/** 
 * @file llavatarnamecache.h
 * @brief Provides lookup of avatar SLIDs ("bobsmith123") and display names
 * ("James Cook") from avatar UUIDs.
 *
 * $LicenseInfo:firstyear=2010&license=viewerlgpl$
 * 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 LLAVATARNAMECACHE_H
#define LLAVATARNAMECACHE_H

#include "llavatarname.h"	// for convenience

#include <boost/signals2.hpp>

class LLSD;
class LLUUID;

namespace LLAvatarNameCache
{
	typedef boost::signals2::signal<void (void)> use_display_name_signal_t;

	// Until the cache is set running, immediate lookups will fail and
	// async lookups will be queued.  This allows us to block requests
	// until we know if the first region supports display names.
	void initClass(bool running, bool usePeopleAPI);
	void cleanupClass();

	// Import/export the name cache to file.
	void importFile(std::istream& istr);
	void exportFile(std::ostream& ostr);

	// On the viewer, usually a simulator capabilitity.
	// If empty, name cache will fall back to using legacy name lookup system.
	void setNameLookupURL(const std::string& name_lookup_url);

	// Do we have a valid lookup URL, i.e. are we trying to use the
	// more recent display name lookup system?
	bool hasNameLookupURL();
	bool usePeopleAPI();
	
	// Periodically makes a batch request for display names not already in
	// cache. Called once per frame.
	void idle();

	// If name is in cache, returns true and fills in provided LLAvatarName
	// otherwise returns false.
	bool get(const LLUUID& agent_id, LLAvatarName *av_name);

	// Callback types for get() below
	typedef boost::signals2::signal<
		void (const LLUUID& agent_id, const LLAvatarName& av_name)>
			callback_signal_t;
	typedef callback_signal_t::slot_type callback_slot_t;
	typedef boost::signals2::connection callback_connection_t;

	// Fetches name information and calls callbacks.
	// If name information is in cache, callbacks will be called immediately.
	callback_connection_t get(const LLUUID& agent_id, callback_slot_t slot);

	// Set display name: flips the switch and triggers the callbacks.
	void setUseDisplayNames(bool use);
	
	void insert(const LLUUID& agent_id, const LLAvatarName& av_name);
	void erase(const LLUUID& agent_id);

    /// Provide some fallback for agents that return errors.
	void handleAgentError(const LLUUID& agent_id);

	// Compute name expiration time from HTTP Cache-Control header,
	// or return default value, in seconds from epoch.
	F64 nameExpirationFromHeaders(const LLSD& headers);

	void addUseDisplayNamesCallback(const use_display_name_signal_t::slot_type& cb);
}

// Parse a cache-control header to get the max-age delta-seconds.
// Returns true if header has max-age param and it parses correctly.
// Exported here to ease unit testing.
bool max_age_from_cache_control(const std::string& cache_control, S32 *max_age);

#endif