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

   This file is part of the JUCE framework.
   Copyright (c) Raw Material Software Limited

   JUCE is an open source framework subject to commercial or open source
   licensing.

   By downloading, installing, or using the JUCE framework, or combining the
   JUCE framework with any other source code, object code, content or any other
   copyrightable work, you agree to the terms of the JUCE End User Licence
   Agreement, and all incorporated terms including the JUCE Privacy Policy and
   the JUCE Website Terms of Service, as applicable, which will bind you. If you
   do not agree to the terms of these agreements, we will not license the JUCE
   framework to you, and you must discontinue the installation or download
   process and cease use of the JUCE framework.

   JUCE End User Licence Agreement: https://juce.com/legal/juce-8-licence/
   JUCE Privacy Policy: https://juce.com/juce-privacy-policy
   JUCE Website Terms of Service: https://juce.com/juce-website-terms-of-service/

   Or:

   You may also use this code under the terms of the AGPLv3:
   https://www.gnu.org/licenses/agpl-3.0.en.html

   THE JUCE FRAMEWORK IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL
   WARRANTIES, WHETHER EXPRESSED OR IMPLIED, INCLUDING WARRANTY OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR 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();

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

                const auto shouldUseES3 = version != defaultGLVersion
                                       && [[UIDevice currentDevice].systemVersion floatValue] >= 7.0;

                [[maybe_unused]] const auto gotContext = (shouldUseES3 && createContext (kEAGLRenderingAPIOpenGLES3, contextToShare))
                                                         || createContext (kEAGLRenderingAPIOpenGLES2, contextToShare);

                jassert (gotContext);

                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.get()];
                    gl::loadFunctions();
                    createGLBuffers();
                    deactivateCurrentContext();
                }
                else
                {
                    jassertfalse;
                }
            }
            else
            {
                jassertfalse;
            }
        }
    }

    ~NativeContext()
    {
        context.reset();
        [view removeFromSuperview];
        [view release];
    }

    InitResult initialiseOnRenderThread (OpenGLContext&)    { return InitResult::success; }

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

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

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

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

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

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

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

            if (openGLversion >= openGL3_2)
            {
                const auto w = lastBounds.getWidth();
                const auto h = lastBounds.getHeight();

                glBlitFramebuffer (0, 0, w, h,
                                   0, 0, w, h,
                                   GL_COLOR_BUFFER_BIT,
                                   GL_NEAREST);
            }
            else
            {
                ::glResolveMultisampleFramebufferAPPLE();
            }
        }

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

        if (! std::exchange (needToRebuildBuffers, false))
            return;

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

    void updateWindowPosition()
    {
        auto* peer = component.getTopLevelComponent()->getPeer();

        if (peer == nullptr)
            return;

        const auto bounds = peer->getAreaCoveredBy (component);
        view.frame = convertToCGRect (bounds);
        glLayer.contentsScale = (CGFloat) (Desktop::getInstance().getDisplays().getPrimaryDisplay()->scale
                                            / component.getDesktopScaleFactor());

        const auto msaaBounds = bounds * glLayer.contentsScale;
        needToRebuildBuffers |= std::exchange (lastBounds, msaaBounds) != msaaBounds;
    }

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

    int getSwapInterval() const noexcept    { return swapFrames; }

    struct Locker
    {
        explicit Locker (NativeContext& ctx) : lock (ctx.mutex) {}
        const ScopedLock lock;
    };

    void addListener (NativeContextListener&) {}
    void removeListener (NativeContextListener&) {}

private:
    CriticalSection mutex;
    Component& component;
    JuceGLView* view = nil;
    CAEAGLLayer* glLayer = nil;
    NSUniquePtr<EAGLContext> context;
    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.reset ([EAGLContext alloc]);

        if (contextToShare != nullptr)
            [context.get() initWithAPI: type  sharegroup: [(EAGLContext*) contextToShare sharegroup]];
        else
            [context.get() initWithAPI: type];

        return 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);

        [[maybe_unused]] bool ok = [context.get() renderbufferStorage: GL_RENDERBUFFER fromDrawable: glLayer];
        jassert (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.get() 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
