/*
** Nofrendo (c) 1998-2000 Matthew Conte (matt@conte.com)
**
**
** This program is free software; you can redistribute it and/or
** modify it under the terms of version 2 of the GNU Library General 
** Public License as published by the Free Software Foundation.
**
** 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 
** Library General Public License for more details.  To obtain a 
** copy of the GNU Library General Public License, write to the Free 
** Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
**
** Any permitted reproduction of these routines, in whole or in part,
** must bear this legend.
**
**
** map050.c
**
** Mapper #50 (SMB2j - 3rd discovered variation)
** Implementation by Firebug
** Mapper information courtesy of Kevin Horton
** $Id: map050.c,v 1.2 2001/04/27 14:37:11 neil Exp $
**
*/

#include "noftypes.h"
#include "nes_mmc.h"
#include "nes.h"
#include "libsnss.h"
#include "log.h"

static struct
{
  bool enabled;
  uint32 counter;
} irq;

/********************************/
/* Mapper #50 IRQ reset routine */
/********************************/
static void map50_irq_reset (void)
{
  /* Turn off IRQs */
  irq.enabled = false;
  irq.counter = 0x0000;

  /* Done */
  return;
}

/**************************************************************/
/* Mapper #50: 3rd discovered variation of SMB2j cart bootleg */
/**************************************************************/
static void map50_init (void)
{
  /* Set the hardwired pages */
  mmc_bankrom (8, 0x6000, 0x0F);
  mmc_bankrom (8, 0x8000, 0x08);
  mmc_bankrom (8, 0xA000, 0x09);
  mmc_bankrom (8, 0xE000, 0x0B);

  /* Reset the IRQ counter */
  map50_irq_reset ();

  /* Done */
  return;
}

/****************************************/
/* Mapper #50 callback for IRQ handling */
/****************************************/
static void map50_hblank (int vblank)
{
   /* Counter is M2 based so it doesn't matter whether */
   /* the PPU is in its VBlank period or not           */
   UNUSED(vblank);

   /* Increment the counter if it is enabled and check for strike */
   if (irq.enabled)
   {
     /* Is there a constant for cycles per scanline? */
     /* If so, someone ought to substitute it here   */
     irq.counter = irq.counter + 114;

     /* IRQ line is hooked to Q12 of the counter */
     if (irq.counter & 0x1000)
     {
       /* Trigger the IRQ */
       nes_irq ();

       /* Reset the counter */
       map50_irq_reset ();
     }
   }
}

/******************************************/
/* Mapper #50 write handler ($4000-$5FFF) */
/******************************************/
static void map50_write (uint32 address, uint8 value)
{
  uint8 selectable_bank;

  /* For address to be decoded, A5 must be high and A6 low */
  if ((address & 0x60) != 0x20) return;

  /* A8 low  = $C000-$DFFF page selection */
  /* A8 high = IRQ timer toggle */
  if (address & 0x100)
  {
    /* IRQ settings */
    if (value & 0x01) irq.enabled = true;
    else              map50_irq_reset ();
  }
  else
  {
    /* Stupid data line swapping */
    selectable_bank = 0x00;
    if (value & 0x08) selectable_bank |= 0x08;
    if (value & 0x04) selectable_bank |= 0x02;
    if (value & 0x02) selectable_bank |= 0x01;
    if (value & 0x01) selectable_bank |= 0x04;
    mmc_bankrom (8, 0xC000, selectable_bank);
  }

  /* Done */
  return;
}

/****************************************************/
/* Shove extra mapper information into a SNSS block */
/****************************************************/
static void map50_setstate (SnssMapperBlock *state)
{
  /* TODO: Store SNSS information */
  UNUSED (state);

  /* Done */
  return;
}

/*****************************************************/
/* Pull extra mapper information out of a SNSS block */
/*****************************************************/
static void map50_getstate (SnssMapperBlock *state)
{
  /* TODO: Retrieve SNSS information */
  UNUSED (state);

  /* Done */
  return;
}

static const map_memwrite map50_memwrite [] =
{
   { 0x4000, 0x5FFF, map50_write },
   {     -1,     -1, NULL }
};

const mapintf_t map50_intf =
{
   50,                               /* Mapper number */
   "SMB2j (3rd discovered variant)", /* Mapper name */
   map50_init,                       /* Initialization routine */
   NULL,                             /* VBlank callback */
   map50_hblank,                     /* HBlank callback */
   map50_getstate,                   /* Get state (SNSS) */
   map50_setstate,                   /* Set state (SNSS) */
   NULL,                             /* Memory read structure */
   map50_memwrite,                   /* Memory write structure */
   NULL                              /* External sound device */
};

/*
** $Log: map050.c,v $
** Revision 1.2  2001/04/27 14:37:11  neil
** wheeee
**
** Revision 1.1  2001/04/27 12:54:40  neil
** blah
**
** Revision 1.1  2001/04/27 10:57:41  neil
** wheee
**
** Revision 1.1  2000/12/27 19:22:13  firebug
** initial revision
**
**
*/