#include <stdlib.h>
#include <string.h>
#include <stddef.h>
#include "wgl_obs.h"

#if defined(__APPLE__)
#include <dlfcn.h>

static void* AppleGLGetProcAddress (const const char *name)
{
	static void* image = NULL;
	
	if (NULL == image)
		image = dlopen("/System/Library/Frameworks/OpenGL.framework/Versions/Current/OpenGL", RTLD_LAZY);

	return (image ? dlsym(image, name) : NULL);
}
#define IntGetProcAddress(name) AppleGLGetProcAddress(name)
#endif /* __APPLE__ */

#if defined(_WIN32)

#ifdef _MSC_VER
#pragma warning(disable: 4055)
#pragma warning(disable: 4054)
#pragma warning(disable: 4996)
#endif
	
static PROC WinGetProcAddress(const char *name)
{
	static HMODULE glMod = NULL;
	PROC pFunc = wglGetProcAddress((LPCSTR)name);

	if (pFunc) return pFunc;

	if (NULL == glMod)
		glMod = GetModuleHandleA("OpenGL32.dll");

	return (PROC)GetProcAddress(glMod, (LPCSTR)name);
}

#define IntGetProcAddress(name) WinGetProcAddress(name)
#endif

/* Linux, FreeBSD, other */
#ifndef IntGetProcAddress
	#ifndef GLX_ARB_get_proc_address
	#define GLX_ARB_get_proc_address 1

	typedef void (*__GLXextFuncPtr)(void);
	extern __GLXextFuncPtr glXGetProcAddressARB (const GLubyte *);

	#endif /* GLX_ARB_get_proc_address */

	#define IntGetProcAddress(name) (*glXGetProcAddressARB)((const GLubyte*)name)
#endif

int wgl_ext_ARB_multisample = wgl_LOAD_FAILED;
int wgl_ext_ARB_extensions_string = wgl_LOAD_FAILED;
int wgl_ext_ARB_pixel_format = wgl_LOAD_FAILED;
int wgl_ext_ARB_pixel_format_float = wgl_LOAD_FAILED;
int wgl_ext_ARB_framebuffer_sRGB = wgl_LOAD_FAILED;
int wgl_ext_ARB_create_context = wgl_LOAD_FAILED;
int wgl_ext_ARB_create_context_profile = wgl_LOAD_FAILED;
int wgl_ext_ARB_create_context_robustness = wgl_LOAD_FAILED;
int wgl_ext_EXT_swap_control = wgl_LOAD_FAILED;
int wgl_ext_EXT_pixel_format_packed_float = wgl_LOAD_FAILED;
int wgl_ext_EXT_create_context_es2_profile = wgl_LOAD_FAILED;
int wgl_ext_EXT_swap_control_tear = wgl_LOAD_FAILED;
int wgl_ext_NV_swap_group = wgl_LOAD_FAILED;

const char * (CODEGEN_FUNCPTR *_ptrc_wglGetExtensionsStringARB)(HDC) = NULL;

static int Load_ARB_extensions_string()
{
	int numFailed = 0;
	_ptrc_wglGetExtensionsStringARB = (const char * (CODEGEN_FUNCPTR *)(HDC))IntGetProcAddress("wglGetExtensionsStringARB");
	if(!_ptrc_wglGetExtensionsStringARB) numFailed++;
	return numFailed;
}

BOOL (CODEGEN_FUNCPTR *_ptrc_wglChoosePixelFormatARB)(HDC, const int *, const FLOAT *, UINT, int *, UINT *) = NULL;
BOOL (CODEGEN_FUNCPTR *_ptrc_wglGetPixelFormatAttribfvARB)(HDC, int, int, UINT, const int *, FLOAT *) = NULL;
BOOL (CODEGEN_FUNCPTR *_ptrc_wglGetPixelFormatAttribivARB)(HDC, int, int, UINT, const int *, int *) = NULL;

static int Load_ARB_pixel_format()
{
	int numFailed = 0;
	_ptrc_wglChoosePixelFormatARB = (BOOL (CODEGEN_FUNCPTR *)(HDC, const int *, const FLOAT *, UINT, int *, UINT *))IntGetProcAddress("wglChoosePixelFormatARB");
	if(!_ptrc_wglChoosePixelFormatARB) numFailed++;
	_ptrc_wglGetPixelFormatAttribfvARB = (BOOL (CODEGEN_FUNCPTR *)(HDC, int, int, UINT, const int *, FLOAT *))IntGetProcAddress("wglGetPixelFormatAttribfvARB");
	if(!_ptrc_wglGetPixelFormatAttribfvARB) numFailed++;
	_ptrc_wglGetPixelFormatAttribivARB = (BOOL (CODEGEN_FUNCPTR *)(HDC, int, int, UINT, const int *, int *))IntGetProcAddress("wglGetPixelFormatAttribivARB");
	if(!_ptrc_wglGetPixelFormatAttribivARB) numFailed++;
	return numFailed;
}

HGLRC (CODEGEN_FUNCPTR *_ptrc_wglCreateContextAttribsARB)(HDC, HGLRC, const int *) = NULL;

static int Load_ARB_create_context()
{
	int numFailed = 0;
	_ptrc_wglCreateContextAttribsARB = (HGLRC (CODEGEN_FUNCPTR *)(HDC, HGLRC, const int *))IntGetProcAddress("wglCreateContextAttribsARB");
	if(!_ptrc_wglCreateContextAttribsARB) numFailed++;
	return numFailed;
}

int (CODEGEN_FUNCPTR *_ptrc_wglGetSwapIntervalEXT)() = NULL;
BOOL (CODEGEN_FUNCPTR *_ptrc_wglSwapIntervalEXT)(int) = NULL;

static int Load_EXT_swap_control()
{
	int numFailed = 0;
	_ptrc_wglGetSwapIntervalEXT = (int (CODEGEN_FUNCPTR *)())IntGetProcAddress("wglGetSwapIntervalEXT");
	if(!_ptrc_wglGetSwapIntervalEXT) numFailed++;
	_ptrc_wglSwapIntervalEXT = (BOOL (CODEGEN_FUNCPTR *)(int))IntGetProcAddress("wglSwapIntervalEXT");
	if(!_ptrc_wglSwapIntervalEXT) numFailed++;
	return numFailed;
}

BOOL (CODEGEN_FUNCPTR *_ptrc_wglBindSwapBarrierNV)(GLuint, GLuint) = NULL;
BOOL (CODEGEN_FUNCPTR *_ptrc_wglJoinSwapGroupNV)(HDC, GLuint) = NULL;
BOOL (CODEGEN_FUNCPTR *_ptrc_wglQueryFrameCountNV)(HDC, GLuint *) = NULL;
BOOL (CODEGEN_FUNCPTR *_ptrc_wglQueryMaxSwapGroupsNV)(HDC, GLuint *, GLuint *) = NULL;
BOOL (CODEGEN_FUNCPTR *_ptrc_wglQuerySwapGroupNV)(HDC, GLuint *, GLuint *) = NULL;
BOOL (CODEGEN_FUNCPTR *_ptrc_wglResetFrameCountNV)(HDC) = NULL;

static int Load_NV_swap_group()
{
	int numFailed = 0;
	_ptrc_wglBindSwapBarrierNV = (BOOL (CODEGEN_FUNCPTR *)(GLuint, GLuint))IntGetProcAddress("wglBindSwapBarrierNV");
	if(!_ptrc_wglBindSwapBarrierNV) numFailed++;
	_ptrc_wglJoinSwapGroupNV = (BOOL (CODEGEN_FUNCPTR *)(HDC, GLuint))IntGetProcAddress("wglJoinSwapGroupNV");
	if(!_ptrc_wglJoinSwapGroupNV) numFailed++;
	_ptrc_wglQueryFrameCountNV = (BOOL (CODEGEN_FUNCPTR *)(HDC, GLuint *))IntGetProcAddress("wglQueryFrameCountNV");
	if(!_ptrc_wglQueryFrameCountNV) numFailed++;
	_ptrc_wglQueryMaxSwapGroupsNV = (BOOL (CODEGEN_FUNCPTR *)(HDC, GLuint *, GLuint *))IntGetProcAddress("wglQueryMaxSwapGroupsNV");
	if(!_ptrc_wglQueryMaxSwapGroupsNV) numFailed++;
	_ptrc_wglQuerySwapGroupNV = (BOOL (CODEGEN_FUNCPTR *)(HDC, GLuint *, GLuint *))IntGetProcAddress("wglQuerySwapGroupNV");
	if(!_ptrc_wglQuerySwapGroupNV) numFailed++;
	_ptrc_wglResetFrameCountNV = (BOOL (CODEGEN_FUNCPTR *)(HDC))IntGetProcAddress("wglResetFrameCountNV");
	if(!_ptrc_wglResetFrameCountNV) numFailed++;
	return numFailed;
}

typedef int (*PFN_LOADFUNCPOINTERS)();
typedef struct wgl_StrToExtMap_s
{
	char *extensionName;
	int *extensionVariable;
	PFN_LOADFUNCPOINTERS LoadExtension;
} wgl_StrToExtMap;

static wgl_StrToExtMap ExtensionMap[13] = {
	{"WGL_ARB_multisample", &wgl_ext_ARB_multisample, NULL},
	{"WGL_ARB_extensions_string", &wgl_ext_ARB_extensions_string, Load_ARB_extensions_string},
	{"WGL_ARB_pixel_format", &wgl_ext_ARB_pixel_format, Load_ARB_pixel_format},
	{"WGL_ARB_pixel_format_float", &wgl_ext_ARB_pixel_format_float, NULL},
	{"WGL_ARB_framebuffer_sRGB", &wgl_ext_ARB_framebuffer_sRGB, NULL},
	{"WGL_ARB_create_context", &wgl_ext_ARB_create_context, Load_ARB_create_context},
	{"WGL_ARB_create_context_profile", &wgl_ext_ARB_create_context_profile, NULL},
	{"WGL_ARB_create_context_robustness", &wgl_ext_ARB_create_context_robustness, NULL},
	{"WGL_EXT_swap_control", &wgl_ext_EXT_swap_control, Load_EXT_swap_control},
	{"WGL_EXT_pixel_format_packed_float", &wgl_ext_EXT_pixel_format_packed_float, NULL},
	{"WGL_EXT_create_context_es2_profile", &wgl_ext_EXT_create_context_es2_profile, NULL},
	{"WGL_EXT_swap_control_tear", &wgl_ext_EXT_swap_control_tear, NULL},
	{"WGL_NV_swap_group", &wgl_ext_NV_swap_group, Load_NV_swap_group},
};

static int g_extensionMapSize = 13;

static wgl_StrToExtMap *FindExtEntry(const char *extensionName)
{
	int loop;
	wgl_StrToExtMap *currLoc = ExtensionMap;
	for(loop = 0; loop < g_extensionMapSize; ++loop, ++currLoc)
	{
		if(strcmp(extensionName, currLoc->extensionName) == 0)
			return currLoc;
	}
	
	return NULL;
}

static void ClearExtensionVars()
{
	wgl_ext_ARB_multisample = wgl_LOAD_FAILED;
	wgl_ext_ARB_extensions_string = wgl_LOAD_FAILED;
	wgl_ext_ARB_pixel_format = wgl_LOAD_FAILED;
	wgl_ext_ARB_pixel_format_float = wgl_LOAD_FAILED;
	wgl_ext_ARB_framebuffer_sRGB = wgl_LOAD_FAILED;
	wgl_ext_ARB_create_context = wgl_LOAD_FAILED;
	wgl_ext_ARB_create_context_profile = wgl_LOAD_FAILED;
	wgl_ext_ARB_create_context_robustness = wgl_LOAD_FAILED;
	wgl_ext_EXT_swap_control = wgl_LOAD_FAILED;
	wgl_ext_EXT_pixel_format_packed_float = wgl_LOAD_FAILED;
	wgl_ext_EXT_create_context_es2_profile = wgl_LOAD_FAILED;
	wgl_ext_EXT_swap_control_tear = wgl_LOAD_FAILED;
	wgl_ext_NV_swap_group = wgl_LOAD_FAILED;
}


static void LoadExtByName(const char *extensionName)
{
	wgl_StrToExtMap *entry = NULL;
	entry = FindExtEntry(extensionName);
	if(entry)
	{
		if(entry->LoadExtension)
		{
			int numFailed = entry->LoadExtension();
			if(numFailed == 0)
			{
				*(entry->extensionVariable) = wgl_LOAD_SUCCEEDED;
			}
			else
			{
				*(entry->extensionVariable) = wgl_LOAD_SUCCEEDED + numFailed;
			}
		}
		else
		{
			*(entry->extensionVariable) = wgl_LOAD_SUCCEEDED;
		}
	}
}


static void ProcExtsFromExtString(const char *strExtList)
{
	size_t iExtListLen = strlen(strExtList);
	const char *strExtListEnd = strExtList + iExtListLen;
	const char *strCurrPos = strExtList;
	char strWorkBuff[256];

	while(*strCurrPos)
	{
		/*Get the extension at our position.*/
		int iStrLen = 0;
		const char *strEndStr = strchr(strCurrPos, ' ');
		int iStop = 0;
		if(strEndStr == NULL)
		{
			strEndStr = strExtListEnd;
			iStop = 1;
		}

		iStrLen = (int)((ptrdiff_t)strEndStr - (ptrdiff_t)strCurrPos);

		if(iStrLen > 255)
			return;

		strncpy(strWorkBuff, strCurrPos, iStrLen);
		strWorkBuff[iStrLen] = '\0';

		LoadExtByName(strWorkBuff);

		strCurrPos = strEndStr + 1;
		if(iStop) break;
	}
}

int wgl_LoadFunctions(HDC hdc)
{
	ClearExtensionVars();
	
	_ptrc_wglGetExtensionsStringARB = (const char * (CODEGEN_FUNCPTR *)(HDC))IntGetProcAddress("wglGetExtensionsStringARB");
	if(!_ptrc_wglGetExtensionsStringARB) return wgl_LOAD_FAILED;
	
	ProcExtsFromExtString((const char *)_ptrc_wglGetExtensionsStringARB(hdc));
	return wgl_LOAD_SUCCEEDED;
}