/*
  ==============================================================================

   This file is part of the JUCE 7 technical preview.
   Copyright (c) 2022 - Raw Material Software Limited

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For the technical preview this file cannot be licensed commercially.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

JUCE_BEGIN_IGNORE_WARNINGS_GCC_LIKE ("-Wdeprecated-declarations")

class OpenGLContext::NativeContext
{
public:
    NativeContext (Component& component,
                   const OpenGLPixelFormat& pixFormat,
                   void* contextToShare,
                   bool shouldUseMultisampling,
                   OpenGLVersion version)
        : owner (component)
    {
        NSOpenGLPixelFormatAttribute attribs[64] = { 0 };
        createAttribs (attribs, version, pixFormat, shouldUseMultisampling);

        NSOpenGLPixelFormat* format = [[NSOpenGLPixelFormat alloc] initWithAttributes: attribs];

        static MouseForwardingNSOpenGLViewClass cls;
        view = [cls.createInstance() initWithFrame: NSMakeRect (0, 0, 100.0f, 100.0f)
                                       pixelFormat: format];

        if ([view respondsToSelector: @selector (setWantsBestResolutionOpenGLSurface:)])
            [view setWantsBestResolutionOpenGLSurface: YES];

        JUCE_BEGIN_IGNORE_WARNINGS_GCC_LIKE ("-Wundeclared-selector")
        [[NSNotificationCenter defaultCenter] addObserver: view
                                                 selector: @selector (_surfaceNeedsUpdate:)
                                                     name: NSViewGlobalFrameDidChangeNotification
                                                   object: view];
        JUCE_END_IGNORE_WARNINGS_GCC_LIKE

        renderContext = [[[NSOpenGLContext alloc] initWithFormat: format
                                                    shareContext: (NSOpenGLContext*) contextToShare] autorelease];

        [view setOpenGLContext: renderContext];
        [format release];

        viewAttachment = NSViewComponent::attachViewToComponent (component, view);
    }

    ~NativeContext()
    {
        [[NSNotificationCenter defaultCenter] removeObserver: view];
        [renderContext clearDrawable];
        [renderContext setView: nil];
        [view setOpenGLContext: nil];
        [view release];
    }

    static void createAttribs (NSOpenGLPixelFormatAttribute* attribs, OpenGLVersion version,
                               const OpenGLPixelFormat& pixFormat, bool shouldUseMultisampling)
    {
        ignoreUnused (version);
        int numAttribs = 0;

        attribs[numAttribs++] = NSOpenGLPFAOpenGLProfile;
        attribs[numAttribs++] = version >= openGL3_2 ? NSOpenGLProfileVersion3_2Core
                                                     : NSOpenGLProfileVersionLegacy;

        attribs[numAttribs++] = NSOpenGLPFADoubleBuffer;
        attribs[numAttribs++] = NSOpenGLPFAClosestPolicy;
        attribs[numAttribs++] = NSOpenGLPFANoRecovery;
        attribs[numAttribs++] = NSOpenGLPFAColorSize;
        attribs[numAttribs++] = (NSOpenGLPixelFormatAttribute) (pixFormat.redBits + pixFormat.greenBits + pixFormat.blueBits);
        attribs[numAttribs++] = NSOpenGLPFAAlphaSize;
        attribs[numAttribs++] = (NSOpenGLPixelFormatAttribute) pixFormat.alphaBits;
        attribs[numAttribs++] = NSOpenGLPFADepthSize;
        attribs[numAttribs++] = (NSOpenGLPixelFormatAttribute) pixFormat.depthBufferBits;
        attribs[numAttribs++] = NSOpenGLPFAStencilSize;
        attribs[numAttribs++] = (NSOpenGLPixelFormatAttribute) pixFormat.stencilBufferBits;
        attribs[numAttribs++] = NSOpenGLPFAAccumSize;
        attribs[numAttribs++] = (NSOpenGLPixelFormatAttribute) (pixFormat.accumulationBufferRedBits + pixFormat.accumulationBufferGreenBits
                                                                   + pixFormat.accumulationBufferBlueBits + pixFormat.accumulationBufferAlphaBits);

        if (shouldUseMultisampling)
        {
            attribs[numAttribs++] = NSOpenGLPFAMultisample;
            attribs[numAttribs++] = NSOpenGLPFASampleBuffers;
            attribs[numAttribs++] = (NSOpenGLPixelFormatAttribute) 1;
            attribs[numAttribs++] = NSOpenGLPFASamples;
            attribs[numAttribs++] = (NSOpenGLPixelFormatAttribute) pixFormat.multisamplingLevel;
        }
    }

    bool initialiseOnRenderThread (OpenGLContext&)    { return true; }
    void shutdownOnRenderThread()                     { deactivateCurrentContext(); }

    bool createdOk() const noexcept                   { return getRawContext() != nullptr; }
    void* getRawContext() const noexcept              { return static_cast<void*> (renderContext); }
    GLuint getFrameBufferID() const noexcept          { return 0; }

    bool makeActive() const noexcept
    {
        jassert (renderContext != nil);

        if ([renderContext view] != view)
            [renderContext setView: view];

        if (NSOpenGLContext* context = [view openGLContext])
        {
            [context makeCurrentContext];
            return true;
        }

        return false;
    }

    bool isActive() const noexcept
    {
        return [NSOpenGLContext currentContext] == renderContext;
    }

    static void deactivateCurrentContext()
    {
        [NSOpenGLContext clearCurrentContext];
    }

    struct Locker
    {
        Locker (NativeContext& nc) : cglContext ((CGLContextObj) [nc.renderContext CGLContextObj])
        {
            CGLLockContext (cglContext);
        }

        ~Locker()
        {
            CGLUnlockContext (cglContext);
        }

    private:
        CGLContextObj cglContext;
    };

    void swapBuffers()
    {
        auto now = Time::getMillisecondCounterHiRes();
        [renderContext flushBuffer];

        if (minSwapTimeMs > 0)
        {
            // When our window is entirely occluded by other windows, flushBuffer
            // fails to wait for the swap interval, so the render loop spins at full
            // speed, burning CPU. This hack detects when things are going too fast
            // and sleeps if necessary.

            auto swapTime = Time::getMillisecondCounterHiRes() - now;
            auto frameTime = (int) (now - lastSwapTime);

            if (swapTime < 0.5 && frameTime < minSwapTimeMs - 3)
            {
                if (underrunCounter > 3)
                {
                    Thread::sleep (2 * (minSwapTimeMs - frameTime));
                    now = Time::getMillisecondCounterHiRes();
                }
                else
                {
                    ++underrunCounter;
                }
            }
            else
            {
                if (underrunCounter > 0)
                    --underrunCounter;
            }
        }

        lastSwapTime = now;
    }

    void updateWindowPosition (Rectangle<int>)
    {
        if (auto* peer = owner.getTopLevelComponent()->getPeer())
        {
            const auto newArea = peer->getAreaCoveredBy (owner);

            if (convertToRectInt ([view frame]) != newArea)
                [view setFrame: makeNSRect (newArea)];
        }
    }

    bool setSwapInterval (int numFramesPerSwapIn)
    {
        numFramesPerSwap = numFramesPerSwapIn;

        // The macOS OpenGL programming guide says that numFramesPerSwap
        // can only be 0 or 1.
        jassert (isPositiveAndBelow (numFramesPerSwap, 2));

        [renderContext setValues: (const GLint*) &numFramesPerSwap
                    forParameter: getSwapIntervalParameter()];

        updateMinSwapTime();

        return true;
    }

    int getSwapInterval() const
    {
        GLint numFrames = 0;
        [renderContext getValues: &numFrames
                    forParameter: getSwapIntervalParameter()];

        return numFrames;
    }

    void setNominalVideoRefreshPeriodS (double periodS)
    {
        jassert (periodS > 0.0);
        videoRefreshPeriodS = periodS;
        updateMinSwapTime();
    }

    void updateMinSwapTime()
    {
        minSwapTimeMs = static_cast<int> (numFramesPerSwap * 1000 * videoRefreshPeriodS);
    }

    static NSOpenGLContextParameter getSwapIntervalParameter()
    {
        #if defined (MAC_OS_X_VERSION_10_12) && MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_12
         if (@available (macOS 10.12, *))
             return NSOpenGLContextParameterSwapInterval;
        #endif

        return NSOpenGLCPSwapInterval;
    }

    Component& owner;
    NSOpenGLContext* renderContext = nil;
    NSOpenGLView* view = nil;
    ReferenceCountedObjectPtr<ReferenceCountedObject> viewAttachment;
    double lastSwapTime = 0;
    std::atomic<int> minSwapTimeMs { 0 };
    int underrunCounter = 0, numFramesPerSwap = 0;
    double videoRefreshPeriodS = 1.0 / 60.0;

    //==============================================================================
    struct MouseForwardingNSOpenGLViewClass  : public ObjCClass<NSOpenGLView>
    {
        MouseForwardingNSOpenGLViewClass()  : ObjCClass<NSOpenGLView> ("JUCEGLView_")
        {
            addMethod (@selector (rightMouseDown:),       rightMouseDown);
            addMethod (@selector (rightMouseUp:),         rightMouseUp);
            addMethod (@selector (acceptsFirstMouse:),    acceptsFirstMouse);
            addMethod (@selector (accessibilityHitTest:), accessibilityHitTest);

            registerClass();
        }

    private:
        static void rightMouseDown (id self, SEL, NSEvent* ev)      { [[(NSOpenGLView*) self superview] rightMouseDown: ev]; }
        static void rightMouseUp   (id self, SEL, NSEvent* ev)      { [[(NSOpenGLView*) self superview] rightMouseUp:   ev]; }
        static BOOL acceptsFirstMouse (id, SEL, NSEvent*)           { return YES; }
        static id accessibilityHitTest (id self, SEL, NSPoint p)    { return [[(NSOpenGLView*) self superview] accessibilityHitTest: p]; }
    };


    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (NativeContext)
};

//==============================================================================
bool OpenGLHelpers::isContextActive()
{
    return CGLGetCurrentContext() != CGLContextObj();
}

JUCE_END_IGNORE_WARNINGS_GCC_LIKE

} // namespace juce