/*
 * Copyright (C) 2016+     AzerothCore <www.azerothcore.org>, released under GNU GPL v2 license, you may redistribute it and/or modify it under version 2 of the License, or (at your option), any later version.
 * Copyright (C) 2008-2016 TrinityCore <http://www.trinitycore.org/>
 * Copyright (C) 2005-2009 MaNGOS <http://getmangos.com/>
 */

/** \addtogroup u2w User to World Communication
 * @{
 * \file WorldSocket.h
 * \author Derex <derex101@gmail.com>
 */

#ifndef _WORLDSOCKET_H
#define _WORLDSOCKET_H

#include "AuthCrypt.h"
#include "Common.h"
#include "Duration.h"
#include <ace/Message_Block.h>
#include <ace/SOCK_Stream.h>
#include <ace/Svc_Handler.h>
#include <ace/Synch_Traits.h>
#include <ace/Thread_Mutex.h>
#include <ace/Unbounded_Queue.h>

#if !defined (ACE_LACKS_PRAGMA_ONCE)
#pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */

class ACE_Message_Block;
class WorldPacket;
class WorldSession;

/// Handler that can communicate over stream sockets.
typedef ACE_Svc_Handler<ACE_SOCK_STREAM, ACE_NULL_SYNCH> WorldHandler;

/**
 * WorldSocket.
 *
 * This class is responsible for the communication with
 * remote clients.
 * Most methods return -1 on failure.
 * The class uses reference counting.
 *
 * For output the class uses one buffer (64K usually) and
 * a queue where it stores packet if there is no place on
 * the queue. The reason this is done, is because the server
 * does really a lot of small-size writes to it, and it doesn't
 * scale well to allocate memory for every. When something is
 * written to the output buffer the socket is not immediately
 * activated for output (again for the same reason), there
 * is 10ms celling (thats why there is Update() method).
 * This concept is similar to TCP_CORK, but TCP_CORK
 * uses 200ms celling. As result overhead generated by
 * sending packets from "producer" threads is minimal,
 * and doing a lot of writes with small size is tolerated.
 *
 * The calls to Update() method are managed by WorldSocketMgr
 * and ReactorRunnable.
 *
 * For input, the class uses one 4096 bytes buffer on stack
 * to which it does recv() calls. And then received data is
 * distributed where its needed. 4096 matches pretty well the
 * traffic generated by client for now.
 *
 * The input/output do speculative reads/writes (AKA it tryes
 * to read all data available in the kernel buffer or tryes to
 * write everything available in userspace buffer),
 * which is ok for using with Level and Edge Triggered IO
 * notification.
 *
 */
class WorldSocket : public WorldHandler
{
public:
    WorldSocket (void);
    virtual ~WorldSocket (void);

    friend class WorldSocketMgr;

    /// Mutex type used for various synchronizations.
    typedef ACE_Thread_Mutex LockType;
    typedef ACE_Guard<LockType> GuardType;

    /// Check if socket is closed.
    bool IsClosed (void) const;

    /// Close the socket.
    void CloseSocket(std::string const& reason);

    /// Get address of connected peer.
    const std::string& GetRemoteAddress (void) const;

    /// Send A packet on the socket, this function is reentrant.
    /// @param pct packet to send
    /// @return -1 of failure
    int SendPacket(const WorldPacket& pct);

    /// Add reference to this object.
    long AddReference (void);

    /// Remove reference to this object.
    long RemoveReference (void);

    /// things called by ACE framework.

    /// Called on open, the void* is the acceptor.
    virtual int open (void*);

    /// Called on failures inside of the acceptor, don't call from your code.
    virtual int close (u_long);

    /// Called when we can read from the socket.
    virtual int handle_input (ACE_HANDLE = ACE_INVALID_HANDLE);

    /// Called when the socket can write.
    virtual int handle_output (ACE_HANDLE = ACE_INVALID_HANDLE);

    /// Called when connection is closed or error happens.
    virtual int handle_close (ACE_HANDLE = ACE_INVALID_HANDLE,
                              ACE_Reactor_Mask = ACE_Event_Handler::ALL_EVENTS_MASK);

    /// Called by WorldSocketMgr/ReactorRunnable.
    int Update (void);

private:
    /// Helper functions for processing incoming data.
    int handle_input_header (void);
    int handle_input_payload (void);
    int handle_input_missing_data (void);

    /// Help functions to mark/unmark the socket for output.
    /// @param g the guard is for m_OutBufferLock, the function will release it
    int cancel_wakeup_output (GuardType& g);
    int schedule_wakeup_output (GuardType& g);

    /// Drain the queue if its not empty.
    int handle_output_queue (GuardType& g);

    /// process one incoming packet.
    /// @param new_pct received packet, note that you need to delete it.
    int ProcessIncoming (WorldPacket* new_pct);

    /// Called by ProcessIncoming() on CMSG_AUTH_SESSION.
    int HandleAuthSession (WorldPacket& recvPacket);

    /// Called by ProcessIncoming() on CMSG_PING.
    int HandlePing (WorldPacket& recvPacket);

private:
    /// Time in which the last ping was received
    SystemTimePoint m_LastPingTime;

    /// Keep track of over-speed pings, to prevent ping flood.
    uint32 m_OverSpeedPings;

    /// Address of the remote peer
    std::string m_Address;

    /// Class used for managing encryption of the headers
    AuthCrypt m_Crypt;

    /// Mutex lock to protect m_Session
    LockType m_SessionLock;

    /// Session to which received packets are routed
    WorldSession* m_Session;

    /// here are stored the fragments of the received data
    WorldPacket* m_RecvWPct;

    /// This block actually refers to m_RecvWPct contents,
    /// which allows easy and safe writing to it.
    /// It wont free memory when its deleted. m_RecvWPct takes care of freeing.
    ACE_Message_Block m_RecvPct;

    /// Fragment of the received header.
    ACE_Message_Block m_Header;

    /// Mutex for protecting output related data.
    LockType m_OutBufferLock;

    /// Buffer used for writing output.
    ACE_Message_Block* m_OutBuffer;

    /// Size of the m_OutBuffer.
    size_t m_OutBufferSize;

    /// True if the socket is registered with the reactor for output
    bool m_OutActive;

    std::array<uint8, 4> m_Seed;
};

#endif  /* _WORLDSOCKET_H */

/// @}