LLAvatarNameCache::requestNamesViaCapability()
{
	// URL format is like:
	// http://pdp60.lindenlab.com:8000/agents/?ids=3941037e-78ab-45f0-b421-bd6e77c1804d&ids=0012809d-7d2d-4c24-9609-af1230a37715&ids=0019aaba-24af-4f0a-aa72-6457953cf7f0
	//
	// Apache can handle URLs of 4096 chars, but let's be conservative
	const U32 NAME_URL_MAX = 4096;
	const U32 NAME_URL_SEND_THRESHOLD = 3000;
	std::string url;
	url.reserve(NAME_URL_MAX);

	std::vector<LLUUID> agent_ids;
	agent_ids.reserve(128);
	
	ask_queue_t::const_iterator it = sAskQueue.begin();
	for ( ; it != sAskQueue.end(); ++it)
	{
		if (url.empty())
		{
			// ...starting new request
			url += sNameLookupURL;
			url += "?ids=";
		}
		else
		{
			// ...continuing existing request
			url += "&ids=";
		}
		url += it->asString();
		agent_ids.push_back(*it);

		if (url.size() > NAME_URL_SEND_THRESHOLD)
		{
			//llinfos << "requestNames " << url << llendl;
			LLHTTPClient::get(url, new LLAvatarNameResponder(agent_ids));
			url.clear();
			agent_ids.clear();
		}
	}

	if (!url.empty())
	{
		//llinfos << "requestNames " << url << llendl;
		LLHTTPClient::get(url, new LLAvatarNameResponder(agent_ids));
		url.clear();
		agent_ids.clear();
	}
}

void LLAvatarNameCache::requestNamesViaLegacy()
{
	// JAMESDEBUG TODO
}

void LLAvatarNameCache::initClass()
{
}

void LLAvatarNameCache::cleanupClass()
{
}

void LLAvatarNameCache::importFile(std::istream& istr)
{
	LLSD data;
	S32 parse_count = LLSDSerialize::fromXMLDocument(data, istr);
	if (parse_count < 1) return;

	// by convention LLSD storage is a map
	// we only store one entry in the map
	LLSD agents = data["agents"];

	LLUUID agent_id;
	LLAvatarName av_name;
	LLSD::map_const_iterator it = agents.beginMap();
	for ( ; it != agents.endMap(); ++it)
	{
		agent_id.set(it->first);
		av_name.fromLLSD( it->second );
		sCache[agent_id] = av_name;
	}
	// entries may have expired since we last ran the viewer, just
	// clean them out now
	eraseExpired();
	llinfos << "loaded " << sCache.size() << llendl;
}

void LLAvatarNameCache::exportFile(std::ostream& ostr)
{
	LLSD agents;
	cache_t::const_iterator it = sCache.begin();
	for ( ; it != sCache.end(); ++it)
	{
		const LLUUID& agent_id = it->first;
		const LLAvatarName& av_name = it->second;
		// key must be a string
		agents[agent_id.asString()] = av_name.asLLSD();
	}
	LLSD data;
	data["agents"] = agents;
	LLSDSerialize::toPrettyXML(data, ostr);
}

void LLAvatarNameCache::setNameLookupURL(const std::string& name_lookup_url)
{
	sNameLookupURL = name_lookup_url;
}

void LLAvatarNameCache::idle()
{
	// 100 ms is the threshold for "user speed" operations, so we can
	// stall for about that long to batch up requests.
	const F32 SECS_BETWEEN_REQUESTS = 0.1f;
	if (!sRequestTimer.checkExpirationAndReset(SECS_BETWEEN_REQUESTS))
	{
		return;
	}

	// Must be large relative to above
	const F32 ERASE_EXPIRED_TIMEOUT = 60.f; // seconds
	if (sEraseExpiredTimer.checkExpirationAndReset(ERASE_EXPIRED_TIMEOUT))
	{
		eraseExpired();
	}

	if (sAskQueue.empty())
	{
		return;
	}

	if (!sNameLookupURL.empty())
	{
		requestNamesViaCapability();
	}
	else
	{
		// ...fall back to legacy name cache system
		requestNamesViaLegacy();
		llwarns << "JAMESDEBUG legacy lookup call" << llendl;
	}

	// Move requests from Ask queue to Pending queue
	F64 now = LLFrameTimer::getTotalSeconds();
	ask_queue_t::const_iterator it = sAskQueue.begin();
	for ( ; it != sAskQueue.end(); ++it)
	{
		sPendingQueue[*it] = now;
	}
	sAskQueue.clear();
}

bool LLAvatarNameCache::isRequestPending(const LLUUID& agent_id)
{
	const F64 PENDING_TIMEOUT_SECS = 5.0 * 60.0;
	F64 now = LLFrameTimer::getTotalSeconds();
	F64 expire_time = now - PENDING_TIMEOUT_SECS;

	pending_queue_t::const_iterator it = sPendingQueue.find(agent_id);
	if (it != sPendingQueue.end())
	{
		bool request_expired = (it->second < expire_time);
		return !request_expired;
	}
	return false;
}

void LLAvatarNameCache::eraseExpired()
{
	F64 now = LLFrameTimer::getTotalSeconds();
	cache_t::iterator it = sCache.begin();
	while (it != sCache.end())
	{
		cache_t::iterator cur = it;
		++it;
		const LLAvatarName& av_name = cur->second;
		if (av_name.mExpires < now)
		{
			sCache.erase(cur);
		}
	}
}

bool LLAvatarNameCache::get(const LLUUID& agent_id, LLAvatarName *av_name)
{
	std::map<LLUUID,LLAvatarName>::iterator it = sCache.find(agent_id);
	if (it != sCache.end())
	{
		*av_name = it->second;
		return true;
	}

	if (!isRequestPending(agent_id))
	{
		sAskQueue.insert(agent_id);
	}

	return false;
}

void LLAvatarNameCache::get(const LLUUID& agent_id, callback_slot_t slot)
{
	std::map<LLUUID,LLAvatarName>::iterator it = sCache.find(agent_id);
	if (it != sCache.end())
	{
		// ...name already exists in cache, fire callback now
		callback_signal_t signal;
		signal.connect(slot);
		signal(agent_id, it->second);
		return;
	}

	// schedule a request
	if (!isRequestPending(agent_id))
	{
		sAskQueue.insert(agent_id);
	}

	// always store additional callback, even if request is pending
	signal_map_t::iterator sig_it = sSignalMap.find(agent_id);
	if (sig_it == sSignalMap.end())
	{
		// ...new callback for this id
		callback_signal_t* signal = new callback_signal_t();
		signal->connect(slot);
		sSignalMap[agent_id] = signal;
	}
	else
	{
		// ...existing callback, bind additional slot
		callback_signal_t* signal = sig_it->second;
		signal->connect(slot);
	}
}


void LLAvatarNameCache::setUseDisplayNames(bool use)
{
	if (use != sUseDisplayNames)
	{
		sUseDisplayNames = use;
		// flush our cache
		sCache.clear();
	}
}

bool LLAvatarNameCache::useDisplayNames()
{
	return sUseDisplayNames;
}

void LLAvatarNameCache::erase(const LLUUID& agent_id)
{
	sCache.erase(agent_id);
}

void LLAvatarNameCache::fetch(const LLUUID& agent_id)
{
	// re-request, even if request is already pending
	sAskQueue.insert(agent_id);
}

void LLAvatarNameCache::insert(const LLUUID& agent_id, const LLAvatarName& av_name)
{
	// *TODO: update timestamp if zero?
	sCache[agent_id] = av_name;
}