/*
    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, ?OneLoneCoder 2019, 2020

*/

#pragma once
#include "net_dequeue_ts.h"
#include "net_common.h"
#include "net_message.h"
#include "net_connection.h"
#include "easylogging++.h"

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

        virtual ~ServerInterface() { Stop(); }

        // Starts the server
        virtual 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;
            }

            LOG(INFO) << "[SERVER] Started\n";
            return true;
        }

        bool isStopped()const {
            return m_asioContext.stopped();
        }

        // Stops the server!
        virtual 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...
            LOG(INFO) << "[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)
                    {
                        LOG(INFO) << "[SERVER] New Connection: " << socket.remote_endpoint();

                        // 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));

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

                            LOG(INFO) << "[" << m_deqConnections.back()->GetID() << "] Connection Approved\n";
                        }
                        else
                        {
                            LOG(INFO) << "[SERVER] Connection Denied";

                            // Connection will go out of scope with no pending tasks, so will
                            // get destroyed automatically (smart pointer)
                        }
                    }
                    else
                    {
                        // Error has occurred during acceptance
                        LOG(INFO) << "[SERVER] New Connection Error: " << ec.message();
                    }

                    // 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
        //	size_t nmaxMessages: Assign -1 to unsigned to unspecify max message count
        //	bool bWait: if queue is empty, wait synchronously until message arrives
        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:
        //Overwritable functions to customize server behaviour

        // Called when a client connects, you can veto the connection by returning false
        virtual bool OnClientConnect(std::shared_ptr<Connection<T>> client) = 0;
        // Called when a client appears to have disconnected
        virtual void OnClientDisconnect(std::shared_ptr<Connection<T>> client) = 0;

        // Called when a message arrives
        virtual void OnMessage(std::shared_ptr<Connection<T>> client, Message<T>& msg) = 0;


    protected:
        // Thread Safe Queue for incoming message packets
        ts_dequeue<OwnedMessage<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 = 100;
    };
}