//========================================================================
// GLFW - An OpenGL framework
// Platform:    Any
// API version: 2.7
// WWW:         http://www.glfw.org/
//------------------------------------------------------------------------
// Copyright (c) 2002-2006 Marcus Geelnard
// Copyright (c) 2006-2010 Camilla Berglund <elmindreda@elmindreda.org>
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented; you must not
//    claim that you wrote the original software. If you use this software
//    in a product, an acknowledgment in the product documentation would
//    be appreciated but is not required.
//
// 2. Altered source versions must be plainly marked as such, and must not
//    be misrepresented as being the original software.
//
// 3. This notice may not be removed or altered from any source
//    distribution.
//
//========================================================================

#include "internal.h"


//************************************************************************
//****                  GLFW internal functions                       ****
//************************************************************************

#ifndef GL_VERSION_3_0
#define GL_NUM_EXTENSIONS                 0x821D
#define GL_CONTEXT_FLAGS                  0x821E
#define GL_CONTEXT_FLAG_FORWARD_COMPATIBLE_BIT 0x0001
#endif

#ifndef GL_VERSION_3_2
#define GL_CONTEXT_CORE_PROFILE_BIT       0x00000001
#define GL_CONTEXT_COMPATIBILITY_PROFILE_BIT 0x00000002
#define GL_CONTEXT_PROFILE_MASK           0x9126
#endif

//========================================================================
// Parses the OpenGL version string and extracts the version number
//========================================================================

void _glfwParseGLVersion( int *major, int *minor, int *rev )
{
    GLuint _major, _minor = 0, _rev = 0;
    const GLubyte *version;
    const GLubyte *ptr;

    // Get OpenGL version string
    version = glGetString( GL_VERSION );
    if( !version )
    {
        return;
    }

    // Parse string
    ptr = version;
    for( _major = 0; *ptr >= '0' && *ptr <= '9'; ptr ++ )
    {
        _major = 10*_major + (*ptr - '0');
    }
    if( *ptr == '.' )
    {
        ptr ++;
        for( _minor = 0; *ptr >= '0' && *ptr <= '9'; ptr ++ )
        {
            _minor = 10*_minor + (*ptr - '0');
        }
        if( *ptr == '.' )
        {
            ptr ++;
            for( _rev = 0; *ptr >= '0' && *ptr <= '9'; ptr ++ )
            {
                _rev = 10*_rev + (*ptr - '0');
            }
        }
    }

    // Return parsed values
    *major = _major;
    *minor = _minor;
    *rev = _rev;
}

//========================================================================
// Check if a string can be found in an OpenGL extension string
//========================================================================

int _glfwStringInExtensionString( const char *string,
                                  const GLubyte *extensions )
{
    const GLubyte *start;
    GLubyte *where, *terminator;

    // It takes a bit of care to be fool-proof about parsing the
    // OpenGL extensions string. Don't be fooled by sub-strings,
    // etc.
    start = extensions;
    for(;;)
    {
        where = (GLubyte *) strstr( (const char *) start, string );
        if( !where )
        {
            return GL_FALSE;
        }
        terminator = where + strlen( string );
        if( where == start || *(where - 1) == ' ' )
        {
            if( *terminator == ' ' || *terminator == '\0' )
            {
                break;
            }
        }
        start = terminator;
    }

    return GL_TRUE;
}


//========================================================================
// Reads back OpenGL context properties from the current context
//========================================================================

void _glfwRefreshContextParams( void )
{
    _glfwParseGLVersion( &_glfwWin.glMajor, &_glfwWin.glMinor,
                         &_glfwWin.glRevision );

    _glfwWin.glProfile = 0;
    _glfwWin.glForward = GL_FALSE;

    // Read back the context profile, if applicable
    if( _glfwWin.glMajor >= 3 )
    {
        GLint flags;
        glGetIntegerv( GL_CONTEXT_FLAGS, &flags );

        if( flags & GL_CONTEXT_FLAG_FORWARD_COMPATIBLE_BIT )
        {
            _glfwWin.glForward = GL_TRUE;
        }
    }

    if( _glfwWin.glMajor > 3 ||
        ( _glfwWin.glMajor == 3 && _glfwWin.glMinor >= 2 ) )
    {
        GLint mask;
        glGetIntegerv( GL_CONTEXT_PROFILE_MASK, &mask );

        if( mask & GL_CONTEXT_COMPATIBILITY_PROFILE_BIT )
        {
            _glfwWin.glProfile = GLFW_OPENGL_COMPAT_PROFILE;
        }
        else if( mask & GL_CONTEXT_CORE_PROFILE_BIT )
        {
            _glfwWin.glProfile = GLFW_OPENGL_CORE_PROFILE;
        }
    }
}


//************************************************************************
//****                    GLFW user functions                         ****
//************************************************************************

//========================================================================
// Check if an OpenGL extension is available at runtime
//========================================================================

GLFWAPI int GLFWAPIENTRY glfwExtensionSupported( const char *extension )
{
    const GLubyte *extensions;
    GLubyte *where;

    // Is GLFW initialized?
    if( !_glfwInitialized || !_glfwWin.opened )
    {
        return GL_FALSE;
    }

    // Extension names should not have spaces
    where = (GLubyte *) strchr( extension, ' ' );
    if( where || *extension == '\0' )
    {
        return GL_FALSE;
    }

    if( _glfwWin.glMajor < 3 )
    {
        // Check if extension is in the old style OpenGL extensions string

        extensions = glGetString( GL_EXTENSIONS );
        if( extensions != NULL )
        {
            if( _glfwStringInExtensionString( extension, extensions ) )
            {
                return GL_TRUE;
            }
        }
    }
    else
    {
        // Check if extension is in the modern OpenGL extensions string list

        GLint count;
        int i;

        glGetIntegerv( GL_NUM_EXTENSIONS, &count );

        for( i = 0;  i < count;  i++ )
        {
             if( strcmp( (const char*) _glfwWin.GetStringi( GL_EXTENSIONS, i ),
                         extension ) == 0 )
             {
                 return GL_TRUE;
             }
        }
    }

    // Additional platform specific extension checking (e.g. WGL)
    if( _glfwPlatformExtensionSupported( extension ) )
    {
        return GL_TRUE;
    }

    return GL_FALSE;
}


//========================================================================
// Get the function pointer to an OpenGL function.  This function can be
// used to get access to extended OpenGL functions.
//========================================================================

GLFWAPI void * GLFWAPIENTRY glfwGetProcAddress( const char *procname )
{
    // Is GLFW initialized?
    if( !_glfwInitialized || !_glfwWin.opened )
    {
        return NULL;
    }

    return _glfwPlatformGetProcAddress( procname );
}


//========================================================================
// Returns the OpenGL version
//========================================================================

GLFWAPI void GLFWAPIENTRY glfwGetGLVersion( int *major, int *minor, int *rev )
{
    // Is GLFW initialized?
    if( !_glfwInitialized || !_glfwWin.opened )
    {
        return;
    }

    if( major != NULL )
    {
        *major = _glfwWin.glMajor;
    }
    if( minor != NULL )
    {
        *minor = _glfwWin.glMinor;
    }
    if( rev != NULL )
    {
        *rev = _glfwWin.glRevision;
    }
}

