using System;
using System.Collections.Generic;
using System.Linq;
using BizHawk.Common;

namespace BizHawk.Emulation.Cores.Computers.Commodore64.Cartridge
{
	public abstract partial class CartridgeDevice
	{
		private sealed class Mapper0005 : CartridgeDevice
		{
			[SaveState.DoNotSave]
			private readonly int[][] _banksA; //8000
			[SaveState.DoNotSave]
			private readonly int[][] _banksB = new int[0][]; //A000
			[SaveState.SaveWithName("BankMask")]
			private readonly int _bankMask;
			[SaveState.SaveWithName("BankNumber")]
			private int _bankNumber;
			[SaveState.DoNotSave]
			private int[] _currentBankA;
			[SaveState.DoNotSave]
			private int[] _currentBankB;
			[SaveState.DoNotSave]
			private readonly int[] _dummyBank;

			public Mapper0005(IList<int> newAddresses, IList<int> newBanks, IList<int[]> newData)
			{
				var count = newAddresses.Count;

				// build dummy bank
				_dummyBank = new int[0x2000];
				for (var i = 0; i < 0x2000; i++)
					_dummyBank[i] = 0xFF; // todo: determine if this is correct

				switch (count)
				{
					case 64:
						pinGame = true;
						pinExRom = false;
						_bankMask = 0x3F;
						_banksA = new int[64][];
						break;
					case 32:
						// this specific config is a weird exception
						pinGame = false;
						pinExRom = false;
						_bankMask = 0x0F;
						_banksA = new int[16][];
						_banksB = new int[16][];
						break;
					case 16:
						pinGame = true;
						pinExRom = false;
						_bankMask = 0x0F;
						_banksA = new int[16][];
						break;
					case 8:
						pinGame = true;
						pinExRom = false;
						_bankMask = 0x07;
						_banksA = new int[8][];
						break;
					case 4:
						pinGame = true;
						pinExRom = false;
						_bankMask = 0x03;
						_banksA = new int[4][];
						break;
					case 2:
						pinGame = true;
						pinExRom = false;
						_bankMask = 0x01;
						_banksA = new int[2][];
						break;
					case 1:
						pinGame = true;
						pinExRom = false;
						_bankMask = 0x00;
						_banksA = new int[1][];
						break;
					default:
						throw new Exception("This looks like an Ocean cartridge but cannot be loaded...");
				}

				// for safety, initialize all banks to dummy
				for (var i = 0; i < _banksA.Length; i++)
					_banksA[i] = _dummyBank;
				for (var i = 0; i < _banksB.Length; i++)
					_banksB[i] = _dummyBank;

				// now load in the banks
				for (var i = 0; i < count; i++)
				{
					switch (newAddresses[i])
					{
						case 0x8000:
							_banksA[newBanks[i] & _bankMask] = newData[i];
							break;
						case 0xA000:
						case 0xE000:
							_banksB[newBanks[i] & _bankMask] = newData[i];
							break;
					}
				}

				BankSet(0);
			}

			private void BankSet(int index)
			{
				_bankNumber = index & _bankMask;
				_currentBankA = !pinExRom ? _banksA[_bankNumber] : _dummyBank;
				_currentBankB = !pinGame ? _banksB[_bankNumber] : _dummyBank;
			}

			public override int Peek8000(int addr)
			{
				return _currentBankA[addr];
			}

			public override int PeekA000(int addr)
			{
				return _currentBankB[addr];
			}

			public override void PokeDE00(int addr, int val)
			{
				if (addr == 0x00)
					BankSet(val);
			}

			public override int Read8000(int addr)
			{
				return _currentBankA[addr];
			}

			public override int ReadA000(int addr)
			{
				return _currentBankB[addr];
			}

			public override void WriteDE00(int addr, int val)
			{
				if (addr == 0x00)
					BankSet(val);
			}

			public override void SyncState(Serializer ser)
			{
				base.SyncState(ser);
				if (ser.IsReader)
					BankSet(_bankNumber);
			}
		}
	}
}