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

namespace BizHawk.Emulation.Cores.Computers.Commodore64.Cartridge
{
    // This is a mapper used commonly by System 3. It is
    // also utilized by the short-lived C64 Game System.

    // Bank select is DExx. You select them by writing to the
    // register DE00+BankNr. For example, bank 01 is a write
    // to DE01.

    public abstract partial class CartridgeDevice
    {
        private class Mapper000F : CartridgeDevice
        {
            [SaveState.DoNotSave]
            private readonly int[][] _banks; //8000
            [SaveState.SaveWithName("BankMask")]
            private readonly int _bankMask;
            [SaveState.SaveWithName("BankNumber")]
            private int _bankNumber;
            [SaveState.SaveWithName("CurrentBank")]
            private int[] _currentBank;

            public Mapper000F(IList<int> newAddresses, IList<int> newBanks, IList<int[]> newData)
            {
                var count = newAddresses.Count;

                pinGame = true;
                pinExRom = false;

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

                switch (count)
                {
                    case 64:
                        _bankMask = 0x3F;
                        _banks = new int[64][];
                        break;
                    case 32:
                        _bankMask = 0x1F;
                        _banks = new int[32][];
                        break;
                    case 16:
                        _bankMask = 0x0F;
                        _banks = new int[16][];
                        break;
                    case 8:
                        _bankMask = 0x07;
                        _banks = new int[8][];
                        break;
                    case 4:
                        _bankMask = 0x03;
                        _banks = new int[4][];
                        break;
                    case 2:
                        _bankMask = 0x01;
                        _banks = new int[2][];
                        break;
                    case 1:
                        _bankMask = 0x00;
                        _banks = new int[1][];
                        break;
                    default:
                        throw new Exception("This looks like a System 3/C64GS cartridge but cannot be loaded...");
                }

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

                // now load in the banks
                for (var i = 0; i < count; i++)
                {
                    if (newAddresses[i] == 0x8000)
                    {
                        _banks[newBanks[i] & _bankMask] = newData[i];
                    }
                }

                BankSet(0);
            }

            protected void BankSet(int index)
            {
                _bankNumber = index & _bankMask;
                UpdateState();
            }

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

            public override void PokeDE00(int addr, int val)
            {
                BankSet(addr);
            }

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

            private void UpdateState()
            {
                _currentBank = _banks[_bankNumber];
            }

            public override void WriteDE00(int addr, int val)
            {
                BankSet(addr);
            }

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