CollectionDataSource

open class CollectionDataSource<Provider: CollectionDataProviderProtocol, Cell: UICollectionViewCell>: NSObject, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout where Cell: ConfigurableCell, Provider.T == Cell.T {

  // MARK: - Private Properties
  let provider: Provider
  let collectionView: UICollectionView

  // Initialize and setup CollectionDataSource
  // CollectionDataSource sets itself as the delegate for UICollectionViewDataSource and UICollectionViewDelegate
  init(collectionView: UICollectionView, provider: Provider) {
    self.collectionView = collectionView
    self.provider = provider
    super.init()
    setup()
  }

  func setup(){
    collectionView.dataSource = self
    collectionView.delegate = self
  }

  public func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return provider.numberOfItems(in: section)
  }

  public func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    return CGSize(width: collectionView.frame.width / 2 - 20, height: 250)
  }

  public func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: Cell.reuseIdentifier, for: indexPath) as? Cell else {
      return UICollectionViewCell()
    }

    let item = provider.item(at: indexPath)
    if let item = item {
      cell.configure(item, at: indexPath)
    }

    return cell
  }
}