using System;
using ParsonsMegadrive.Core.Interfaces;

namespace ParsonsMegaDrive.Core.Memory
{
    public class MdMemoryBus : IMemoryBus
    {
        // For testing, we'll just give it a flat 16MB array to represent the whole address space.
        // Later, we will map this properly to ROM (0x000000), Work RAM (0xFF0000), etc.
        private readonly byte[] _memory = new byte[16 * 1024 * 1024];

        public byte Read8(uint address)
        {
            return _memory[address & 0xFFFFFF]; // 24-bit address mask
        }

        public void Write8(uint address, byte value)
        {
            _memory[address & 0xFFFFFF] = value;
        }

        public ushort Read16(uint address)
        {
            // BIG-ENDIAN: High byte comes first!
            byte high = Read8(address);
            byte low = Read8(address + 1);
            return (ushort)((high << 8) | low);
        }

        public void Write16(uint address, ushort value)
        {
            Write8(address, (byte)(value >> 8));   // High byte
            Write8(address + 1, (byte)(value & 0xFF)); // Low byte
        }

        public uint Read32(uint address)
        {
            ushort highWord = Read16(address);
            ushort lowWord = Read16(address + 2);
            return (uint)((highWord << 16) | lowWord);
        }

        public void Write32(uint address, uint value)
        {
            Write16(address, (ushort)(value >> 16));
            Write16(address + 2, (ushort)(value & 0xFFFF));
        }
    }
}