final class InfiniteScrollingCollectionView<T>: UIView, UICollectionViewDataSource {
    init() {
        self.sections = Property(value: [])
        
        super.init(frame: .zero)

        self.addSubview(self.collectionView)
        
        self.collectionView.dataSource = self
        self.collectionView.delegate = self
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    // MARK: -
    
    private let sections: Property<[Section<T>]>
    
    // MARK: -
    
    private let collectionView: UICollectionView = {
        let view = UICollectionView()
        
        return view
    }()
    
    // MARK: - UICollectionViewDataSource
    
    @objc func numberOfSections(in collectionView: UICollectionView) -> Int {
        return self.sections.value.count
    }
    
    @objc func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return self.sections.value[section].size
    }
    
    @objc func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        return collectionView.dequeueReusableCell(withReuseIdentifier: "TODO", for: indexPath)
    }
}

fileprivate enum Section<T> {
    case loaded(Data)
    case notLoaded(expectedCount: Int)
    
    var size: Int {
        switch self {
        case let .loaded(data):
            return data.count
            
        case let .notLoaded(count):
            return count
        }
    }
}

extension InfiniteScrollingCollectionView: UICollectionViewDelegate {
    
}

struct Property<T> {
    let value: T
}