//
//  IJSVGExporter.m
//  IJSVGExample
//
//  Created by Curtis Hard on 06/01/2017.
//  Copyright © 2017 Curtis Hard. All rights reserved.
//

#import "IJSVGExporter.h"
#import "IJSVG.h"
#import "IJSVGGradientLayer.h"
#import "IJSVGRadialGradient.h"
#import "IJSVGLinearGradient.h"
#import "IJSVGPatternLayer.h"
#import "IJSVGImageLayer.h"
#import "IJSVGShapeLayer.h"
#import "IJSVGGroupLayer.h"
#import "IJSVGStrokeLayer.h"
#import "IJSVGMath.h"
#import "IJSVGExporterPathInstruction.h"

@implementation IJSVGExporter

#define XML_DOC_VERSION 1.1f
#define XML_DOC_NS @"http://www.w3.org/2000/svg"
#define XML_DOC_NSXLINK @"http://www.w3.org/1999/xlink"
#define XML_DOCTYPE_VERSION @"1.0"
#define XML_DOC_CHARSET @"UTF-8"
#define XML_DOC_GENERATOR @"Generated by IJSVG (https://github.com/iconjar/IJSVG)"

@synthesize title;
@synthesize description;

BOOL IJSVGExporterHasOption(IJSVGExporterOptions options, NSInteger option)
{
    return (options & option) != 0;
};

const NSArray * IJSVGShortCharacterArray()
{
    static NSArray * _array;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _array = [@[@"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",@"i",@"j",@"k",@"l",
                    @"m",@"n",@"o",@"p",@"q",@"r",@"s",@"t",@"u",@"v",@"w",@"x",@"y",@"z",
                    @"A",@"B",@"C",@"D",@"E",@"F",@"G",@"H",@"I",@"J",@"K",@"L",
                    @"M",@"N",@"O",@"P",@"Q",@"R",@"S",@"T",@"U",@"V",@"W",@"X",@"Y",@"Z"] retain];
    });
    return _array;
}

const NSArray * IJSVGInheritableAttributes()
{
    static NSArray * _attributes;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _attributes = [@[
                         @"clip-rule",
                         @"color",
                         @"color-interpolation",
                         @"color-interpolation-filters",
                         @"color-profile",
                         @"color-rendering",
                         @"cursor",
                         @"direction",
                         @"fill",
                         @"fill-opacity",
                         @"fill-rule",
                         @"font",
                         @"font-family",
                         @"font-size",
                         @"font-size-adjust",
                         @"font-stretch",
                         @"font-style",
                         @"font-variant",
                         @"font-weight",
                         @"glyph-orientation-horizontal",
                         @"glyph-orientation-vertical",
                         @"image-rendering",
                         @"kerning",
                         @"letter-spacing",
                         @"marker",
                         @"marker-end",
                         @"marker-mid",
                         @"marker-start",
                         @"pointer-events",
                         @"shape-rendering",
                         @"stroke",
                         @"stroke-dasharray",
                         @"stroke-dashoffset",
                         @"stroke-linecap",
                         @"stroke-linejoin",
                         @"stroke-miterlimit",
                         @"stroke-opacity",
                         @"stroke-width",
                         @"text-anchor",
                         @"text-rendering",
                         @"visibility",
                         @"white-space",
                         @"word-spacing",
                         @"writing-mode"] retain];
    });
    return _attributes;
}

void IJSVGApplyAttributesToElement(NSDictionary *attributes, NSXMLElement *element) {
    [element setAttributesAsDictionary:attributes];
};

NSDictionary * IJSVGElementAttributeDictionary(NSXMLElement * element) {
    NSMutableDictionary * dict = [[[NSMutableDictionary alloc] init] autorelease];
    for(NSXMLNode * attribute in element.attributes) {
        dict[attribute.name] = attribute.stringValue;
    }
    return dict;
};

NSString * IJSVGHashURL(NSString * key) {
    return [NSString stringWithFormat:@"url(#%@)",key];
};

NSString * IJSVGHash(NSString * key) {
    return [@"#" stringByAppendingString:key];
}

- (void)dealloc
{
    [_scaledRootNode release], _scaledRootNode = nil;
    [_svg release], _svg = nil;
    [_dom release], _dom = nil;
    [_defElement release], _defElement = nil;
    [title release], title = nil;
    [description release], description = nil;
    [super dealloc];
}

- (id)initWithSVG:(IJSVG *)svg
             size:(CGSize)size
          options:(IJSVGExporterOptions)options
{
    if((self = [super init]) != nil) {
        _options = options;
        _size = size;
        _svg = [svg retain];
        
        // clear memory as soon as possible
        @autoreleasepool {
            [self _prepare];
        }
    }
    return self;
}

- (NSXMLElement *)defElement
{
    if(_defElement != nil) {
        return _defElement;
    }
    return _defElement = [[NSXMLElement alloc] initWithName:@"defs"];
}

- (NSString *)viewBoxWithRect:(NSRect)rect
{
    char * buffer;
    asprintf(&buffer, "%g %g %g %g", rect.origin.x, rect.origin.y,
             rect.size.width, rect.size.height);
    NSString * viewBox = [NSString stringWithCString:buffer
                                            encoding:NSUTF8StringEncoding];
    free(buffer);
    return viewBox;
}

- (NSXMLElement *)rootNode
{
    // generates the root document
    NSXMLElement * root = [[[NSXMLElement alloc] initWithName:@"svg"] autorelease];
    
    // sort out viewbox
    NSRect viewBox = _svg.viewBox;
    NSDictionary * attributes = @{
                                  @"viewBox":[self viewBoxWithRect:viewBox],
                                  @"version": [NSString stringWithFormat:@"%g",XML_DOC_VERSION],
                                  @"xmlns": XML_DOC_NS,
                                  @"xmlns:xlink": XML_DOC_NSXLINK
                                  };
    
    // add on width and height unless specified otherwise
    if((_options & IJSVGExporterOptionRemoveWidthHeightAttributes) == 0) {
        NSMutableDictionary * attDict = [[attributes mutableCopy] autorelease];
        attDict[@"width"] = IJSVGShortFloatString(_size.width);
        attDict[@"height"] = IJSVGShortFloatString(_size.height);
        attributes = [[attDict copy] autorelease];
    }
    
    // was there a size set?
    if(CGSizeEqualToSize(CGSizeZero, _size) == NO &&
       (_size.width != viewBox.size.width && _size.height != viewBox.size.height)) {
        
        // copy the attributes
        NSMutableDictionary * att = [[attributes mutableCopy] autorelease];
        att[@"width"] = IJSVGShortFloatString(_size.width);
        att[@"height"] = IJSVGShortFloatString(_size.height);
        
        // scale the whole SVG to fit the specified size
        if((_options & IJSVGExporterOptionScaleToSizeIfNecessary) != 0) {
            // work out the scale
            CGFloat scale = MIN(_size.width/viewBox.size.width,
                                _size.height/viewBox.size.height);
            
            // actually do the scale
            if(scale != 1.f) {
                NSString * scaleString = [NSString stringWithFormat:@"scale(%g)",scale];
                NSDictionary * transform = @{@"transform":scaleString};
                
                // create the main group and apply transform
                _scaledRootNode = [[NSXMLElement alloc] initWithName:@"g"];
                IJSVGApplyAttributesToElement(transform, _scaledRootNode);
                
                // add it back onto root
                [root addChild:_scaledRootNode];
                
                // compute x and y, dont multiply 0
                const CGFloat x = viewBox.origin.x == 0.f ? 0.f : (viewBox.origin.x * scale);
                const CGFloat y = viewBox.origin.y == 0.f ? 0.f : (viewBox.origin.y * scale);
                
                // reset the viewbox for the exported SVG
                att[@"viewBox"] = [self viewBoxWithRect:(NSRect){
                    .origin = NSMakePoint(x, y),
                    .size = NSMakeSize(_size.width, _size.height)
                }];
            }
        }
        
        // reset attributes
        attributes = [[att copy] autorelease];
    }
    
    // apply the attributes
    IJSVGApplyAttributesToElement(attributes, root);
    return root;
}

- (NSString *)generateID
{
    const NSArray * chars = IJSVGShortCharacterArray();
    if(_idCount < chars.count) {
        return chars[_idCount++];
    }
    
    if((_idCount % chars.count) == 0) {
        _shortIdCount++;
    }
    return [NSString stringWithFormat:@"%@%ld",chars[(_idCount++ % chars.count)],_shortIdCount];
}

- (void)_prepare
{
    // create the stand alone DOM
    _dom = [[NSXMLDocument alloc] initWithRootElement:[self rootNode]];
    _dom.version = XML_DOCTYPE_VERSION;
    _dom.characterEncoding = XML_DOC_CHARSET;
    
    // sort out header
    
    // sort out stuff, so here we go...
    [self _recursiveParseFromLayer:_svg.layer
                       intoElement:(_scaledRootNode?:_dom.rootElement)];
    
    // this needs to be added incase it needs to be cleaned
    NSXMLElement * defNode = [self defElement];
    if(defNode.childCount != 0) {
        [_dom.rootElement insertChild:[self defElement]
                              atIndex:0];
    }
    
    // cleanup
    [self _cleanup];
    
    // could had been removed during cleaning process needs to be added back in!
    if(defNode.childCount != 0 && defNode.parent == nil) {
        [_dom.rootElement insertChild:[self defElement]
                              atIndex:0];
    }
    
    // add generator
    NSXMLNode * generatorNode = [[[NSXMLNode alloc] initWithKind:NSXMLCommentKind] autorelease];
    generatorNode.stringValue = XML_DOC_GENERATOR;
    [_dom.rootElement insertChild:generatorNode
                          atIndex:0];
}

- (void)_cleanup
{
    // remove hidden elements
    if((_options & IJSVGExporterOptionRemoveHiddenElements) != 0) {
        [self _removeHiddenElements];
    }
    
    // convert any duplicate paths into use
    if((_options & IJSVGExporterOptionCreateUseForPaths) != 0) {
        [self _convertUseElements];
    }
    
    // cleanup def
    if((_options & IJSVGExporterOptionRemoveUselessDef) != 0) {
        [self _cleanDef];
    }
    
    // collapse groups
    if((_options & IJSVGExporterOptionCollapseGroups) != 0) {
        [self _collapseGroups];
    }
    
    // clean any blank groups
    if((_options & IJSVGExporterOptionRemoveUselessGroups) != 0) {
        [self _cleanEmptyGroups];
    }
    
    // sort attributes
    if((_options & IJSVGExporterOptionSortAttributes) != 0) {
        [self _sortAttributesOnElement:_dom.rootElement];
    }
    
    // compress groups together
    if((_options & IJSVGExporterOptionCollapseGroups) != 0) {
        [self _compressGroups];
    }
    
    // collapse gradients?
    if((_options & IJSVGExporterOptionCollapseGradients) != 0) {
        [self _collapseGradients];
    }
    
    // create classes?
    if((_options & IJSVGExporterOptionCreateClasses) != 0) {
        [self _createClasses];
    }
    
    // move attributes to group
    if((_options & IJSVGExporterOptionMoveAttributesToGroup) != 0) {
        [self _moveAttributesToGroupWithElement:_dom.rootElement];
    }
}

- (void)_createClasses
{
    const NSArray * inhert = IJSVGInheritableAttributes();
    NSArray<NSXMLElement *> * elements = [_dom nodesForXPath:@"//*"
                                                       error:nil];
    NSMutableDictionary * rules = [[[NSMutableDictionary alloc] init] autorelease];
    for(NSXMLElement * element in elements) {
        NSDictionary * inhertEl = [self intersectableAttributes:IJSVGElementAttributeDictionary(element)
                                          inheritableAttributes:inhert];
        NSString * styles = [self styleSheetRulesFromDictionary:inhertEl];
        NSString * className = nil;
        if((className = [rules objectForKey:styles]) == nil) {
            className = [NSString stringWithFormat:@"%@",[self generateID]];
            rules[styles] = className;
        }
        
        for(NSString * attributeName in inhertEl) {
            [element removeAttributeForName:attributeName];
        }
        IJSVGApplyAttributesToElement(@{@"class":className},element);
    }
    
    // add styles to dom
    NSXMLElement * styles = [[[NSXMLElement alloc] initWithName:@"style"] autorelease];
    NSXMLNode * node = [[[NSXMLNode alloc] initWithKind:NSXMLTextKind] autorelease];
    
    NSMutableArray * classes = [[[NSMutableArray alloc] initWithCapacity:rules.count] autorelease];
    for(NSString * r in rules) {
        [classes addObject:[NSString stringWithFormat:@".%@%@",rules[r],r]];
    }
    node.stringValue = [classes componentsJoinedByString:@""];
    [styles addChild:node];
    [_dom.rootElement insertChild:styles atIndex:0];
}

- (NSString *)styleSheetRulesFromDictionary:(NSDictionary *)dict
{
    NSMutableArray * array = [[[NSMutableArray alloc] initWithCapacity:dict.count] autorelease];
    for(NSString * key in dict.allKeys) {
        [array addObject:[NSString stringWithFormat:@"%@: %@;",key,dict[key]]];
    }
    return [NSString stringWithFormat:@"{%@}",[array componentsJoinedByString:@" "]];
}

- (void)_sortAttributesOnElement:(NSXMLElement *)element
{
    // only apply to XML elements, not XMLNodes
    if([element isKindOfClass:[NSXMLElement class]] == NO) {
        return;
    }
    [self sortAttributesOnElement:element];
    for(NSXMLElement * child in element.children) {
        [self _sortAttributesOnElement:child];
    }
}

- (void)_removeHiddenElements
{
    // find any elements where they have a style, but the element itself
    // must not be in the defs
    NSArray<NSXMLElement *> * elements = [_dom nodesForXPath:@"//*[@display='none']"
                                                       error:nil];
    
    for(NSXMLElement * element in elements) {
        NSXMLElement * parent = (NSXMLElement *)element.parent;
        [parent removeChildAtIndex:element.index];
    }
}

- (void)_collapseGradients
{
    NSString * xPath = @"//defs/*[self::linearGradient or self::radialGradient]";
    NSArray<NSXMLElement *> * gradients = [_dom nodesForXPath:xPath error:nil];
    for(NSInteger i = 0; i < gradients.count; i++) {
        if(i != 0) {
            NSXMLElement * gradientA = gradients[i];
            NSXMLElement * gradientB = nil;
            for(NSInteger s = (i - 1); s >= 0; s--) {
                gradientB = gradients[s];
                if([self compareElementChildren:gradientA toElement:gradientB] == YES) {
                    NSString * idString = [gradientB attributeForName:@"id"].stringValue;
                    if(idString == nil || idString.length == 0) {
                        idString = [self generateID];
                        IJSVGApplyAttributesToElement(@{@"id":idString}, gradientB);
                    }
                    NSDictionary * atts = @{@"xlink:href":IJSVGHash(idString)};
                    IJSVGApplyAttributesToElement(atts, gradientA);
                    [gradientA setChildren:nil];
                    break;
                }
            }
        }
    }
}

- (BOOL)compareElementChildren:(NSXMLElement *)element
                     toElement:(NSXMLElement *)toElement
{
    NSArray * childrenA = element.children;
    NSArray * childrenB = toElement.children;
    if(childrenA.count != childrenB.count) {
        return NO;
    }
    for(NSInteger i = 0; i < childrenA.count; i++) {
        NSXMLElement * childA = childrenA[i];
        NSXMLElement * childB = childrenB[i];
        if([self compareElement:childA withElement:childB] == NO) {
            return NO;
        }
    }
    return YES;
}

- (void)_moveAttributesToGroupWithElement:(NSXMLElement *)parentElement
{
    
    const NSArray * excludedNodes = @[@"script",@"style",@"defs"];
    if([excludedNodes containsObject:parentElement.name] == YES) {
        return;
    }
    
    const NSArray * inheritableAttributes = IJSVGInheritableAttributes();
    
    NSDictionary * intersection = @{};
    NSMutableArray * grouped = [[[NSMutableArray alloc] init] autorelease];
    
    NSInteger counter = 0;
    NSInteger size = parentElement.childCount - 1;
    for(NSXMLElement * element in parentElement.children) {
        
        NSDictionary * attributes = [self intersectableAttributes:IJSVGElementAttributeDictionary(element)
                                            inheritableAttributes:inheritableAttributes];
        
        if(intersection.count == 0) {
            intersection = attributes;
        }
        
        NSDictionary * dict = [self intersectionInheritableAttributes:intersection
                                                    currentAttributes:attributes
                                                inheritableAttributes:inheritableAttributes];
        
        for(NSString * attributeToRemove in dict.allKeys) {
            [element removeAttributeForName:attributeToRemove];
        }
        if(dict != nil) {
            [grouped addObject:element];
        }
        
        if(dict == nil || counter == size) {
            if(grouped.count > 1) {
                NSXMLElement * groupElement = [[[NSXMLElement alloc] initWithName:@"g"] autorelease];
                NSXMLElement * lastElement = (NSXMLElement *)grouped.lastObject;
                NSInteger index = lastElement.index;
                [parentElement replaceChildAtIndex:index withNode:groupElement];
                for(NSXMLElement * elementToGroup in grouped) {
                    [elementToGroup detach];
                    [groupElement addChild:elementToGroup];
                }
                IJSVGApplyAttributesToElement(intersection, groupElement);
            } else {
                if(grouped.count == 1) {
                    NSXMLElement * onlyElement = (NSXMLElement *)grouped.lastObject;
                    IJSVGApplyAttributesToElement(intersection, onlyElement);
                }
            }
            intersection = @{};
            [grouped removeAllObjects];
        }
        
        counter++;
    }
}

- (NSDictionary *)intersectableAttributes:(NSDictionary *)atts
                    inheritableAttributes:(const NSArray *)inheritable
{
    NSMutableDictionary * dict = [[[NSMutableDictionary alloc] init] autorelease];
    for(NSString * key in atts.allKeys) {
        if([inheritable containsObject:key]) {
            dict[key] = atts[key];
        }
    }
    return dict;
}

- (NSDictionary *)intersectionInheritableAttributes:(NSDictionary *)newAttributes
                                  currentAttributes:(NSDictionary *)currentAttributes
                              inheritableAttributes:(const NSArray *)inheritableAtts
{
    NSMutableDictionary * dict = [[[NSMutableDictionary alloc] init] autorelease];
    for(NSString * key in newAttributes.allKeys) {
        // make sure they are the same and
        // they are inheritable
        if([currentAttributes objectForKey:key] == nil) {
            return nil;
        }
        
        if([currentAttributes objectForKey:key] != nil &&
           [inheritableAtts containsObject:key] &&
           [newAttributes[key] isEqualToString:currentAttributes[key]]) {
            dict[key] = currentAttributes[key];
        }
    }
    
    // nothing to return, kill it
    if(dict.count == 0) {
        return nil;
    }
    return dict;
}

- (void)_cleanDef
{
    NSXMLElement * defNode = [self defElement];
    if(defNode.children == 0) {
        NSXMLElement * parent = (NSXMLElement *)defNode.parent;
        [parent removeChildAtIndex:defNode.index];
    }
}

- (void)_cleanEmptyGroups
{
    @autoreleasepool {
        // cleanup any groups that are completely useless
        NSArray * groups = [_dom nodesForXPath:@"//g" error:nil];
        for(NSXMLElement * element in groups) {
            NSXMLElement * parent = (NSXMLElement *)element.parent;
            if(element.childCount == 0) {
                // empty group
                [(NSXMLElement *)element.parent removeChildAtIndex:element.index];
            } else if(element.attributes.count == 0) {
                // no useful data on the group
                NSInteger index = element.index;
                for(NSXMLElement * child in element.children) {
                    [(NSXMLElement *)child.parent removeChildAtIndex:child.index];
                    [parent insertChild:child
                                atIndex:index++];
                }
                [parent removeChildAtIndex:element.index];
            }
        }
    }
}

- (void)_compressGroups
{
    NSArray * groups = [_dom nodesForXPath:@"//g" error:nil];
    for(NSXMLElement * group in groups) {
        
        // whats the next group?
        if(group.parent == nil) {
            continue;
        }
        
        // compare each group with its next sibling
        NSXMLElement * nextGroup = (NSXMLElement *)group.nextSibling;
        while([self compareElement:group withElement:nextGroup]) {
            // move each child into the older group
            for(NSXMLElement * child in nextGroup.children) {
                [nextGroup removeChildAtIndex:child.index];
                [group addChild:child];
            }
            
            // remove the newer
            NSXMLElement * n = nextGroup;
            nextGroup = (NSXMLElement *)nextGroup.nextSibling;
            [(NSXMLElement *)n.parent removeChildAtIndex:n.index];
        }
    }
    
}

- (void)_collapseGroups
{
    NSArray * groups = [_dom nodesForXPath:@"//g" error:nil];
    const NSArray * inheritable = IJSVGInheritableAttributes();
    for(NSXMLElement * group in groups) {
        
        // dont do anything due to it being referenced
        if([group attributeForName:@"id"] != nil) {
            return;
        }
        
        if(group.attributes.count != 0 && group.children.count == 1) {
            
            // grab the first child as its a loner
            NSXMLElement * child = (NSXMLElement *)group.children[0];
            if([child attributeForName:@"transform"] != nil) {
                continue;
            }
            
            for(NSXMLNode * gAttribute in group.attributes) {
                
                // if it just doesnt have the attriute, just add it
                if([child attributeForName:gAttribute.name] == NO) {
                    // remove first, or throws a wobbly
                    [group removeAttributeForName:gAttribute.name];
                    [child addAttribute:gAttribute];
                } else if([gAttribute.name isEqualToString:@"transform"]) {
                    // transform requires concatination
                    NSXMLNode * childTransform = [child attributeForName:@"transform"];
                    childTransform.stringValue = [NSString stringWithFormat:@"%@ %@",
                                                  gAttribute.stringValue, childTransform.stringValue];
                    
                } else if([inheritable containsObject:gAttribute.name] == NO) {
                    // if its not inheritable, only remove it if its not equal
                    NSXMLNode * aAtt = [child attributeForName:gAttribute.name];
                    if(aAtt == nil || (aAtt != nil && [aAtt.stringValue isEqualToString:gAttribute.stringValue] == NO)) {
                        continue;
                    }
                }
                [group removeAttributeForName:gAttribute.name];
            }
            
            // remove the group as its useless!
            if(group.attributes.count == 0) {
                [child detach];
                [(NSXMLElement *)group.parent replaceChildAtIndex:group.index
                                                         withNode:child];
            }
        }
    }
}

- (BOOL)compareElement:(NSXMLElement *)element
           withElement:(NSXMLElement *)anotherElement
{
    // not a matching element
    if([element.name isEqualToString:anotherElement.name] == NO ||
       element.attributes.count != anotherElement.attributes.count) {
        return NO;
    }
    
    // compare attributes
    for(NSXMLNode * attribute in element.attributes) {
        NSString * compareString = [anotherElement attributeForName:attribute.name].stringValue;
        if([attribute.stringValue isEqualToString:compareString] == NO) {
            return NO;
        }
    }
    return YES;
}

- (void)_convertUseElements
{
    @autoreleasepool {
        NSArray * paths = [_dom nodesForXPath:@"//path"
                                        error:nil];
        
        NSCountedSet * set = [[[NSCountedSet alloc] init] autorelease];
        for(NSXMLElement * element in paths) {
            [set addObject:[element attributeForName:@"d"].stringValue];
        }
        
        NSMutableDictionary * defs = [[[NSMutableDictionary alloc] init] autorelease];
        
        // now actually compute them
        for(NSXMLElement * element in paths) {
            NSString * data = [element attributeForName:@"d"].stringValue;
            if([set countForObject:data] == 1) {
                continue;
            }
            
            // at this point, we know the path is being used more then once
            NSXMLElement * defParentElement = nil;
            if((defParentElement = [defs objectForKey:data]) == nil) {
                // create the def
                NSXMLElement * element = [[[NSXMLElement alloc] init] autorelease];
                element.name = @"path";
                
                NSDictionary * atts = @{@"d":data,
                                        @"id":[self generateID]};
                IJSVGApplyAttributesToElement(atts, element);
                
                // store it against the def
                defs[data] = element;
                defParentElement = element;
            }
            
            // we know at this point, we need to swap out the path to a use
            NSXMLElement * use = [[[NSXMLElement alloc] init] autorelease];
            use.name = @"use";
            
            // grab the id
            NSString * pathId = [defParentElement attributeForName:@"id"].stringValue;
            
            NSXMLNode * useAttribute = [[[NSXMLNode alloc] initWithKind:NSXMLAttributeKind] autorelease];
            useAttribute.name = @"xlink:href";
            useAttribute.stringValue = IJSVGHash(pathId);
            [use addAttribute:useAttribute];
            
            // remove the d attribute
            for(NSXMLNode * attribute in element.attributes) {
                if([attribute.name isEqualToString:@"d"]) {
                    continue;
                }
                [element removeAttributeForName:attribute.name];
                [use addAttribute:attribute];
            }
            
            // swap it out
            [(NSXMLElement *)element.parent replaceChildAtIndex:element.index
                                                       withNode:use];
        }
        
        // add the defs back in
        NSXMLElement * def = [self defElement];
        for(NSXMLElement * defElement in defs.allValues) {
            [def addChild:defElement];
        }
    }
}

- (void)_recursiveParseFromLayer:(IJSVGLayer *)layer
                     intoElement:(NSXMLElement *)element
{
    // is a shape
    if([layer class] == [IJSVGShapeLayer class]) {
        NSXMLElement * child = [self elementForShape:(IJSVGShapeLayer  *)layer
                                          fromParent:element];
        if(child != nil) {
            [element addChild:child];
        }
    } else if([layer isKindOfClass:[IJSVGImageLayer class]]) {
        NSXMLElement * child = [self elementForImage:(IJSVGImageLayer *)layer
                                          fromParent:element];
        if(child != nil) {
            [element addChild:child];
        }
    } else if([layer isKindOfClass:[IJSVGGroupLayer class]]) {
        // assume its probably a group?
        NSXMLElement * child = [self elementForGroup:layer
                                          fromParent:element];
        if(child != nil) {
            [element addChild:child];
        }
    }
}

- (void)applyTransformToElement:(NSXMLElement *)element
                      fromLayer:(IJSVGLayer *)layer
{
    CGAffineTransform transform = layer.affineTransform;
    if(CGAffineTransformEqualToTransform(transform, CGAffineTransformIdentity) == YES) {
        return;
    }
    
    // append the string
    NSString * transformStr = [IJSVGTransform affineTransformToSVGMatrixString:transform];
    
    // apply it to the node
    IJSVGApplyAttributesToElement(@{@"transform":transformStr},element);
}

- (NSXMLElement *)elementForGroup:(IJSVGLayer *)layer
                       fromParent:(NSXMLElement *)parent
{
    // create the element
    NSXMLElement * e = [[[NSXMLElement alloc] init] autorelease];
    e.name = @"g";
    
    // stick defaults
    [self applyDefaultsToElement:e
                       fromLayer:layer];
    
    // add group children
    for(IJSVGLayer * childLayer in layer.sublayers) {
        [self _recursiveParseFromLayer:childLayer
                           intoElement:e];
    }
    
    return e;
}

- (NSString *)base64EncodedStringFromCGImage:(CGImageRef)image
{
    if(image == nil) {
        return nil;
    }
    
    // convert the CGImage into an NSImage
    NSBitmapImageRep * rep = [[[NSBitmapImageRep alloc] initWithCGImage:image] autorelease];
    
    // work out the data
    NSData * data = [rep representationUsingType:NSBitmapImageFileTypePNG
                                      properties:@{}];
    
    NSString * base64String = [data base64EncodedStringWithOptions:0];
    return [@"data:image/png;base64," stringByAppendingString:base64String];
}

- (void)applyPatternFromLayer:(IJSVGPatternLayer *)layer
                  parentLayer:(IJSVGLayer *)parentLayer
                       stroke:(BOOL)stroke
                    toElement:(NSXMLElement *)element
{
    // now we need the pattern
    IJSVGGroupLayer * patternLayer = (IJSVGGroupLayer *)layer.pattern;
    
    NSXMLElement * patternElement = [self elementForGroup:patternLayer
                                               fromParent:nil];
    patternElement.name = @"pattern";
    
    NSMutableDictionary * dict = [[[NSMutableDictionary alloc] init] autorelease];
    dict[@"id"] = [self generateID];
    dict[@"width"] = IJSVGShortFloatString(layer.patternNode.width.value);
    dict[@"height"] = IJSVGShortFloatString(layer.patternNode.height.value);
    
    // sort out x and y position
    IJSVGUnitLength * x = layer.patternNode.x;
    IJSVGUnitLength * y = layer.patternNode.y;
    
    if(x.value != 0) {
        dict[@"x"] = [layer.patternNode.x stringValue];
    }
    
    if(y.value != 0) {
        dict[@"y"] = [layer.patternNode.y stringValue];
    }
    
    
    IJSVGApplyAttributesToElement(dict, patternElement);
    
    [[self defElement] addChild:patternElement];
    
    // now the use statement
    NSXMLElement * useElement = [[[NSXMLElement alloc] init] autorelease];
    useElement.name = @"use";
    
    // now add the fill
    NSDictionary * aDict = nil;
    if(stroke == NO) {
        aDict = @{@"fill":IJSVGHashURL([patternElement attributeForName:@"id"].stringValue)};
        IJSVGApplyAttributesToElement(aDict, element);
        
        // fill opacity
        if(patternLayer.opacity != 1.f) {
            IJSVGApplyAttributesToElement(@{@"fill-opacity":IJSVGShortFloatString(patternLayer.opacity)}, element);
        }
    } else {
        aDict = @{@"stroke":IJSVGHashURL([patternElement attributeForName:@"id"].stringValue)};
        IJSVGApplyAttributesToElement(aDict, element);
    }
}

- (void)applyGradientFromLayer:(IJSVGGradientLayer *)layer
                   parentLayer:(IJSVGLayer *)parentLayer
                        stroke:(BOOL)stroke
                     toElement:(NSXMLElement *)element
{
    IJSVGGradient * gradient = layer.gradient;
    NSString * gradKey = [self generateID];
    NSXMLElement * gradientElement = [[[NSXMLElement alloc] init] autorelease];
    
    // work out linear gradient
    if([gradient isKindOfClass:[IJSVGLinearGradient class]]) {
        
        IJSVGLinearGradient * lGradient = (IJSVGLinearGradient *)gradient;
        gradientElement.name = @"linearGradient";
        NSDictionary * dict = @{@"id":gradKey,
                                @"x1":lGradient.x1.stringValue,
                                @"y1":lGradient.y1.stringValue,
                                @"x2":lGradient.x2.stringValue,
                                @"y2":lGradient.y2.stringValue};
        
        // give it the attibutes
        IJSVGApplyAttributesToElement(dict, gradientElement);
    } else {
        
        // assume radial
        IJSVGRadialGradient * rGradient = (IJSVGRadialGradient *)gradient;
        gradientElement.name = @"radialGradient";
        NSDictionary * dict = @{@"id":gradKey,
                                @"cx":rGradient.cx.stringValue,
                                @"cy":rGradient.cy.stringValue,
                                @"fx":rGradient.fx.stringValue,
                                @"fy":rGradient.fy.stringValue,
                                @"r":rGradient.radius.stringValue};
        
        // give it the attributes
        IJSVGApplyAttributesToElement(dict, gradientElement);
    }
    
    // apply the units
    if(layer.gradient.units == IJSVGUnitUserSpaceOnUse) {
        IJSVGApplyAttributesToElement(@{@"gradientUnits":@"userSpaceOnUse"},
                                      gradientElement);
    }
    
    // add the stops
    NSGradient * grad = layer.gradient.gradient;
    IJSVGColorList * sheet = layer.gradient.colorList;
    NSInteger noStops = grad.numberOfColorStops;
    for(NSInteger i = 0; i < noStops; i++) {
        
        // grab each color from the gradient
        NSColor * aColor = nil;
        CGFloat location;
        [grad getColor:&aColor
              location:&location
               atIndex:i];
        
        if(sheet != nil) {
            aColor = [sheet proposedColorForColor:aColor];
        }
        
        // create the stop element
        NSXMLElement * stop = [[[NSXMLElement alloc] init] autorelease];
        stop.name = @"stop";
        
        NSMutableDictionary * atts = [[[NSMutableDictionary alloc] init] autorelease];
        atts[@"offset"] = [NSString stringWithFormat:@"%g%%",(location*100)];
        
        // add the color
        NSString * stopColor = [IJSVGColor colorStringFromColor:aColor
                                                       forceHex:YES
                                                 allowShorthand:YES];
        if([stopColor isEqualToString:@"#000000"] == NO) {
            atts[@"stop-color"] = stopColor;
        }
        
        // we need to work out the color at this point, annoyingly...
        CGFloat opacity = aColor.alphaComponent;
        
        // is opacity is equal to 1, no need to add it as spec
        // defaults opacity to 1 anyway :)
        if(opacity != 1.f) {
            atts[@"stop-opacity"] = IJSVGShortFloatStringWithPrecision(opacity, 2);
        }
        
        // att the attributes
        
        IJSVGApplyAttributesToElement(atts, stop);
        
        // append the stop the gradient
        [gradientElement addChild:stop];
    }
    
    // append it to the defs
    [[self defElement] addChild:gradientElement];
    
    // work out the transform
    NSArray * transforms = layer.gradient.transforms;
    if(transforms.count != 0.f) {
        CGAffineTransform transform = IJSVGConcatTransforms(transforms);
        NSString * transformString = [IJSVGTransform affineTransformToSVGMatrixString:transform];
        IJSVGApplyAttributesToElement(@{@"gradientTransform":transformString}, gradientElement);
    }
    
    // add it to the element passed in
    if(stroke == NO) {
        IJSVGApplyAttributesToElement(@{@"fill":IJSVGHashURL(gradKey)}, element);
        
        // fill opacity
        if(layer.opacity != 1.f) {
            IJSVGApplyAttributesToElement(@{@"fill-opacity":IJSVGShortFloatStringWithPrecision(layer.opacity,2)}, element);
        }
    } else {
        IJSVGApplyAttributesToElement(@{@"stroke":IJSVGHashURL(gradKey)}, element);
    }
}

- (CGAffineTransform)affineTransformFromTransforms:(NSArray<IJSVGTransform *> *)transforms
{
    CGAffineTransform t = CGAffineTransformIdentity;
    for(IJSVGTransform * transform in transforms) {
        t = CGAffineTransformConcat( t, [transform CGAffineTransform]);
    }
    return t;
}

- (NSXMLElement *)elementForImage:(IJSVGImageLayer *)layer
                       fromParent:(NSXMLElement *)parent
{
    NSString * base64String = [self base64EncodedStringFromCGImage:(CGImageRef)layer.contents];
    if(base64String == nil || layer.contents == nil) {
        return nil;
    }
    
    // image element for the SVG
    NSXMLElement * imageElement = [[[NSXMLElement alloc] init] autorelease];
    imageElement.name = @"image";
    
    NSMutableDictionary * dict =  [[[NSMutableDictionary alloc] init] autorelease];
    dict[@"id"] = [self generateID];
    dict[@"width"] = IJSVGShortFloatString(layer.frame.size.width);
    dict[@"height"] = IJSVGShortFloatString(layer.frame.size.height);
    dict[@"xlink:href"] = base64String;
    
    // work out any position
    if(layer.frame.origin.x != 0.f) {
        dict[@"x"] = IJSVGShortFloatString(layer.frame.origin.x);
    }
    if(layer.frame.origin.y != 0.f) {
        dict[@"y"] = IJSVGShortFloatString(layer.frame.origin.y);
    }
    
    // add the attributes
    IJSVGApplyAttributesToElement(dict, imageElement);
    return imageElement;
}

- (NSXMLElement *)elementForShape:(IJSVGShapeLayer  *)layer
                       fromParent:(NSXMLElement *)parent
{
    NSXMLElement * e = [[[NSXMLElement alloc] init] autorelease];
    e.name = @"path";
    CGPathRef path = layer.path;
    
    // copy the path as we want to translate
    CGAffineTransform trans = CGAffineTransformMakeTranslation(layer.originalPathOrigin.x,
                                                               layer.originalPathOrigin.y);
    CGPathRef transformPath = CGPathCreateCopyByTransformingPath(path, &trans);
    
    NSMutableDictionary * dict = [[[NSMutableDictionary alloc] init] autorelease];
    
    // path
    dict[@"d"] = [self pathFromCGPath:transformPath];
    
    CGPathRelease(transformPath);
    
    // work out even odd rule
    if([layer.fillRule isEqualToString:kCAFillRuleNonZero] == NO) {
        dict[@"fill-rule"] = @"evenodd";
    }
    
    // fill color
    if(layer.fillColor != nil) {
        NSColor * fillColor = [NSColor colorWithCGColor:layer.fillColor];
        NSString * colorString = [IJSVGColor colorStringFromColor:fillColor];
        
        // could be none
        if(colorString != nil) {
            dict[@"fill"] = colorString;
        }
    }
    
    // is there a gradient fill?
    if(layer.gradientFillLayer != nil) {
        [self applyGradientFromLayer:layer.gradientFillLayer
                         parentLayer:(IJSVGLayer *)layer
                              stroke:NO
                           toElement:e];
    }
    
    // is there a pattern?
    if(layer.patternFillLayer != nil) {
        [self applyPatternFromLayer:layer.patternFillLayer
                        parentLayer:(IJSVGLayer *)layer
                             stroke:NO
                          toElement:e];
    }
    
    // is there a stroke layer?
    if(layer.strokeLayer != nil) {
        // check the type
        IJSVGStrokeLayer * strokeLayer = layer.strokeLayer;
        if([strokeLayer isKindOfClass:[IJSVGShapeLayer  class]]) {
            // stroke
            if(strokeLayer.lineWidth != 0.f) {
                dict[@"stroke-width"] = IJSVGShortFloatString(strokeLayer.lineWidth);
            }
            
            // stroke gradient
            if(layer.gradientStrokeLayer != nil) {
                [self applyGradientFromLayer:layer.gradientStrokeLayer
                                 parentLayer:(IJSVGPatternLayer *)layer
                                      stroke:YES
                                   toElement:e];
                
            } else if(layer.patternStrokeLayer != nil) {
                // stroke pattern
                [self applyPatternFromLayer:layer.patternStrokeLayer
                                parentLayer:(IJSVGPatternLayer *)layer
                                     stroke:YES
                                  toElement:e];
                
            } else if(strokeLayer.strokeColor != nil) {
                NSColor * strokeColor = [NSColor colorWithCGColor:strokeLayer.strokeColor];
                NSString * strokeColorString = [IJSVGColor colorStringFromColor:strokeColor];
                
                // could be none
                if(strokeColorString != nil) {
                    dict[@"stroke"] = strokeColorString;
                    if([strokeColorString isEqualToString:@"none"] == YES) {
                        // remove the stroke width as its completely useless
                        [dict removeObjectForKey:@"stroke-width"];
                    }
                }
            }
            
            // work out line cap
            if([strokeLayer.lineCap isEqualToString:kCALineCapButt] == NO) {
                NSString * capStyle = nil;
                if([strokeLayer.lineCap isEqualToString:kCALineCapRound]) {
                    capStyle = @"round";
                } else if([strokeLayer.lineCap isEqualToString:kCALineCapSquare]) {
                    capStyle = @"square";
                }
                if(capStyle != nil) {
                    dict[@"stroke-linecap"] = capStyle;
                }
            }
            
            // work out line join
            if([strokeLayer.lineJoin isEqualToString:kCALineJoinMiter] == NO) {
                NSString * joinStyle = nil;
                if([strokeLayer.lineJoin isEqualToString:kCALineJoinBevel]) {
                    joinStyle = @"bevel";
                } else if([strokeLayer.lineJoin isEqualToString:kCALineJoinRound]) {
                    joinStyle = @"round";
                }
                if(joinStyle != nil) {
                    dict[@"stroke-linejoin"] = joinStyle;
                }
            }
            
            // work out dash offset...
            if(strokeLayer.lineDashPhase != 0.f) {
                dict[@"stroke-dashoffset"] = IJSVGShortFloatString(strokeLayer.lineDashPhase);
            }
            
            // work out dash array
            if(strokeLayer.lineDashPattern.count != 0) {
                dict[@"stroke-dasharray"] = [strokeLayer.lineDashPattern componentsJoinedByString:@" "];
            }
            
        }
    }
    
    // apply the attributes
    IJSVGApplyAttributesToElement(dict, e);
    
    // apple defaults
    [self applyDefaultsToElement:e
                       fromLayer:(IJSVGLayer *)layer];
    return e;
}

- (void)applyDefaultsToElement:(NSXMLElement *)element
                     fromLayer:(IJSVGLayer *)layer
{
    NSMutableDictionary * dict = [[[NSMutableDictionary alloc] init] autorelease];
    
    // opacity
    if(layer.opacity != 1.f) {
        dict[@"opacity"] = IJSVGShortFloatStringWithPrecision(layer.opacity,2);
    }
    
    // blendmode - we only every apply a stylesheet blend mode
    NSMutableDictionary * style = [[[NSMutableDictionary alloc] init] autorelease];
    if(layer.blendingMode != kCGBlendModeNormal) {
        NSString * str = [IJSVGUtils mixBlendingModeForBlendMode:(IJSVGBlendMode)layer.blendingMode];
        if(str != nil) {
            style[@"mix-blend-mode"] = str;
        }
    }
    
    // hidden?
    if(layer.isHidden) {
        style[@"display"] = @"none";
    }
    
    if(style.count != 0) {
        NSMutableString * styleString = [[[NSMutableString alloc] init] autorelease];
        for(NSString * styleKey in style.allKeys) {
            NSString * format = [NSString stringWithFormat:@"%@:%@;",styleKey, style[styleKey]];
            [styleString appendString:format];
        }
        dict[@"style"] = styleString;
    }
    
    
    // add atttributes
    IJSVGApplyAttributesToElement(dict, element);
    
    // apply transforms
    [self applyTransformToElement:element
                        fromLayer:layer];
    
    // add any masks...
    if(layer.mask != nil) {
        [self applyMaskToElement:element
                       fromLayer:layer];
    }
}

- (void)applyMaskToElement:(NSXMLElement *)element
                 fromLayer:(IJSVGLayer *)layer
{
    // create the element
    NSXMLElement * mask = [[[NSXMLElement alloc] init] autorelease];
    mask.name = @"mask";
    
    // create the key
    NSString * maskKey = [self generateID];
    NSMutableDictionary * dict = [[[NSMutableDictionary alloc] init] autorelease];
    dict[@"id"] = maskKey;
    dict[@"maskContentUnits"] = @"userSpaceOnUse";
    dict[@"maskUnits"] = @"objectBoundingBox";
    
    if(layer.mask.frame.origin.x != 0.f) {
        dict[@"x"] = IJSVGShortFloatString(layer.mask.frame.origin.x);
    }
    if(layer.mask.frame.origin.y != 0.f) {
        dict[@"y"] = IJSVGShortFloatString(layer.mask.frame.origin.y);
    }
    
    IJSVGApplyAttributesToElement(dict, mask);
    
    // add the cool stuff
    [self _recursiveParseFromLayer:(IJSVGLayer *)layer.mask
                       intoElement:mask];
    
    // add mask id to element
    IJSVGApplyAttributesToElement(@{@"mask":IJSVGHashURL(maskKey)}, element);
    
    // add it defs
    [[self defElement] addChild:mask];
}

- (NSString *)SVGString
{
    NSXMLNodeOptions options = NSXMLNodePrettyPrint;
    if((_options & IJSVGExporterOptionCompressOutput) != 0) {
        options = NSXMLNodeOptionsNone;
    }
    return [_dom XMLStringWithOptions:options];
}

- (NSData *)SVGData
{
    return [[self SVGString] dataUsingEncoding:NSUTF8StringEncoding];
}

#pragma mark CGPath stuff

- (NSString *)pathFromCGPath:(CGPathRef)path
{
    // string to store the path in
    NSArray * instructions = [IJSVGExporterPathInstruction instructionsFromPath:path];
    
    // work out what to do...
    if((_options & IJSVGExporterOptionCleanupPaths) != 0) {
        [IJSVGExporterPathInstruction convertInstructionsToRelativeCoordinates:instructions];
    }
    return [IJSVGExporterPathInstruction pathStringFromInstructions:instructions];
}

void IJSVGExporterPathCaller(void * info, const CGPathElement * pathElement) {
    IJSVGCGPathHandler handler = (IJSVGCGPathHandler)info;
    handler(pathElement);
};

- (void)sortAttributesOnElement:(NSXMLElement *)element
{
    const NSArray * order = @[@"id",@"width",@"height",@"x",@"x1",@"x2",
                              @"y",@"y1",@"y2",@"cx",@"cy",@"r",@"fill",
                              @"stroke",@"marker",@"d",@"points",@"transform",
                              @"gradientTransform", @"xlink:href"];
    
    // grab the attributes
    NSArray<NSXMLNode *>* attributes = element.attributes;
    NSInteger count = attributes.count;
    
    // sort the attributes using a custom sort
    NSArray * sorted = [attributes sortedArrayUsingComparator:^NSComparisonResult(id  _Nonnull obj1, id  _Nonnull obj2) {
        // tell compiler we are nodes
        NSXMLNode * attribute1 = (NSXMLNode *)obj1;
        NSXMLNode * attribute2 = (NSXMLNode *)obj2;
        
        // base index
        float aIndex = count;
        float bIndex = count;
        
        // loop around each order string
        for(NSInteger i = 0; i < order.count; i++) {
            if([attribute1.name isEqualToString:order[i]]) {
                aIndex = i;
            } else if([attribute1.name rangeOfString:[order[i] stringByAppendingString:@"-"]].location == 0) {
                aIndex = i + .5;
            }
            if([attribute2.name isEqualToString:order[i]]) {
                bIndex = i;
            } else if([attribute2.name rangeOfString:[order[i] stringByAppendingString:@"-"]].location == 0) {
                bIndex = i + .5;
            }
        }
        
        // return the comparison set
        if(aIndex != bIndex) {
            if(aIndex > bIndex) {
                return NSOrderedDescending;
            } else {
                return NSOrderedAscending;
            }
        }
        return [attribute1.name compare:attribute2.name];
    }];
    
    // remove all attributes
    for(NSXMLNode * node in attributes) {
        [element removeAttributeForName:node.name];
    }
    
    // add them back on in order
    for(NSXMLNode * attribute in sorted) {
        [element addAttribute:attribute];
    }
    
}

@end