using System;

namespace BizHawk.Emulation.Computers.Commodore64.MOS
{
    public class LatchedPort
    {
        public byte Direction;
        public byte Latch;

        public LatchedPort()
        {
            Direction = 0x00;
            Latch = 0x00;
        }

        // data works like this in these types of systems:
        // 
        //  directionA  directionB  result
        //  0           0           1
        //  1           0           latchA
        //  0           1           latchB
        //  1           1           latchA && latchB
        //
        // however because this uses transistor logic, there are cases where wired-ands
        // cause the pull-up resistors not to be enough to keep the bus bit set to 1 when
        // both the direction and latch are 1 (the keyboard and joystick port 2 can do this.)
        // the class does not handle this case as it must be handled differently in every occurrence.

        public byte ReadInput(byte bus)
        {
            return (byte)((Latch & Direction) | ((Direction ^ 0xFF) & bus));
        }

        public byte ReadOutput()
        {
            return (byte)((Latch & Direction) | (Direction ^ 0xFF));
        }

        public void SyncState(Serializer ser)
        {
            Sync.SyncObject(ser, this);
        }
    }

    public class LatchedBooleanPort
    {
        public bool Direction;
        public bool Latch;

        public LatchedBooleanPort()
        {
            Direction = false;
            Latch = false;
        }

        //  data    dir     bus     out
        //  0       0       0       0
        //  0       0       1       1

        //  0       1       0       0
        //  0       1       1       0

        //  1       0       0       0
        //  1       0       1       1

        //  1       1       0       1
        //  1       1       1       1

        public bool ReadInput(bool bus)
        {
            return (Direction && Latch) || (!Direction && bus);
        }

        public bool ReadOutput()
        {
            return (Latch || !Direction);
        }

        public void SyncState(Serializer ser)
        {
            Sync.SyncObject(ser, this);
        }
    }
}