Swiftgram/Source/Details/ASCollectionFlowLayoutDelegate.m

//
//  ASCollectionFlowLayoutDelegate.m
//  Texture
//
//  Copyright (c) 2014-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under the BSD-style license found in the
//  LICENSE file in the /ASDK-Licenses directory of this source tree. An additional
//  grant of patent rights can be found in the PATENTS file in the same directory.
//
//  Modifications to this file made after 4/13/2017 are: Copyright (c) 2017-present,
//  Pinterest, Inc.  Licensed under the Apache License, Version 2.0 (the "License");
//  you may not use this file except in compliance with the License.
//  You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//

#import <AsyncDisplayKit/ASCollectionFlowLayoutDelegate.h>

#import <AsyncDisplayKit/ASCellNode+Internal.h>
#import <AsyncDisplayKit/ASCollectionLayoutState.h>
#import <AsyncDisplayKit/ASCollectionElement.h>
#import <AsyncDisplayKit/ASCollectionLayoutContext.h>
#import <AsyncDisplayKit/ASCollectionLayoutDefines.h>
#import <AsyncDisplayKit/ASElementMap.h>
#import <AsyncDisplayKit/ASLayout.h>
#import <AsyncDisplayKit/ASStackLayoutSpec.h>

@implementation ASCollectionFlowLayoutDelegate {
  ASScrollDirection _scrollableDirections;
}

- (instancetype)init
{
  return [self initWithScrollableDirections:ASScrollDirectionVerticalDirections];
}

- (instancetype)initWithScrollableDirections:(ASScrollDirection)scrollableDirections
{
  self = [super init];
  if (self) {
    _scrollableDirections = scrollableDirections;
  }
  return self;
}

- (ASScrollDirection)scrollableDirections
{
  ASDisplayNodeAssertMainThread();
  return _scrollableDirections;
}

- (id)additionalInfoForLayoutWithElements:(ASElementMap *)elements
{
  ASDisplayNodeAssertMainThread();
  return nil;
}

+ (ASCollectionLayoutState *)calculateLayoutWithContext:(ASCollectionLayoutContext *)context
{
  ASElementMap *elements = context.elements;
  NSMutableArray<ASCellNode *> *children = ASArrayByFlatMapping(elements.itemElements, ASCollectionElement *element, element.node);
  if (children.count == 0) {
    return [[ASCollectionLayoutState alloc] initWithContext:context];
  }
  
  ASStackLayoutSpec *stackSpec = [ASStackLayoutSpec stackLayoutSpecWithDirection:ASStackLayoutDirectionHorizontal
                                                                         spacing:0
                                                                  justifyContent:ASStackLayoutJustifyContentStart
                                                                      alignItems:ASStackLayoutAlignItemsStart
                                                                        flexWrap:ASStackLayoutFlexWrapWrap
                                                                    alignContent:ASStackLayoutAlignContentStart
                                                                        children:children];
  stackSpec.concurrent = YES;

  ASSizeRange sizeRange = ASSizeRangeForCollectionLayoutThatFitsViewportSize(context.viewportSize, context.scrollableDirections);
  ASLayout *layout = [stackSpec layoutThatFits:sizeRange];

  return [[ASCollectionLayoutState alloc] initWithContext:context layout:layout getElementBlock:^ASCollectionElement * _Nullable(ASLayout * _Nonnull sublayout) {
    ASCellNode *node = ASDynamicCast(sublayout.layoutElement, ASCellNode);
    return node ? node.collectionElement : nil;
  }];
}

@end