// [License]
// The Ariba-Underlay Copyright
//
// Copyright (c) 2008-2009, Institute of Telematics, Universität Karlsruhe (TH)
//
// Institute of Telematics
// Universität Karlsruhe (TH)
// Zirkel 2, 76128 Karlsruhe
// Germany
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE INSTITUTE OF TELEMATICS ``AS IS'' AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE ARIBA PROJECT OR
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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// The views and conclusions contained in the software and documentation
// are those of the authors and should not be interpreted as representing
// official policies, either expressed or implied, of the Institute of
// Telematics.
// [License]

#include "ariba/overlay/BaseOverlay.h"
#include "ariba/overlay/messages/OverlayMsg.h"

#include "Chord.h"
#include "detail/chord_routing_table.hpp"

//#include "messages/Discovery.h"  // XXX DEPRECATED

namespace ariba {
namespace overlay {

enum signalMessageTypes {
	typeDiscovery = OverlayMsg::typeSignalingStart + 0x01,
	typeLeave = OverlayMsg::typeSignalingStart + 0x02,
};

typedef chord_routing_table::item route_item;

using ariba::transport::system_priority;

use_logging_cpp( Chord );


////// Messages
struct DiscoveryMessage
{
    /**
     * DiscoveryMessage
     * - type
     * - data
     * - Endpoint
     */

    // type enum
    enum type_ {
        invalid = 0,
        normal = 1,
        successor = 2,
        predecessor = 3
    };

    
    // data
    uint8_t type;
    uint8_t ttl;
    EndpointDescriptor endpoint;

    // serialize
    reboost::message_t serialize()
    {
        // serialize endpoint
        reboost::message_t msg = endpoint.serialize();
        
        // serialize type and ttl
        uint8_t* buff1 = msg.push_front(2*sizeof(uint8_t)).mutable_data();
        buff1[0] = type;
        buff1[1] = ttl;
        
        return msg;
    }
    
    //deserialize
    reboost::shared_buffer_t deserialize(reboost::shared_buffer_t buff)
    {
        // deserialize type and ttl
        const uint8_t* bytes = buff.data();
        type = bytes[0];
        ttl = bytes[1];
        
        // deserialize endpoint
        return endpoint.deserialize(buff(2*sizeof(uint8_t)));
    }
};


Chord::Chord(BaseOverlay& _baseoverlay, const NodeID& _nodeid,
		OverlayStructureEvents* _eventsReceiver, const OverlayParameterSet& param) :
	OverlayInterface(_baseoverlay, _nodeid, _eventsReceiver, param) {

	// create routing table
	this->table = new chord_routing_table(_nodeid, 4);
	orphan_removal_counter = 0;
	discovery_count = 0;
	stabilize_counter = 0;
	stabilize_finger = 0;
}

Chord::~Chord() {

	// delete routing table
	delete table;
}

/// helper: sets up a link using the base overlay
LinkID Chord::setup(const EndpointDescriptor& endpoint, const NodeID& remote ) {

	// check if we already have a connection
	for (size_t i=0; i<table->size(); i++)
		if ((*table)[i]->ref_count > 0 && (*table)[i]->id == remote && !((*table)[i]->info.isUnspecified()))
			return LinkID::UNSPECIFIED;

	// check if we are already trying to establish a link
	for (size_t i=0; i<pending.size(); i++)
		if ( pending[i] == remote ) {
			logging_debug("Already trying to establish a link to node "
				<< remote.toString() );
			return LinkID::UNSPECIFIED;
		}

	// adding node to list of pending connections
	pending.push_back( remote );

	logging_info("Request to setup link to " << endpoint.toString() );

	// establish link via base overlay
	return baseoverlay.establishLink( endpoint, remote,
			OverlayInterface::OVERLAY_SERVICE_ID );
}

/// helper: sends a message using the "base overlay"
void Chord::send( OverlayMsg* msg, const LinkID& link ) {
	if (link.isUnspecified())
        return;
    
	baseoverlay.send_link( msg, link, system_priority::OVERLAY );
}

void Chord::send_node( OverlayMsg* message, const NodeID& remote )
{
    try
    {
        baseoverlay.send( message, remote, system_priority::OVERLAY );
    }
    catch ( message_not_sent& e )
    {
        logging_warn("Chord: Could not send message to " << remote
                << ": " << e.what());
    }
}

/// sends a discovery message
void Chord::send_discovery_to(const NodeID& remote, int ttl) {
	LinkID link = getNextLinkId(remote);
	if ( remote == nodeid || link.isUnspecified()) return;
	if ( table->size() == 0 ) return;
	ttl = 2;

	OverlayMsg msg( typeDiscovery );
	msg.setRegisterRelay(true);
	
	// create DiscoveryMessage
	DiscoveryMessage dmsg;
	dmsg.type = DiscoveryMessage::normal;
	dmsg.ttl = ttl;
	dmsg.endpoint = baseoverlay.getEndpointDescriptor();

	msg.set_payload_message(dmsg.serialize());

	// send to node
    try
    {
        baseoverlay.send_node( &msg, remote, system_priority::OVERLAY );
    }
    catch ( message_not_sent& e )
    {
        logging_warn("Chord: Could not send message to " << remote
                << ": " << e.what());
    }
}

void Chord::discover_neighbors( const LinkID& link ) {
	uint8_t ttl = 1;
	
    // FIXME try-catch for the send operations
    
    // create DiscoveryMessage
    DiscoveryMessage dmsg;
    dmsg.ttl = ttl;
    dmsg.endpoint = baseoverlay.getEndpointDescriptor();
	{
		// send predecessor discovery
		OverlayMsg msg( typeDiscovery );
		msg.setRegisterRelay(true);

		// set type
	    dmsg.type = DiscoveryMessage::predecessor;

	    // send
	    msg.set_payload_message(dmsg.serialize());
		send(&msg, link);
	}
	{
		// send successor discovery
		OverlayMsg msg( typeDiscovery );
//		msg.setSourceEndpoint( baseoverlay.getEndpointDescriptor() );  // XXX this was redundand, wasn't it?
		msg.setRegisterRelay(true);

		// set type
        dmsg.type = DiscoveryMessage::successor;

        // send
        msg.set_payload_message(dmsg.serialize());
		send(&msg, link);
	}
}


void Chord::createOverlay() {
}

void Chord::deleteOverlay() {

}

void Chord::joinOverlay(const EndpointDescriptor& boot) {
	logging_info( "joining Chord overlay structure through end-point " <<
			(boot.isUnspecified() ? "local" : boot.toString()) );

	// initiator? no->setup first link
	if (!boot.isUnspecified())
		bootstrapLinks.push_back( setup(boot) );

	// timer for stabilization management
//	Timer::setInterval(1000);  // TODO find an appropriate interval!
	Timer::setInterval(10000);  // XXX testing...
	Timer::start();
}

void Chord::leaveOverlay() {
	Timer::stop();
	for (size_t i = 0; i < table->size(); i++) {
		route_item* it = (*table)[i];
		OverlayMsg msg( typeLeave );
		send( &msg, it->info );
	}
}

/// @see OverlayInterface.h
const EndpointDescriptor& Chord::resolveNode(const NodeID& node) {
	const route_item* item = table->get(node);
	if (item == NULL || item->info.isUnspecified()) return EndpointDescriptor::UNSPECIFIED();
	return baseoverlay.getEndpointDescriptor(item->info);
}

/// @see OverlayInterface.h
bool Chord::isClosestNodeTo( const NodeID& node ) {
	return table->is_closest_to(node);
}

/// @see OverlayInterface.h
const LinkID& Chord::getNextLinkId( const NodeID& id ) const {
	// get next hop
	const route_item* item = table->get_next_hop(id);

	// returns a unspecified id when this is itself
	if (item == NULL || item->id == nodeid)
		return LinkID::UNSPECIFIED;

	/// return routing info
	return item->info;
}

std::vector<const LinkID*> Chord::getSortedLinkIdsTowardsNode(
    const NodeID& id, int num ) const
{
    std::vector<const LinkID*> ret;
    
    switch ( num )
    {
        // special case: just call »getNextLinkId«
        case 1:
        {
            ret.push_back(&getNextLinkId(id));
            
            break;
        }
        
        // * calculate top 2 *
        case 0:
        case 2:
        {
            std::vector<const route_item*> items = table->get_next_2_hops(id);
            
            ret.reserve(items.size());
            
            BOOST_FOREACH( const route_item* item, items )
            {
                ret.push_back(&item->info);
            }
            
            break;
        }
        
        // NOTE: implement real sorting, if needed (and handle "case 0" properly, then)
        default:
        {
            throw std::runtime_error("Not implemented. (Chord::getSortedLinkIdsTowardsNode with num != 2)");
            
            break;
        }
    }
    
    return ret;
}


/// @see OverlayInterface.h
const NodeID& Chord::getNextNodeId( const NodeID& id ) const {
	// get next hop
	const route_item* item = table->get_next_hop(id);
	
	// return unspecified if no next hop could be found
	if (item == NULL) {
		return NodeID::UNSPECIFIED;
	}
	
	return item->id;
}

OverlayInterface::NodeList Chord::getKnownNodes(bool deep) const {
	OverlayInterface::NodeList nodelist;

	if( deep ){
		// all nodes that I know, fingers, succ/pred
		for (size_t i = 0; i < table->size(); i++){
			if ((*table)[i]->ref_count != 0
					&& !(*table)[i]->info.isUnspecified())
				nodelist.push_back((*table)[i]->id);
		}
	} else {
		// only succ and pred
		if( table->get_predesessor() != NULL ){
			nodelist.push_back( *(table->get_predesessor()) );
		}
		if( table->get_successor() != NULL ){
			OverlayInterface::NodeList::iterator i =
				std::find( nodelist.begin(), nodelist.end(), *(table->get_successor()) );
			if( i == nodelist.end() )
				nodelist.push_back( *(table->get_successor()) );
		}
	}

	return nodelist;
}

/// @see CommunicationListener.h
/// @see OverlayInterface.h
void Chord::onLinkUp(const LinkID& lnk, const NodeID& remote) {
	logging_info("link_up: link=" << lnk.toString() << " remote=" <<
			remote.toString() );
	for (vector<NodeID>::iterator i=pending.begin(); i!=pending.end(); i++)
		if (*i == remote) {
			pending.erase(i);
			break;
		}

	if (remote==nodeid) {
		logging_warn("dropping link that has been established to myself (nodes have same nodeid?)");
		logging_warn("NodeID: " << remote);
		baseoverlay.dropLink(lnk);
		return;
	}

	route_item* item = table->insert(remote);

	// item added to routing table?
	if (item != NULL) { // yes-> add to routing table
		logging_info("new routing neighbor: " << remote.toString()
				<< " with link " << lnk.toString());

		// replace with new link if link is "better"
		if (item->info!=lnk && item->info.isUnspecified()==false) {
			if (baseoverlay.compare( item->info, lnk ) == 1) {
				logging_info("Replacing link due to concurrent link establishment.");
				baseoverlay.dropLink(item->info);
				item->info = lnk;
			}
		} else {
			item->info = lnk;
		}

		// discover neighbors of new overlay neighbor
		showLinks();
	} else { // no-> add orphan entry to routing table
		logging_info("new orphan: " << remote.toString()
				<< " with link " << lnk.toString());
		table->insert_orphan(remote)->info = lnk;
	}

	// erase bootstrap link
	vector<LinkID>::iterator it = std::find(bootstrapLinks.begin(), bootstrapLinks.end(), lnk);
	if( it != bootstrapLinks.end() ) bootstrapLinks.erase( it );
}

/// @see CommunicationListener.h or @see OverlayInterface.h
void Chord::onLinkDown(const LinkID& lnk, const NodeID& remote) {
    // XXX logging_debug
	logging_info("link_down (Chord): link=" << lnk.toString() << " remote=" <<
			remote.toString() );

	// remove link from routing table
	route_item* item = table->get(remote);
	if (item!=NULL && item->info==lnk) {
		item->info = LinkID::UNSPECIFIED;
		table->remove(remote);
	}
}

/// @see CommunicationListener.h
/// @see OverlayInterface.h
void Chord::onMessage(OverlayMsg* msg,
        reboost::shared_buffer_t sub_msg,
        const NodeID& remote,
		const LinkID& link) {

	// handle messages
	switch ((signalMessageTypes) msg->getType()) {

	// discovery request
	case typeDiscovery:
	{
		// deserialize discovery message
		DiscoveryMessage dmsg;
		dmsg.deserialize(sub_msg);
		
		logging_debug("Received discovery message with"
			    << " src=" << msg->getSourceNode().toString()
				<< " dst=" << msg->getDestinationNode().toString()
				<< " ttl=" << (int)dmsg.ttl
				<< " type=" << (int)dmsg.type
		);

		// add discovery node id
		bool found = false;
		BOOST_FOREACH( NodeID& value, discovery )
			if (value == msg->getSourceNode()) {
				found = true;
				break;
			}
		if (!found) discovery.push_back(msg->getSourceNode());

		// check if source node can be added to routing table and setup link
		if (msg->getSourceNode() != nodeid)
			setup( dmsg.endpoint, msg->getSourceNode() );

		// process discovery message -------------------------- switch start --
		switch ( dmsg.type )
		{
            // normal: route discovery message like every other message
            case DiscoveryMessage::normal:
            {
                // closest node? yes-> split to follow successor and predecessor
                if ( table->is_closest_to(msg->getDestinationNode()) )
                {
                    logging_debug("Discovery split:");
                    if (!table->get_successor()->isUnspecified())
                    {
                        OverlayMsg omsg(*msg);
                        
                        dmsg.type = DiscoveryMessage::successor;
                        omsg.set_payload_message(dmsg.serialize());

                        logging_debug("* Routing to successor "
                                << table->get_successor()->toString() );
                        send_node( &omsg, *table->get_successor() );
                    }
    
                    // send predecessor message
                    if (!table->get_predesessor()->isUnspecified())
                    {
                        OverlayMsg omsg(*msg);
                        
                        dmsg.type = DiscoveryMessage::predecessor;
                        omsg.set_payload_message(dmsg.serialize());

                        logging_debug("* Routing to predecessor "
                                << table->get_predesessor()->toString() );
                        send_node( &omsg, *table->get_predesessor() );
                    }
                }
                // no-> route message
                else
                {
                    baseoverlay.route( msg );
                }
                break;
            }
    
            // successor mode: follow the successor until TTL is zero
            case DiscoveryMessage::successor:
            case DiscoveryMessage::predecessor:
            {
                // reached destination? no->forward!
                if (msg->getDestinationNode() != nodeid)
                {
                    OverlayMsg omsg(*msg);
                    omsg.setService(OverlayInterface::OVERLAY_SERVICE_ID);
                    
                    omsg.set_payload_message(dmsg.serialize());
                    
                    baseoverlay.route( &omsg );
                    break;
                }
    
                // time to live ended? yes-> stop routing
                if (dmsg.ttl == 0 || dmsg.ttl > 10) break;
    
                // decrease time-to-live
                dmsg.ttl--;
    
                const route_item* item = NULL;
                if (dmsg.type == DiscoveryMessage::successor &&
                        table->get_successor() != NULL)
                {
                    item = table->get(*table->get_successor());
                }
                else if (table->get_predesessor() != NULL)
                {
                        item = table->get(*table->get_predesessor());
                }
                if (item == NULL)
                    break;
    
                logging_debug("Routing discovery message to succ/pred "
                    << item->id.toString() );
                OverlayMsg omsg(*msg);
                omsg.setService(OverlayInterface::OVERLAY_SERVICE_ID);
                omsg.setDestinationNode(item->id);
                
                omsg.set_payload_message(dmsg.serialize());
                
                send_node( &omsg, omsg.getDestinationNode() );
                break;
            }
            case DiscoveryMessage::invalid:
                break;
    
            default:
                break;
            }
            // process discovery message ---------------------------- switch end --
    
            break;
        }
    
        // leave
        case typeLeave: {
            if (link!=LinkID::UNSPECIFIED) {
                route_item* item = table->get(remote);
                if (item!=NULL) item->info = LinkID::UNSPECIFIED;
                table->remove(remote);
                baseoverlay.dropLink(link);
            }
            break;
        }
	}
}

void Chord::eventFunction() {
	stabilize_counter++;
	if (stabilize_counter < 0 || stabilize_counter == 2) {

		// reset counter
		stabilize_counter = 0;

		// clear pending connections
		pending.clear();

		// get number of real neighbors
		size_t numNeighbors = 0;
		for (size_t i = 0; i < table->size(); i++) {
			route_item* it = (*table)[i];
			if (it->ref_count != 0 && !it->info.isUnspecified()) numNeighbors++;
		}
		logging_info("Running stabilization: #links="
				<< table->size() << " #neighbors=" << numNeighbors );

		// updating neighbors
		logging_debug("Discover new ring neighbors");
		for (size_t i=0; i<table->size(); i++) {
			LinkID id = (*table)[i]->info;
			if (!id.isUnspecified()) discover_neighbors(id);
		}

		// sending discovery
		logging_debug("Sending discovery message to my neighbors and fingers");
		stabilize_finger = ((stabilize_finger+1) % table->get_finger_table_size() );
		const NodeID disc = table->get_finger_table(stabilize_finger).get_compare().get_center();
		if (disc != nodeid)
			send_discovery_to(disc);

		// remove orphan links
		orphan_removal_counter++;
		if (orphan_removal_counter <0 || orphan_removal_counter >= 2) {
			logging_info("Discovered nodes: ");
			BOOST_FOREACH( NodeID& id, discovery )
				logging_info("* " << id.toString());
			discovery.clear();
			logging_info("Running orphan removal");
			orphan_removal_counter = 0;
			for (size_t i = 0; i < table->size(); i++) {
				route_item* it = (*table)[i];
				if (it->ref_count == 0 && !it->info.isUnspecified()) {
					logging_info("Dropping orphaned link " << it->info.toString() << " to " << it->id.toString());
					table->insert(it->id);
					if (it->ref_count==0) {
						LinkID id = it->info;
						it->info = LinkID::UNSPECIFIED;
						baseoverlay.dropLink(id);
					}
				}
			}
		}
	}
}

void Chord::showLinks() {
	logging_info("--- chord routing information ----------------------------------");
	logging_info("predecessor: " << (table->get_predesessor()==NULL? "<none>" :
		table->get_predesessor()->toString()) );
	logging_info("node_id    : " << nodeid.toString() );
	logging_info("successor  : " << (table->get_successor()==NULL? "<none>" :
		table->get_successor()->toString()));
	logging_info("----------------------------------------------------------------");
}

/// @see OverlayInterface.h
std::string Chord::debugInformation() const {
	std::ostringstream s;
	s << "protocol   : Chord" << endl;
	s << "node_id    : " << nodeid.toString() << endl;
	s << "predecessor: " << (table->get_predesessor()==NULL? "<none>" :
		table->get_predesessor()->toString()) << endl;
	s << "successor  : " << (table->get_successor()==NULL? "<none>" :
		table->get_successor()->toString()) << endl;
	s << "nodes: " << endl;
	for (size_t i = 0; i < table->size(); i++) {
		route_item* it = (*table)[i];
		if (it->ref_count != 0 && !it->info.isUnspecified()) {
			s << it->id.toString().substr(0,6)
			  << " using " << it->info.toString().substr(0,6) << endl;
		}
	}
	return s.str();
}



}} // namespace ariba, overlay