using System;
using System.Runtime.InteropServices;

[StructLayout(LayoutKind.Sequential, Pack = 0)]
public class QuakeParms
{
    private const int MaxArgs = 50;     // Corresponds with MAX_NUM_ARGVS in engine
        
    [MarshalAs(UnmanagedType.LPStr)]
    public string baseDir;
        
    [MarshalAs(UnmanagedType.LPStr)]
    public string userDir;
        
    public int argc;
        
    [MarshalAs(UnmanagedType.LPArray, SizeConst = MaxArgs)] 
    public IntPtr[] argv;
        
    public IntPtr memBase;
        
    public int memSize;

    public int numCpus;

    public int errState;

    private IntPtr nativeBlock;

    public IntPtr ToNativePtr()
    {
        if (nativeBlock == IntPtr.Zero)
            nativeBlock = Marshal.AllocHGlobal(Marshal.SizeOf<QuakeParms>());
        
        Marshal.StructureToPtr(this, nativeBlock, false);
        return nativeBlock;
    }

    public void SetArguments(string[] arguments)
    {
        argc = arguments.Length;
        argv = new IntPtr[MaxArgs];
        for (int i = 0; i < arguments.Length && i < MaxArgs; ++i)
        {
            argv[i] = Marshal.StringToHGlobalAnsi(arguments[i]);
        }
    }

    public void AllocateMemory(int memorySize)
    {
        memSize = memorySize;
        memBase = Marshal.AllocHGlobal(memorySize);
        if (memBase == IntPtr.Zero)
        {
            throw new OutOfMemoryException($"Could not allocate {memorySize / 1024 / 1024} MB of heap memory!");
        }
    }
        
    public void Destroy()
    {
        if (nativeBlock != IntPtr.Zero)
        {
            Marshal.FreeHGlobal(nativeBlock);
            nativeBlock = IntPtr.Zero;
        }
        
        if (memBase != IntPtr.Zero)
        {
            Marshal.FreeHGlobal(memBase);
            memBase = IntPtr.Zero;
        }

        if (argv != null)
        {
            for (int i = 0; i < argv.Length; ++i)
            {
                if (argv[i] != IntPtr.Zero)
                {
                    Marshal.FreeHGlobal(argv[i]);
                    argv[i] = IntPtr.Zero;
                }
            }
        }
    }
}