#region --- License ---
/* Copyright (c) 2007 Stefanos Apostolopoulos
 * See license.txt for license info
 */
#endregion

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

using OpenTK.Graphics;

namespace OpenTK.Platform.X11
{
    /// \internal
    /// <summary>
    /// Provides methods to create and control an opengl context on the X11 platform.
    /// This class supports OpenTK, and is not intended for use by OpenTK programs.
    /// </summary>
    internal sealed class X11GLContext : DesktopGraphicsContext
    {
        #region Fields

        // We assume that we cannot move a GL context to a different display connection.
        // For this reason, we'll "lock" onto the display of the window used in the context
        // constructor and we'll throw an exception if the user ever tries to make the context
        // current on window originating from a different display.
        IntPtr display;
        X11WindowInfo currentWindow;
        bool vsync_ext_supported;
        bool vsync_mesa_supported;
        bool vsync_sgi_supported;
        bool vsync_tear_supported;
        int sgi_swap_interval = 1; // As defined in GLX_SGI_swap_control
        readonly X11GraphicsMode ModeSelector = new X11GraphicsMode();
        string extensions = null;

        #endregion

        #region --- Constructors ---

        static X11GLContext()
        {
            new Glx().LoadEntryPoints();
        }

        public X11GLContext(GraphicsMode mode, IWindowInfo window, IGraphicsContext shared, bool direct,
            int major, int minor, GraphicsContextFlags flags)
        {
            if (mode == null)
                throw new ArgumentNullException("mode");
            if (window == null)
                throw new ArgumentNullException("window");

            // Do not move this lower, as almost everything requires the Display
            // property to be correctly set.
            Display = ((X11WindowInfo)window).Display;

            // Check that GLX is supported. We cannot proceed to create
            // an OpenGL context without the GLX extension.
            int error_base;
            int event_base;
            int glx_major;
            int glx_minor;
            using (new XLock(Display))
            {
                bool supported = Glx.QueryExtension(Display, out error_base, out event_base);
                supported &= Glx.QueryVersion(Display, out glx_major, out glx_minor);
                if (supported)
                {
                    Debug.Print("[X11] GLX supported. Version is {0}.{1}", glx_major, glx_minor);
                }
                else
                {
                    throw new NotSupportedException("[X11] GLX extension is not supported.");
                }
            }

            IntPtr visual = IntPtr.Zero;
            IntPtr fbconfig = IntPtr.Zero;

            // Once a window has a visual, we cannot use a different
            // visual on the OpenGL context, or glXMakeCurrent might fail.
            // Note: we should only check X11WindowInfo.Visual, as that
            // is the only property that can be set by Utilities.CreateX11WindowInfo.
            currentWindow = (X11WindowInfo)window;
            if (currentWindow.Visual != IntPtr.Zero)
            {
                visual = currentWindow.Visual;
                fbconfig = currentWindow.FBConfig;
                Mode = currentWindow.GraphicsMode;
            }

            if (Mode == null || !Mode.Index.HasValue)
            {
                Mode = ModeSelector.SelectGraphicsMode(mode, out visual, out fbconfig);
            }

            ContextHandle shareHandle = shared != null ?
                (shared as IGraphicsContextInternal).Context : (ContextHandle)IntPtr.Zero;
            
            Debug.Write("Creating X11GLContext context: ");
            Debug.Write(direct ? "direct, " : "indirect, ");
            Debug.WriteLine(shareHandle.Handle == IntPtr.Zero ? "not shared... " :
                String.Format("shared with ({0})... ", shareHandle));
            
            // Try using the new context creation method. If it fails, fall back to the old one.
            // For each of these methods, we try two times to create a context:
            // one with the "direct" flag intact, the other with the flag inversed.
            // HACK: It seems that Catalyst 9.1 - 9.4 on Linux have problems with contexts created through
            // GLX_ARB_create_context, including hideous input lag, no vsync and other madness.
            // Use legacy context creation if the user doesn't request a 3.0+ context.
            if (fbconfig != IntPtr.Zero && (major * 10 + minor >= 30) && SupportsCreateContextAttribs(Display, currentWindow))
            {
                Handle = CreateContextAttribs(Display, currentWindow.Screen,
                    fbconfig, direct, major, minor, flags, shareHandle);
            }
            
            if (Handle == ContextHandle.Zero)
            {
                Handle = CreateContextLegacy(Display, visual, direct, shareHandle);
            }
            
            if (Handle != ContextHandle.Zero)
                Debug.Print("Context created (id: {0}).", Handle);
            else
                throw new GraphicsContextException("Failed to create OpenGL context. Glx.CreateContext call returned 0.");

            using (new XLock(Display))
            {
                if (!Glx.IsDirect(Display, Handle.Handle))
                    Debug.Print("Warning: Context is not direct.");
            }
        }

        public X11GLContext(ContextHandle handle, IWindowInfo window, IGraphicsContext shared, bool direct,
            int major, int minor, GraphicsContextFlags flags)
        {
            if (handle == ContextHandle.Zero)
                throw new ArgumentException("handle");
            if (window == null)
                throw new ArgumentNullException("window");

            Handle = handle;
            currentWindow = (X11WindowInfo)window;
            Display = currentWindow.Display;
        }

        #endregion

        #region --- Private Methods ---

        static ContextHandle CreateContextAttribs(
            IntPtr display, int screen, IntPtr fbconfig,
            bool direct, int major, int minor,
            GraphicsContextFlags flags, ContextHandle shareContext)
        {
            Debug.Write("Using GLX_ARB_create_context... ");
            IntPtr context = IntPtr.Zero;

            {
                // We need the FB config for the current GraphicsMode.
                List<int> attributes = new List<int>();
                attributes.Add((int)ArbCreateContext.MajorVersion);
                attributes.Add(major);
                attributes.Add((int)ArbCreateContext.MinorVersion);
                attributes.Add(minor);
                if (flags != 0)
                {
                    attributes.Add((int)ArbCreateContext.Flags);
                    attributes.Add((int)GetARBContextFlags(flags));
                    attributes.Add((int)ArbCreateContext.ProfileMask);
                    attributes.Add((int)GetARBProfileFlags(flags));
                }
                // According to the docs, " <attribList> specifies a list of attributes for the context.
                // The list consists of a sequence of <name,value> pairs terminated by the
                // value 0. [...]"
                // Is this a single 0, or a <0, 0> pair? (Defensive coding: add two zeroes just in case).
                attributes.Add(0);
                attributes.Add(0);

                using (new XLock(display))
                {
                    context = Glx.Arb.CreateContextAttribs(display, fbconfig, shareContext.Handle, direct, attributes.ToArray());
                    if (context == IntPtr.Zero)
                    {
                        Debug.Write(String.Format("failed. Trying direct: {0}... ", !direct));
                        context = Glx.Arb.CreateContextAttribs(display, fbconfig, shareContext.Handle, !direct, attributes.ToArray());
                    }
                }

                if (context == IntPtr.Zero)
                    Debug.WriteLine("failed.");
                else
                    Debug.WriteLine("success!");
            }

            return new ContextHandle(context);
        }

        static ContextHandle CreateContextLegacy(IntPtr display,
            IntPtr info, bool direct, ContextHandle shareContext)
        {
            Debug.Write("Using legacy context creation... ");
            IntPtr context;

            using (new XLock(display))
            {
                context = Glx.CreateContext(display, info, shareContext.Handle, direct);
                if (context == IntPtr.Zero)
                {
                    Debug.WriteLine(String.Format("failed. Trying direct: {0}... ", !direct));
                    context = Glx.CreateContext(display, info, shareContext.Handle, !direct);
                }
            }

            return new ContextHandle(context);
        }

        IntPtr Display
        {
            get { return display; }
            set
            {
                if (value == IntPtr.Zero)
                    throw new ArgumentOutOfRangeException();
                if (display != IntPtr.Zero)
                    throw new InvalidOperationException("The display connection may not be changed after being set.");
                display = value;
            }
        }

        static ArbCreateContext GetARBContextFlags(GraphicsContextFlags flags)
        {
            ArbCreateContext result = 0;
            result |= (flags & GraphicsContextFlags.Debug) != 0 ? ArbCreateContext.DebugBit : 0;
            return result;
        }

        static ArbCreateContext GetARBProfileFlags(GraphicsContextFlags flags)
        {
            ArbCreateContext result = 0;
            result |= (flags & GraphicsContextFlags.ForwardCompatible) != 0 ?
                ArbCreateContext.CoreProfileBit : ArbCreateContext.CompatibilityProfileBit;
            return result;
        }

        bool SupportsExtension(IntPtr display, X11WindowInfo window, string e)
        {
            if (window == null)
                throw new ArgumentNullException("window");
            if (e == null)
                throw new ArgumentNullException("e");
            if (window.Display != display)
                throw new InvalidOperationException();

            if (String.IsNullOrEmpty(extensions))
            {
                using (new XLock(display))
                {
                    extensions = Glx.QueryExtensionsString(display, window.Screen);
                }
            }
            return !String.IsNullOrEmpty(extensions) && extensions.Contains(e);
        }

        bool SupportsCreateContextAttribs(IntPtr display, X11WindowInfo window)
        {
            return
                SupportsExtension(display, window, "GLX_ARB_create_context") &&
                SupportsExtension(display, window, "GLX_ARB_create_context_profile");
        }

        #endregion

        #region --- IGraphicsContext Members ---

        #region SwapBuffers()

        public override void SwapBuffers()
        {
            if (Display == IntPtr.Zero || currentWindow.Handle == IntPtr.Zero)
                throw new InvalidOperationException(
                    String.Format("Window is invalid. Display ({0}), Handle ({1}).", Display, currentWindow.Handle));
            using (new XLock(Display))
            {
                Glx.SwapBuffers(Display, currentWindow.Handle);
            }
        }

        #endregion

        #region MakeCurrent

        public override void MakeCurrent(IWindowInfo window)
        {
            if (window == currentWindow && IsCurrent)
                return;

            if (window != null && ((X11WindowInfo)window).Display != Display)
                throw new InvalidOperationException("MakeCurrent() may only be called on windows originating from the same display that spawned this GL context.");

            if (window == null)
            {
                Debug.Write(String.Format("Releasing context {0} from thread {1} (Display: {2})... ",
                        Handle, System.Threading.Thread.CurrentThread.ManagedThreadId, Display));

                bool result;
                using (new XLock(Display))
                {
                    result = Glx.MakeCurrent(Display, IntPtr.Zero, IntPtr.Zero);
                    if (result)
                    {
                        currentWindow = null;
                    }
                }
                Debug.Print("{0}", result ? "done!" : "failed.");
            }
            else
            {
                X11WindowInfo w = (X11WindowInfo)window;
                bool result;

                Debug.Write(String.Format("Making context {0} current on thread {1} (Display: {2}, Screen: {3}, Window: {4})... ",
                        Handle, System.Threading.Thread.CurrentThread.ManagedThreadId, Display, w.Screen, w.Handle));

                if (Display == IntPtr.Zero || w.Handle == IntPtr.Zero || Handle == ContextHandle.Zero)
                    throw new InvalidOperationException("Invalid display, window or context.");

                using (new XLock(Display))
                {
                    result = Glx.MakeCurrent(Display, w.Handle, Handle);
                    if (result)
                    {
                        currentWindow = w;
                    }
                }

                if (!result)
                    throw new GraphicsContextException("Failed to make context current.");
                else
                    Debug.WriteLine("done!");
            }

            currentWindow = (X11WindowInfo)window;
        }

        #endregion

        #region IsCurrent

        public override bool IsCurrent
        {
            get
            {
                using (new XLock(Display))
                {
                    return Glx.GetCurrentContext() == Handle.Handle;
                }
            }
        }

        #endregion

        #region SwapInterval

        public override int SwapInterval
        {
            get
            {
                if (currentWindow == null)
                {
                    Debug.Print("Context must be current");
                    throw new InvalidOperationException();
                }

                using (new XLock(display))
                {
                    if (vsync_ext_supported)
                    {
                        int value;
                        Glx.QueryDrawable(Display, currentWindow.Handle, GLXAttribute.SWAP_INTERVAL_EXT, out value);
                        return value;
                    }
                    else if (vsync_mesa_supported)
                    {
                        return Glx.Mesa.GetSwapInterval();
                    }
                    else if (vsync_sgi_supported)
                    {
                        return sgi_swap_interval;
                    }

                    return 0;
                }
            }
            set
            {
                if (currentWindow == null)
                {
                    Debug.Print("Context must be current");
                    throw new InvalidOperationException();
                }

                if (value < 0 && !vsync_tear_supported)
                {
                    value = 1;
                }

                ErrorCode error_code = 0;
                using (new XLock(Display))
                {
                    if (vsync_ext_supported)
                    {
                        Glx.Ext.SwapInterval(Display, currentWindow.Handle, value);
                    }
                    else if (vsync_mesa_supported)
                    {
                        error_code = Glx.Mesa.SwapInterval(value);
                    }
                    else if (vsync_sgi_supported)
                    {
                        error_code = Glx.Sgi.SwapInterval(value);
                    }
                }

                if (error_code == X11.ErrorCode.NO_ERROR)
                    sgi_swap_interval = value;
                else
                    Debug.Print("VSync = {0} failed, error code: {1}.", value, error_code);
            }
        }

        #endregion

        #region LoadAll

        public override void LoadAll()
        {
            // Note: GLX entry points are always available, even
            // for extensions that are not currently supported by
            // the underlying driver. This means we can only check
            // the extension strings for support, not the entry
            // points themselves.
            vsync_ext_supported =
                SupportsExtension(display, currentWindow, "GLX_EXT_swap_control");
            vsync_mesa_supported =
                SupportsExtension(display, currentWindow, "GLX_MESA_swap_control");
            vsync_sgi_supported =
                SupportsExtension(display, currentWindow, "GLX_SGI_swap_control");
            vsync_tear_supported =
                SupportsExtension(display, currentWindow, "GLX_EXT_swap_control_tear");

            Debug.Print("Context supports vsync: {0}.",
                vsync_ext_supported || vsync_mesa_supported || vsync_sgi_supported);
            Debug.Print("Context supports adaptive vsync: {0}.",
                vsync_tear_supported);

            base.LoadAll();
        }

        #endregion

        #endregion

        #region --- IGraphicsContextInternal Members ---

        #region GetAddress

        public override IntPtr GetAddress(IntPtr function)
        {
            using (new XLock(Display))
            {
                return Glx.GetProcAddress(function);
            }
        }

        #endregion

        #endregion

        #region --- IDisposable Members ---

        protected override void Dispose(bool manuallyCalled)
        {
            if (!IsDisposed)
            {
                if (manuallyCalled)
                {
                    IntPtr display = Display;

                    if (IsCurrent)
                    {
                        using (new XLock(display))
                        {
                            Glx.MakeCurrent(display, IntPtr.Zero, IntPtr.Zero);
                        }
                    }
                    using (new XLock(display))
                    {
                        Glx.DestroyContext(display, Handle);
                    }
                }
            }
            else
            {
                Debug.Print("[Warning] {0} leaked.", this.GetType().Name);
            }
            IsDisposed = true;
        }

        #endregion
    }
}