using System.IO;
using StbiSharp;
using static OpenGL.GL;

namespace OpenGLTutorial.Rendering.Display {
    public class Texture {

        public static Texture Empty => new(null);

        public int Width { get; private set; }
        public int Height { get; private set; }
        
        private uint Address { get; set; }
        private string Path { get; }
        private bool _loaded = false;

        public Texture(string path) {
            Path = path;
        }

        public unsafe void Load() {
            if (_loaded) return;
            _loaded = true;
            Address = glGenTexture();
            glBindTexture(GL_TEXTURE_2D, Address);
            
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

            if (string.IsNullOrEmpty(Path)) {
                LoadEmpty();
                return;
            }

            using var stream = File.OpenRead(Path);
            using var memoryStream = new MemoryStream();
            stream.CopyTo(memoryStream);
            StbiImage image = Stbi.LoadFromMemory(memoryStream, 0);
            int format = image.NumChannels == 3 ? GL_RGB : GL_RGBA;
            fixed(byte* data = &image.Data[0])
                glTexImage2D(GL_TEXTURE_2D, 0, format, image.Width, image.Height, 0, format, GL_UNSIGNED_BYTE, data);
            Width = image.Width;
            Height = image.Height;
            
            glBindTexture(GL_TEXTURE_2D, 0);
        }

        private unsafe void LoadEmpty() {
            byte[] pixels = {255, 255, 255, 255};

            fixed (byte* data = &pixels[0]) {
                glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 1, 1, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
            }

            Width = 1;
            Height = 1;
            
            glBindTexture(GL_TEXTURE_2D, 0);
        }

        public void Use() {
            glBindTexture(GL_TEXTURE_2D, Address);
        }

        public void Delete() {
            glBindTexture(GL_TEXTURE_2D, 0);
            glDeleteTexture(Address);
        }
        
    }
}