using System.Runtime.InteropServices;

namespace Meum.Core.Messages;

[StructLayout(LayoutKind.Sequential)]
public struct DataMessageHeader
{
    // 0xb65d6d - meum in 6-bit ascii encoding
    // 02 - DataMessageHeader
    private const uint correct_magic = 0xb65d6d02;
    
    /// warning: check with <see cref="ThrowIfInvalid"/> 
    public uint magic;
    /// warning: can be any int
    public MessageTypeCode type_code;
    /// warning: check with <see cref="ThrowIfInvalid"/> 
    public int data_size;
    
    
    public DataMessageHeader(MessageTypeCode t, int size)
    {
        magic = correct_magic;
        type_code = t;
        data_size = size;
    }
    
    public void ThrowIfInvalid()
    {
        if(magic != correct_magic)
            throw new Exception($"Invalid DataMessageHeader magic: {magic}");
        if(data_size < 1)
            throw new Exception($"Invalid DataMessageHeader data size: {data_size}");
    }
}