// VisualBoyAdvance - Nintendo Gameboy/GameboyAdvance (TM) emulator.
// Copyright (C) 1999-2003 Forgotten
// Copyright (C) 2005 Forgotten and the VBA development team

// 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, 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.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software Foundation,
// Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

#include "../mednafen.h"
#include "GBA.h"
#include "Globals.h"
#include "Port.h"

#include <time.h>
#include <memory.h>

enum RTCSTATE { IDLE, COMMAND, DATA, READDATA };

typedef struct {
  uint8 byte0;
  uint8 byte1;
  uint8 byte2;
  uint8 command;
  int dataLen;
  int bits;
  RTCSTATE state;
  uint8 data[12];
  // reserved variables for future
  uint8 reserved[12];
  bool8 reserved2;
  uint32 reserved3;
} RTCCLOCKDATA;

static RTCCLOCKDATA rtcClockData;
static bool8 rtcEnabled = false;

void rtcEnable(bool8 e)
{
  rtcEnabled = e;
}

bool8 rtcIsEnabled()
{
  return rtcEnabled;
}

uint16 rtcRead(uint32 address)
{
  if(rtcEnabled) {
    if(address == 0x80000c8)
      return rtcClockData.byte2;
    else if(address == 0x80000c6)
      return rtcClockData.byte1;
    else if(address == 0x80000c4) {
      return rtcClockData.byte0;
    }
  }
  
  return READ16LE((&rom[address & 0x1FFFFFE]));
}

static uint8 toBCD(uint8 value)
{
  value = value % 100;
  int l = value % 10;
  int h = value / 10;
  return h * 16 + l;
}

bool8 rtcWrite(uint32 address, uint16 value)
{
  if(!rtcEnabled)
    return false;
  
  if(address == 0x80000c8) {
    rtcClockData.byte2 = (uint8)value; // enable ?
  } else if(address == 0x80000c6) {
    rtcClockData.byte1 = (uint8)value; // read/write
  } else if(address == 0x80000c4) {
    if(rtcClockData.byte2 & 1) {
      if(rtcClockData.state == IDLE && rtcClockData.byte0 == 1 && value == 5) {
          rtcClockData.state = COMMAND;
          rtcClockData.bits = 0;
          rtcClockData.command = 0;
      } else if(!(rtcClockData.byte0 & 1) && (value & 1)) { // bit transfer
        rtcClockData.byte0 = (uint8)value;        
        switch(rtcClockData.state) {
        case COMMAND:
          rtcClockData.command |= ((value & 2) >> 1) << (7-rtcClockData.bits);
          rtcClockData.bits++;
          if(rtcClockData.bits == 8) {
            rtcClockData.bits = 0;
            switch(rtcClockData.command) {
            case 0x60:
              // not sure what this command does but it doesn't take parameters
              // maybe it is a reset or stop
              rtcClockData.state = IDLE;
              rtcClockData.bits = 0;
              break;
            case 0x62:
              // this sets the control state but not sure what those values are
              rtcClockData.state = READDATA;
              rtcClockData.dataLen = 1;
              break;
            case 0x63:
              rtcClockData.dataLen = 1;
              rtcClockData.data[0] = 0x40;
              rtcClockData.state = DATA;
              break;
           case 0x64:
              break;
            case 0x65:
              {
                struct tm *newtime;
                time_t long_time;

                time( &long_time );                /* Get time as long integer. */
                newtime = localtime( &long_time ); /* Convert to local time. */
                
                rtcClockData.dataLen = 7;
                rtcClockData.data[0] = toBCD(newtime->tm_year);
                rtcClockData.data[1] = toBCD(newtime->tm_mon+1);
                rtcClockData.data[2] = toBCD(newtime->tm_mday);
                rtcClockData.data[3] = toBCD(newtime->tm_wday);
                rtcClockData.data[4] = toBCD(newtime->tm_hour);
                rtcClockData.data[5] = toBCD(newtime->tm_min);
                rtcClockData.data[6] = toBCD(newtime->tm_sec);
                rtcClockData.state = DATA;
              }
              break;              
            case 0x67:
              {
                struct tm *newtime;
                time_t long_time;

                time( &long_time );                /* Get time as long integer. */
                newtime = localtime( &long_time ); /* Convert to local time. */
                
                rtcClockData.dataLen = 3;
                rtcClockData.data[0] = toBCD(newtime->tm_hour);
                rtcClockData.data[1] = toBCD(newtime->tm_min);
                rtcClockData.data[2] = toBCD(newtime->tm_sec);
                rtcClockData.state = DATA;
              }
              break;
            default:
              //systemMessage(0, N_("Unknown RTC command %02x"), rtcClockData.command);
              rtcClockData.state = IDLE;
              break;
            }
          }
          break;
        case DATA:
          if(rtcClockData.byte1 & 2) {
          } else {
            rtcClockData.byte0 = (rtcClockData.byte0 & ~2) |
              ((rtcClockData.data[rtcClockData.bits >> 3] >>
                (rtcClockData.bits & 7)) & 1)*2;
            rtcClockData.bits++;
            if(rtcClockData.bits == 8*rtcClockData.dataLen) {
              rtcClockData.bits = 0;
              rtcClockData.state = IDLE;
            }
          }
          break;
        case READDATA:
          if(!(rtcClockData.byte1 & 2)) {
          } else {
            rtcClockData.data[rtcClockData.bits >> 3] =
              (rtcClockData.data[rtcClockData.bits >> 3] >> 1) |
              ((value << 6) & 128);
            rtcClockData.bits++;
            if(rtcClockData.bits == 8*rtcClockData.dataLen) {
              rtcClockData.bits = 0;
              rtcClockData.state = IDLE;
            }
          }
          break;
		default:
          break;
        }
      } else
        rtcClockData.byte0 = (uint8)value;
    }
  }
  return true;
}

void rtcReset()
{
  memset(&rtcClockData, 0, sizeof(rtcClockData));
  
  rtcClockData.byte0 = 0;
  rtcClockData.byte1 = 0;
  rtcClockData.byte2 = 0;
  rtcClockData.command = 0;
  rtcClockData.dataLen = 0;
  rtcClockData.bits = 0;
  rtcClockData.state = IDLE;
}
