/*
 * Copyright © 2013-2014 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

/**
 * @file dispatch_common.c
 *
 * Implements common code shared by the generated GL/EGL/GLX dispatch code.
 *
 * A collection of some important specs on getting GL function pointers.
 *
 * From the linux GL ABI (http://www.opengl.org/registry/ABI/):
 *
 *     "3.4. The libraries must export all OpenGL 1.2, GLU 1.3, GLX 1.3, and
 *           ARB_multitexture entry points statically.
 *
 *      3.5. Because non-ARB extensions vary so widely and are constantly
 *           increasing in number, it's infeasible to require that they all be
 *           supported, and extensions can always be added to hardware drivers
 *           after the base link libraries are released. These drivers are
 *           dynamically loaded by libGL, so extensions not in the base
 *           library must also be obtained dynamically.
 *
 *      3.6. To perform the dynamic query, libGL also must export an entry
 *           point called
 *
 *           void (*glXGetProcAddressARB(const GLubyte *))(); 
 *
 *      The full specification of this function is available separately. It
 *      takes the string name of a GL or GLX entry point and returns a pointer
 *      to a function implementing that entry point. It is functionally
 *      identical to the wglGetProcAddress query defined by the Windows OpenGL
 *      library, except that the function pointers returned are context
 *      independent, unlike the WGL query."
 *
 * From the EGL 1.4 spec:
 *
 *    "Client API function pointers returned by eglGetProcAddress are
 *     independent of the display and the currently bound client API context,
 *     and may be used by any client API context which supports the extension.
 *
 *     eglGetProcAddress may be queried for all of the following functions:
 *
 *     • All EGL and client API extension functions supported by the
 *       implementation (whether those extensions are supported by the current
 *       client API context or not). This includes any mandatory OpenGL ES
 *       extensions.
 *
 *     eglGetProcAddress may not be queried for core (non-extension) functions
 *     in EGL or client APIs 20 .
 *
 *     For functions that are queryable with eglGetProcAddress,
 *     implementations may choose to also export those functions statically
 *     from the object libraries im- plementing those functions. However,
 *     portable clients cannot rely on this behavior.
 *
 * From the GLX 1.4 spec:
 *
 *     "glXGetProcAddress may be queried for all of the following functions:
 *
 *      • All GL and GLX extension functions supported by the implementation
 *        (whether those extensions are supported by the current context or
 *        not).
 *
 *      • All core (non-extension) functions in GL and GLX from version 1.0 up
 *        to and including the versions of those specifications supported by
 *        the implementation, as determined by glGetString(GL VERSION) and
 *        glXQueryVersion queries."
 */

#include <assert.h>
#include <stdlib.h>
#ifdef _WIN32
#include <windows.h>
#else
#include <dlfcn.h>
#include <err.h>
#include <pthread.h>
#endif
#include <string.h>
#include <ctype.h>
#include <stdio.h>

#include "dispatch_common.h"

#ifdef __APPLE__
#define GLX_LIB "/opt/X11/lib/libGL.1.dylib"
#elif defined(__ANDROID__)
#define GLX_LIB "libGLESv2.so"
#else
#define GLX_LIB "libGL.so.1"
#endif

#ifdef __ANDROID__
#define EGL_LIB "libEGL.so"
#define GLES1_LIB "libGLESv1_CM.so"
#define GLES2_LIB "libGLESv2.so"
#elif defined _WIN32
#define EGL_LIB "libEGL.dll"
#define GLES1_LIB "libGLES_CM.dll"
#define GLES2_LIB "libGLESv2.dll"
#else
#define EGL_LIB "libEGL.so.1"
#define GLES1_LIB "libGLESv1_CM.so.1"
#define GLES2_LIB "libGLESv2.so.2"
#endif

#ifdef __GNUC__
#define CONSTRUCT(_func) static void _func (void) __attribute__((constructor));
#define DESTRUCT(_func) static void _func (void) __attribute__((destructor));
#elif defined (_MSC_VER) && (_MSC_VER >= 1500)
#define CONSTRUCT(_func) \
  static void _func(void); \
  static int _func ## _wrapper(void) { _func(); return 0; } \
  __pragma(section(".CRT$XCU",read)) \
  __declspec(allocate(".CRT$XCU")) static int (* _array ## _func)(void) = _func ## _wrapper;

#define DESTRUCT(_func) \
  static void _func(void); \
  static int _func ## _constructor(void) { atexit (_func); return 0; } \
  __pragma(section(".CRT$XCU",read)) \
  __declspec(allocate(".CRT$XCU")) static int (* _array ## _func)(void) = _func ## _constructor;

#else
#error "You will need constructor support for your compiler"
#endif

struct api {
#ifndef _WIN32
    /**
     * Locking for making sure we don't double-dlopen().
     */
    pthread_mutex_t mutex;
#endif

    /** dlopen() return value for libGL.so.1. */
    void *glx_handle;

    /**
     * dlopen() return value for OS X's GL library.
     *
     * On linux, glx_handle is used instead.
     */
    void *gl_handle;

    /** dlopen() return value for libEGL.so.1 */
    void *egl_handle;

    /** dlopen() return value for libGLESv1_CM.so.1 */
    void *gles1_handle;

    /** dlopen() return value for libGLESv2.so.2 */
    void *gles2_handle;

    /**
     * This value gets incremented when any thread is in
     * glBegin()/glEnd() called through epoxy.
     *
     * We're not guaranteed to be called through our wrapper, so the
     * conservative paths also try to handle the failure cases they'll
     * see if begin_count didn't reflect reality.  It's also a bit of
     * a bug that the conservative paths might return success because
     * some other thread was in epoxy glBegin/glEnd while our thread
     * is trying to resolve, but given that it's basically just for
     * informative error messages, we shouldn't need to care.
     */
    long begin_count;
};

static struct api api = {
#ifndef _WIN32
    .mutex = PTHREAD_MUTEX_INITIALIZER,
#else
	0,
#endif
};

static bool library_initialized;

#if EPOXY_SUPPORT_EGL
static EGLenum
epoxy_egl_get_current_gl_context_api(void);
#endif

CONSTRUCT (library_init)

static void
library_init(void)
{
    library_initialized = true;
}

static bool
get_dlopen_handle(void **handle, const char *lib_name, bool exit_on_fail)
{
    if (*handle)
        return true;

    if (!library_initialized) {
        fprintf(stderr,
                "Attempting to dlopen() while in the dynamic linker.\n");
        abort();
    }

#ifdef _WIN32
    EPOXY_UNUSED(exit_on_fail);
    *handle = LoadLibraryA(lib_name);
#else
    pthread_mutex_lock(&api.mutex);
    if (!*handle) {
        *handle = dlopen(lib_name, RTLD_LAZY | RTLD_LOCAL);
        if (!*handle) {
            if (exit_on_fail) {
                fprintf(stderr, "Couldn't open %s: %s\n", lib_name, dlerror());
                exit(1);
            } else {
                (void)dlerror();
            }
        }
    }
    pthread_mutex_unlock(&api.mutex);
#endif

    return *handle != NULL;
}

static void *
do_dlsym(void **handle, const char *lib_name, const char *name,
         bool exit_on_fail)
{
    void *result;
    const char *error = "";

    if (!get_dlopen_handle(handle, lib_name, exit_on_fail))
        return NULL;

#ifdef _WIN32
    result = GetProcAddress(*handle, name);
#else
    result = dlsym(*handle, name);
    if (!result)
        error = dlerror();
#endif
    if (!result && exit_on_fail) {
        fprintf(stderr,"%s() not found in %s: %s\n", name, lib_name, error);
        exit(1);
    }

    return result;
}

EPOXY_IMPORTEXPORT bool
epoxy_is_desktop_gl(void)
{
    const char *es_prefix = "OpenGL ES";
    const char *version;

#if EPOXY_SUPPORT_EGL
    /* PowerVR's OpenGL ES implementation (and perhaps other) don't
     * comply with the standard, which states that
     * "glGetString(GL_VERSION)" should return a string starting with
     * "OpenGL ES". Therefore, to distinguish desktop OpenGL from
     * OpenGL ES, we must also check the context type through EGL (we
     * can do that as PowerVR is only usable through EGL).
     */
    if (epoxy_current_context_is_egl()) {
        switch (epoxy_egl_get_current_gl_context_api()) {
        case EGL_OPENGL_API:     return true;
        case EGL_OPENGL_ES_API:  return false;
        case EGL_NONE:
        default:  break;
        }
    }
#endif

    if (api.begin_count)
        return true;

    version = (const char *)glGetString(GL_VERSION);

    /* If we didn't get a version back, there are only two things that
     * could have happened: either malloc failure (which basically
     * doesn't exist), or we were called within a glBegin()/glEnd().
     * Assume the second, which only exists for desktop GL.
     */
    if (!version)
        return true;

    return strncmp(es_prefix, version, strlen(es_prefix));
}

#if defined _MSC_VER
#pragma warning(push)
#pragma warning(disable: 4996)
#endif

static int
epoxy_internal_gl_version(int error_version)
{
    const char *version = (const char *)glGetString(GL_VERSION);
    GLint major, minor;
    int scanf_count;

    if (!version)
        return error_version;

    /* skip to version number */
    while (!isdigit(*version) && *version != '\0')
        version++;

    /* Interpret version number */
    scanf_count = sscanf(version, "%i.%i", &major, &minor);
    if (scanf_count != 2) {
        fprintf(stderr, "Unable to interpret GL_VERSION string: %s\n",
                version);
        exit(1);
    }
    return 10 * major + minor;
}

#if defined _MSC_VER
#pragma warning(pop)
#endif

EPOXY_IMPORTEXPORT int
epoxy_gl_version(void)
{
    return epoxy_internal_gl_version(0);
}

int
epoxy_conservative_gl_version(void)
{
    if (api.begin_count)
        return 100;

    return epoxy_internal_gl_version(100);
}

bool
epoxy_extension_in_string(const char *extension_list, const char *ext)
{
    if (!extension_list)
        return false;
    const char *ptr = extension_list;
    size_t len = strlen(ext);

    /* Make sure that don't just find an extension with our name as a prefix. */
    while (true) {
        ptr = strstr(ptr, ext);
        if (!ptr)
            return false;

        if (ptr[len] == ' ' || ptr[len] == 0)
            return true;
        ptr += len;
    }
}

static bool
epoxy_internal_has_gl_extension(const char *ext, bool invalid_op_mode)
{
    if (epoxy_gl_version() < 30) {
        const char *exts = (const char *)glGetString(GL_EXTENSIONS);
        if (!exts)
            return invalid_op_mode;
        return epoxy_extension_in_string(exts, ext);
    } else {
        int num_extensions;
        int i;

        glGetIntegerv(GL_NUM_EXTENSIONS, &num_extensions);
        if (num_extensions == 0)
            return invalid_op_mode;

        for (i = 0; i < num_extensions; i++) {
            const char *gl_ext = (const char *)glGetStringi(GL_EXTENSIONS, i);
            if (strcmp(ext, gl_ext) == 0)
                return true;
        }

        return false;
    }
}

/**
 * Tests whether the currently bound context is EGL or other (GLX, WGL, etc.).
 */
EPOXY_IMPORTEXPORT bool
epoxy_current_context_is_egl(void)
{
#if EPOXY_SUPPORT_EGL
    if (      get_dlopen_handle (&api.egl_handle, EGL_LIB, false)
          &&  epoxy_egl_get_current_gl_context_api() != EGL_NONE)
        return true;
#endif

    return false;
}

/**
 * Returns true if the given GL extension is supported in the current context.
 *
 * Note that this function can't be called from within glBegin()/glEnd().
 *
 * \sa epoxy_has_egl_extension()
 * \sa epoxy_has_glx_extension()
 */
EPOXY_IMPORTEXPORT bool
epoxy_has_gl_extension(const char *ext)
{
    return epoxy_internal_has_gl_extension(ext, false);
}

bool
epoxy_conservative_has_gl_extension(const char *ext)
{
    if (api.begin_count)
        return true;

    return epoxy_internal_has_gl_extension(ext, true);
}

void *
epoxy_egl_dlsym(const char *name)
{
    return do_dlsym(&api.egl_handle, EGL_LIB, name, true);
}

void *
epoxy_glx_dlsym(const char *name)
{
    return do_dlsym(&api.glx_handle, GLX_LIB, name, true);
}

void *
epoxy_gl_dlsym(const char *name)
{
#ifdef _WIN32
    return do_dlsym(&api.gl_handle, "OPENGL32", name, true);
#elif defined(__APPLE__)
    return do_dlsym(&api.gl_handle,
                    "/System/Library/Frameworks/OpenGL.framework/Versions/Current/OpenGL",
                    name, true);
#else
    /* There's no library for desktop GL support independent of GLX. */
    return epoxy_glx_dlsym(name);
#endif
}

void *
epoxy_gles1_dlsym(const char *name)
{
    if (!epoxy_current_context_is_egl()) {
        return epoxy_get_proc_address(name);
    } else {
        return do_dlsym(&api.gles1_handle, GLES1_LIB, name, true);
    }
}

void *
epoxy_gles2_dlsym(const char *name)
{
    if (!epoxy_current_context_is_egl()) {
        return epoxy_get_proc_address(name);
    } else {
        return do_dlsym(&api.gles2_handle, GLES2_LIB, name, true);
    }
}

/**
 * Does the appropriate dlsym() or eglGetProcAddress() for GLES3
 * functions.
 *
 * Mesa interpreted GLES as intending that the GLES3 functions were
 * available only through eglGetProcAddress() and not dlsym(), while
 * ARM's Mali drivers interpreted GLES as intending that GLES3
 * functions were available only through dlsym() and not
 * eglGetProcAddress().  Thanks, Khronos.
 */
void *
epoxy_gles3_dlsym(const char *name)
{
    if (!epoxy_current_context_is_egl()) {
        return epoxy_get_proc_address(name);
    } else {
        void *func = do_dlsym(&api.gles2_handle, GLES2_LIB, name, false);

        if (func)
            return func;

        return epoxy_get_proc_address(name);
    }
}

/**
 * Performs either the dlsym or glXGetProcAddress()-equivalent for
 * core functions in desktop GL.
 */
void *
epoxy_get_core_proc_address(const char *name, int core_version)
{
#ifdef _WIN32
    int core_symbol_support = 11;
#elif defined(__ANDROID__)
    /**
     * All symbols must be resolved through eglGetProcAddress
     * on Android
     */
    int core_symbol_support = 0;
#else
    int core_symbol_support = 12;
#endif

    if (core_version <= core_symbol_support) {
        return epoxy_gl_dlsym(name);
    } else {
        return epoxy_get_proc_address(name);
    }
}

#if EPOXY_SUPPORT_EGL
static EGLenum
epoxy_egl_get_current_gl_context_api(void)
{
    EGLDisplay eglDisplay = eglGetCurrentDisplay();
    EGLContext eglContext = eglGetCurrentContext();
    EGLint eglContextClientType = EGL_NONE;
    return      eglQueryContext(eglDisplay, eglContext, EGL_CONTEXT_CLIENT_TYPE,
                                &eglContextClientType) == EGL_TRUE
           ?    (EGLenum)eglContextClientType
           :    EGL_NONE;
}
#endif /* EPOXY_SUPPORT_EGL */

/**
 * Performs the dlsym() for the core GL 1.0 functions that we use for
 * determining version and extension support for deciding on dlsym
 * versus glXGetProcAddress() for all other functions.
 *
 * This needs to succeed on implementations without GLX (since
 * glGetString() and glGetIntegerv() are both in GLES1/2 as well, and
 * at call time we don't know for sure what API they're trying to use
 * without inspecting contexts ourselves).
 */
void *
epoxy_get_bootstrap_proc_address(const char *name)
{
    /* If epoxy hasn't loaded any API-specific library yet, try to
     * figure out what API the context is using and use that library,
     * since future calls will also use that API (this prevents a
     * non-X11 ES2 context from loading a bunch of X11 junk).
     */
#if EPOXY_SUPPORT_EGL
    get_dlopen_handle(&api.egl_handle, EGL_LIB, false);
    if (api.egl_handle) {
        switch (epoxy_egl_get_current_gl_context_api()) {
        case EGL_OPENGL_API:
            return epoxy_gl_dlsym(name);
        case EGL_OPENGL_ES_API: {
            EGLDisplay eglDisplay = eglGetCurrentDisplay();
            EGLContext eglContext = eglGetCurrentContext();
            EGLint glesVer = -1;
            if (      eglDisplay != EGL_NO_DISPLAY
                  &&  eglContext != EGL_NO_CONTEXT
                  &&  eglQueryContext(eglDisplay, eglContext,
                        EGL_CONTEXT_CLIENT_VERSION, &glesVer) == EGL_TRUE)
                return glesVer >= 2  ?  epoxy_gles2_dlsym(name) : epoxy_gles1_dlsym(name);
            else
                return NULL;
        }
        }
    }
#endif /* EPOXY_SUPPORT_EGL */

    return epoxy_gl_dlsym(name);
    
}

void *
epoxy_get_proc_address(const char *name)
{
#if EPOXY_SUPPORT_EGL
    if (epoxy_current_context_is_egl())
        return eglGetProcAddress(name);
#endif
#if EPOXY_SUPPORT_WGL
    void *func = wglGetProcAddress(name);
    return func  ?  func  :  epoxy_gl_dlsym(name);
#endif
#if defined(__APPLE__)
    return epoxy_gl_dlsym(name);
#endif
#if EPOXY_SUPPORT_GLX
    return glXGetProcAddressARB((const GLubyte *)name);
#endif
    return NULL;
}

WRAPPER_VISIBILITY (void)
WRAPPER(epoxy_glBegin)(GLenum primtype)
{
#ifdef _WIN32
    InterlockedIncrement(&api.begin_count);
#else
    pthread_mutex_lock(&api.mutex);
    api.begin_count++;
    pthread_mutex_unlock(&api.mutex);
#endif

    epoxy_glBegin_unwrapped(primtype);
}

WRAPPER_VISIBILITY (void)
WRAPPER(epoxy_glEnd)(void)
{
    epoxy_glEnd_unwrapped();

#ifdef _WIN32
    InterlockedDecrement(&api.begin_count);
#else
    pthread_mutex_lock(&api.mutex);
    api.begin_count--;
    pthread_mutex_unlock(&api.mutex);
#endif
}

EPOXY_IMPORTEXPORT PFNGLBEGINPROC epoxy_glBegin = epoxy_glBegin_wrapped;
EPOXY_IMPORTEXPORT PFNGLENDPROC epoxy_glEnd = epoxy_glEnd_wrapped;