using System;
using System.Collections.Generic;

namespace MCEmuCore.GBMonolith
{
    public struct OpCode
    {
        public readonly byte Instruction;
        public byte? Arg1;
        public byte? Arg2;
    }
    class Cpu
    {
        const byte ZERO_FLAG =  0b10000000;
        const byte SUB_FLAG =   0b01000000;
        const byte HALF_CARRY = 0b00100000;
        const byte FULL_CARRY = 0b00010000;
        private readonly CpuRegisters registers;
        #region OpCodes
        
        private readonly Dictionary<byte, Func<OpCode, bool>> OpCodeTable;
        #endregion

        public Cpu()
        {
            registers = new CpuRegisters();
            
            OpCodeTable = new Dictionary<byte, Func<OpCode, bool>>()
            {
                {0x00, (op) => {
                    registers.PC += 1;
                    return true;
                } },
                {0x01, (op) =>
                {
                    // LD BC,d16
                    if (op.Arg1.HasValue && op.Arg2.HasValue)
                    {
                        ushort operand = (ushort)(op.Arg2 + (op.Arg1 << 8));
                        registers.BC = operand;
                        registers.PC += 3;
                        return true;
                    }
                    else
                    {
                        throw new InvalidOperationException(op, "Missing arguments for LD BC");
	                }
                } },
                {0x02, (op) =>
                {
                    // LD (BC), A
                    throw new NotImplementedException("LD (BC), A");
                } },
                {0x03, (op) =>
                {
                    registers.BC += 1;
                    registers.PC += 1;
                    return true;
                } },
                {0x04, (op) =>
                {
                    // INC B
                    byte reg = (byte)(registers.B + 1);
                    registers.B = reg;

                    registers.Flags.Subtract = false;
                    registers.Flags.Zero = reg == 0;
                    registers.Flags.HalfCarry = reg == 16;

                    registers.PC += 1;
                    return true;
                } }
            };
        }
    }


    [Serializable]
    public class InvalidOperationException : Exception
    {
        public OpCode OpCode { get; set; }
        public InvalidOperationException() { }
        public InvalidOperationException(OpCode opCode, string message) : base(message)
        {
            OpCode = opCode;
        }
        public InvalidOperationException(string message) : base(message) { }
        public InvalidOperationException(string message, Exception inner) : base(message, inner) { }
        protected InvalidOperationException(
          System.Runtime.Serialization.SerializationInfo info,
          System.Runtime.Serialization.StreamingContext context) : base(info, context) { }
    }
}