//
//  SVGRadialGradientElement.m
//  SVGKit-iOS
//
//  Created by lizhuoli on 2018/10/15.
//  Copyright © 2018年 na. All rights reserved.
//

#import "SVGRadialGradientElement.h"
#import "SVGElement_ForParser.h"
#import "SVGUtils.h"
#import "SVGGradientLayer.h"

// `kCAGradientLayerRadial` this symbol is available since iOS 3.2/tvOS 9.0/macOS 10.6, but it's not externed to public header until Xcode 10 with iOS 12 SDK, so we define it for user who still use old SDK version.
#define kCAGradientLayerRadial @"radial"

@interface SVGRadialGradientElement ()

@property (nonatomic) BOOL hasSynthesizedProperties;
@property (nonatomic) SVGLength *cx;
@property (nonatomic) SVGLength *cy;
@property (nonatomic) SVGLength *r;
@property (nonatomic) SVGLength *fx;
@property (nonatomic) SVGLength *fy;
@property (nonatomic) SVGLength *fr;

@end

@implementation SVGRadialGradientElement

- (SVGGradientLayer *)newGradientLayerForObjectRect:(CGRect)objectRect viewportRect:(SVGRect)viewportRect transform:(CGAffineTransform)absoluteTransform {
    SVGGradientLayer *gradientLayer = [[SVGGradientLayer alloc] init];
    BOOL inUserSpace = self.gradientUnits == SVG_UNIT_TYPE_USERSPACEONUSE;
    CGRect rectForRelativeUnits = inUserSpace ? CGRectFromSVGRect( viewportRect ) : objectRect;
    
    gradientLayer.frame = objectRect;
    
    NSString *cxAttr = [self getAttributeInheritedIfNil:@"cx"];
    NSString *cyAttr = [self getAttributeInheritedIfNil:@"cy"];
    NSString *rAttr = [self getAttributeInheritedIfNil:@"r"];
    NSString *fxAttr = [self getAttributeInheritedIfNil:@"fx"];
    NSString *fyAttr = [self getAttributeInheritedIfNil:@"fy"];
    NSString *frAttr = [self getAttributeInheritedIfNil:@"fr"];
    SVGLength* svgCX = [SVGLength svgLengthFromNSString:cxAttr.length > 0 ? cxAttr : @"50%"];
    SVGLength* svgCY = [SVGLength svgLengthFromNSString:cyAttr.length > 0 ? cyAttr : @"50%"];
    SVGLength* svgR = [SVGLength svgLengthFromNSString:rAttr.length > 0 ? rAttr : @"50%"];
    // focal value
    SVGLength* svgFX = fxAttr.length > 0 ? [SVGLength svgLengthFromNSString:fxAttr] : svgCX;
    SVGLength* svgFY = fyAttr.length > 0 ? [SVGLength svgLengthFromNSString:fyAttr] : svgCY;
    SVGLength* svgFR = [SVGLength svgLengthFromNSString:frAttr.length > 0 ? frAttr : @"0%"];
    // This is a tempory workaround. Apple's `CAGradientLayer` does not support focal point for radial gradient. We have to use the low-level API `CGContextDrawRadialGradient` and using custom software-render for focal point. So it does not works for `SVGLayredView` which is hardware-render by CA render server.
    if (fxAttr.length > 0 || fyAttr.length > 0 || frAttr.length > 0) {
        SVGKitLogWarn(@"The radialGradient element #%@ contains focal value: (fx:%@, fy: %@, fr:%@). The focul value is only supported on `SVGFastimageView` and it will be ignored when rendering in SVGLayredView.", [self getAttribute:@"id"], fxAttr, fyAttr, frAttr);
    }
    self.cx = svgCX;
    self.cy = svgCY;
    self.r = svgR;
    self.fx = svgFX;
    self.fy = svgFY;
    self.fr = svgFR;
    
    // these should really be two separate code paths (objectBoundingBox and userSpaceOnUse), but we simplify the logic using `rectForRelativeUnits`
    CGFloat width = CGRectGetWidth(rectForRelativeUnits);
    CGFloat height = CGRectGetHeight(rectForRelativeUnits);
    CGFloat cx = [svgCX pixelsValueWithGradientDimension:width];
    CGFloat cy = [svgCY pixelsValueWithGradientDimension:height];
    CGFloat val = MIN(width, height);
    CGFloat radius = [svgR pixelsValueWithGradientDimension:val];
    
    CGFloat fx = [svgFX pixelsValueWithGradientDimension:width];
    CGFloat fy = [svgFY pixelsValueWithGradientDimension:height];
    
    CGPoint startPoint = CGPointMake(cx, cy);
    CGPoint endPoint = CGPointMake(fx, fy);
    CGAffineTransform selfTransform = self.transform;
    
    if (inUserSpace)
    {
        // work out the new radius
        CGFloat rad = radius * 2.f;
        CGRect rect = CGRectMake(startPoint.x, startPoint.y, rad, rad);
        rect = CGRectApplyAffineTransform(rect, self.transform);
        rect = CGRectApplyAffineTransform(rect, absoluteTransform);
        radius = CGRectGetHeight(rect) / 2.f;
    }
    
    if (!inUserSpace)
    {
        // SVG spec: transform if width or height is not equal
        if(CGRectGetWidth(objectRect) != CGRectGetHeight(objectRect)) {
            CGAffineTransform tr = CGAffineTransformMakeTranslation(startPoint.x,
                                                                    startPoint.y);
            if(CGRectGetWidth(objectRect) > CGRectGetHeight(objectRect)) {
                tr = CGAffineTransformScale(tr, CGRectGetWidth(objectRect)/CGRectGetHeight(objectRect), 1);
            } else {
                tr = CGAffineTransformScale(tr, 1.f, CGRectGetHeight(objectRect)/CGRectGetWidth(objectRect));
            }
            tr = CGAffineTransformTranslate(tr, -startPoint.x, -startPoint.y);
            selfTransform = CGAffineTransformConcat(tr, selfTransform);
        }
    }
    
    CGSize size = CGSizeMake(radius, radius);
    startPoint = CGPointApplyAffineTransform(startPoint, selfTransform);
    endPoint = CGPointApplyAffineTransform(endPoint, selfTransform);
    size = CGSizeApplyAffineTransform(size, selfTransform);
    if (inUserSpace)
    {
        // apply the absolute position
        startPoint = CGPointApplyAffineTransform(startPoint, absoluteTransform);
        startPoint.x = startPoint.x - CGRectGetMinX(objectRect);
        startPoint.y = startPoint.y - CGRectGetMinY(objectRect);
        endPoint = CGPointApplyAffineTransform(endPoint, absoluteTransform);
        endPoint.x = endPoint.x - CGRectGetMaxX(objectRect) + CGRectGetWidth(objectRect);
        endPoint.y = endPoint.y - CGRectGetMaxY(objectRect) + CGRectGetHeight(objectRect);
        size = CGSizeApplyAffineTransform(size, selfTransform);
    }
    
    CGPoint gradientStartPoint = startPoint;
    CGPoint gradientEndPoint = endPoint;
    
    // convert to percent
    CGPoint centerPoint = gradientStartPoint;
    gradientStartPoint = CGPointMake((centerPoint.x) / CGRectGetWidth(objectRect), centerPoint.y / CGRectGetHeight(objectRect));
    gradientEndPoint = CGPointMake((centerPoint.x + size.width) / CGRectGetWidth(objectRect), (centerPoint.y + size.height) / CGRectGetHeight(objectRect));

    // Suck. When using `SVGLayredImageView`, the layer rendering is submitted to CA render server, and your custom `renderInContex:` code will not work. So we just set both built-in value (CAGradientLayer property) && custom value (SVGGradientLayer property)
    // FIX-ME: built-in value (not match the SVG spec, all the focal value will be ignored)
    gradientLayer.startPoint = gradientStartPoint;
    gradientLayer.endPoint = gradientEndPoint;
    gradientLayer.type = kCAGradientLayerRadial;
    // custom value (match the SVG spec)
    gradientLayer.gradientElement = self;
    gradientLayer.objectRect = objectRect;
    gradientLayer.viewportRect = viewportRect;
    gradientLayer.absoluteTransform = absoluteTransform;
    
    if (svgR.value <= 0 || self.colors.count == 1) {
        //  SVG spec: <r> A value of lower or equal to zero will cause the area to be painted as a single color using the color and opacity of the last gradient <stop>.
        SVGGradientStop *lastStop = self.stops.lastObject;
        gradientLayer.backgroundColor = CGColorWithSVGColor(lastStop.stopColor);
        gradientLayer.opacity = lastStop.stopOpacity;
    } else {
        [gradientLayer setColors:self.colors];
        [gradientLayer setLocations:self.locations];
    }
    
    SVGKitLogVerbose(@"[%@] set gradient layer start = %@", [self class], NSStringFromCGPoint(gradientLayer.startPoint));
    SVGKitLogVerbose(@"[%@] set gradient layer end = %@", [self class], NSStringFromCGPoint(gradientLayer.endPoint));
    SVGKitLogVerbose(@"[%@] set gradient layer colors = %@", [self class], self.colors);
    SVGKitLogVerbose(@"[%@] set gradient layer locations = %@", [self class], self.locations);
    
    return gradientLayer;
}

- (void)synthesizeProperties {
    if (self.hasSynthesizedProperties)
        return;
    self.hasSynthesizedProperties = YES;
    
    NSString* gradientID = [self getAttributeNS:@"http://www.w3.org/1999/xlink" localName:@"href"];
    
    if ([gradientID length])
    {
        if ([gradientID hasPrefix:@"#"])
            gradientID = [gradientID substringFromIndex:1];
        
        SVGRadialGradientElement* baseGradient = (SVGRadialGradientElement*) [self.rootOfCurrentDocumentFragment getElementById:gradientID];
        NSString* svgNamespace = @"http://www.w3.org/2000/svg";
        
        if (baseGradient)
        {
            [baseGradient synthesizeProperties];
            
            if (!self.stops && baseGradient.stops)
            {
                for (SVGGradientStop* stop in baseGradient.stops)
                    [self addStop:stop];
            }
            NSArray *keys = [NSArray arrayWithObjects:@"cx", @"cy", @"r", @"fx", @"fy", @"fr", @"gradientUnits", @"gradientTransform", @"spreadMethod", nil];
            
            for (NSString* key in keys)
            {
                if (![self hasAttribute:key] && [baseGradient hasAttribute:key])
                    [self setAttributeNS:svgNamespace qualifiedName:key value:[baseGradient getAttribute:key]];
            }
            
        }
    }
}

@end