text: /**
   * Copyright (c) 2015-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 <UIKit/UIKit.h>
  
  #import <CSSLayout/CSSLayout.h>
  #import "RCTComponent.h"
  #import "RCTRootView.h"
  
  @class RCTSparseArray;
  
  typedef NS_ENUM(NSUInteger, RCTUpdateLifecycle) {
    RCTUpdateLifecycleUninitialized = 0,
    RCTUpdateLifecycleComputed,
    RCTUpdateLifecycleDirtied,
  };
  
  typedef void (^RCTApplierBlock)(NSDictionary<NSNumber *, UIView *> *viewRegistry);
  
  /**
   * ShadowView tree mirrors RCT view tree. Every node is highly stateful.
   * 1. A node is in one of three lifecycles: uninitialized, computed, dirtied.
   * 1. RCTBridge may call any of the padding/margin/width/height/top/left setters. A setter would dirty
   *    the node and all of its ancestors.
   * 2. At the end of each Bridge transaction, we call collectUpdatedFrames:widthConstraint:heightConstraint
   *    at the root node to recursively lay out the entire hierarchy.
   * 3. If a node is "computed" and the constraint passed from above is identical to the constraint used to
   *    perform the last computation, we skip laying out the subtree entirely.
   */
  @interface RCTShadowView : NSObject <RCTComponent>
  
  /**
   * RCTComponent interface.
   */
  - (NSArray<RCTShadowView *> *)reactSubviews NS_REQUIRES_SUPER;
  - (RCTShadowView *)reactSuperview NS_REQUIRES_SUPER;
  - (void)insertReactSubview:(RCTShadowView *)subview atIndex:(NSInteger)atIndex NS_REQUIRES_SUPER;
  - (void)removeReactSubview:(RCTShadowView *)subview NS_REQUIRES_SUPER;
  
  @property (nonatomic, weak, readonly) RCTShadowView *superview;
  @property (nonatomic, assign, readonly) css_node_t *cssNode;
  @property (nonatomic, copy) NSString *viewName;
  @property (nonatomic, strong) UIColor *backgroundColor; // Used to propagate to children
  @property (nonatomic, assign) RCTUpdateLifecycle layoutLifecycle;
  @property (nonatomic, copy) RCTDirectEventBlock onLayout;
  
  /**
   * isNewView - Used to track the first time the view is introduced into the hierarchy.  It is initialized YES, then is
   * set to NO in RCTUIManager after the layout pass is done and all frames have been extracted to be applied to the
   * corresponding UIViews.
   */
  @property (nonatomic, assign, getter=isNewView) BOOL newView;
  
  /**
   * isHidden - RCTUIManager uses this to determine whether or not the UIView should be hidden. Useful if the
   * ShadowView determines that its UIView will be clipped and wants to hide it.
   */
  @property (nonatomic, assign, getter=isHidden) BOOL hidden;
  
  /**
   * Position and dimensions.
   * Defaults to { 0, 0, NAN, NAN }.
   */
  @property (nonatomic, assign) CGFloat top;
  @property (nonatomic, assign) CGFloat left;
  @property (nonatomic, assign) CGFloat bottom;
  @property (nonatomic, assign) CGFloat right;
  
  @property (nonatomic, assign) CGFloat width;
  @property (nonatomic, assign) CGFloat height;
  
  @property (nonatomic, assign) CGFloat minWidth;
  @property (nonatomic, assign) CGFloat maxWidth;
  @property (nonatomic, assign) CGFloat minHeight;
  @property (nonatomic, assign) CGFloat maxHeight;
  
  @property (nonatomic, assign) CGRect frame;
  
  - (void)setTopLeft:(CGPoint)topLeft;
  - (void)setSize:(CGSize)size;
  
  /**
   * Set the natural size of the view, which is used when no explicit size is set.
   * Use UIViewNoIntrinsicMetric to ignore a dimension.
   */
  - (void)setIntrinsicContentSize:(CGSize)size;
  
  /**
   * Border. Defaults to { 0, 0, 0, 0 }.
   */
  @property (nonatomic, assign) CGFloat borderWidth;
  @property (nonatomic, assign) CGFloat borderTopWidth;
  @property (nonatomic, assign) CGFloat borderLeftWidth;
  @property (nonatomic, assign) CGFloat borderBottomWidth;
  @property (nonatomic, assign) CGFloat borderRightWidth;
  
  /**
   * Margin. Defaults to { 0, 0, 0, 0 }.
   */
  @property (nonatomic, assign) CGFloat margin;
  @property (nonatomic, assign) CGFloat marginVertical;
  @property (nonatomic, assign) CGFloat marginHorizontal;
  @property (nonatomic, assign) CGFloat marginTop;
  @property (nonatomic, assign) CGFloat marginLeft;
  @property (nonatomic, assign) CGFloat marginBottom;
  @property (nonatomic, assign) CGFloat marginRight;
  
  /**
   * Padding. Defaults to { 0, 0, 0, 0 }.
   */
  @property (nonatomic, assign) CGFloat padding;
  @property (nonatomic, assign) CGFloat paddingVertical;
  @property (nonatomic, assign) CGFloat paddingHorizontal;
  @property (nonatomic, assign) CGFloat paddingTop;
  @property (nonatomic, assign) CGFloat paddingLeft;
  @property (nonatomic, assign) CGFloat paddingBottom;
  @property (nonatomic, assign) CGFloat paddingRight;
  
  - (UIEdgeInsets)paddingAsInsets;
  
  /**
   * Flexbox properties. All zero/disabled by default
   */
  @property (nonatomic, assign) css_flex_direction_t flexDirection;
  @property (nonatomic, assign) css_justify_t justifyContent;
  @property (nonatomic, assign) css_align_t alignSelf;
  @property (nonatomic, assign) css_align_t alignItems;
  @property (nonatomic, assign) css_position_type_t position;
  @property (nonatomic, assign) css_wrap_type_t flexWrap;
  @property (nonatomic, assign) CGFloat flex;
  
  /**
   * z-index, used to override sibling order in the view
   */
  @property (nonatomic, assign) NSInteger zIndex;
  
  /**
   * Calculate property changes that need to be propagated to the view.
   * The applierBlocks set contains RCTApplierBlock functions that must be applied
   * on the main thread in order to update the view.
   */
  - (void)collectUpdatedProperties:(NSMutableSet<RCTApplierBlock> *)applierBlocks
                  parentProperties:(NSDictionary<NSString *, id> *)parentProperties;
  
  /**
   * Process the updated properties and apply them to view. Shadow view classes
   * that add additional propagating properties should override this method.
   */
  - (NSDictionary<NSString *, id> *)processUpdatedProperties:(NSMutableSet<RCTApplierBlock> *)applierBlocks
                                            parentProperties:(NSDictionary<NSString *, id> *)parentProperties NS_REQUIRES_SUPER;
  
  /**
   * Can be called by a parent on a child in order to calculate all views whose frame needs
   * updating in that branch. Adds these frames to `viewsWithNewFrame`. Useful if layout
   * enters a view where flex doesn't apply (e.g. Text) and then you want to resume flex
   * layout on a subview.
   */
  - (void)collectUpdatedFrames:(NSMutableSet<RCTShadowView *> *)viewsWithNewFrame
                     withFrame:(CGRect)frame
                        hidden:(BOOL)hidden
              absolutePosition:(CGPoint)absolutePosition;
  
  /**
   * Apply the CSS layout.
   * This method also calls `applyLayoutToChildren:` internally. The functionality
   * is split into two methods so subclasses can override `applyLayoutToChildren:`
   * while using default implementation of `applyLayoutNode:`.
   */
  - (void)applyLayoutNode:(css_node_t *)node
        viewsWithNewFrame:(NSMutableSet<RCTShadowView *> *)viewsWithNewFrame
         absolutePosition:(CGPoint)absolutePosition NS_REQUIRES_SUPER;
  
  /**
   * Enumerate the child nodes and tell them to apply layout.
   */
  - (void)applyLayoutToChildren:(css_node_t *)node
              viewsWithNewFrame:(NSMutableSet<RCTShadowView *> *)viewsWithNewFrame
               absolutePosition:(CGPoint)absolutePosition;
  
  /**
   * The following are implementation details exposed to subclasses. Do not call them directly
   */
  - (void)fillCSSNode:(css_node_t *)node NS_REQUIRES_SUPER;
  - (void)dirtyLayout NS_REQUIRES_SUPER;
  - (BOOL)isLayoutDirty;
  
  - (void)dirtyPropagation NS_REQUIRES_SUPER;
  - (BOOL)isPropagationDirty;
  
  - (void)dirtyText NS_REQUIRES_SUPER;
  - (void)setTextComputed NS_REQUIRES_SUPER;
  - (BOOL)isTextDirty;
  
  /**
   * As described in RCTComponent protocol.
   */
  - (void)didUpdateReactSubviews NS_REQUIRES_SUPER;
  - (void)didSetProps:(NSArray<NSString *> *)changedProps NS_REQUIRES_SUPER;
  
  /**
   * Computes the recursive offset, meaning the sum of all descendant offsets -
   * this is the sum of all positions inset from parents. This is not merely the
   * sum of `top`/`left`s, as this function uses the *actual* positions of
   * children, not the style specified positions - it computes this based on the
   * resulting layout. It does not yet compensate for native scroll view insets or
   * transforms or anchor points.
   */
  - (CGRect)measureLayoutRelativeToAncestor:(RCTShadowView *)ancestor;
  
  @end
  