#region --- License ---
/* Copyright (c) 2006, 2007 Stefanos Apostolopoulos
 * Contributions from Erik Ylvisaker
 * See license.txt for license info
 */
#endregion

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

using OpenTK.OpenGL;
using System.Diagnostics;


namespace OpenTK.Platform.Windows
{
    public sealed class WinGLContext : OpenTK.Platform.IGLContext, IDisposable
    {
        private IntPtr deviceContext;
        private IntPtr renderContext;
        static private IntPtr opengl32Handle;
        static private readonly string opengl32Name = "OPENGL32.DLL";
        private IntPtr windowHandle;

        private bool disposed;

        #region --- Contructors ---

        public WinGLContext(IntPtr windowHandle)
            : this(windowHandle, new DisplayMode(640, 480, new ColorDepth(32), 16, 0, 0, 2, false, false, false, 0.0f))
        {
        }

        public WinGLContext(IntPtr windowHandle, DisplayMode mode)
        {
            Trace.WriteLine(String.Format("Creating opengl context (driver: {0})", this.ToString()));
            Trace.Indent();

            this.windowHandle = windowHandle;
            Trace.WriteLine(String.Format("Window handle: {0}", windowHandle));

            PrepareContext(mode);

            CreateContext();

            Trace.Unindent();
        }

        #endregion

        public void CreateContext()
        {
            Trace.Write("Creating render context... ");
            renderContext = Wgl.CreateContext(deviceContext);
            Trace.WriteLine(String.Format("done! (id: {0})", renderContext));
        }

        public void PrepareContext(DisplayMode mode)
        {
            // Dynamically load the OpenGL32.dll in order to use the extension loading capabilities of Wgl.
            if (opengl32Handle == IntPtr.Zero)
            {
                opengl32Handle = API.LoadLibrary(opengl32Name);
                if (opengl32Handle == IntPtr.Zero)
                {
                    //System.Diagnostics.Debug.WriteLine("LoadLibrary({0}) set error code: {1}. Will not load extensions.", _dll_name, error_code);
                    throw new ApplicationException(
                        String.Format(
                            "LoadLibrary(\"{0}\") call failed with code {1}",
                            opengl32Name,
                            Marshal.GetLastWin32Error()
                        )
                    );
                }
                Trace.WriteLine(String.Format("Loaded opengl32.dll: {0}", opengl32Handle));
            }

            deviceContext = API.GetDC(windowHandle);
            Trace.WriteLine(String.Format("Device context: {0}", deviceContext));

            Trace.Write("Setting pixel format... ");
            API.PixelFormatDescriptor pixelFormat = new API.PixelFormatDescriptor();

            pixelFormat.ColorBits = (byte)(mode.Color.Red + mode.Color.Green + mode.Color.Blue);
            pixelFormat.RedBits = (byte)mode.Color.Red;
            pixelFormat.GreenBits = (byte)mode.Color.Green;
            pixelFormat.BlueBits = (byte)mode.Color.Blue;
            pixelFormat.AlphaBits = (byte)mode.Color.Alpha;
            /*
            if (accum != null)
            {
                pixelFormat.AccumBits = (byte)(accum.Red + accum.Green + accum.Blue);
                pixelFormat.AccumRedBits = (byte)accum.Red;
                pixelFormat.AccumGreenBits = (byte)accum.Green;
                pixelFormat.AccumBlueBits = (byte)accum.Blue;
                pixelFormat.AccumAlphaBits = (byte)accum.Alpha;
            }
            */
            pixelFormat.DepthBits = (byte)mode.DepthBits;
            pixelFormat.StencilBits = (byte)mode.StencilBits;

            if (mode.DepthBits <= 0)
            {
                pixelFormat.Flags |= API.PixelFormatDescriptorFlags.DEPTH_DONTCARE;
            }

            if (mode.Stereo)
            {
                pixelFormat.Flags |= API.PixelFormatDescriptorFlags.STEREO;
            }

            if (mode.Buffers > 1)
            {
                pixelFormat.Flags |= API.PixelFormatDescriptorFlags.DOUBLEBUFFER;
            }

            // TODO: More elaborate mode setting, using DescribePixelFormat.

            int pixel = API.ChoosePixelFormat(deviceContext, pixelFormat);

            if (pixel == 0)
            {
                throw new ApplicationException("The requested pixel format is not supported by the hardware configuration.");
            }

            API.SetPixelFormat(deviceContext, pixel, pixelFormat);

            Trace.WriteLine(String.Format("done! (format: {0})", pixel));
        }

        #region --- IGLContext Members ---

        #region public void SwapBuffers()

        public void SwapBuffers()
        {
            API.SwapBuffers(deviceContext);
        }

        #endregion

        #region public IntPtr GetAddress(string function_string)

        public IntPtr GetAddress(string function_string)
        {
            return Wgl.GetProcAddress(function_string);
        }

        #endregion

        #region public void MakeCurrent()
        
        public void MakeCurrent()
        {
            Wgl.MakeCurrent(deviceContext, renderContext);
        }

	    #endregion

        #region public DisplayMode[] GetDisplayModes()

        public IEnumerable<DisplayMode> GetDisplayModes()
        {
            List<DisplayMode> modes = new List<DisplayMode>();
            bool done = false;
            int index = 0;

            while (!done)
            {
                API.DeviceMode currentMode = new API.DeviceMode();
                IntPtr handle = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(API.DeviceMode)));
                Marshal.StructureToPtr(currentMode, handle, true);

                done = (API.EnumDisplaySettings(null, index++, handle) != 0) ? false : true;
                int error = Marshal.GetLastWin32Error();

                Marshal.PtrToStructure(handle, currentMode);
                Marshal.FreeHGlobal(handle);

                if (error != 0)
                {
                    Console.WriteLine("Error: {0}", error);
                    continue;
                }
                if (done)
                    break;

                //DisplayMode mode = new DisplayMode(currentMode.PelsWidth, currentMode.PelsHeight);
                DisplayMode mode = new DisplayMode(
                    currentMode.PelsWidth,
                    currentMode.PelsHeight,
                    new ColorDepth(currentMode.BitsPerPel),
                    0,
                    0,
                    0,
                    0,
                    false,
                    false,
                    false,
                    currentMode.DisplayFrequency
                );

                modes.Add(mode);
            }

            return modes.ToArray();
        }

        #endregion

        #endregion

        #region --- IDisposable Members ---

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        private void Dispose(bool calledManually)
        {
            if (!disposed)
            {
                // Clean unmanaged resources here:
                Wgl.MakeCurrent(deviceContext, renderContext);
                Wgl.DeleteContext(renderContext);
                API.ReleaseDC(windowHandle, deviceContext);
                API.FreeLibrary(opengl32Handle);

                if (calledManually)
                {
                    // Safe to clean managed resources
                }
                disposed = true;
            }
        }

        ~WinGLContext()
        {
            Dispose(false);
        }

        #region public void ReleaseResources()

        private void ReleaseResources()
        {
            if (renderContext != IntPtr.Zero)
            {
                if (!Wgl.DeleteContext(renderContext))
                {
                    throw new ApplicationException(
                        "Could not destroy the OpenGL render context. Error: " + Marshal.GetLastWin32Error()
                    );
                }
                renderContext = IntPtr.Zero;
            }

            if (opengl32Handle != IntPtr.Zero)
            {
                if (!API.FreeLibrary(opengl32Handle))
                {
                    throw new ApplicationException(
                        "FreeLibray call failed ('opengl32.dll'), Error: " + Marshal.GetLastWin32Error()
                    );
                }
                opengl32Handle = IntPtr.Zero;
            }
        }

        #endregion

        #endregion
    }
}