#include "i2-discovery.h"

using namespace icinga;

/**
 * GetName
 *
 * Returns the name of this component.
 *
 * @returns The name.
 */
string DiscoveryComponent::GetName(void) const
{
	return "discoverycomponent";
}

/**
 * Start
 *
 * Starts the discovery component.
 */
void DiscoveryComponent::Start(void)
{
	m_DiscoveryEndpoint = make_shared<VirtualEndpoint>();

	long isBroker = 0;
	GetConfig()->GetPropertyInteger("broker", &isBroker);
	m_Broker = (isBroker != 0);

	if (IsBroker()) {
		m_DiscoveryEndpoint->RegisterMethodSource("discovery::NewComponent");
		m_DiscoveryEndpoint->RegisterMethodHandler("discovery::RegisterComponent",
			bind_weak(&DiscoveryComponent::RegisterComponentMessageHandler, shared_from_this()));
	}

	m_DiscoveryEndpoint->RegisterMethodSource("discovery::RegisterComponent");
	m_DiscoveryEndpoint->RegisterMethodHandler("discovery::NewComponent",
		bind_weak(&DiscoveryComponent::NewComponentMessageHandler, shared_from_this()));
	m_DiscoveryEndpoint->RegisterMethodHandler("discovery::Welcome",
		bind_weak(&DiscoveryComponent::WelcomeMessageHandler, shared_from_this()));

	GetEndpointManager()->ForEachEndpoint(bind(&DiscoveryComponent::NewEndpointHandler, this, _1));
	GetEndpointManager()->OnNewEndpoint += bind_weak(&DiscoveryComponent::NewEndpointHandler, shared_from_this());

	GetEndpointManager()->RegisterEndpoint(m_DiscoveryEndpoint);

	/* create the reconnect timer */
	m_DiscoveryTimer = make_shared<Timer>();
	m_DiscoveryTimer->SetInterval(30);
	m_DiscoveryTimer->OnTimerExpired += bind_weak(&DiscoveryComponent::DiscoveryTimerHandler, shared_from_this());
	m_DiscoveryTimer->Start();
}

/**
 * Stop
 *
 * Stops the discovery component.
 */
void DiscoveryComponent::Stop(void)
{
	EndpointManager::Ptr mgr = GetEndpointManager();

	if (mgr)
		mgr->UnregisterEndpoint(m_DiscoveryEndpoint);
}

/**
 * CheckExistingEndpoint
 *
 * Checks whether the specified endpoint is already connected
 * and disconnects older endpoints.
 *
 * @param endpoint The endpoint that is to be checked.
 * @param neea Event arguments for another endpoint.
 * @returns 0
 */
int DiscoveryComponent::CheckExistingEndpoint(Endpoint::Ptr endpoint, const NewEndpointEventArgs& neea)
{
	if (endpoint == neea.Endpoint)
		return 0;

	if (!neea.Endpoint->IsConnected())
		return 0;

	if (endpoint->GetIdentity() == neea.Endpoint->GetIdentity()) {
		Application::Log("Detected duplicate identity (" + endpoint->GetIdentity() + " - Disconnecting old endpoint.");

		neea.Endpoint->Stop();
		GetEndpointManager()->UnregisterEndpoint(neea.Endpoint);
	}

	return 0;
}

/**
 * NewEndpointHandler
 *
 * Registers handlers for new endpoints.
 *
 * @param neea Event arguments for the new endpoint.
 * @returns 0
 */
int DiscoveryComponent::NewEndpointHandler(const NewEndpointEventArgs& neea)
{
	neea.Endpoint->OnIdentityChanged += bind_weak(&DiscoveryComponent::NewIdentityHandler, shared_from_this());

	if (IsBroker()) {
		/* accept discovery::RegisterComponent messages from any endpoint */
		neea.Endpoint->RegisterMethodSource("discovery::RegisterComponent");
	}

	/* accept discovery::Welcome messages from any endpoint */
	neea.Endpoint->RegisterMethodSource("discovery::Welcome");

	return 0;
}

/**
 * DiscoverySinkHandler
 *
 * Registers a new message sink for a component.
 *
 * @param nmea Event args for the new message sink.
 * @param info The component registration information.
 * @returns 0
 */
int DiscoveryComponent::DiscoverySinkHandler(const NewMethodEventArgs& nmea, ComponentDiscoveryInfo::Ptr info) const
{
	info->SubscribedMethods.insert(nmea.Method);
	return 0;
}

/**
 * DiscoverySourceHandler
 *
 * Registers a new message source for a component.
 *
 * @param nmea Event args for the new message source.
 * @param info The component registration information.
 * @returns 0
 */
int DiscoveryComponent::DiscoverySourceHandler(const NewMethodEventArgs& nmea, ComponentDiscoveryInfo::Ptr info) const
{
	info->PublishedMethods.insert(nmea.Method);
	return 0;
}

/**
 * DiscoveryEndpointHandler
 *
 * Registers message sinks/sources in the specified component information object.
 *
 * @param neea Event arguments for the endpoint.
 * @param info Component information object.
 * @return 0
 */
int DiscoveryComponent::DiscoveryEndpointHandler(const NewEndpointEventArgs& neea, ComponentDiscoveryInfo::Ptr info) const
{
	neea.Endpoint->ForEachMethodSink(bind(&DiscoveryComponent::DiscoverySinkHandler, this, _1, info));
	neea.Endpoint->ForEachMethodSource(bind(&DiscoveryComponent::DiscoverySourceHandler, this, _1, info));
	return 0;
}

/**
 * GetComponentDiscoveryInfo
 *
 * Retrieves the component information object for the specified component.
 *
 * @param component The identity of the component.
 * @param info Pointer to the information object.
 * @returns true if the info object was successfully retrieved, false otherwise.
 */
bool DiscoveryComponent::GetComponentDiscoveryInfo(string component, ComponentDiscoveryInfo::Ptr *info) const
{
	if (component == GetEndpointManager()->GetIdentity()) {
		/* Build fake discovery info for ourselves */
		*info = make_shared<ComponentDiscoveryInfo>();
		GetEndpointManager()->ForEachEndpoint(bind(&DiscoveryComponent::DiscoveryEndpointHandler, this, _1, *info));
		
		(*info)->LastSeen = 0;
		(*info)->Node = GetIcingaApplication()->GetNode();
		(*info)->Service = GetIcingaApplication()->GetService();

		return true;
	}

	map<string, ComponentDiscoveryInfo::Ptr>::const_iterator i;

	i = m_Components.find(component);

	if (i == m_Components.end())
		return false;

	*info = i->second;
	return true;
}

/**
 * IsBroker
 *
 * Returns whether this component is a broker.
 *
 * @returns true if the component is a broker, false otherwise.
 */
bool DiscoveryComponent::IsBroker(void) const
{
	return m_Broker;
}

/**
 * NewIdentityHandler
 *
 * Deals with a new endpoint whose identity has just become known.
 *
 * @param ea Event arguments for the component.
 * @returns 0
 */
int DiscoveryComponent::NewIdentityHandler(const EventArgs& ea)
{
	Endpoint::Ptr endpoint = static_pointer_cast<Endpoint>(ea.Source);
	string identity = endpoint->GetIdentity();

	if (identity == GetEndpointManager()->GetIdentity()) {
		Application::Log("Detected loop-back connection - Disconnecting endpoint.");

		endpoint->Stop();
		GetEndpointManager()->UnregisterEndpoint(endpoint);

		return 0;
	}

	GetEndpointManager()->ForEachEndpoint(bind(&DiscoveryComponent::CheckExistingEndpoint, this, endpoint, _1));

	ConfigCollection::Ptr brokerCollection = GetApplication()->GetConfigHive()->GetCollection("broker");
	if (brokerCollection->GetObject(identity)) {
		/* accept discovery::NewComponent messages from brokers */
		endpoint->RegisterMethodSource("discovery::NewComponent");
	}

	// we assume the other component _always_ wants
	// discovery::RegisterComponent messages from us
	endpoint->RegisterMethodSink("discovery::RegisterComponent");

	// send a discovery::RegisterComponent message, if the
	// other component is a broker this makes sure
	// the broker knows about our message types
	SendDiscoveryMessage("discovery::RegisterComponent", GetEndpointManager()->GetIdentity(), endpoint);

	map<string, ComponentDiscoveryInfo::Ptr>::iterator i;

	if (IsBroker()) {
		// we assume the other component _always_ wants
		// discovery::NewComponent messages from us
		endpoint->RegisterMethodSink("discovery::NewComponent");

		// send discovery::NewComponent message for ourselves
		SendDiscoveryMessage("discovery::NewComponent", GetEndpointManager()->GetIdentity(), endpoint);

		// send discovery::NewComponent messages for all components
		// we know about
		for (i = m_Components.begin(); i != m_Components.end(); i++) {
			SendDiscoveryMessage("discovery::NewComponent", i->first, endpoint);
		}
	}

	// check if we already know the other component
	i = m_Components.find(endpoint->GetIdentity());

	if (i == m_Components.end()) {
		// we don't know the other component yet, so
		// wait until we get a discovery::NewComponent message
		// from a broker
		return 0;
	}

	FinishDiscoverySetup(endpoint);

	return 0;
}

/**
 * WelcomeMessageHandler
 *
 * Processes discovery::Welcome messages.
 *
 * @param nrea Event arguments for the request.
 * @returns 0
 */
int DiscoveryComponent::WelcomeMessageHandler(const NewRequestEventArgs& nrea)
{
	Endpoint::Ptr endpoint = nrea.Sender;

	if (endpoint->GetReceivedWelcome())
		return 0;

	endpoint->SetReceivedWelcome(true);

	if (endpoint->GetSentWelcome()) {
		EventArgs ea;
		ea.Source = shared_from_this();
		endpoint->OnSessionEstablished(ea);
	}

	return 0;
}

/**
 * FinishDiscoverySetup
 *
 * Finishes the welcome handshake for a new component
 * by registering message sinks/sources for the component
 * and sending a welcome message if necessary.
 *
 * @param endpoint The endpoint to set up.
 */
void DiscoveryComponent::FinishDiscoverySetup(Endpoint::Ptr endpoint)
{
	if (endpoint->GetSentWelcome())
		return;

	// we assume the other component _always_ wants
	// discovery::Welcome messages from us
	endpoint->RegisterMethodSink("discovery::Welcome");
	JsonRpcRequest request;
	request.SetMethod("discovery::Welcome");
	GetEndpointManager()->SendUnicastRequest(m_DiscoveryEndpoint, endpoint, request);

	endpoint->SetSentWelcome(true);

	ComponentDiscoveryInfo::Ptr info;

	if (GetComponentDiscoveryInfo(endpoint->GetIdentity(), &info)) {
		set<string>::iterator i;
		for (i = info->PublishedMethods.begin(); i != info->PublishedMethods.end(); i++)
			endpoint->RegisterMethodSource(*i);

		for (i = info->SubscribedMethods.begin(); i != info->SubscribedMethods.end(); i++)
			endpoint->RegisterMethodSink(*i);
	}

	if (endpoint->GetReceivedWelcome()) {
		EventArgs ea;
		ea.Source = shared_from_this();
		endpoint->OnSessionEstablished(ea);
	}
}

/**
 * SendDiscoveryMessage
 *
 * Sends a discovery message for the specified identity using the
 * specified message type.
 *
 * @param method The method to use for the message ("discovery::NewComponent" or "discovery::RegisterComponent").
 * @param identity The identity of the component for which a message should be sent.
 * @param recipient The recipient of the message. A multicast message is sent if this parameter is empty.
 */
void DiscoveryComponent::SendDiscoveryMessage(string method, string identity, Endpoint::Ptr recipient)
{
	JsonRpcRequest request;
	request.SetMethod(method);
	
	DiscoveryMessage params;
	request.SetParams(params);

	params.SetIdentity(identity);

	Message subscriptions;
	params.SetSubscribes(subscriptions);

	Message publications;
	params.SetProvides(publications);

	ComponentDiscoveryInfo::Ptr info;

	if (!GetComponentDiscoveryInfo(identity, &info))
		return;

	if (!info->Node.empty() && !info->Service.empty()) {
		params.SetNode(info->Node);
		params.SetService(info->Service);
	}

	set<string>::iterator i;
	for (i = info->PublishedMethods.begin(); i != info->PublishedMethods.end(); i++)
		publications.AddUnnamedPropertyString(*i);

	for (i = info->SubscribedMethods.begin(); i != info->SubscribedMethods.end(); i++)
		subscriptions.AddUnnamedPropertyString(*i);

	if (recipient)
		GetEndpointManager()->SendUnicastRequest(m_DiscoveryEndpoint, recipient, request);
	else
		GetEndpointManager()->SendMulticastRequest(m_DiscoveryEndpoint, request);
}

/**
 * ProcessDiscoveryMessage
 *
 * Processes a discovery message by registering the component in the
 * discovery component registry.
 *
 * @param identity The authorative identity of the component.
 * @param message The discovery message.
 */
void DiscoveryComponent::ProcessDiscoveryMessage(string identity, DiscoveryMessage message)
{
	/* ignore discovery messages that are about ourselves */
	if (identity == GetEndpointManager()->GetIdentity())
		return;

	ComponentDiscoveryInfo::Ptr info = make_shared<ComponentDiscoveryInfo>();

	time(&(info->LastSeen));

	message.GetNode(&info->Node);
	message.GetService(&info->Service);

	Message provides;
	if (message.GetProvides(&provides)) {
		DictionaryIterator i;
		for (i = provides.GetDictionary()->Begin(); i != provides.GetDictionary()->End(); i++) {
			if (IsBroker()) {
				/* TODO: Add authorisation checks here */
			}
			info->PublishedMethods.insert(i->second);
		}
	}

	Message subscribes;
	if (message.GetSubscribes(&subscribes)) {
		DictionaryIterator i;
		for (i = subscribes.GetDictionary()->Begin(); i != subscribes.GetDictionary()->End(); i++) {
			if (IsBroker()) {
				/* TODO: Add authorisation checks here */
			}
			info->SubscribedMethods.insert(i->second);
		}
	}

	map<string, ComponentDiscoveryInfo::Ptr>::iterator i;

	i  = m_Components.find(identity);

	if (i != m_Components.end())
		m_Components.erase(i);

	m_Components[identity] = info;

	if (IsBroker())
		SendDiscoveryMessage("discovery::NewComponent", identity, Endpoint::Ptr());

	Endpoint::Ptr endpoint = GetEndpointManager()->GetEndpointByIdentity(identity);
	if (endpoint)
		FinishDiscoverySetup(endpoint);
}

/**
 * NewComponentMessageHandler
 *
 * Processes "discovery::NewComponent" messages.
 *
 * @param nrea Event arguments for the request.
 * @returns 0
 */
int DiscoveryComponent::NewComponentMessageHandler(const NewRequestEventArgs& nrea)
{
	DiscoveryMessage message;
	nrea.Request.GetParams(&message);

	string identity;
	if (!message.GetIdentity(&identity))
		return 0;

	ProcessDiscoveryMessage(identity, message);
	return 0;
}

/**
 * RegisterComponentMessageHandler
 *
 * Processes "discovery::RegisterComponent" messages.
 *
 * @param nrea Event arguments for the request.
 * @returns 0
 */
int DiscoveryComponent::RegisterComponentMessageHandler(const NewRequestEventArgs& nrea)
{
	/* ignore discovery::RegisterComponent messages when we're not a broker */
	if (!IsBroker())
		return 0;

	DiscoveryMessage message;
	nrea.Request.GetParams(&message);
	ProcessDiscoveryMessage(nrea.Sender->GetIdentity(), message);

	return 0;
}

/**
 * BrokerConfigHandler
 *
 * Processes "broker" config objects.
 *
 * @param ea Event arguments for the new config object.
 * @returns 0
 */
int DiscoveryComponent::BrokerConfigHandler(const EventArgs& ea)
{
	ConfigObject::Ptr object = static_pointer_cast<ConfigObject>(ea.Source);

	EndpointManager::Ptr endpointManager = GetEndpointManager();

	/* Check if we're already connected to this broker. */
	if (endpointManager->GetEndpointByIdentity(object->GetName()))
		return 0;

	string node;
	if (!object->GetPropertyString("node", &node))
		throw InvalidArgumentException("'node' property required for 'broker' config object.");

	string service;
	if (!object->GetPropertyString("service", &service))
		throw InvalidArgumentException("'service' property required for 'broker' config object.");

	/* reconnect to this broker */
	endpointManager->AddConnection(node, service);

	return 0;
}

/**
 * DiscoveryTimerHandler
 *
 * Checks whether we have to reconnect to other components and removes stale
 * components from the registry.
 *
 * @param tea Event arguments for the timer.
 * @returns 0
 */
int DiscoveryComponent::DiscoveryTimerHandler(const TimerEventArgs& tea)
{
	EndpointManager::Ptr endpointManager = GetEndpointManager();
	
	time_t now;
	time(&now);

	/* check whether we have to reconnect to one of our upstream brokers */
	ConfigCollection::Ptr brokerCollection = GetApplication()->GetConfigHive()->GetCollection("broker");
	brokerCollection->ForEachObject(bind(&DiscoveryComponent::BrokerConfigHandler, this, _1));

	map<string, ComponentDiscoveryInfo::Ptr>::iterator i;
	for (i = m_Components.begin(); i != m_Components.end(); ) {
		string identity = i->first;
		ComponentDiscoveryInfo::Ptr info = i->second;

		if (info->LastSeen < now - DiscoveryComponent::RegistrationTTL) {
			/* unregister this component if its registration has expired */
			i = m_Components.erase(i);
			continue;
		}

		if (IsBroker()) {
			/* send discovery message to all connected components to
			   refresh their TTL for this component */
			SendDiscoveryMessage("discovery::NewComponent", i->first, Endpoint::Ptr());
		}

		Endpoint::Ptr endpoint = endpointManager->GetEndpointByIdentity(identity);
		if (endpoint && endpoint->IsConnected()) {
			/* update LastSeen if we're still connected to this endpoint */
			info->LastSeen = now;
		} else {
			/* TODO: figure out whether we actually want to connect to this component (_always_ if IsBroker() == true) */
			/* try and reconnect to this component */
			endpointManager->AddConnection(info->Node, info->Service);
		}

		i++;
	}

	return 0;
}

EXPORT_COMPONENT(DiscoveryComponent);