//
// TCPServer.h
//
// Library: Net
// Package: TCPServer
// Module:  TCPServer
//
// Definition of the TCPServer class.
//
// Copyright (c) 2005-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef Net_TCPServer_INCLUDED
#define Net_TCPServer_INCLUDED


#include "Poco/Net/Net.h"
#include "Poco/Net/ServerSocket.h"
#include "Poco/Net/TCPServerConnectionFactory.h"
#include "Poco/Net/TCPServerParams.h"
#include "Poco/RefCountedObject.h"
#include "Poco/AutoPtr.h"
#include "Poco/Runnable.h"
#include "Poco/Thread.h"
#include "Poco/ThreadPool.h"
#include <atomic>


namespace Poco {
namespace Net {


class TCPServerDispatcher;
class StreamSocket;


class Net_API TCPServerConnectionFilter: public Poco::RefCountedObject
	/// A TCPServerConnectionFilter can be used to reject incoming connections
	/// before passing them on to the TCPServerDispatcher and
	/// starting a thread to handle them.
	///
	/// An example use case is white-list or black-list IP address filtering.
	///
	/// Subclasses must override the accept() method.
{
public:
	using Ptr = Poco::AutoPtr<TCPServerConnectionFilter>;

	virtual bool accept(const StreamSocket& socket) = 0;
		/// Returns true if the given StreamSocket connection should
		/// be handled, and passed on to the TCPServerDispatcher.
		///
		/// Returns false if the socket should be closed immediately.
		///
		/// The socket can be prevented from being closed immediately
		/// if false is returned by creating a copy of the socket.
		/// This can be used to handle certain socket connections in
		/// a special way, outside the TCPServer framework.

protected:
	virtual ~TCPServerConnectionFilter();
};


class Net_API TCPServer: public Poco::Runnable
	/// This class implements a multithreaded TCP server.
	///
	/// The server uses a ServerSocket to listen for incoming
	/// connections. The ServerSocket must have been bound to
	/// an address before it is passed to the TCPServer constructor.
	/// Additionally, the ServerSocket must be put into listening
	/// state before the TCPServer is started by calling the start()
	/// method.
	///
	/// The server uses a thread pool to assign threads to incoming
	/// connections. Before incoming connections are assigned to
	/// a connection thread, they are put into a queue.
	/// Connection threads fetch new connections from the queue as soon
	/// as they become free. Thus, a connection thread may serve more
	/// than one connection.
	///
	/// As soon as a connection thread fetches the next connection from
	/// the queue, it creates a TCPServerConnection object for it
	/// (using the TCPServerConnectionFactory passed to the constructor)
	/// and calls the TCPServerConnection's start() method. When the
	/// start() method returns, the connection object is deleted.
	///
	/// The number of connection threads is adjusted dynamically, depending
	/// on the number of connections waiting to be served.
	///
	/// It is possible to specify a maximum number of queued connections.
	/// This prevents the connection queue from overflowing in the
	/// case of an extreme server load. In such a case, connections that
	/// cannot be queued are silently and immediately closed.
	///
	/// TCPServer uses a separate thread to accept incoming connections.
	/// Thus, the call to start() returns immediately, and the server
	/// continues to run in the background.
	///
	/// To stop the server from accepting new connections, call stop().
	///
	/// After calling stop(), no new connections will be accepted and
	/// all queued connections will be discarded.
	/// Already served connections, however, will continue being served.
{
public:
	TCPServer(TCPServerConnectionFactory::Ptr pFactory, Poco::UInt16 portNumber = 0, TCPServerParams::Ptr pParams = 0);
		/// Creates the TCPServer, with ServerSocket listening on the given port.
		/// Default port is zero, allowing any available port. The port number
		/// can be queried through TCPServer::port() member.
		///
		/// The server takes ownership of the TCPServerConnectionFactory
		/// and deletes it when it's no longer needed.
		///
		/// The server also takes ownership of the TCPServerParams object.
		/// If no TCPServerParams object is given, the server's TCPServerDispatcher
		/// creates its own one.
		///
		/// New threads are taken from the default thread pool.

	TCPServer(TCPServerConnectionFactory::Ptr pFactory, const ServerSocket& socket, TCPServerParams::Ptr pParams = 0);
		/// Creates the TCPServer, using the given ServerSocket.
		///
		/// The server takes ownership of the TCPServerConnectionFactory
		/// and deletes it when it's no longer needed.
		///
		/// The server also takes ownership of the TCPServerParams object.
		/// If no TCPServerParams object is given, the server's TCPServerDispatcher
		/// creates its own one.
		///
		/// New threads are taken from the default thread pool.

	TCPServer(TCPServerConnectionFactory::Ptr pFactory, Poco::ThreadPool& threadPool, const ServerSocket& socket, TCPServerParams::Ptr pParams = 0);
		/// Creates the TCPServer, using the given ServerSocket.
		///
		/// The server takes ownership of the TCPServerConnectionFactory
		/// and deletes it when it's no longer needed.
		///
		/// The server also takes ownership of the TCPServerParams object.
		/// If no TCPServerParams object is given, the server's TCPServerDispatcher
		/// creates its own one.
		///
		/// New threads are taken from the given thread pool.

	virtual ~TCPServer();
		/// Destroys the TCPServer and its TCPServerConnectionFactory.

	const TCPServerParams& params() const;
		/// Returns a const reference to the TCPServerParam object
		/// used by the server's TCPServerDispatcher.

	void start();
		/// Starts the server. A new thread will be
		/// created that waits for and accepts incoming
		/// connections.
		///
		/// Before start() is called, the ServerSocket passed to
		/// TCPServer must have been bound and put into listening state.

	void stop();
		/// Stops the server.
		///
		/// No new connections will be accepted.
		/// Already handled connections will continue to be served.
		///
		/// Once the server has been stopped, it cannot be restarted.

	int currentThreads() const;
		/// Returns the number of currently used connection threads.

	int maxThreads() const;
		/// Returns the maximum number of threads available.

	int totalConnections() const;
		/// Returns the total number of handled connections.

	int currentConnections() const;
		/// Returns the number of currently handled connections.

	int maxConcurrentConnections() const;
		/// Returns the maximum number of concurrently handled connections.

	int queuedConnections() const;
		/// Returns the number of queued connections.

	int refusedConnections() const;
		/// Returns the number of refused connections.

	const ServerSocket& socket() const;
		/// Returns the underlying server socket.

	Poco::UInt16 port() const;
		/// Returns the port the server socket listens on.

	void setConnectionFilter(const TCPServerConnectionFilter::Ptr& pFilter);
		/// Sets a TCPServerConnectionFilter. Can also be used to remove
		/// a filter by passing a null pointer.
		///
		/// To avoid a potential race condition, the filter must
		/// be set before the TCPServer is started. Trying to set
		/// the filter after start() has been called will trigger
		/// an assertion.

	TCPServerConnectionFilter::Ptr getConnectionFilter() const;
		/// Returns the TCPServerConnectionFilter set with setConnectionFilter(),
		/// or null pointer if no filter has been set.

protected:
	void run();
		/// Runs the server. The server will run until
		/// the stop() method is called, or the server
		/// object is destroyed, which implicitly calls
		/// the stop() method.

	static std::string threadName(const ServerSocket& socket);
		/// Returns a thread name for the server thread.

private:
	TCPServer();
	TCPServer(const TCPServer&);
	TCPServer& operator = (const TCPServer&);

	ServerSocket _socket;
	TCPServerDispatcher* _pDispatcher;
	TCPServerConnectionFilter::Ptr _pConnectionFilter;
	Poco::Thread _thread;
	std::atomic<bool> _stopped;
};


//
// inlines
//
inline const ServerSocket& TCPServer::socket() const
{
	return _socket;
}


inline Poco::UInt16 TCPServer::port() const
{
	return _socket.address().port();
}


inline TCPServerConnectionFilter::Ptr TCPServer::getConnectionFilter() const
{
	return _pConnectionFilter;
}


} } // namespace Poco::Net


#endif // Net_TCPServer_INCLUDED