/* 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 root directory of this source tree. An additional grant

* of patent rights can be found in the PATENTS file in the same directory.

*/

#import "ASCollectionView.h"

#import "ASAssert.h"

#import "ASRangeController.h"

#pragma mark -

#pragma mark Proxying.

/**

* ASCollectionView intercepts and/or overrides a few of UICollectionView's critical data source and delegate methods.

*

* Any selector included in this function *MUST* be implemented by ASCollectionView.

*/

static BOOL _isInterceptedSelector(SEL sel)

{

return (

// handled by ASCollectionView node<->cell machinery

sel == @selector(collectionView:cellForItemAtIndexPath:) ||

sel == @selector(collectionView:layout:sizeForItemAtIndexPath:) ||

// handled by ASRangeController

sel == @selector(numberOfSectionsInCollectionView:) ||

sel == @selector(collectionView:numberOfItemsInSection:) ||

// used for ASRangeController visibility updates

sel == @selector(collectionView:willDisplayCell:forItemAtIndexPath:) ||

sel == @selector(collectionView:didEndDisplayingCell:forItemAtIndexPath:)

);

}

/**

* Stand-in for UICollectionViewDataSource and UICollectionViewDelegate. Any method calls we intercept are routed to ASCollectionView;

* everything else leaves AsyncDisplayKit safely and arrives at the original intended data source and delegate.

*/

@interface _ASCollectionViewProxy : NSProxy

- (instancetype)initWithTarget:(id<NSObject>)target interceptor:(ASCollectionView *)interceptor;

@end

@implementation _ASCollectionViewProxy {

id<NSObject> __weak _target;

ASCollectionView * __weak _interceptor;

}

- (instancetype)initWithTarget:(id<NSObject>)target interceptor:(ASCollectionView *)interceptor

{

// -[NSProxy init] is undefined

if (!self) {

return nil;

}

ASDisplayNodeAssert(target, @"target must not be nil");

ASDisplayNodeAssert(interceptor, @"interceptor must not be nil");

_target = target;

_interceptor = interceptor;

return self;

}

- (BOOL)respondsToSelector:(SEL)aSelector

{

return (_isInterceptedSelector(aSelector) || [_target respondsToSelector:aSelector]);

}

- (id)forwardingTargetForSelector:(SEL)aSelector

{

if (_isInterceptedSelector(aSelector)) {

return _interceptor;

}

return [_target respondsToSelector:aSelector] ? _target : nil;

}

@end

#pragma mark -

#pragma mark ASCollectionView.

@interface ASCollectionView () <ASRangeControllerDelegate> {

_ASCollectionViewProxy *_proxyDataSource;

_ASCollectionViewProxy *_proxyDelegate;

ASRangeController *_rangeController;

}

@end

@implementation ASCollectionView

#pragma mark -

#pragma mark Lifecycle.

- (instancetype)initWithFrame:(CGRect)frame collectionViewLayout:(UICollectionViewLayout *)layout

{

if (!(self = [super initWithFrame:frame collectionViewLayout:layout]))

return nil;

_rangeController = [[ASRangeController alloc] init];

_rangeController.delegate = self;

[self registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"_ASCollectionViewCell"];

return self;

}

#pragma mark -

#pragma mark Overrides.

- (void)reloadData

{

[_rangeController rebuildData];

[super reloadData];

}

- (void)setDataSource:(id<UICollectionViewDataSource>)dataSource

{

ASDisplayNodeAssert(NO, @"ASCollectionView uses asyncDataSource, not UICollectionView's dataSource property.");

}

- (void)setDelegate:(id<UICollectionViewDelegate>)delegate

{

// Our UIScrollView superclass sets its delegate to nil on dealloc. Only assert if we get a non-nil value here.

ASDisplayNodeAssert(delegate == nil, @"ASCollectionView uses asyncDelegate, not UICollectionView's delegate property.");

}

- (void)setAsyncDataSource:(id<ASCollectionViewDataSource>)asyncDataSource

{

if (_asyncDataSource == asyncDataSource)

return;

_asyncDataSource = asyncDataSource;

_proxyDataSource = [[_ASCollectionViewProxy alloc] initWithTarget:_asyncDataSource interceptor:self];

super.dataSource = (id<UICollectionViewDataSource>)_proxyDataSource;

}

- (void)setAsyncDelegate:(id<ASCollectionViewDelegate>)asyncDelegate

{

if (_asyncDelegate == asyncDelegate)

return;

_asyncDelegate = asyncDelegate;

_proxyDelegate = [[_ASCollectionViewProxy alloc] initWithTarget:_asyncDelegate interceptor:self];

super.delegate = (id<UICollectionViewDelegate>)_proxyDelegate;

}

- (ASRangeTuningParameters)rangeTuningParameters

{

return _rangeController.tuningParameters;

}

- (void)setRangeTuningParameters:(ASRangeTuningParameters)tuningParameters

{

_rangeController.tuningParameters = tuningParameters;

}

- (void)appendNodesWithIndexPaths:(NSArray *)indexPaths

{

[_rangeController appendNodesWithIndexPaths:indexPaths];

}

- (CGSize)calculatedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath

{

return [_rangeController calculatedSizeForNodeAtIndexPath:indexPath];

}

#pragma mark Assertions.

- (void)throwUnimplementedException

{

[[NSException exceptionWithName:@"UnimplementedException"

reason:@"ASCollectionView's update/editing support is not yet implemented. Please see ASCollectionView.h."

userInfo:nil] raise];

}

- (void)insertSections:(NSIndexSet *)sections

{

[self throwUnimplementedException];

}

- (void)deleteSections:(NSIndexSet *)sections

{

[self throwUnimplementedException];

}

- (void)reloadSections:(NSIndexSet *)sections

{

[self throwUnimplementedException];

}

- (void)moveSection:(NSInteger)section toSection:(NSInteger)newSection

{

[self throwUnimplementedException];

}

- (void)insertItemsAtIndexPaths:(NSArray *)indexPaths

{

[self throwUnimplementedException];

}

- (void)deleteItemsAtIndexPaths:(NSArray *)indexPaths

{

[self throwUnimplementedException];

}

- (void)reloadItemsAtIndexPaths:(NSArray *)indexPaths

{

[self throwUnimplementedException];

}

- (void)moveItemAtIndexPath:(NSIndexPath *)indexPath toIndexPath:(NSIndexPath *)newIndexPath

{

[self throwUnimplementedException];

}

#pragma mark -

#pragma mark Intercepted selectors.

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath

{

static NSString *reuseIdentifier = @"_ASCollectionViewCell";

UICollectionViewCell *cell = [self dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];

[_rangeController configureContentView:cell.contentView forIndexPath:indexPath];

return cell;

}

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath

{

return [_rangeController calculatedSizeForNodeAtIndexPath:indexPath];

}

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView

{

return [_rangeController numberOfSizedSections];

}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section

{

return [_rangeController numberOfSizedRowsInSection:section];

}

- (void)collectionView:(UICollectionView *)collectionView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath

{

[_rangeController visibleNodeIndexPathsDidChange];

if ([_asyncDelegate respondsToSelector:@selector(collectionView:willDisplayNodeForItemAtIndexPath:)]) {

[_asyncDelegate collectionView:self willDisplayNodeForItemAtIndexPath:indexPath];

}

}

- (void)collectionView:(UICollectionView *)collectionView didEndDisplayingCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath

{

[_rangeController visibleNodeIndexPathsDidChange];

if ([_asyncDelegate respondsToSelector:@selector(collectionView:didEndDisplayingNodeForItemAtIndexPath:)]) {

[_asyncDelegate collectionView:self didEndDisplayingNodeForItemAtIndexPath:indexPath];

}

}

#pragma mark -

#pragma mark ASRangeControllerDelegate.

- (NSArray *)rangeControllerVisibleNodeIndexPaths:(ASRangeController *)rangeController

{

ASDisplayNodeAssertMainThread();

return [[self indexPathsForVisibleItems] sortedArrayUsingSelector:@selector(compare:)];

}

- (CGSize)rangeControllerViewportSize:(ASRangeController *)rangeController

{

ASDisplayNodeAssertMainThread();

return self.bounds.size;

}

- (NSInteger)rangeControllerSections:(ASRangeController *)rangeController

{

ASDisplayNodeAssertMainThread();

if ([_asyncDataSource respondsToSelector:@selector(numberOfSectionsInCollectionView:)]) {

return [_asyncDataSource numberOfSectionsInCollectionView:self];

} else {

return 1;

}

}

- (NSInteger)rangeController:(ASRangeController *)rangeController rowsInSection:(NSInteger)section

{

ASDisplayNodeAssertMainThread();

return [_asyncDataSource collectionView:self numberOfItemsInSection:section];

}

- (ASCellNode *)rangeController:(ASRangeController *)rangeController nodeForIndexPath:(NSIndexPath *)indexPath

{

ASDisplayNodeAssertNotMainThread();

return [_asyncDataSource collectionView:self nodeForItemAtIndexPath:indexPath];

}

- (CGSize)rangeController:(ASRangeController *)rangeController constrainedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath

{

ASDisplayNodeAssertNotMainThread();

CGSize contentSize = [self.collectionViewLayout collectionViewContentSize];

CGSize viewSize = self.bounds.size;

CGFloat constrainedWidth = viewSize.width == contentSize.width ? viewSize.width : FLT_MAX;

CGFloat constrainedHeight = viewSize.height == contentSize.height ? viewSize.height : FLT_MAX;

return CGSizeMake(constrainedWidth, constrainedHeight);

}

- (void)rangeController:(ASRangeController *)rangeController didSizeNodesWithIndexPaths:(NSArray *)indexPaths

{

ASDisplayNodeAssertMainThread();

[UIView performWithoutAnimation:^{

[self performBatchUpdates:^{

// -insertItemsAtIndexPaths: is insufficient; UICollectionView also needs to be notified of section changes

NSInteger sectionCount = [super numberOfSections];

NSInteger newSectionCount = [_rangeController numberOfSizedSections];

if (newSectionCount > sectionCount) {

NSRange range = NSMakeRange(sectionCount, newSectionCount - sectionCount);

NSIndexSet *sections = [NSIndexSet indexSetWithIndexesInRange:range];

[super insertSections:sections];

}

[super insertItemsAtIndexPaths:indexPaths];

} completion:nil];

}];

}

@end