//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// DESCRIPTION:
//     Main loop code.
//

#include "essence/include.h"

#include "config.h"

#include "d_event.h"
#include "d_loop.h"
#include "d_ticcmd.h"

#include "i_system.h"
#include "i_timer.h"
#include "i_video.h"

#include "m_argv.h"
#include "m_fixed.h"

#include "net_client.h"
#include "net_gui.h"
#include "net_io.h"
#include "net_query.h"
#include "net_server.h"
#include "net_loop.h"

// The complete set of data for a particular tic.

typedef struct
{
    ticcmd_t cmds[NET_MAXPLAYERS];
    boolean ingame[NET_MAXPLAYERS];
} ticcmd_set_t;

//
// gametic is the tic about to (or currently being) run
// maketic is the tic that hasn't had control made for it yet
// recvtic is the latest tic received from the server.
//
// a gametic cannot be run until ticcmds are received for it
// from all players.
//

static ticcmd_set_t ticdata[BACKUPTICS];

// The index of the next tic to be made (with a call to BuildTiccmd).

static int maketic;

// The number of complete tics received from the server so far.

static int recvtic;

// The number of tics that have been run (using RunTic) so far.

int gametic;

// When set to true, a single tic is run each time TryRunTics() is called.
// This is used for -timedemo mode.

boolean singletics = false;

// Index of the local player.

static int localplayer;

// Used for original sync code.

static int skiptics = 0;

// Reduce the bandwidth needed by sampling game input less and transmitting
// less.  If ticdup is 2, sample half normal, 3 = one third normal, etc.

int ticdup;

// Amount to offset the timer for game sync.

fixed_t  offsetms;

// Use new client syncronisation code

static boolean new_sync = true;

// Callback functions for loop code.

static loop_interface_t *loop_interface = NULL;

// Current players in the multiplayer game.
// This is distinct from playeringame[] used by the game code, which may
// modify playeringame[] when playing back multiplayer demos.

static boolean local_playeringame[NET_MAXPLAYERS];

// Requested player class "sent" to the server on connect.
// If we are only doing a single player game then this needs to be remembered
// and saved in the game settings.

static int player_class;


// 35 fps clock adjusted by offsetms milliseconds

static int GetAdjustedTime(void)
{
    int time_ms;

    time_ms = I_GetTimeMS();

    if (new_sync)
    {
	// Use the adjustments from net_client.c only if we are
	// using the new sync mode.

        time_ms += (offsetms / FRACUNIT);
    }

    return (time_ms * TICRATE) / 1000;
}

static boolean BuildNewTic(void)
{
    int	gameticdiv;
    ticcmd_t cmd;

    gameticdiv = gametic/ticdup;

    I_StartTic ();
    loop_interface->ProcessEvents();

    // Always run the menu

    loop_interface->RunMenu();

    if (drone)
    {
        // In drone mode, do not generate any ticcmds.

        return false;
    }

    if (new_sync)
    {
       // If playing single player, do not allow tics to buffer
       // up very far

       if (!net_client_connected && maketic - gameticdiv > 2)
           return false;

       // Never go more than ~200ms ahead

       if (maketic - gameticdiv > 8)
           return false;
    }
    else
    {
       if (maketic - gameticdiv >= 5)
           return false;
    }

    ES_memset(&cmd, 0, sizeof(ticcmd_t));
    loop_interface->BuildTiccmd(&cmd, maketic);

#ifdef FEATURE_MULTIPLAYER

    if (net_client_connected)
    {
        NET_CL_SendTiccmd(&cmd, maketic);
    }

#endif
    ticdata[maketic % BACKUPTICS].cmds[localplayer] = cmd;
    ticdata[maketic % BACKUPTICS].ingame[localplayer] = true;

    ++maketic;

    return true;
}

//
// NetUpdate
// Builds ticcmds for console player,
// sends out a packet
//
int      lasttime;

void NetUpdate (void)
{
    int nowtime;
    int newtics;
    int	i;

    // If we are running with singletics (timing a demo), this
    // is all done separately.

    if (singletics)
        return;

#ifdef FEATURE_MULTIPLAYER

    // Run network subsystems

    NET_CL_Run();
    NET_SV_Run();

#endif

    // check time
    nowtime = GetAdjustedTime() / ticdup;
    newtics = nowtime - lasttime;

    lasttime = nowtime;

    if (skiptics <= newtics)
    {
        newtics -= skiptics;
        skiptics = 0;
    }
    else
    {
        skiptics -= newtics;
        newtics = 0;
    }

    // build new ticcmds for console player

    for (i=0 ; i < newtics; i++)
    {
        if (!BuildNewTic())
        {
            break;
        }
    }
}

static void D_Disconnected(void)
{
    // In drone mode, the game cannot continue once disconnected.

    if (drone)
    {
        I_Error("Disconnected from server in drone mode.");
    }

    // disconnected from server

    ES_debugf("Disconnected from server.\n");
}

//
// Invoked by the network engine when a complete set of ticcmds is
// available.
//

void D_ReceiveTic(ticcmd_t *ticcmds, boolean *players_mask)
{
    size_t i;

    // Disconnected from server?

    if (ticcmds == NULL && players_mask == NULL)
    {
        D_Disconnected();
        return;
    }

    for (i = 0; i < NET_MAXPLAYERS; ++i)
    {
        if (!drone && i == localplayer)
        {
            // This is us.  Don't overwrite it.
        }
        else
        {
            ticdata[recvtic % BACKUPTICS].cmds[i] = ticcmds[i];
            ticdata[recvtic % BACKUPTICS].ingame[i] = players_mask[i];
        }
    }

    ++recvtic;
}

//
// Start game loop
//
// Called after the screen is set but before the game starts running.
//

void D_StartGameLoop(void)
{
    lasttime = GetAdjustedTime() / ticdup;
}

void D_StartNetGame(net_gamesettings_t *settings,
                    netgame_startup_callback_t callback)
{
    settings->consoleplayer = 0;
	settings->num_players = 1;
	settings->player_classes[0] = player_class;
	settings->new_sync = 0;
	settings->extratics = 1;
	settings->ticdup = 1;

	ticdup = settings->ticdup;
	new_sync = settings->new_sync;
}

boolean D_InitNetGame(net_connect_data_t *connect_data)
{
    boolean result = false;
#ifdef FEATURE_MULTIPLAYER
    net_addr_t *addr = NULL;
    int i;
#endif

    // Call D_QuitNetGame on exit:

    I_AtExit(D_QuitNetGame, true);

    player_class = connect_data->player_class;

#ifdef FEATURE_MULTIPLAYER

    //!
    // @category net
    //
    // Start a multiplayer server, listening for connections.
    //

    if (M_CheckParm("-server") > 0
     || M_CheckParm("-privateserver") > 0)
    {
        NET_SV_Init();
        NET_SV_AddModule(&net_loop_server_module);
        NET_SV_AddModule(&net_sdl_module);
        NET_SV_RegisterWithMaster();

        net_loop_client_module.InitClient();
        addr = net_loop_client_module.ResolveAddress(NULL);
    }
    else
    {
        //!
        // @category net
        //
        // Automatically search the local LAN for a multiplayer
        // server and join it.
        //

        i = M_CheckParm("-autojoin");

        if (i > 0)
        {
            addr = NET_FindLANServer();

            if (addr == NULL)
            {
                I_Error("No server found on local LAN");
            }
        }

        //!
        // @arg <address>
        // @category net
        //
        // Connect to a multiplayer server running on the given
        // address.
        //

        i = M_CheckParmWithArgs("-connect", 1);

        if (i > 0)
        {
            net_sdl_module.InitClient();
            addr = net_sdl_module.ResolveAddress(myargv[i+1]);

            if (addr == NULL)
            {
                I_Error("Unable to resolve '%s'\n", myargv[i+1]);
            }
        }
    }

    if (addr != NULL)
    {
        if (M_CheckParm("-drone") > 0)
        {
            connect_data->drone = true;
        }

        if (!NET_CL_Connect(addr, connect_data))
        {
            I_Error("D_InitNetGame: Failed to connect to %s\n",
                    NET_AddrToString(addr));
        }

        ES_debuf("D_InitNetGame: Connected to %s\n", NET_AddrToString(addr));

        // Wait for launch message received from server.

        NET_WaitForLaunch();

        result = true;
    }
#endif

    return result;
}


//
// D_QuitNetGame
// Called before quitting to leave a net game
// without hanging the other players
//
void D_QuitNetGame (void)
{
#ifdef FEATURE_MULTIPLAYER
    NET_SV_Shutdown();
    NET_CL_Disconnect();
#endif
}

static int GetLowTic(void)
{
    int lowtic;

    lowtic = maketic;

#ifdef FEATURE_MULTIPLAYER
    if (net_client_connected)
    {
        if (drone || recvtic < lowtic)
        {
            lowtic = recvtic;
        }
    }
#endif

    return lowtic;
}

static int frameon;
static int frameskip[4];
static int oldnettics;

static void OldNetSync(void)
{
    unsigned int i;
    int keyplayer = -1;

    frameon++;

    // ideally maketic should be 1 - 3 tics above lowtic
    // if we are consistantly slower, speed up time

    for (i=0 ; i<NET_MAXPLAYERS ; i++)
    {
        if (local_playeringame[i])
        {
            keyplayer = i;
            break;
        }
    }

    if (keyplayer < 0)
    {
        // If there are no players, we can never advance anyway

        return;
    }

    if (localplayer == keyplayer)
    {
        // the key player does not adapt
    }
    else
    {
        if (maketic <= recvtic)
        {
            lasttime--;
        }

        frameskip[frameon & 3] = oldnettics > recvtic;
        oldnettics = maketic;

        if (frameskip[0] && frameskip[1] && frameskip[2] && frameskip[3])
        {
            skiptics = 1;
        }
    }
}

// Returns true if there are players in the game:

static boolean PlayersInGame(void)
{
    boolean result = false;
    unsigned int i;

    // If we are connected to a server, check if there are any players
    // in the game.
    if (net_client_connected)
    {
        for (i = 0; i < NET_MAXPLAYERS; ++i)
        {
            result = result || local_playeringame[i];
        }
    }

    // Whether single or multi-player, unless we are running as a drone,
    // we are in the game.

    if (!drone)
    {
        result = true;
    }

    return result;
}

// When using ticdup, certain values must be cleared out when running
// the duplicate ticcmds.

static void TicdupSquash(ticcmd_set_t *set)
{
    ticcmd_t *cmd;
    unsigned int i;

    for (i = 0; i < NET_MAXPLAYERS ; ++i)
    {
        cmd = &set->cmds[i];
        cmd->chatchar = 0;
        if (cmd->buttons & BT_SPECIAL)
            cmd->buttons = 0;
    }
}

// When running in single player mode, clear all the ingame[] array
// except the local player.

static void SinglePlayerClear(ticcmd_set_t *set)
{
    unsigned int i;

    for (i = 0; i < NET_MAXPLAYERS; ++i)
    {
        if (i != localplayer)
        {
            set->ingame[i] = false;
        }
    }
}

//
// TryRunTics
//

void TryRunTics (void)
{
    int	i;
    int	lowtic;
    int	entertic;
    static int oldentertics;
    int realtics;
    int	availabletics;
    int	counts;

    // get real tics
    entertic = I_GetTime() / ticdup;
    realtics = entertic - oldentertics;
    oldentertics = entertic;

    // in singletics mode, run a single tic every time this function
    // is called.

    if (singletics)
    {
        BuildNewTic();
    }
    else
    {
        NetUpdate();
    }

    lowtic = GetLowTic();

    availabletics = lowtic - gametic/ticdup;

    // decide how many tics to run

    if (new_sync)
    {
	    counts = availabletics;
    }
    else
    {
        // decide how many tics to run
        if (realtics < availabletics-1)
            counts = realtics+1;
        else if (realtics < availabletics)
            counts = realtics;
        else
            counts = availabletics;

        if (counts < 1)
            counts = 1;

        if (net_client_connected)
        {
            OldNetSync();
        }
    }

    if (counts < 1) counts = 1;

    // wait for new tics if needed
    while (!PlayersInGame() || lowtic < gametic/ticdup + counts)
    {
	    NetUpdate();

        lowtic = GetLowTic();

        if (lowtic < gametic/ticdup) I_Error("TryRunTics: lowtic < gametic");

        // Don't stay in this loop forever. The menu is still running,
        // so return to update the screen

        if (I_GetTime() / ticdup - entertic > 0)
        {
            return;
        }

        I_Sleep(1);
    }

    // run the count * ticdup dics
    while (counts--)
    {
        ticcmd_set_t *set;

        if (!PlayersInGame())
        {
            return;
        }

        set = &ticdata[(gametic / ticdup) % BACKUPTICS];

        if (!net_client_connected)
        {
            SinglePlayerClear(set);
        }

        for (i=0; i<ticdup; i++)
        {
            if (gametic/ticdup > lowtic) I_Error ("gametic>lowtic");

            ES_memcpy(local_playeringame, set->ingame, sizeof(local_playeringame));

            loop_interface->RunTic(set->cmds, set->ingame);
            gametic++;

            // modify command for duplicated tics
            TicdupSquash(set);
        }

	    NetUpdate(); // check for new console commands
    }
}

void D_RegisterLoopCallbacks(loop_interface_t *i)
{
    loop_interface = i;
}