using Core.Interfaces;
using System.Diagnostics;
using static System.Runtime.InteropServices.JavaScript.JSType;

namespace Core.Io
{
    public class IO_Bus
{
        public byte BorderColorIndex { get; private set; } = 7;
        public bool BeeperState { get; private set; } = false;
        public byte[] KeyboardRows = new byte[8] { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };

    public byte ReadPort(ushort portAddress)
    {
        // The Spectrum ULA responds to any even port address (where the lowest bit is 0)
        if ((portAddress & 0x01) == 0)
        {
            byte highByte = (byte)(portAddress >> 8); // The B register!
            byte result = 0xFF; // Start assuming no keys are pressed

            // The ROM pulls a specific bit low (0) in the high byte to request a row.
            // Sometimes it pulls multiple bits low to scan multiple rows at once, so we AND the results.
            if ((highByte & 0x01) == 0) result &= KeyboardRows[0]; // 0xFE: CAPS, Z, X, C, V
            if ((highByte & 0x02) == 0) result &= KeyboardRows[1]; // 0xFD: A, S, D, F, G
            if ((highByte & 0x04) == 0) result &= KeyboardRows[2]; // 0xFB: Q, W, E, R, T
            if ((highByte & 0x08) == 0) result &= KeyboardRows[3]; // 0xF7: 1, 2, 3, 4, 5
            if ((highByte & 0x10) == 0) result &= KeyboardRows[4]; // 0xEF: 0, 9, 8, 7, 6
            if ((highByte & 0x20) == 0) result &= KeyboardRows[5]; // 0xDF: P, O, I, U, Y
            if ((highByte & 0x40) == 0) result &= KeyboardRows[6]; // 0xBF: ENTER, L, K, J, H
            if ((highByte & 0x80) == 0) result &= KeyboardRows[7]; // 0x7F: SPACE, SYM, M, N, B

            // The top 3 bits (5, 6, 7) are unused by the keyboard and usually return 1 on a real Spectrum
            return (byte)(result | 0xE0);
        }

        // Return 0xFF for unhandled ports
        return 0xFF; 
    }

        public void WritePort(ushort portAddress, byte portValue)
        {
            // The ULA intercepts any write to an even port address
            if ((portAddress & 0x01) == 0)
            {
                // The bottom 3 bits (0-2) define the border color
                BorderColorIndex = (byte)(portValue & 0x07);

                // Bit 4 controls the speaker
                BeeperState = (portValue & 0x10) != 0;

                // Bit 3 handles the cassette MIC output
            }
        }
    }
}