using System;
using System.Collections.Generic;
using System.Text;
using System.Drawing;
using OpenTK.Graphics.OpenGL;

namespace HelperClasses
{
    public class FboRenderTexture : IDisposable
    {
        public int textureId = 0;
        private int fboId = 0;

        public Size textureSize;

        public FboRenderTexture(int width, int height)
        {
            this.textureSize = new Size(width, height);
        }

        public FboRenderTexture(Size size)
        {
            this.textureSize = size;

            Init();
        }

        private void Init()
        {
            // Generate the texture.
            GL.GenTextures(1, out textureId);
            GL.BindTexture(TextureTarget.Texture2D, textureId);
            GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgba8, size.Width, size.Height, 0, PixelFormat.Rgba, PixelType.UnsignedByte, IntPtr.Zero);
            GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)TextureMinFilter.Linear);
            GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)TextureMagFilter.Linear);
            GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapS, (int)TextureWrapMode.ClampToBorder);
            GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapT, (int)TextureWrapMode.ClampToBorder);

            // Create a FBO and attach the texture.
            GL.Ext.GenFramebuffers(1, out fboId);
            GL.Ext.BindFramebuffer(FramebufferTarget.FramebufferExt, fboId);
            GL.Ext.FramebufferTexture2D(FramebufferTarget.FramebufferExt,
                FramebufferAttachment.ColorAttachment0Ext, TextureTarget.Texture2D, textureId, 0);

            CheckErrors();

            // Set up the FBO for drawing.
            GL.PushAttrib(AttribMask.ViewportBit);
            {
                GL.Viewport(0, 0, textureSize.Width, textureSize.Height);

                // Just clear the FBO.
                GL.Clear(ClearBufferMask.ColorBufferBit);
            }
            GL.PopAttrib();

            // Disable rendering into the FBO
            GL.Ext.BindFramebuffer(FramebufferTarget.FramebufferExt, 0);
        }

        // Track whether Dispose has been called.
        private bool disposed = false;

        public void Dispose()
        {
            Dispose(true);

            GC.SuppressFinalize(this);
        }

        private void Dispose(bool disposing)
        {
            if (!this.disposed)
            {
                if (disposing)
                {
                    // Clean up what we allocated before exiting
                    if (textureId != 0)
                        GL.DeleteTextures(1, ref textureId);

                    if (fboId != 0)
                        GL.Ext.DeleteFramebuffers(1, ref fboId);

                    disposed = true;
                }
            }
        }

        public void BeginDrawing()
        {
            // Attach the framebuffer.
            GL.Ext.BindFramebuffer(FramebufferTarget.FramebufferExt, fboId);
            
            GL.PushAttrib(AttribMask.ViewportBit);

            // Setup the viewport to be the texturesize.
            GL.Viewport(0, 0, textureSize.Width, textureSize.Height);
        }

        public void EndDrawing()
        {
            GL.PopAttrib();

            GL.Ext.BindFramebuffer(FramebufferTarget.FramebufferExt, 0); // disable rendering into the FBO

        }

        private void CheckErrors()
        {
            switch (GL.Ext.CheckFramebufferStatus(FramebufferTarget.FramebufferExt))
            {
                case FramebufferErrorCode.FramebufferCompleteExt:
                    {
                        Console.WriteLine("FBO: The framebuffer is complete and valid for rendering.");
                        break;
                    }
                case FramebufferErrorCode.FramebufferIncompleteAttachmentExt:
                    {
                        Console.WriteLine("FBO: One or more attachment points are not framebuffer attachment complete. This could mean there’s no texture attached or the format isn’t renderable. For color textures this means the base format must be RGB or RGBA and for depth textures it must be a DEPTH_COMPONENT format. Other causes of this error are that the width or height is zero or the z-offset is out of range in case of render to volume.");
                        break;
                    }
                case FramebufferErrorCode.FramebufferIncompleteMissingAttachmentExt:
                    {
                        Console.WriteLine("FBO: There are no attachments.");
                        break;
                    }
                /* case  FramebufferErrorCode.GL_FRAMEBUFFER_INCOMPLETE_DUPLICATE_ATTACHMENT_EXT: 
                     {
                         Console.WriteLine("FBO: An object has been attached to more than one attachment point.");
                         break;
                     }*/
                case FramebufferErrorCode.FramebufferIncompleteDimensionsExt:
                    {
                        Console.WriteLine("FBO: Attachments are of different size. All attachments must have the same width and height.");
                        break;
                    }
                case FramebufferErrorCode.FramebufferIncompleteFormatsExt:
                    {
                        Console.WriteLine("FBO: The color attachments have different format. All color attachments must have the same format.");
                        break;
                    }
                case FramebufferErrorCode.FramebufferIncompleteDrawBufferExt:
                    {
                        Console.WriteLine("FBO: An attachment point referenced by GL.DrawBuffers() doesn’t have an attachment.");
                        break;
                    }
                case FramebufferErrorCode.FramebufferIncompleteReadBufferExt:
                    {
                        Console.WriteLine("FBO: The attachment point referenced by GL.ReadBuffers() doesn’t have an attachment.");
                        break;
                    }
                case FramebufferErrorCode.FramebufferUnsupportedExt:
                    {
                        Console.WriteLine("FBO: This particular FBO configuration is not supported by the implementation.");
                        break;
                    }
                default:
                    {
                        Console.WriteLine("FBO: Status unknown. (yes, this is really bad.)");
                        break;
                    }
            }

            // using FBO might have changed states, e.g. the FBO might not support stereoscopic views or double buffering
            int[] queryinfo = new int[6];
            GL.GetInteger(GetPName.MaxColorAttachmentsExt, out queryinfo[0]);
            GL.GetInteger(GetPName.AuxBuffers, out queryinfo[1]);
            GL.GetInteger(GetPName.MaxDrawBuffers, out queryinfo[2]);
            GL.GetInteger(GetPName.Stereo, out queryinfo[3]);
            GL.GetInteger(GetPName.Samples, out queryinfo[4]);
            GL.GetInteger(GetPName.Doublebuffer, out queryinfo[5]);
            Console.WriteLine("max. ColorBuffers: " + queryinfo[0] + " max. AuxBuffers: " + queryinfo[1] + " max. DrawBuffers: " + queryinfo[2] +
                               "\nStereo: " + queryinfo[3] + " Samples: " + queryinfo[4] + " DoubleBuffer: " + queryinfo[5]);

            Console.WriteLine("Last GL Error: " + GL.GetError());
        }
    }
}