/* FCE Ultra - NES/Famicom Emulator
 *
 * Copyright notice for this file:
 *  Copyright (C) 2012 CaH4e3
 *
 * 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.
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include "mapinc.h"

static uint8 preg[4], creg[8];
static uint8 IRQa, mirr;
static int32 IRQCount, IRQLatch;

static SFORMAT StateRegs[] =
{
	{ preg, 4, "PREG" },
	{ creg, 8, "CREG" },
	{ &mirr, 1, "MIRR" },
	{ &IRQa, 1, "IRQA" },
	{ &IRQCount, 4, "IRQC" },
	{ &IRQLatch, 4, "IRQL" },
	{ 0 }
};

static void Sync(void) {
	int i;
	for (i = 0; i < 8; i++) setchr1(i << 10, creg[i]);
	setprg8(0x8000, preg[0]);
	setprg8(0xA000, preg[1]);
	setprg8(0xC000, preg[2]);
	setprg8(0xE000, ~0);
	if (mirr & 2)
		setmirror(MI_0);
	else
		setmirror(mirr & 1);
}

static DECLFW(M18WriteIRQ) {
	switch (A & 0xF003) {
	case 0xE000: IRQLatch &= 0xFFF0; IRQLatch |= (V & 0x0f) << 0x0; break;
	case 0xE001: IRQLatch &= 0xFF0F; IRQLatch |= (V & 0x0f) << 0x4; break;
	case 0xE002: IRQLatch &= 0xF0FF; IRQLatch |= (V & 0x0f) << 0x8; break;
	case 0xE003: IRQLatch &= 0x0FFF; IRQLatch |= (V & 0x0f) << 0xC; break;
	case 0xF000: IRQCount = IRQLatch; break;
	case 0xF001: IRQa = V & 1; X6502_IRQEnd(FCEU_IQEXT); break;
	case 0xF002: mirr = V & 3; Sync(); break;
	}
}

static DECLFW(M18WritePrg) {
	uint32 i = ((A >> 1) & 1) | ((A - 0x8000) >> 11);
	preg[i] &= (0xF0) >> ((A & 1) << 2);
	preg[i] |= (V & 0xF) << ((A & 1) << 2);
	Sync();
}

static DECLFW(M18WriteChr) {
	uint32 i = ((A >> 1) & 1) | ((A - 0xA000) >> 11);
	creg[i] &= (0xF0) >> ((A & 1) << 2);
	creg[i] |= (V & 0xF) << ((A & 1) << 2);
	Sync();
}

static void M18Power(void) {
	preg[0] = 0;
	preg[1] = 1;
	preg[2] = ~1;
	preg[3] = ~0;
	Sync();
	SetReadHandler(0x8000, 0xFFFF, CartBR);
	SetWriteHandler(0x8000, 0x9FFF, M18WritePrg);
	SetWriteHandler(0xA000, 0xDFFF, M18WriteChr);
	SetWriteHandler(0xE000, 0xFFFF, M18WriteIRQ);
}

static void M18IRQHook(int a) {
	if (IRQa && IRQCount) {
		IRQCount -= a;
		if (IRQCount <= 0) {
			X6502_IRQBegin(FCEU_IQEXT);
			IRQCount = 0;
			IRQa = 0;
		}
	}
}

static void StateRestore(int version) {
	Sync();
}

void Mapper18_Init(CartInfo *info) {
	info->Power = M18Power;
	MapIRQHook = M18IRQHook;
	GameStateRestore = StateRestore;

	AddExState(&StateRegs, ~0, 0, 0);
}