//  Created by P on 2024/11/18.


#import "UIView+GradientLayer.h"
#import <QuartzCore/QuartzCore.h>

@implementation UIView (GradientLayer)

static NSString * const kGradientLayerName = @"GradientLayer";
static void *kGradientObserverKey = &kGradientObserverKey;


- (void)addGradientBackgroundWithColors:(NSArray<UIColor *> *)colors
                              startPoint:(CGPoint)startPoint
                                endPoint:(CGPoint)endPoint
                             cornerRadius:(CGFloat)cornerRadius {
    
    [self removeGradientBackground];

    
    CAGradientLayer *gradientLayer = [CAGradientLayer layer];
    gradientLayer.name = kGradientLayerName;
    gradientLayer.colors = [self cgColorsFromUIColors:colors];
    gradientLayer.startPoint = startPoint;
    gradientLayer.endPoint = endPoint;
    gradientLayer.cornerRadius = cornerRadius;

    
    gradientLayer.frame = self.bounds;

    [self.layer insertSublayer:gradientLayer atIndex:0];

    
    [self setupLayoutObserverForGradientLayer:gradientLayer];
}


- (void)updateGradientBackgroundWithColors:(NSArray<UIColor *> *)colors
                                 startPoint:(CGPoint)startPoint
                                   endPoint:(CGPoint)endPoint {
    CAGradientLayer *gradientLayer = [self gradientLayer];
    if (gradientLayer) {
        gradientLayer.colors = [self cgColorsFromUIColors:colors];
        gradientLayer.startPoint = startPoint;
        gradientLayer.endPoint = endPoint;
    }
}


- (void)removeGradientBackground {
    
    CAGradientLayer *gradientLayer = [self gradientLayer];
    if (gradientLayer) {
        [gradientLayer removeFromSuperlayer];
    }

    
    if ([self hasAddedObserver]) {
        [self removeObserver:self forKeyPath:@"bounds"];
        [self setHasAddedObserver:NO];
    }
}


- (CAGradientLayer *)gradientLayer {
    for (CALayer *layer in self.layer.sublayers) {
        if ([layer.name isEqualToString:kGradientLayerName] &&
            [layer isKindOfClass:[CAGradientLayer class]]) {
            return (CAGradientLayer *)layer;
        }
    }
    return nil;
}


- (void)setupLayoutObserverForGradientLayer:(CAGradientLayer *)gradientLayer {
    if (![self hasAddedObserver]) {
        [self addObserver:self forKeyPath:@"bounds" options:NSKeyValueObservingOptionNew context:(__bridge void *)gradientLayer];
        [self setHasAddedObserver:YES];
    }
}


- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary<NSKeyValueChangeKey,id> *)change
                       context:(void *)context {
    if ([keyPath isEqualToString:@"bounds"]) {
        CAGradientLayer *gradientLayer = (__bridge CAGradientLayer *)context;
        gradientLayer.frame = self.bounds;
    } else {
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
}


- (NSArray *)cgColorsFromUIColors:(NSArray<UIColor *> *)colors {
    NSMutableArray *cgColors = [NSMutableArray array];
    for (UIColor *color in colors) {
        [cgColors addObject:(id)color.CGColor];
    }
    return [cgColors copy];
}


- (BOOL)hasAddedObserver {
    return [objc_getAssociatedObject(self, kGradientObserverKey) boolValue];
}


- (void)setHasAddedObserver:(BOOL)added {
    objc_setAssociatedObject(self, kGradientObserverKey, @(added), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}


@end