// Educational Virtual Machine
// by ethical.blue Magazine

internal class Program
{
    static void Main(string[] args)
    {
        List<byte> program = [];

        program.Add((byte)Opcode.mov);
        program.Add((byte)Register.r1);
        program.AddRange(BitConverter.GetBytes(0xFF0000FF));

        program.Add((byte)Opcode.mov);
        program.Add((byte)Register.r2);
        program.AddRange(BitConverter.GetBytes(0xFF00FF00));

        program.Add((byte)Opcode.xor);
        program.Add((byte)Register.r1);
        program.Add((byte)Register.r2);

        program.Add((byte)Opcode.halt);

        VM vm = new();
        vm.Run([.. program]);
    }
    enum Opcode : byte
    {
        mov = 0x01,
        xor = 0x02,
        halt = 0xFF
    }
    enum Register : byte
    {
        r1 = 0x00,
        r2 = 0x01
    }
    internal class VM
    {
        int[] Registers = [0, 0];
        int IP = 0;
        public void Run(byte[] bytecode)
        {
            IP = 0;
            bool running = true;
            while(IP < bytecode.Length & running)
            {
                var opcode = (Opcode)bytecode[IP++];
                switch(opcode)
                {
                    case Opcode.mov:
                        Mov(bytecode);
                        break;
                    case Opcode.xor:
                        Xor(bytecode);
                        break;
                    case Opcode.halt:
                        running = false;
                        break;
                }
            }
        }
        void Mov(byte[] bytecode)
        {
            byte i = bytecode[IP++];
            Registers[i] = 
                BitConverter.ToInt32(bytecode, IP);
            IP += sizeof(int);
        }
        void Xor(byte[] bytecode)
        {
            Registers[bytecode[IP++]] ^= 
                Registers[bytecode[IP++]];
        }
    }
}