Provider.swift

//
//  Provider.swift
//  CollectionKit
//
//  Created by Luke Zhao on 2017-07-23.
//  Copyright © 2017 lkzhao. All rights reserved.
//

import UIKit

public protocol Provider {
  var identifier: String? { get }

  // data
  var numberOfItems: Int { get }
  func identifier(at: Int) -> String

  // layout
  func layout(collectionSize: CGSize)
  func visible(in visibleFrame: CGRect) -> (indexes: [Int], frame: CGRect)
  var contentSize: CGSize { get }
  func frame(at: Int) -> CGRect

  // event
  func willReload()
  func didReload()

  func animator(at: Int) -> Animator?

  // determines if a context belongs to current provider
  func hasReloadable(_ reloadable: CollectionReloadable) -> Bool

  func flattenedProvider() -> ItemProvider
}

extension Provider {
  public func willReload() {}
  public func didReload() {}
}