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
{
	public class KoreanMSX8kMapperCartridge : ICartridge
	{
		byte[] romData;

		[StateRequired]
		readonly byte[] pagingRegisters;

		[StateRequired]
		byte bankMask;

		public KoreanMSX8kMapperCartridge(int romSize, int ramSize)
		{
			pagingRegisters = new byte[4];

			romData = new byte[romSize];
		}

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

			var romSizeRounded = 1;
			while (romSizeRounded < romData.Length) romSizeRounded <<= 1;

			bankMask = (byte)((romSizeRounded >> 13) - 1);
		}

		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 & 0xE000)
			{
				case 0x0000: return romData[(0x00 << 13) | (address & 0x1FFF)];
				case 0x2000: return romData[(0x01 << 13) | (address & 0x1FFF)];
				case 0x4000: return romData[(pagingRegisters[2] << 13) | (address & 0x1FFF)];
				case 0x6000: return romData[(pagingRegisters[3] << 13) | (address & 0x1FFF)];
				case 0x8000: return romData[(pagingRegisters[0] << 13) | (address & 0x1FFF)];
				case 0xA000: return romData[(pagingRegisters[1] << 13) | (address & 0x1FFF)];
				default: throw new EmulationException(string.Format("Korean MSX 8k mapper: Cannot read from cartridge address 0x{0:X4}", address));
			}
		}

		public void Write(ushort address, byte value)
		{
			if (address >= 0x0000 && address <= 0x0003)
			{
				pagingRegisters[address & 0x0003] = (byte)(value & bankMask);
			}
		}
	}
}