//
//  ASLayout.h
//  AsyncDisplayKit
//
//  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.
//

#pragma once

#import <UIKit/UIKit.h>
#import <AsyncDisplayKit/ASAssert.h>
#import <AsyncDisplayKit/ASLayoutable.h>
#import <AsyncDisplayKit/ASDimension.h>

NS_ASSUME_NONNULL_BEGIN

ASDISPLAYNODE_EXTERN_C_BEGIN

extern CGPoint const CGPointNull;

extern BOOL CGPointIsNull(CGPoint point);

/**
 * Safely calculates the layout of the given root layoutable by guarding against nil nodes.
 * @param rootLayoutable The root node to calculate the layout for.
 * @param sizeRange The size range to calculate the root layout within.
 */
extern ASLayout *ASCalculateRootLayout(id<ASLayoutable> rootLayoutable, const ASSizeRange sizeRange);

/**
 * Safely computes the layout of the given node by guarding against nil nodes.
 * @param component The component to calculate the layout for.
 * @param sizeRange The size range to calculate the node layout within.
 * @param parentSize The parent size of the node to calculate the layout for.
 */
extern ASLayout *ASCalculateLayout(id<ASLayoutable> layoutable, const ASSizeRange sizeRange, const CGSize parentSize);

ASDISPLAYNODE_EXTERN_C_END

/**
 * A node in the layout tree that represents the size and position of the object that created it (ASLayoutable).
 */
@interface ASLayout : NSObject

/**
 * The underlying object described by this layout
 */
@property (nonatomic, weak, readonly) id<ASLayoutable> layoutable;

/**
 * The type of ASLayoutable that created this layout
 */
@property (nonatomic, assign, readonly) ASLayoutableType type;

/**
 * Size of the current layout
 */
@property (nonatomic, assign, readonly) CGSize size;

/**
 * Position in parent. Default to CGPointNull.
 * 
 * @discussion When being used as a sublayout, this property must not equal CGPointNull.
 */
@property (nonatomic, assign, readwrite) CGPoint position;

/**
 * Array of ASLayouts. Each must have a valid non-null position.
 */
@property (nonatomic, copy, readonly) NSArray<ASLayout *> *sublayouts;

/**
 * @abstract Returns a valid frame for the current layout computed with the size and position.
 * @discussion Clamps the layout's origin or position to 0 if any of the calculated values are infinite.
 */
@property (nonatomic, assign, readonly) CGRect frame;

/**
 * Designated initializer
 */
- (instancetype)initWithLayoutable:(id<ASLayoutable>)layoutable
                              size:(CGSize)size
                          position:(CGPoint)position
                        sublayouts:(nullable NSArray<ASLayout *> *)sublayouts NS_DESIGNATED_INITIALIZER;

/**
 * Convenience class initializer for layout construction.
 *
 * @param layoutable The backing ASLayoutable object.
 * @param size             The size of this layout.
 * @param position         The position of this layout within its parent (if available).
 * @param sublayouts       Sublayouts belong to the new layout.
 */
+ (instancetype)layoutWithLayoutable:(id<ASLayoutable>)layoutable
                                size:(CGSize)size
                            position:(CGPoint)position
                          sublayouts:(nullable NSArray<ASLayout *> *)sublayouts;

/**
 * Convenience initializer that has CGPointNull position.
 * Best used by ASDisplayNode subclasses that are manually creating a layout for -calculateLayoutThatFits:,
 * or for ASLayoutSpec subclasses that are referencing the "self" level in the layout tree,
 * or for creating a sublayout of which the position is yet to be determined.
 *
 * @param layoutable  The backing ASLayoutable object.
 * @param size              The size of this layout.
 * @param sublayouts        Sublayouts belong to the new layout.
 */
+ (instancetype)layoutWithLayoutable:(id<ASLayoutable>)layoutable
                                size:(CGSize)size
                          sublayouts:(nullable NSArray<ASLayout *> *)sublayouts;

/**
 * Convenience that has CGPointNull position and no sublayouts.
 * Best used for creating a layout that has no sublayouts, and is either a root one
 * or a sublayout of which the position is yet to be determined.
 *
 * @param layoutable The backing ASLayoutable object.
 * @param size             The size of this layout.
 */
+ (instancetype)layoutWithLayoutable:(id<ASLayoutable>)layoutable
                                size:(CGSize)size;
/**
 * Convenience initializer that creates a layout based on the values of the given layout, with a new position
 *
 * @param layout           The layout to use to create the new layout
 * @param position         The position of the new layout
 */
+ (instancetype)layoutWithLayout:(ASLayout *)layout position:(CGPoint)position;

/**
 * Traverses the existing layout tree and generates a new tree that represents only ASDisplayNode layouts
 */
- (ASLayout *)filteredNodeLayoutTree;

@end

@interface ASLayout (Unavailable)

- (instancetype)init __unavailable;

@end

#pragma mark - Debugging

@interface ASLayout (Debugging)

/**
 * Recrusively output the description of the layout tree.
 */
- (NSString *)recursiveDescription;

@end

NS_ASSUME_NONNULL_END