olcPixelGameEngine/Videos/Networking/Parts1&2/net_server.h

/*
	MMO Client/Server Framework using ASIO
	"Happy Birthday Mrs Javidx9!" - javidx9

	Videos:
	Part #1: https://youtu.be/2hNdkYInj4g
	Part #2: https://youtu.be/UbjxGvrDrbw

	License (OLC-3)
	~~~~~~~~~~~~~~~

	Copyright 2018 - 2020 OneLoneCoder.com

	Redistribution and use in source and binary forms, with or without
	modification, are permitted provided that the following conditions
	are met:

	1. Redistributions or derivations of source code must retain the above
	copyright notice, this list of conditions and the following disclaimer.

	2. Redistributions or derivative works in binary form must reproduce
	the above copyright notice. This list of conditions and the following
	disclaimer must be reproduced in the documentation and/or other
	materials provided with the distribution.

	3. Neither the name of the copyright holder nor the names of its
	contributors may be used to endorse or promote products derived
	from this software without specific prior written permission.

	THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	"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 COPYRIGHT
	HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	Links
	~~~~~
	YouTube:	https://www.youtube.com/javidx9
	Discord:	https://discord.gg/WhwHUMV
	Twitter:	https://www.twitter.com/javidx9
	Twitch:		https://www.twitch.tv/javidx9
	GitHub:		https://www.github.com/onelonecoder
	Homepage:	https://www.onelonecoder.com

	Author
	~~~~~~
	David Barr, aka javidx9, <20>OneLoneCoder 2019, 2020

*/

#pragma once

#include "net_common.h"
#include "net_tsqueue.h"
#include "net_message.h"
#include "net_connection.h"

namespace olc
{
	namespace net
	{
		template<typename T>
		class server_interface
		{
		public:
			// Create a server, ready to listen on specified port
			server_interface(uint16_t port)
				: m_asioAcceptor(m_asioContext, asio::ip::tcp::endpoint(asio::ip::tcp::v4(), port))
			{

			}

			virtual ~server_interface()
			{
				// May as well try and tidy up
				Stop();
			}

			// Starts the server!
			bool Start()
			{
				try
				{
					// Issue a task to the asio context - This is important
					// as it will prime the context with "work", and stop it
					// from exiting immediately. Since this is a server, we 
					// want it primed ready to handle clients trying to
					// connect.
					WaitForClientConnection();

					// Launch the asio context in its own thread
					m_threadContext = std::thread([this]() { m_asioContext.run(); });
				}
				catch (std::exception& e)
				{
					// Something prohibited the server from listening
					std::cerr << "[SERVER] Exception: " << e.what() << "\n";
					return false;
				}

				std::cout << "[SERVER] Started!\n";
				return true;
			}

			// Stops the server!
			void Stop()
			{
				// Request the context to close
				m_asioContext.stop();

				// Tidy up the context thread
				if (m_threadContext.joinable()) m_threadContext.join();

				// Inform someone, anybody, if they care...
				std::cout << "[SERVER] Stopped!\n";
			}

			// ASYNC - Instruct asio to wait for connection
			void WaitForClientConnection()
			{
				// Prime context with an instruction to wait until a socket connects. This
				// is the purpose of an "acceptor" object. It will provide a unique socket
				// for each incoming connection attempt
				m_asioAcceptor.async_accept(
					[this](std::error_code ec, asio::ip::tcp::socket socket)
					{
						// Triggered by incoming connection request
						if (!ec)
						{
							// Display some useful(?) information
							std::cout << "[SERVER] New Connection: " << socket.remote_endpoint() << "\n";

							// Create a new connection to handle this client 
							std::shared_ptr<connection<T>> newconn = 
								std::make_shared<connection<T>>(connection<T>::owner::server, 
									m_asioContext, std::move(socket), m_qMessagesIn);
							
							

							// Give the user server a chance to deny connection
							if (OnClientConnect(newconn))
							{								
								// Connection allowed, so add to container of new connections
								m_deqConnections.push_back(std::move(newconn));

								// And very important! Issue a task to the connection's
								// asio context to sit and wait for bytes to arrive!
								m_deqConnections.back()->ConnectToClient(nIDCounter++);

								std::cout << "[" << m_deqConnections.back()->GetID() << "] Connection Approved\n";
							}
							else
							{
								std::cout << "[-----] Connection Denied\n";

								// Connection will go out of scope with no pending tasks, so will
								// get destroyed automagically due to the wonder of smart pointers
							}
						}
						else
						{
							// Error has occurred during acceptance
							std::cout << "[SERVER] New Connection Error: " << ec.message() << "\n";
						}

						// Prime the asio context with more work - again simply wait for
						// another connection...
						WaitForClientConnection();
					});
			}

			// Send a message to a specific client
			void MessageClient(std::shared_ptr<connection<T>> client, const message<T>& msg)
			{
				// Check client is legitimate...
				if (client && client->IsConnected())
				{
					// ...and post the message via the connection
					client->Send(msg);
				}
				else
				{
					// If we cant communicate with client then we may as 
					// well remove the client - let the server know, it may
					// be tracking it somehow
					OnClientDisconnect(client);

					// Off you go now, bye bye!
					client.reset();

					// Then physically remove it from the container
					m_deqConnections.erase(
						std::remove(m_deqConnections.begin(), m_deqConnections.end(), client), m_deqConnections.end());
				}
			}
			
			// Send message to all clients
			void MessageAllClients(const message<T>& msg, std::shared_ptr<connection<T>> pIgnoreClient = nullptr)
			{
				bool bInvalidClientExists = false;

				// Iterate through all clients in container
				for (auto& client : m_deqConnections)
				{
					// Check client is connected...
					if (client && client->IsConnected())
					{
						// ..it is!
						if(client != pIgnoreClient)
							client->Send(msg);
					}
					else
					{
						// The client couldnt be contacted, so assume it has
						// disconnected.
						OnClientDisconnect(client);
						client.reset();

						// Set this flag to then remove dead clients from container
						bInvalidClientExists = true;
					}
				}

				// Remove dead clients, all in one go - this way, we dont invalidate the
				// container as we iterated through it.
				if (bInvalidClientExists)
					m_deqConnections.erase(
						std::remove(m_deqConnections.begin(), m_deqConnections.end(), nullptr), m_deqConnections.end());
			}

			// Force server to respond to incoming messages
			void Update(size_t nMaxMessages = -1, bool bWait = false)
			{
				if (bWait) m_qMessagesIn.wait();

				// Process as many messages as you can up to the value
				// specified
				size_t nMessageCount = 0;
				while (nMessageCount < nMaxMessages && !m_qMessagesIn.empty())
				{
					// Grab the front message
					auto msg = m_qMessagesIn.pop_front();

					// Pass to message handler
					OnMessage(msg.remote, msg.msg);

					nMessageCount++;
				}
			}

		protected:
			// This server class should override thse functions to implement
			// customised functionality

			// Called when a client connects, you can veto the connection by returning false
			virtual bool OnClientConnect(std::shared_ptr<connection<T>> client)
			{
				return false;
			}

			// Called when a client appears to have disconnected
			virtual void OnClientDisconnect(std::shared_ptr<connection<T>> client)
			{

			}

			// Called when a message arrives
			virtual void OnMessage(std::shared_ptr<connection<T>> client, message<T>& msg)
			{

			}


		protected:
			// Thread Safe Queue for incoming message packets
			tsqueue<owned_message<T>> m_qMessagesIn;

			// Container of active validated connections
			std::deque<std::shared_ptr<connection<T>>> m_deqConnections;

			// Order of declaration is important - it is also the order of initialisation
			asio::io_context m_asioContext;
			std::thread m_threadContext;

			// These things need an asio context
			asio::ip::tcp::acceptor m_asioAcceptor; // Handles new incoming connection attempts...

			// Clients will be identified in the "wider system" via an ID
			uint32_t nIDCounter = 10000;
		};
	}
}