text: //
  //  ASSectionController.h
  //  Texture
  //
  //  Copyright (c) Facebook, Inc. and its affiliates.  All rights reserved.
  //  Changes after 4/13/2017 are: Copyright (c) Pinterest, Inc.  All rights reserved.
  //  Licensed under Apache 2.0: http://www.apache.org/licenses/LICENSE-2.0
  //
  
  #import <Foundation/Foundation.h>
  #import "ASBlockTypes.h"
  #import "ASDimension.h"
  
  NS_ASSUME_NONNULL_BEGIN
  
  @class ASBatchContext;
  
  /**
   * A protocol that your section controllers should conform to, in order to be used with Texture.
   *
   * @note Your supplementary view source should conform to @c ASSupplementaryNodeSource.
   */
  @protocol ASSectionController <NSObject>
  
  @optional
  
  /**
   * A method to provide the node block for the item at the given index.
   * The node block you return will be run asynchronously off the main thread,
   * so it's important to retrieve any objects from your section _outside_ the block
   * because by the time the block is run, the array may have changed.
   *
   * @param index The index of the item.
   * @return A block to be run concurrently to build the node for this item.
   * @see collectionNode:nodeBlockForItemAtIndexPath:
   */
  - (ASCellNodeBlock)nodeBlockForItemAtIndex:(NSInteger)index;
  
  /**
   * Similar to -collectionView:cellForItemAtIndexPath:.
   *
   * Note: only called if nodeBlockForItemAtIndex: returns nil.
   *
   * @param index The index of the item.
   *
   * @return A node to display for the given item. This will be called on the main thread and should
   *   not implement reuse (it will be called once per item).  Unlike UICollectionView's version,
   *   this method is not called when the item is about to display.
   */
  - (ASCellNode *)nodeForItemAtIndex:(NSInteger)index;
  
  /**
   * Asks the section controller whether it should batch fetch because the user is
   * near the end of the current data set.
   *
   * @discussion Use this method to conditionally fetch batches. Example use cases are: limiting the total number of
   * objects that can be fetched or no network connection.
   *
   * If not implemented, the assumed return value is @c YES.
   */
  - (BOOL)shouldBatchFetch;
  
  /**
   * Asks the section controller to begin fetching more content (tail loading) because
   * the user is near the end of the current data set.
   *
   * @param context A context object that must be notified when the batch fetch is completed.
   *
   * @discussion You must eventually call -completeBatchFetching: with an argument of YES in order to receive future
   * notifications to do batch fetches. This method is called on a background queue.
   */
  - (void)beginBatchFetchWithContext:(ASBatchContext *)context;
  
  /**
   * A method to provide the size range used for measuring the item
   * at the given index.
   *
   * @param index The index of the item.
   * @return A size range used for asynchronously measuring the node at this index.
   * @see collectionNode:constrainedSizeForItemAtIndexPath:
   */
  - (ASSizeRange)sizeRangeForItemAtIndex:(NSInteger)index;
  
  @end
  
  NS_ASSUME_NONNULL_END
  