//

// PSTCollectionViewLayout.h

// PSPDFKit

//

// Copyright (c) 2012 Peter Steinberger. All rights reserved.

//

#import "PSTCollectionViewCommon.h"

#import <CoreGraphics/CoreGraphics.h>

#import <QuartzCore/QuartzCore.h>

typedef NS_ENUM(NSUInteger, PSTCollectionViewItemType) {

PSTCollectionViewItemTypeCell,

PSTCollectionViewItemTypeSupplementaryView,

PSTCollectionViewItemTypeDecorationView

};

// The PSTCollectionViewLayout class is provided as an abstract class for subclassing to define custom collection layouts.

// Defining a custom layout is an advanced operation intended for applications with complex needs.

@class PSTCollectionViewLayoutAttributes, PSTCollectionView;

@interface PSTCollectionViewLayoutAttributes : NSObject <NSCopying>

@property (nonatomic) CGRect frame;

@property (nonatomic) CGPoint center;

@property (nonatomic) CGSize size;

@property (nonatomic) CATransform3D transform3D;

@property (nonatomic) CGFloat alpha;

@property (nonatomic) NSInteger zIndex; // default is 0

@property (nonatomic, getter=isHidden) BOOL hidden; // As an optimization, PSTCollectionView might not create a view for items whose hidden attribute is YES

@property (nonatomic, strong) NSIndexPath *indexPath;

+ (instancetype)layoutAttributesForCellWithIndexPath:(NSIndexPath *)indexPath;

+ (instancetype)layoutAttributesForSupplementaryViewOfKind:(NSString *)elementKind withIndexPath:(NSIndexPath *)indexPath;

+ (instancetype)layoutAttributesForDecorationViewWithReuseIdentifier:(NSString *)reuseIdentifier withIndexPath:(NSIndexPath*)indexPath;

/*

+ (id)layoutAttributesForDecorationViewOfKind:(id)arg1 withIndexPath:(id)arg2;

- (id)initialLayoutAttributesForInsertedDecorationElementOfKind:(id)arg1 atIndexPath:(id)arg2;

- (BOOL)_isEquivalentTo:(id)arg1;

*/

@end

@interface PSTCollectionViewLayoutAttributes(Private)

@property (nonatomic, readonly) NSString *representedElementKind;

@property (nonatomic, readonly) PSTCollectionViewItemType representedElementCategory;

- (BOOL)isDecorationView;

- (BOOL)isSupplementaryView;

- (BOOL)isCell;

@end

typedef NS_ENUM(NSInteger, PSTCollectionUpdateAction) {

PSTCollectionUpdateActionInsert,

PSTCollectionUpdateActionDelete,

PSTCollectionUpdateActionReload,

PSTCollectionUpdateActionMove,

PSTCollectionUpdateActionNone

};

/*

@interface PSTCollectionViewUpdateItem : NSObject {

@private

NSIndexPath* _initialIndexPath;

NSIndexPath* _finalIndexPath;

PSTCollectionUpdateAction _updateAction;

id _gap;

}

@property (nonatomic, readonly) NSIndexPath *indexPathBeforeUpdate; // nil for PSTCollectionUpdateActionInsert

@property (nonatomic, readonly) NSIndexPath *indexPathAfterUpdate; // nil for PSTCollectionUpdateActionDelete

@property (nonatomic, readonly) PSTCollectionUpdateAction updateAction;

@end

*/

// used internally for deserialization until I figure out the proper way.

extern NSString *const PSTCollectionViewLayoutAwokeFromNib;

@interface PSTCollectionViewLayout : NSObject <NSCoding>

// Methods in this class are meant to be overridden and will be called by its collection view to gather layout information.

// To get the truth on the current state of the collection view, call methods on PSTCollectionView rather than these.

@property (nonatomic, unsafe_unretained, readonly) PSTCollectionView *collectionView;

// Call -invalidateLayout to indicate that the collection view needs to requery the layout information.

// Subclasses must always call super if they override.

- (void)invalidateLayout;

/// @name Registering Decoration Views

- (void)registerClass:(Class)viewClass forDecorationViewWithReuseIdentifier:(NSString *)identifier;

- (void)registerNib:(UINib *)nib forDecorationViewWithReuseIdentifier:(NSString *)identifier;

@end

@interface PSTCollectionViewLayout (SubclassingHooks)

// The collection view calls -prepareLayout once at its first layout as the first message to the layout instance.

// The collection view calls -prepareLayout again after layout is invalidated and before requerying the layout information.

// Subclasses should always call super if they override.

- (void)prepareLayout;

// PSTCollectionView calls these four methods to determine the layout information.

// Implement -layoutAttributesForElementsInRect: to return layout attributes for for supplementary or decoration views, or to perform layout in an as-needed-on-screen fashion.

// Additionally, all layout subclasses should implement -layoutAttributesForItemAtIndexPath: to return layout attributes instances on demand for specific index paths.

// If the layout supports any supplementary or decoration view types, it should also implement the respective atIndexPath: methods for those types.

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect; // return an array layout attributes instances for all the views in the given rect

- (PSTCollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath;

- (PSTCollectionViewLayoutAttributes *)layoutAttributesForSupplementaryViewOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath;

- (PSTCollectionViewLayoutAttributes *)layoutAttributesForDecorationViewWithReuseIdentifier:(NSString*)identifier atIndexPath:(NSIndexPath *)indexPath;

- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds; // return YES to cause the collection view to requery the layout for geometry information

- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset withScrollingVelocity:(CGPoint)velocity; // return a point at which to rest after scrolling - for layouts that want snap-to-point scrolling behavior

- (CGSize)collectionViewContentSize; // the collection view calls this to update its content size any time it queries new layout information - at least one of the width and height fields must match the respective field of the collection view's bounds

@end

@interface PSTCollectionViewLayout (UpdateSupportHooks)

// This method is called when there is an update with deletes/inserts to the collection view.

// It will be called prior to calling the initial/final layout attribute methods below to give the layout an opportunity to do batch computations for the insertion and deletion layout attributes.

// The updateItems parameter is an array of PSTCollectionViewUpdateItem instances for each element that is moving to a new index path.

- (void)prepareForCollectionViewUpdates:(NSArray *)updateItems;

// This method is called inside an animation block after all items have been laid out for a collection view update.

// Subclasses can use this opportunity to layout their 'layout-owned' decoration views in response to the update.

- (void)finalizeCollectionViewUpdates;

// Collection view calls these methods to determine the starting layout for animating in newly inserted views, or the ending layout for animating out deleted views

- (PSTCollectionViewLayoutAttributes *)initialLayoutAttributesForInsertedItemAtIndexPath:(NSIndexPath *)itemIndexPath;

- (PSTCollectionViewLayoutAttributes *)finalLayoutAttributesForDeletedItemAtIndexPath:(NSIndexPath *)itemIndexPath;

- (PSTCollectionViewLayoutAttributes *)initialLayoutAttributesForInsertedSupplementaryElementOfKind:(NSString *)elementKind atIndexPath:(NSIndexPath *)elementIndexPath;

- (PSTCollectionViewLayoutAttributes *)finalLayoutAttributesForDeletedSupplementaryElementOfKind:(NSString *)elementKind atIndexPath:(NSIndexPath *)elementIndexPath;

@end

@interface PSTCollectionViewLayout (Private)

- (void)setCollectionViewBoundsSize:(CGSize)size;

@end