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

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2020 - Raw Material Software Limited

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

   For this technical preview, this file is not subject to commercial licensing.

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

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

@interface JuceGLView   : UIView
{
}
+ (Class) layerClass;
@end

@implementation JuceGLView
+ (Class) layerClass
{
    return [CAEAGLLayer class];
}
@end

extern "C" GLvoid glResolveMultisampleFramebufferAPPLE();

namespace juce
{

class OpenGLContext::NativeContext
{
public:
    NativeContext (Component& c,
                   const OpenGLPixelFormat& pixFormat,
                   void* contextToShare,
                   bool multisampling,
                   OpenGLVersion version)
        : component (c), openGLversion (version),
          useDepthBuffer (pixFormat.depthBufferBits > 0),
          useMSAA (multisampling)
    {
        JUCE_AUTORELEASEPOOL
        {
            if (auto* peer = component.getPeer())
            {
                auto bounds = peer->getAreaCoveredBy (component);

                view = [[JuceGLView alloc] initWithFrame: convertToCGRect (bounds)];
                view.opaque = YES;
                view.hidden = NO;
                view.backgroundColor = [UIColor blackColor];
                view.userInteractionEnabled = NO;

                glLayer = (CAEAGLLayer*) [view layer];
                glLayer.opaque = true;

                updateWindowPosition (bounds);

                [((UIView*) peer->getNativeHandle()) addSubview: view];

                if (version == openGL3_2 && [[UIDevice currentDevice].systemVersion floatValue] >= 7.0)
                {
                    if (! createContext (kEAGLRenderingAPIOpenGLES3, contextToShare))
                    {
                        releaseContext();
                        createContext (kEAGLRenderingAPIOpenGLES2, contextToShare);
                    }
                }
                else
                {
                    createContext (kEAGLRenderingAPIOpenGLES2, contextToShare);
                }

                if (context != nil)
                {
                    // I'd prefer to put this stuff in the initialiseOnRenderThread() call, but doing
                    // so causes mysterious timing-related failures.
                    [EAGLContext setCurrentContext: context];
                    createGLBuffers();
                    deactivateCurrentContext();
                }
                else
                {
                    jassertfalse;
                }
            }
            else
            {
                jassertfalse;
            }
        }
    }

    ~NativeContext()
    {
        releaseContext();
        [view removeFromSuperview];
        [view release];
    }

    bool initialiseOnRenderThread (OpenGLContext&)    { return true; }

    void shutdownOnRenderThread()
    {
        JUCE_CHECK_OPENGL_ERROR
        freeGLBuffers();
        deactivateCurrentContext();
    }

    bool createdOk() const noexcept             { return getRawContext() != nullptr; }
    void* getRawContext() const noexcept        { return context; }
    GLuint getFrameBufferID() const noexcept    { return useMSAA ? msaaBufferHandle : frameBufferHandle; }

    bool makeActive() const noexcept
    {
        if (! [EAGLContext setCurrentContext: context])
            return false;

        glBindFramebuffer (GL_FRAMEBUFFER, useMSAA ? msaaBufferHandle
                                                   : frameBufferHandle);
        return true;
    }

    bool isActive() const noexcept
    {
        return [EAGLContext currentContext] == context;
    }

    static void deactivateCurrentContext()
    {
        [EAGLContext setCurrentContext: nil];
    }

    void swapBuffers()
    {
        if (useMSAA)
        {
            glBindFramebuffer (GL_DRAW_FRAMEBUFFER, frameBufferHandle);
            glBindFramebuffer (GL_READ_FRAMEBUFFER, msaaBufferHandle);

            if (openGLversion >= openGL3_2)
            {
                glBlitFramebuffer (0, 0, lastBounds.getWidth(), lastBounds.getHeight(),
                                   0, 0, lastBounds.getWidth(), lastBounds.getHeight(),
                                   GL_COLOR_BUFFER_BIT, GL_NEAREST);
            }
            else
            {
                glResolveMultisampleFramebufferAPPLE();
            }
        }

        glBindRenderbuffer (GL_RENDERBUFFER, colorBufferHandle);
        [context presentRenderbuffer: GL_RENDERBUFFER];

        if (needToRebuildBuffers)
        {
            needToRebuildBuffers = false;

            freeGLBuffers();
            createGLBuffers();
            makeActive();
        }
    }

    void updateWindowPosition (Rectangle<int> bounds)
    {
        view.frame = convertToCGRect (bounds);
        glLayer.contentsScale = (CGFloat) (Desktop::getInstance().getDisplays().getMainDisplay().scale
                                            / component.getDesktopScaleFactor());

        if (lastBounds != bounds)
        {
            lastBounds = bounds;
            needToRebuildBuffers = true;
        }
    }

    bool setSwapInterval (int numFramesPerSwap) noexcept
    {
        swapFrames = numFramesPerSwap;
        return false;
    }

    int getSwapInterval() const noexcept    { return swapFrames; }

    struct Locker { Locker (NativeContext&) {} };

private:
    Component& component;
    JuceGLView* view = nil;
    CAEAGLLayer* glLayer = nil;
    EAGLContext* context = nil;
    const OpenGLVersion openGLversion;
    const bool useDepthBuffer, useMSAA;

    GLuint frameBufferHandle = 0, colorBufferHandle = 0, depthBufferHandle = 0,
           msaaColorHandle = 0, msaaBufferHandle = 0;

    Rectangle<int> lastBounds;
    int swapFrames = 0;
    bool needToRebuildBuffers = false;

    bool createContext (EAGLRenderingAPI type, void* contextToShare)
    {
        jassert (context == nil);
        context = [EAGLContext alloc];

        context = contextToShare != nullptr
                    ? [context initWithAPI: type  sharegroup: [(EAGLContext*) contextToShare sharegroup]]
                    : [context initWithAPI: type];

        return context != nil;
    }

    void releaseContext()
    {
        [context release];
        context = nil;
    }

    //==============================================================================
    void createGLBuffers()
    {
        glGenFramebuffers (1, &frameBufferHandle);
        glGenRenderbuffers (1, &colorBufferHandle);

        glBindFramebuffer (GL_FRAMEBUFFER, frameBufferHandle);
        glBindRenderbuffer (GL_RENDERBUFFER, colorBufferHandle);

        glFramebufferRenderbuffer (GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, colorBufferHandle);

        bool ok = [context renderbufferStorage: GL_RENDERBUFFER fromDrawable: glLayer];
        jassert (ok); ignoreUnused (ok);

        GLint width, height;
        glGetRenderbufferParameteriv (GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &width);
        glGetRenderbufferParameteriv (GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &height);

        if (useMSAA)
        {
            glGenFramebuffers (1, &msaaBufferHandle);
            glGenRenderbuffers (1, &msaaColorHandle);

            glBindFramebuffer (GL_FRAMEBUFFER, msaaBufferHandle);
            glBindRenderbuffer (GL_RENDERBUFFER, msaaColorHandle);

            glRenderbufferStorageMultisample (GL_RENDERBUFFER, 4, GL_RGBA8, width, height);

            glFramebufferRenderbuffer (GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, msaaColorHandle);
        }

        if (useDepthBuffer)
        {
            glGenRenderbuffers (1, &depthBufferHandle);
            glBindRenderbuffer (GL_RENDERBUFFER, depthBufferHandle);

            if (useMSAA)
                glRenderbufferStorageMultisample (GL_RENDERBUFFER, 4, GL_DEPTH_COMPONENT16, width, height);
            else
                glRenderbufferStorage (GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, width, height);

            glFramebufferRenderbuffer (GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthBufferHandle);
        }

        jassert (glCheckFramebufferStatus (GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE);
        JUCE_CHECK_OPENGL_ERROR
    }

    void freeGLBuffers()
    {
        JUCE_CHECK_OPENGL_ERROR
        [context renderbufferStorage: GL_RENDERBUFFER fromDrawable: nil];

        deleteFrameBuffer (frameBufferHandle);
        deleteFrameBuffer (msaaBufferHandle);
        deleteRenderBuffer (colorBufferHandle);
        deleteRenderBuffer (depthBufferHandle);
        deleteRenderBuffer (msaaColorHandle);

        JUCE_CHECK_OPENGL_ERROR
    }

    static void deleteFrameBuffer  (GLuint& i)   { if (i != 0) glDeleteFramebuffers  (1, &i); i = 0; }
    static void deleteRenderBuffer (GLuint& i)   { if (i != 0) glDeleteRenderbuffers (1, &i); i = 0; }

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (NativeContext)
};

//==============================================================================
bool OpenGLHelpers::isContextActive()
{
    return [EAGLContext currentContext] != nil;
}

} // namespace juce