/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2024 Sam Lantinga <slouken@libsdl.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 "SDL_internal.h"

// NSOpenGL implementation of SDL OpenGL support

#ifdef SDL_VIDEO_OPENGL_CGL
#include "SDL_cocoavideo.h"
#include "SDL_cocoaopengl.h"
#include "SDL_cocoaopengles.h"

#include <OpenGL/CGLTypes.h>
#include <OpenGL/OpenGL.h>
#include <OpenGL/CGLRenderers.h>

#include <SDL3/SDL_opengl.h>
#include "../../SDL_hints_c.h"

#define DEFAULT_OPENGL "/System/Library/Frameworks/OpenGL.framework/Libraries/libGL.dylib"

// We still support OpenGL as long as Apple offers it, deprecated or not, so disable deprecation warnings about it.
#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
#endif

// _Nullable is available starting Xcode 7
#ifdef __has_feature
#if __has_feature(nullability)
#define HAS_FEATURE_NULLABLE
#endif
#endif
#ifndef HAS_FEATURE_NULLABLE
#define _Nullable
#endif

static bool SDL_opengl_async_dispatch = false;

static void SDLCALL SDL_OpenGLAsyncDispatchChanged(void *userdata, const char *name, const char *oldValue, const char *hint)
{
    SDL_opengl_async_dispatch = SDL_GetStringBoolean(hint, false);
}

static CVReturn DisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeStamp *now, const CVTimeStamp *outputTime, CVOptionFlags flagsIn, CVOptionFlags *flagsOut, void *displayLinkContext)
{
    SDL3OpenGLContext *nscontext = (__bridge SDL3OpenGLContext *)displayLinkContext;

    // printf("DISPLAY LINK! %u\n", (unsigned int) SDL_GetTicks());
    const int setting = SDL_AtomicGet(&nscontext->swapIntervalSetting);
    if (setting != 0) { // nothing to do if vsync is disabled, don't even lock
        SDL_LockMutex(nscontext->swapIntervalMutex);
        SDL_AtomicAdd(&nscontext->swapIntervalsPassed, 1);
        SDL_SignalCondition(nscontext->swapIntervalCond);
        SDL_UnlockMutex(nscontext->swapIntervalMutex);
    }

    return kCVReturnSuccess;
}

@implementation SDL3OpenGLContext : NSOpenGLContext

- (id)initWithFormat:(NSOpenGLPixelFormat *)format
        shareContext:(NSOpenGLContext *)share
{
    self = [super initWithFormat:format shareContext:share];
    if (self) {
        self.openglPixelFormat = format;
        SDL_AtomicSet(&self->dirty, 0);
        self->window = NULL;
        SDL_AtomicSet(&self->swapIntervalSetting, 0);
        SDL_AtomicSet(&self->swapIntervalsPassed, 0);
        self->swapIntervalCond = SDL_CreateCondition();
        self->swapIntervalMutex = SDL_CreateMutex();
        if (!self->swapIntervalCond || !self->swapIntervalMutex) {
            return nil;
        }

        // !!! FIXME: check return values.
        CVDisplayLinkCreateWithActiveCGDisplays(&self->displayLink);
        CVDisplayLinkSetOutputCallback(self->displayLink, &DisplayLinkCallback, (__bridge void *_Nullable)self);
        CVDisplayLinkSetCurrentCGDisplayFromOpenGLContext(self->displayLink, [self CGLContextObj], [format CGLPixelFormatObj]);
        CVDisplayLinkStart(displayLink);
    }

    SDL_AddHintCallback(SDL_HINT_MAC_OPENGL_ASYNC_DISPATCH, SDL_OpenGLAsyncDispatchChanged, NULL);
    return self;
}

- (void)movedToNewScreen
{
    if (self->displayLink) {
        CVDisplayLinkSetCurrentCGDisplayFromOpenGLContext(self->displayLink, [self CGLContextObj], [[self openglPixelFormat] CGLPixelFormatObj]);
    }
}

- (void)scheduleUpdate
{
    SDL_AtomicAdd(&self->dirty, 1);
}

// This should only be called on the thread on which a user is using the context.
- (void)updateIfNeeded
{
    const int value = SDL_AtomicSet(&self->dirty, 0);
    if (value > 0) {
        // We call the real underlying update here, since -[SDL3OpenGLContext update] just calls us.
        [self explicitUpdate];
    }
}

// This should only be called on the thread on which a user is using the context.
- (void)update
{
    // This ensures that regular 'update' calls clear the atomic dirty flag.
    [self scheduleUpdate];
    [self updateIfNeeded];
}

// Updates the drawable for the contexts and manages related state.
- (void)setWindow:(SDL_Window *)newWindow
{
    if (self->window) {
        SDL_CocoaWindowData *oldwindowdata = (__bridge SDL_CocoaWindowData *)self->window->internal;

        // Make sure to remove us from the old window's context list, or we'll get scheduled updates from it too.
        NSMutableArray *contexts = oldwindowdata.nscontexts;
        @synchronized(contexts) {
            [contexts removeObject:self];
        }
    }

    self->window = newWindow;

    if (newWindow) {
        SDL_CocoaWindowData *windowdata = (__bridge SDL_CocoaWindowData *)newWindow->internal;
        NSView *contentview = windowdata.sdlContentView;

        // Now sign up for scheduled updates for the new window.
        NSMutableArray *contexts = windowdata.nscontexts;
        @synchronized(contexts) {
            [contexts addObject:self];
        }

        if ([self view] != contentview) {
            if ([NSThread isMainThread]) {
                [self setView:contentview];
            } else {
                dispatch_sync(dispatch_get_main_queue(), ^{
                  [self setView:contentview];
                });
            }
            if (self == [NSOpenGLContext currentContext]) {
                [self explicitUpdate];
            } else {
                [self scheduleUpdate];
            }
        }
    } else {
        if ([NSThread isMainThread]) {
            [self setView:nil];
        } else {
            dispatch_sync(dispatch_get_main_queue(), ^{ [self setView:nil]; });
        }
    }
}

- (SDL_Window *)window
{
    return self->window;
}

- (void)explicitUpdate
{
    if ([NSThread isMainThread]) {
        [super update];
    } else {
        if (SDL_opengl_async_dispatch) {
            dispatch_async(dispatch_get_main_queue(), ^{
              [super update];
            });
        } else {
            dispatch_sync(dispatch_get_main_queue(), ^{
              [super update];
            });
        }
    }
}

- (void)cleanup
{
    [self setWindow:NULL];

    SDL_RemoveHintCallback(SDL_HINT_MAC_OPENGL_ASYNC_DISPATCH, SDL_OpenGLAsyncDispatchChanged, NULL);
    if (self->displayLink) {
        CVDisplayLinkRelease(self->displayLink);
        self->displayLink = nil;
    }
    if (self->swapIntervalCond) {
        SDL_DestroyCondition(self->swapIntervalCond);
        self->swapIntervalCond = NULL;
    }
    if (self->swapIntervalMutex) {
        SDL_DestroyMutex(self->swapIntervalMutex);
        self->swapIntervalMutex = NULL;
    }
}

@end

bool Cocoa_GL_LoadLibrary(SDL_VideoDevice *_this, const char *path)
{
    // Load the OpenGL library
    if (path == NULL) {
        path = SDL_GetHint(SDL_HINT_OPENGL_LIBRARY);
    }
    if (path == NULL) {
        path = DEFAULT_OPENGL;
    }
    _this->gl_config.dll_handle = SDL_LoadObject(path);
    if (!_this->gl_config.dll_handle) {
        return false;
    }
    SDL_strlcpy(_this->gl_config.driver_path, path,
                SDL_arraysize(_this->gl_config.driver_path));
    return true;
}

SDL_FunctionPointer Cocoa_GL_GetProcAddress(SDL_VideoDevice *_this, const char *proc)
{
    return SDL_LoadFunction(_this->gl_config.dll_handle, proc);
}

void Cocoa_GL_UnloadLibrary(SDL_VideoDevice *_this)
{
    SDL_UnloadObject(_this->gl_config.dll_handle);
    _this->gl_config.dll_handle = NULL;
}

SDL_GLContext Cocoa_GL_CreateContext(SDL_VideoDevice *_this, SDL_Window *window)
{
    @autoreleasepool {
        SDL_VideoDisplay *display = SDL_GetVideoDisplayForWindow(window);
        SDL_DisplayData *displaydata = (SDL_DisplayData *)display->internal;
        NSOpenGLPixelFormatAttribute attr[32];
        NSOpenGLPixelFormat *fmt;
        SDL3OpenGLContext *context;
        SDL_GLContext sdlcontext;
        NSOpenGLContext *share_context = nil;
        int i = 0;
        const char *glversion;
        int glversion_major;
        int glversion_minor;
        NSOpenGLPixelFormatAttribute profile;
        int interval;
        int opaque;

        if (_this->gl_config.profile_mask == SDL_GL_CONTEXT_PROFILE_ES) {
#ifdef SDL_VIDEO_OPENGL_EGL
            // Switch to EGL based functions
            Cocoa_GL_UnloadLibrary(_this);
            _this->GL_LoadLibrary = Cocoa_GLES_LoadLibrary;
            _this->GL_GetProcAddress = Cocoa_GLES_GetProcAddress;
            _this->GL_UnloadLibrary = Cocoa_GLES_UnloadLibrary;
            _this->GL_CreateContext = Cocoa_GLES_CreateContext;
            _this->GL_MakeCurrent = Cocoa_GLES_MakeCurrent;
            _this->GL_SetSwapInterval = Cocoa_GLES_SetSwapInterval;
            _this->GL_GetSwapInterval = Cocoa_GLES_GetSwapInterval;
            _this->GL_SwapWindow = Cocoa_GLES_SwapWindow;
            _this->GL_DestroyContext = Cocoa_GLES_DestroyContext;

            if (Cocoa_GLES_LoadLibrary(_this, NULL) != 0) {
                return NULL;
            }
            return Cocoa_GLES_CreateContext(_this, window);
#else
            SDL_SetError("SDL not configured with EGL support");
            return NULL;
#endif
        }

        attr[i++] = NSOpenGLPFAAllowOfflineRenderers;

        profile = NSOpenGLProfileVersionLegacy;
        if (_this->gl_config.profile_mask == SDL_GL_CONTEXT_PROFILE_CORE) {
            profile = NSOpenGLProfileVersion3_2Core;
        }
        attr[i++] = NSOpenGLPFAOpenGLProfile;
        attr[i++] = profile;

        attr[i++] = NSOpenGLPFAColorSize;
        attr[i++] = SDL_BYTESPERPIXEL(display->current_mode->format) * 8;

        attr[i++] = NSOpenGLPFADepthSize;
        attr[i++] = _this->gl_config.depth_size;

        if (_this->gl_config.double_buffer) {
            attr[i++] = NSOpenGLPFADoubleBuffer;
        }

        if (_this->gl_config.stereo) {
            attr[i++] = NSOpenGLPFAStereo;
        }

        if (_this->gl_config.stencil_size) {
            attr[i++] = NSOpenGLPFAStencilSize;
            attr[i++] = _this->gl_config.stencil_size;
        }

        if ((_this->gl_config.accum_red_size +
             _this->gl_config.accum_green_size +
             _this->gl_config.accum_blue_size +
             _this->gl_config.accum_alpha_size) > 0) {
            attr[i++] = NSOpenGLPFAAccumSize;
            attr[i++] = _this->gl_config.accum_red_size + _this->gl_config.accum_green_size + _this->gl_config.accum_blue_size + _this->gl_config.accum_alpha_size;
        }

        if (_this->gl_config.multisamplebuffers) {
            attr[i++] = NSOpenGLPFASampleBuffers;
            attr[i++] = _this->gl_config.multisamplebuffers;
        }

        if (_this->gl_config.multisamplesamples) {
            attr[i++] = NSOpenGLPFASamples;
            attr[i++] = _this->gl_config.multisamplesamples;
            attr[i++] = NSOpenGLPFANoRecovery;
        }
        if (_this->gl_config.floatbuffers) {
            attr[i++] = NSOpenGLPFAColorFloat;
        }

        if (_this->gl_config.accelerated >= 0) {
            if (_this->gl_config.accelerated) {
                attr[i++] = NSOpenGLPFAAccelerated;
            } else {
                attr[i++] = NSOpenGLPFARendererID;
                attr[i++] = kCGLRendererGenericFloatID;
            }
        }

        attr[i++] = NSOpenGLPFAScreenMask;
        attr[i++] = CGDisplayIDToOpenGLDisplayMask(displaydata->display);
        attr[i] = 0;

        fmt = [[NSOpenGLPixelFormat alloc] initWithAttributes:attr];
        if (fmt == nil) {
            SDL_SetError("Failed creating OpenGL pixel format");
            return NULL;
        }

        if (_this->gl_config.share_with_current_context) {
            share_context = (__bridge NSOpenGLContext *)SDL_GL_GetCurrentContext();
        }

        context = [[SDL3OpenGLContext alloc] initWithFormat:fmt shareContext:share_context];

        if (context == nil) {
            SDL_SetError("Failed creating OpenGL context");
            return NULL;
        }

        sdlcontext = (SDL_GLContext)CFBridgingRetain(context);

        // vsync is handled separately by synchronizing with a display link.
        interval = 0;
        [context setValues:&interval forParameter:NSOpenGLCPSwapInterval];

        opaque = (window->flags & SDL_WINDOW_TRANSPARENT) ? 0 : 1;
        [context setValues:&opaque forParameter:NSOpenGLCPSurfaceOpacity];

        if (!Cocoa_GL_MakeCurrent(_this, window, sdlcontext)) {
            SDL_GL_DestroyContext(sdlcontext);
            SDL_SetError("Failed making OpenGL context current");
            return NULL;
        }

        if (_this->gl_config.major_version < 3 &&
            _this->gl_config.profile_mask == 0 &&
            _this->gl_config.flags == 0) {
            // This is a legacy profile, so to match other backends, we're done.
        } else {
            const GLubyte *(APIENTRY * glGetStringFunc)(GLenum);

            glGetStringFunc = (const GLubyte *(APIENTRY *)(GLenum))SDL_GL_GetProcAddress("glGetString");
            if (!glGetStringFunc) {
                SDL_GL_DestroyContext(sdlcontext);
                SDL_SetError("Failed getting OpenGL glGetString entry point");
                return NULL;
            }

            glversion = (const char *)glGetStringFunc(GL_VERSION);
            if (glversion == NULL) {
                SDL_GL_DestroyContext(sdlcontext);
                SDL_SetError("Failed getting OpenGL context version");
                return NULL;
            }

            if (SDL_sscanf(glversion, "%d.%d", &glversion_major, &glversion_minor) != 2) {
                SDL_GL_DestroyContext(sdlcontext);
                SDL_SetError("Failed parsing OpenGL context version");
                return NULL;
            }

            if ((glversion_major < _this->gl_config.major_version) ||
                ((glversion_major == _this->gl_config.major_version) && (glversion_minor < _this->gl_config.minor_version))) {
                SDL_GL_DestroyContext(sdlcontext);
                SDL_SetError("Failed creating OpenGL context at version requested");
                return NULL;
            }

            /* In the future we'll want to do this, but to match other platforms
               we'll leave the OpenGL version the way it is for now
             */
            // _this->gl_config.major_version = glversion_major;
            // _this->gl_config.minor_version = glversion_minor;
        }
        return sdlcontext;
    }
}

bool Cocoa_GL_MakeCurrent(SDL_VideoDevice *_this, SDL_Window *window, SDL_GLContext context)
{
    @autoreleasepool {
        if (context) {
            SDL3OpenGLContext *nscontext = (__bridge SDL3OpenGLContext *)context;
            if ([nscontext window] != window) {
                [nscontext setWindow:window];
                [nscontext updateIfNeeded];
            }
            [nscontext makeCurrentContext];
        } else {
            [NSOpenGLContext clearCurrentContext];
        }

        return true;
    }
}

bool Cocoa_GL_SetSwapInterval(SDL_VideoDevice *_this, int interval)
{
    @autoreleasepool {
        SDL3OpenGLContext *nscontext = (__bridge SDL3OpenGLContext *)SDL_GL_GetCurrentContext();
        bool result;

        if (nscontext == nil) {
            result = SDL_SetError("No current OpenGL context");
        } else {
            SDL_LockMutex(nscontext->swapIntervalMutex);
            SDL_AtomicSet(&nscontext->swapIntervalsPassed, 0);
            SDL_AtomicSet(&nscontext->swapIntervalSetting, interval);
            SDL_UnlockMutex(nscontext->swapIntervalMutex);
            result = true;
        }

        return result;
    }
}

bool Cocoa_GL_GetSwapInterval(SDL_VideoDevice *_this, int *interval)
{
    @autoreleasepool {
        SDL3OpenGLContext *nscontext = (__bridge SDL3OpenGLContext *)SDL_GL_GetCurrentContext();
        if (nscontext) {
            *interval = SDL_AtomicGet(&nscontext->swapIntervalSetting);
            return true;
        } else {
            return SDL_SetError("no OpenGL context");
        }
    }
}

bool Cocoa_GL_SwapWindow(SDL_VideoDevice *_this, SDL_Window *window)
{
    @autoreleasepool {
        SDL3OpenGLContext *nscontext = (__bridge SDL3OpenGLContext *)SDL_GL_GetCurrentContext();
        SDL_CocoaVideoData *videodata = (__bridge SDL_CocoaVideoData *)_this->internal;
        const int setting = SDL_AtomicGet(&nscontext->swapIntervalSetting);

        if (setting == 0) {
            // nothing to do if vsync is disabled, don't even lock
        } else if (setting < 0) { // late swap tearing
            SDL_LockMutex(nscontext->swapIntervalMutex);
            while (SDL_AtomicGet(&nscontext->swapIntervalsPassed) == 0) {
                SDL_WaitCondition(nscontext->swapIntervalCond, nscontext->swapIntervalMutex);
            }
            SDL_AtomicSet(&nscontext->swapIntervalsPassed, 0);
            SDL_UnlockMutex(nscontext->swapIntervalMutex);
        } else {
            SDL_LockMutex(nscontext->swapIntervalMutex);
            do { // always wait here so we know we just hit a swap interval.
                SDL_WaitCondition(nscontext->swapIntervalCond, nscontext->swapIntervalMutex);
            } while ((SDL_AtomicGet(&nscontext->swapIntervalsPassed) % setting) != 0);
            SDL_AtomicSet(&nscontext->swapIntervalsPassed, 0);
            SDL_UnlockMutex(nscontext->swapIntervalMutex);
        }

        // { static Uint64 prev = 0; const Uint64 now = SDL_GetTicks(); const unsigned int diff = (unsigned int) (now - prev); prev = now; printf("GLSWAPBUFFERS TICKS %u\n", diff); }

        /* on 10.14 ("Mojave") and later, this deadlocks if two contexts in two
           threads try to swap at the same time, so put a mutex around it. */
        SDL_LockMutex(videodata.swaplock);
        [nscontext flushBuffer];
        [nscontext updateIfNeeded];
        SDL_UnlockMutex(videodata.swaplock);
        return true;
    }
}

bool Cocoa_GL_DestroyContext(SDL_VideoDevice *_this, SDL_GLContext context)
{
    @autoreleasepool {
        SDL3OpenGLContext *nscontext = (__bridge SDL3OpenGLContext *)context;
        [nscontext cleanup];
        CFRelease(context);
    }
    return true;
}

// We still support OpenGL as long as Apple offers it, deprecated or not, so disable deprecation warnings about it.
#ifdef __clang__
#pragma clang diagnostic pop
#endif

#endif // SDL_VIDEO_OPENGL_CGL
