using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;

using Essgee.Exceptions;
using Essgee.Utilities;

namespace Essgee.Emulation.Cartridges.Sega
{
	/* http://www.smspower.org/forums/post69724#69724 */

	public class Multicart4PakAllActionCartridge : ICartridge
	{
		byte[] romData;

		[StateRequired]
		readonly int romMask;

		[StateRequired]
		int romBank0, romBank1, romBank2;

		public Multicart4PakAllActionCartridge(int romSize, int ramSize)
		{
			romData = new byte[romSize];

			romMask = 1;
			while (romMask < romSize) romMask <<= 1;
			romMask -= 1;

			romBank0 = romBank1 = romBank2 = 0;
		}

		public void LoadRom(byte[] data)
		{
			Buffer.BlockCopy(data, 0, romData, 0, Math.Min(data.Length, romData.Length));
		}

		public void LoadRam(byte[] data)
		{
			//
		}

		public byte[] GetRomData()
		{
			return romData;
		}

		public byte[] GetRamData()
		{
			return null;
		}

		public bool IsRamSaveNeeded()
		{
			return false;
		}

		public ushort GetLowerBound()
		{
			return 0x0000;
		}

		public ushort GetUpperBound()
		{
			return 0xBFFF;
		}

		public void Step(int clockCyclesInStep)
		{
			/* Nothing to do */
		}

		public byte Read(ushort address)
		{
			switch (address & 0xC000)
			{
				case 0x0000:
					return romData[((romBank0 << 14) | (address & 0x3FFF))];

				case 0x4000:
					return romData[((romBank1 << 14) | (address & 0x3FFF))];

				case 0x8000:
					return romData[((((romBank0 & 0x30) + romBank2) << 14) | (address & 0x3FFF))];

				default:
					throw new EmulationException(string.Format("4 Pak mapper: Cannot read from cartridge address 0x{0:X4}", address));
			}
		}

		public void Write(ushort address, byte value)
		{
			// TODO: really just these addresses? no mirroring?
			if (address == 0x3FFE)
				romBank0 = value;
			else if (address == 0x7FFF)
				romBank1 = value;
			else if (address == 0xBFFF)
				romBank2 = value;
		}
	}
}