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

namespace CPF.Skia
{
	internal class Glx
	{
		private const string libGL = "libGL";

		public const int GL_TEXTURE_2D = 0x0DE1;
		public const int GL_UNSIGNED_BYTE = 0x1401;
		public const int GL_RGBA = 0x1908;
		public const int GL_RGBA8 = 0x8058;

		public const int GLX_USE_GL = 1;
		public const int GLX_BUFFER_SIZE = 2;
		public const int GLX_LEVEL = 3;
		public const int GLX_RGBA = 4;
		public const int GLX_DOUBLEBUFFER = 5;
		public const int GLX_STEREO = 6;
		public const int GLX_AUX_BUFFERS = 7;
		public const int GLX_RED_SIZE = 8;
		public const int GLX_GREEN_SIZE = 9;
		public const int GLX_BLUE_SIZE = 10;
		public const int GLX_ALPHA_SIZE = 11;
		public const int GLX_DEPTH_SIZE = 12;
		public const int GLX_STENCIL_SIZE = 13;
		public const int GLX_ACCUM_RED_SIZE = 14;
		public const int GLX_ACCUM_GREEN_SIZE = 15;
		public const int GLX_ACCUM_BLUE_SIZE = 16;
		public const int GLX_ACCUM_ALPHA_SIZE = 17;

		public const int GLX_DRAWABLE_TYPE = 0x8010;
		public const int GLX_RENDER_TYPE = 0x8011;
		public const int GLX_X_RENDERABLE = 0x8012;
		public const int GLX_RGBA_TYPE = 0x8014;
		public const int GLX_COLOR_INDEX_TYPE = 0x8015;

		public const int GLX_PIXMAP_BIT = 0x00000002;
		
		public const int GLX_RGBA_BIT = 0x00000001;

		public const int GLX_SAMPLE_BUFFERS = 0x186a0;
		public const int GLX_SAMPLES = 0x186a1;

		public const int GLX_CONTEXT_DEBUG_BIT_ARB = 0x00000001;
		public const int GLX_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB = 0x00000002;
		public const int GLX_CONTEXT_MAJOR_VERSION_ARB = 0x2091;
		public const int GLX_CONTEXT_MINOR_VERSION_ARB = 0x2092;
		public const int GLX_CONTEXT_FLAGS_ARB = 0x2094;

		public const int GLX_CONTEXT_CORE_PROFILE_BIT_ARB = 0x00000001;
		public const int GLX_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB = 0x00000002;
		public const int GLX_CONTEXT_PROFILE_MASK_ARB = 0x9126;

		static Glx()
		{
			var ptr = glXGetProcAddressARB("glXCreateContextAttribsARB");
			if (ptr != IntPtr.Zero) {
				glXCreateContextAttribsARB = (glXCreateContextAttribsARBDelegate)Marshal.GetDelegateForFunctionPointer(ptr, typeof(glXCreateContextAttribsARBDelegate));
			}
		}
		[DllImport(libGL)]
		public static extern void glGetIntegerv(int name, out int rv);
		[DllImport(libGL)]
		public extern static bool glXQueryVersion(IntPtr dpy, out int maj, out int min);
		[DllImport(libGL)]
		public extern static IntPtr glXChooseFBConfig(IntPtr dpy, int screen, [In] int[] attribList, out int nitems);
		public static IntPtr[] ChooseFBConfig(IntPtr dpy, int screen, int[] attribList)
		{
			int nitems;
			var fbcArrayPtr = glXChooseFBConfig(dpy, screen, attribList, out nitems);
			
			var fbcArray = new IntPtr[nitems];
			Marshal.Copy(fbcArrayPtr, fbcArray, 0, nitems);
			
			Xlib.XFree(fbcArrayPtr);

			return fbcArray;
		}
		[DllImport(libGL)]
		public extern static IntPtr glXGetVisualFromFBConfig(IntPtr dpy, IntPtr config);
		public static XVisualInfo GetVisualFromFBConfig(IntPtr dpy, IntPtr config)
		{
			var visualPtr = glXGetVisualFromFBConfig(dpy, config);
			if (visualPtr == IntPtr.Zero) {
				throw new Exception("Failed to retrieve visual from framebuffer config.");
			}

			var visual = (XVisualInfo) Marshal.PtrToStructure(visualPtr, typeof(XVisualInfo));

			Xlib.XFree(visualPtr);

			return visual;
		}
		[DllImport(libGL)]
		public extern static bool glXMakeCurrent(IntPtr dpy, IntPtr drawable, IntPtr ctx);
		[DllImport(libGL)]
		public extern static bool glXSwapBuffers(IntPtr dpy, IntPtr drawable);
		[DllImport(libGL)]
		public extern static bool glXIsDirect(IntPtr dpy, IntPtr ctx);
		[DllImport(libGL)]
		public extern static int glXGetFBConfigAttrib(IntPtr dpy, IntPtr config, int attribute, out int value);
		[DllImport(libGL)]
		public extern static IntPtr glXCreateGLXPixmap(IntPtr dpy, ref XVisualInfo visual, IntPtr pixmap);
		[DllImport(libGL)]
		public extern static void glXDestroyGLXPixmap(IntPtr dpy, IntPtr pixmap);
		[DllImport(libGL)]
		public extern static void glXDestroyContext(IntPtr dpy, IntPtr ctx);
		[DllImport(libGL)]
		public extern static IntPtr glXQueryExtensionsString(IntPtr dpy, int screen);
		public static string QueryExtensionsString(IntPtr dpy, int screen)
		{
			return Marshal.PtrToStringAnsi(glXQueryExtensionsString(dpy, screen));
		}
		public static string[] QueryExtensions(IntPtr dpy, int screen)
		{
			var str = QueryExtensionsString(dpy, screen);
			if (string.IsNullOrEmpty(str)) {
				return new string[0];
			}
			return str.Split(' ');
		}
		[DllImport(libGL)]
		public extern static IntPtr glXGetProcAddressARB(string procname);
		[DllImport(libGL)]
		public extern static IntPtr glXCreateNewContext(IntPtr dpy, IntPtr config, int renderType, IntPtr shareList, int direct);
		public static readonly glXCreateContextAttribsARBDelegate glXCreateContextAttribsARB;
		public delegate IntPtr glXCreateContextAttribsARBDelegate(IntPtr dpy, IntPtr config, IntPtr share_context, int direct, int[] attrib_list);
		[DllImport(libGL)]
		public static extern void glGenTextures(int n, uint[] textures);
		[DllImport(libGL)]
		public static extern void glDeleteTextures(int n, uint[] textures);
		[DllImport(libGL)]
		public static extern void glBindTexture(uint target, uint texture);
		[DllImport(libGL)]
		public static extern void glTexImage2D(uint target, int level, int internalformat, int width, int height, int border, uint format, uint type, IntPtr pixels);
	}
}