using System;
using System.Runtime.InteropServices;
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.PixelFormats;
using SlatedGameToolkit.Framework.Exceptions;
using SlatedGameToolkit.Framework.Graphics.OpenGL;
using SlatedGameToolkit.Framework.Graphics.Textures;

namespace SlatedGameToolkit.Commons.Loaders
{
    public static class TextureLoader
    {
        /// <summary>
        /// Loads a texture using SDL2's image library.
        /// Therefore, technically, this function should be able to laod any format SDL2 Image can load.
        /// </summary>
        /// <param name="path">The path of the texture to load.</param>
        /// <param name="glContext">The OpenGL context the texture is to be associated with. May be null.</param>
        /// <returns>An OpenGL Texture associated with the given context.</returns>
        public static Texture LoadTexture(string path, GLContext glContext)
        {
            TextureData textureData;
            using (Image<Rgba32> image = Image.Load<Rgba32>(path))
            {
                byte[] pixelData;
                Span<Rgba32> pixelDataSpan;
                if (image.TryGetSinglePixelSpan(out pixelDataSpan)) {
                    pixelData = MemoryMarshal.AsBytes(pixelDataSpan).ToArray();
                } else {
                    throw new FrameworkUsageException("Image too large!");
                }
                textureData = new TextureData(image.Width, image.Height, pixelData);
            }

            return new Texture(textureData, glContext);
        }
    }
}