SKShapeNode+Utility.mm

//
//  SKShapeNode+Utility.m
//  Dynamics
//
//  Created by Jonathan Wight on 6/14/13.
//  Copyright (c) 2013 toxicsoftware. All rights reserved.
//

#import "SKShapeNode+Utility.h"

@implementation SKShapeNode (Utility)

+ (instancetype)shapeNodeWithCircleOfRadius:(CGFloat)r
    {
    SKShapeNode *theShapeNode = [SKShapeNode node];
    CGPathRef thePath = CGPathCreateWithEllipseInRect((CGRect){ { -r, -r }, { r * 2, r * 2 } }, NULL);
    theShapeNode.path = thePath;
    CGPathRelease(thePath);
    return(theShapeNode);
    }

- (void)inferPhysicsBody
    {
    SKPhysicsBody *theBody = NULL;
    NSMutableArray *theArray = [NSMutableArray array];
    CGPathApply(self.path, (__bridge void *)theArray, &MyCGPathApplierFunction);

    if (theArray.count == 6)
        {
        NSString *s = [[NSString alloc] initWithData:[NSJSONSerialization dataWithJSONObject:theArray options:0 error:NULL] encoding:NSASCIIStringEncoding];
        static NSRegularExpression *regex = NULL;
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            // The un-escaped version follows:
            // \[\{"type":0,"points":\[\[(.+),0\]\]\},\{"type":3,"points":\[\[\1,(.+)\],\[\2,\1\],\[0,\1\]\]\},\{"type":3,"points":\[\[-\2,\1\],\[-\1,\2\],\[-\1,0\]\]\},\{"type":3,"points":\[\[-\1,-\2\],\[-\2,-\1\],\[0,-\1\]\]\},\{"type":3,"points":\[\[\2,-\1\],\[\1,-\2\],\[\1,0\]\]\},\{"type":4\}\]
            regex = [NSRegularExpression regularExpressionWithPattern:@"\\[\\{\"type\":0,\"points\":\\[\\[(.+),0\\]\\]\\},\\{\"type\":3,\"points\":\\[\\[\\1,(.+)\\],\\[\\2,\\1\\],\\[0,\\1\\]\\]\\},\\{\"type\":3,\"points\":\\[\\[-\\2,\\1\\],\\[-\\1,\\2\\],\\[-\\1,0\\]\\]\\},\\{\"type\":3,\"points\":\\[\\[-\\1,-\\2\\],\\[-\\2,-\\1\\],\\[0,-\\1\\]\\]\\},\\{\"type\":3,\"points\":\\[\\[\\2,-\\1\\],\\[\\1,-\\2\\],\\[\\1,0\\]\\]\\},\\{\"type\":4\\}\\]" options:NSRegularExpressionCaseInsensitive | NSRegularExpressionAnchorsMatchLines error:NULL];
        });

        NSTextCheckingResult *theMatch = [regex firstMatchInString:s options:0 range:(NSRange){ 0, s.length }];
        if (theMatch != NULL)
            {
            CGFloat theRadius = [theArray[0][@"points"][0][0] floatValue];
            theBody = [SKPhysicsBody bodyWithCircleOfRadius:theRadius];
            }
        }

    if (theBody == NULL)
        {
        NSParameterAssert(self.path != NULL);
        theBody = [SKPhysicsBody bodyWithPolygonFromPath:self.path];
        }

    self.physicsBody = theBody;
    }

#pragma mark -

static void MyCGPathApplierFunction(void *info, const CGPathElement *element)
    {
    NSMutableArray *theArray = (__bridge NSMutableArray *)info;

    NSArray *thePoints = NULL;

    switch (element->type)
        {
        case kCGPathElementMoveToPoint:
            thePoints = @[ @[ @(element->points[0].x), @(element->points[0].y) ] ];
            break;
        case kCGPathElementAddLineToPoint:
            thePoints = @[ @[ @(element->points[0].x), @(element->points[0].y) ] ];
            break;
        case kCGPathElementAddQuadCurveToPoint:
            thePoints = @[
                @[ @(element->points[0].x), @(element->points[0].y) ],
                @[ @(element->points[1].x), @(element->points[1].y) ],
                @[ @(element->points[2].x), @(element->points[2].y) ],
                @[ @(element->points[3].x), @(element->points[3].y) ],
                ];
            break;
        case kCGPathElementAddCurveToPoint:
            thePoints = @[
                @[ @(element->points[0].x), @(element->points[0].y) ],
                @[ @(element->points[1].x), @(element->points[1].y) ],
                @[ @(element->points[2].x), @(element->points[2].y) ],
                ];
            break;
        case kCGPathElementCloseSubpath:
            break;
        }

    if (thePoints)
        {
        [theArray addObject:@{ @"type": @(element->type), @"points": thePoints }];
        }
    else
        {
        [theArray addObject:@{ @"type": @(element->type) }];
        }
    }

@end