using System;
using System.Runtime.InteropServices;

/// <summary>
/// Managed equivalent of texture_t
/// </summary>
[StructLayout(LayoutKind.Sequential, Pack = 0, CharSet = CharSet.Ansi)]
public struct QTexture
{
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 16)] public string name;
    public uint width, height;
    public IntPtr glTexture;    // Pointer to gltexture_t
    public IntPtr fullBright;   // Pointer to gltexture_t
    public IntPtr warpImage;    // Pointer to gltexture_t

    public uint TextureNum => QGLTexture.TexNumFromPtr(glTexture);
    public uint FullBrightNum => QGLTexture.TexNumFromPtr(fullBright);
    public uint WarpImageNum => QGLTexture.TexNumFromPtr(warpImage);
    
    // Rest of the fields are left out, so we don't unnecessarily marshal any unused data
}

/// <summary>
/// Managed equivalent of gltexture_t
/// </summary>
[StructLayout(LayoutKind.Sequential, Pack = 0, CharSet = CharSet.Ansi)]
public class QGLTexture
{
    public uint texNum;
    public IntPtr next;
    public IntPtr owner;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 64)] public string name;
    public uint width;
    public uint height;
    public QTexPrefs flags;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = QConstants.MaxQPath)] public string sourceFile;
    public UIntPtr sourceOffset;
    public QTexSourceFormat sourceFormat;
    public uint sourceWidth;
    public uint sourceHeight;
    public ushort sourceCrc;
    public char shirt;
    public char pants;
    public int visFrame;
    
    // Conveniently make use of the fact that texNum is the first field in QGLTexture,
    // so we don't have to marshal the entire struct to get the texture number out of it.
    public static uint TexNumFromPtr(IntPtr ptr) => ptr == IntPtr.Zero ? 0 : unchecked((uint)Marshal.ReadInt32(ptr));
}

/// <summary>
/// Managed equivalent of srcformat
/// </summary>
public enum QTexSourceFormat
{
    Indexed,
    Lightmap,
    Rgba,
}

/// <summary>
/// Managed equivalent of TEXPRF_ defines
/// </summary>
[Flags]
public enum QTexPrefs: uint
{
    None = 0x0000,
    Mipmap = 0x0001,
    Linear = 0x0002,
    Nearest = 0x0004,
    Alpha = 0x0008,
    Pad = 0x0010,
    Persist = 0x0020,
    Overwrite = 0x0040,
    NoPicMip = 0x0080,
    FullBright = 0x0100,
    NoBright = 0x0200,
    ConChars = 0x0400,
    WarpImage = 0x0800,
}