namespace BizHawk.Emulation.Consoles.Sega
{
    public partial class SMS
    {
        // The CodeMasters mapper has 3 banks of 16kb, like the Sega mapper.
        // The differences are that the paging control addresses are different, and the first 1K of ROM is not protected.
        // Bank 0: Control Address $0000 - Maps $0000 - $3FFF
        // Bank 1: Control Address $4000 - Maps $4000 - $7FFF
        // Bank 2: Control Address $8000 - Maps $8000 - $BFFF
        // System RAM is at $C000+ as in the Sega mapper.

        byte ReadMemoryCM(ushort address)
        {
            if (address < BankSize * 1) return RomData[(RomBank0 * BankSize) + address];
            if (address < BankSize * 2) return RomData[(RomBank1 * BankSize) + (address & BankSizeMask)];
            if (address < BankSize * 3) return RomData[(RomBank2 * BankSize) + (address & BankSizeMask)];

            return SystemRam[address & RamSizeMask];
        }

        void WriteMemoryCM(ushort address, byte value)
        {
            if (address >= 0xC000)
                SystemRam[address & RamSizeMask] = value;

            else if (address == 0x0000) RomBank0 = (byte)(value % RomBanks);
            else if (address == 0x4000) RomBank1 = (byte)(value % RomBanks);
            else if (address == 0x8000) RomBank2 = (byte)(value % RomBanks);
        }

        void InitCodeMastersMapper()
        {
            Cpu.ReadMemory = ReadMemoryCM;
            Cpu.WriteMemory = WriteMemoryCM;
            WriteMemoryCM(0x0000, 0);
            WriteMemoryCM(0x4000, 1);
            WriteMemoryCM(0x8000, 2);
        }
    }
}