Add formatting to NSAttributedString initilalized from Markdown

PopRichString+Markdown.m

//
//  PopRichString+Markdown.m
//  Pop
//
//  Created by Nicholas Moore on 29/11/2022.
//

#import "PopRichString+Markdown.h"
#import "NMKit.h"

@implementation PopRichString (Markdown)

// add formatting to a NSAttributedString that has been constructed from Markdown
+ (NSAttributedString *)addFormattingToString:(NSAttributedString *)attrString withBaseFont:(NSFont *)baseFont paragraphSpacing:(BOOL)paraSpace
{
    NMLogTemp(@"AddFormattingWithBaseFont:\n%@", attrString);
    if (![attrString isKindOfClass:[NSAttributedString class]]||![baseFont isKindOfClass:[NSFont class]]) {
        return nil;
    }
    const NSRange fullRange=NSMakeRange(0, attrString.length);
    
    // default paragraph style
    NSParagraphStyle *const defaultParagraphStyle = [[NSParagraphStyle alloc] init];
    
    // indenting unit to match the default tab stops
    const CGFloat unit=defaultParagraphStyle.tabStops[0].location;
    // the bullet indenting is based on how TextEdit does it
    const CGFloat bulletUnit=unit*0.3;
    
    // paragraph styles
    NSParagraphStyle *const listItemParagraphStyle = defaultParagraphStyle.copy;
    NSParagraphStyle *const headerParagraphStyle = defaultParagraphStyle.copy;
    NSMutableParagraphStyle *const indentedBlockParagraphStyle = defaultParagraphStyle.mutableCopy;
    indentedBlockParagraphStyle.headIndent = unit;
    indentedBlockParagraphStyle.firstLineHeadIndent = unit;
    NSParagraphStyle *const codeBlockParagraphStyle = indentedBlockParagraphStyle.copy;
    NSParagraphStyle *const quoteBlockParagraphStyle = indentedBlockParagraphStyle.copy;
    
    if (@available(macOS 12.0, *)) {
        NSMutableAttributedString *mas=[attrString mutableCopy];
        [mas addAttribute:NSFontAttributeName value:baseFont range:fullRange];
        
        // inline intents
        [attrString enumerateAttribute:NSInlinePresentationIntentAttributeName inRange:fullRange options:0 usingBlock:^(NSNumber * _Nullable intentObj, NSRange range, BOOL * _Nonnull stop) {
            NSUInteger intent = [intentObj unsignedIntegerValue];
            if (intent&NSInlinePresentationIntentEmphasized) {
                NSFont *newFont = [NSFont fontWithDescriptor:[baseFont.fontDescriptor fontDescriptorWithSymbolicTraits:NSFontItalicTrait] size:baseFont.pointSize];
                [mas addAttribute:NSFontAttributeName value:newFont range:range];
            }
            if (intent&NSInlinePresentationIntentStronglyEmphasized) {
                NSFont *newFont = [NSFont fontWithDescriptor:[baseFont.fontDescriptor fontDescriptorWithSymbolicTraits:NSFontBoldTrait] size:baseFont.pointSize];
                [mas addAttribute:NSFontAttributeName value:newFont range:range];
            }
            if (intent&NSInlinePresentationIntentStrikethrough) {
                [mas addAttribute:NSStrikethroughStyleAttributeName value:@(NSUnderlineStyleSingle) range:range];
            }
            if (intent&NSInlinePresentationIntentCode) {
                NSFont *newFont = [NSFont monospacedSystemFontOfSize:baseFont.pointSize weight:NSFontWeightRegular];
                [mas addAttribute:NSFontAttributeName value:newFont range:range];
            }
        }];
        //TODO
        //NSInlinePresentationIntentSoftBreak
        //NSInlinePresentationIntentLineBreak
        //NSInlinePresentationIntentInlineHTML
        //NSInlinePresentationIntentBlockHTML
        
        // block intents
        __block NSInteger previousListId=0;
        __block BOOL lastBlock=YES;
        __block BOOL listItem=NO;
        // We use .reversed() iteration to be able to add characters to the string without breaking ranges
        NSMutableDictionary *textListsLookup=[NSMutableDictionary dictionary];
        [attrString enumerateAttribute:NSPresentationIntentAttributeName inRange:NSMakeRange(0,attrString.length) options:NSAttributedStringEnumerationReverse usingBlock:^(NSPresentationIntent * _Nullable intent, const NSRange inRange, BOOL * _Nonnull stop) {
            NMLogTemp(@"intent: %@", intent);
            NSRange outRange=inRange;
            BOOL listItemFollows=listItem;
            listItem=NO;
            BOOL firstItem=NO, lastItem=NO, codeBlock=NO;
            NSMutableParagraphStyle *paragraphStyle=defaultParagraphStyle.mutableCopy;
            NSMutableArray *textLists=[NSMutableArray array];
            do {
                switch (intent.intentKind) {
                    case NSPresentationIntentKindParagraph:
                        break;
                    case NSPresentationIntentKindHeader:
                    {
                        NSFont *newFont=baseFont;
                        switch (intent.headerLevel) {
                            case 1:
                                newFont = [NSFont fontWithDescriptor:[baseFont.fontDescriptor fontDescriptorWithSymbolicTraits:NSFontBoldTrait] size:baseFont.pointSize*1.8];
                                break;
                            case 2:
                                newFont = [NSFont fontWithDescriptor:[baseFont.fontDescriptor fontDescriptorWithSymbolicTraits:NSFontBoldTrait] size:baseFont.pointSize*1.5];
                                break;
                            case 3:
                                newFont = [NSFont fontWithDescriptor:[baseFont.fontDescriptor fontDescriptorWithSymbolicTraits:NSFontBoldTrait] size:baseFont.pointSize*1.2];
                                break;
                            default:
                                newFont = [NSFont fontWithDescriptor:[baseFont.fontDescriptor fontDescriptorWithSymbolicTraits:NSFontBoldTrait] size:baseFont.pointSize*1.0];
                                break;
                        }
                        [mas addAttribute:NSFontAttributeName value:newFont range:outRange];
                        paragraphStyle=headerParagraphStyle.mutableCopy;
                    }
                        break;
                    case NSPresentationIntentKindOrderedList:
                    case NSPresentationIntentKindUnorderedList:
                        NMLogTemp(@"LIST");
                        if (intent.indentationLevel==0) {
                            lastItem = intent.identity!=previousListId;
                            previousListId=intent.identity;
                        }
                        break;
                        
                    case NSPresentationIntentKindListItem:
                        NMLogTemp(@"LIST ITEM");
                        if (!firstItem) {
                            firstItem=intent.ordinal==1&&intent.indentationLevel==1;
                        }
                        
                        if (intent.parentIntent) {
                            NSNumber *parentId=@(intent.parentIntent.identity);
                            NSTextList *list=textListsLookup[parentId];
                            if (!list) {
                                NSTextListMarkerFormat markerFormat=NSTextListMarkerHyphen;
                                if (intent.parentIntent.intentKind == NSPresentationIntentKindUnorderedList) {
                                    NSUInteger markerIndex=MIN(intent.parentIntent.indentationLevel,2);
                                    NMLogTemp(@"MARKER INDEX %@", @(markerIndex));
                                    markerFormat=@[NSTextListMarkerDisc, NSTextListMarkerCircle, NSTextListMarkerSquare][markerIndex];
                                } else if (intent.parentIntent.intentKind == NSPresentationIntentKindOrderedList) {
                                    markerFormat=NSTextListMarkerDecimal;
                                }
                                list=[[NSTextList alloc] initWithMarkerFormat:markerFormat options:0];
                                textListsLookup[parentId]=list;
                            }
                            [textLists insertObject:list atIndex:0];
                            
                            // insert actual bullet
                            if (!listItem) {
                                paragraphStyle=listItemParagraphStyle.mutableCopy;
                                NSString *bullet=[NSString stringWithFormat:@"\t%@\t", [list markerForItemNumber:intent.ordinal]];
                                NMLogTemp(@"BULLET IS %@", bullet);
                                [mas insertAttributedString:[[NSAttributedString alloc] initWithString:bullet attributes:@{NSFontAttributeName: baseFont}] atIndex:outRange.location];
                                outRange.length+=bullet.length;
                                paragraphStyle.tabStops=@[
                                    [[NSTextTab alloc] initWithTextAlignment:NSTextAlignmentLeft location:unit*intent.indentationLevel options:@{}],
                                    [[NSTextTab alloc] initWithTextAlignment:NSTextAlignmentLeft location:unit*(intent.indentationLevel-1)+bulletUnit options:@{}],
                                ];
                                paragraphStyle.headIndent=unit*intent.indentationLevel;
                            }
                            paragraphStyle.textLists=textLists;
                            listItem=YES;
                        }
                        break;
                    case NSPresentationIntentKindCodeBlock:
                        [mas addAttribute:NSFontAttributeName value:[NSFont monospacedSystemFontOfSize:baseFont.pointSize weight:NSFontWeightRegular] range:outRange];
                        paragraphStyle = codeBlockParagraphStyle.mutableCopy;
                        codeBlock=YES;
                        break;
                    case NSPresentationIntentKindBlockQuote:
                        paragraphStyle = quoteBlockParagraphStyle.mutableCopy;
                        break;
                    default:
                        break;
                }
                intent = intent.parentIntent;
            } while(intent);
            NMLogTemp(@"TEXT LISTS %@", textLists);
            
            //TODO
            //NSPresentationIntentKindThematicBreak,
            //NSPresentationIntentKindTable,
            //NSPresentationIntentKindTableHeaderRow,
            //NSPresentationIntentKindTableRow,
            //NSPresentationIntentKindTableCell,
            
            NMLogTemp(@"spacing: %@ / listItem %@ firstitem %@ lastItem %@", NMLimitString([attrString attributedSubstringFromRange:inRange].string, 10, nil),
                      @(listItem), @(firstItem), @(lastItem));
            
            NSMutableString *newlineAppend=[@"" mutableCopy];
            // add spacing for paragraphs
            if (!codeBlock) {
                [newlineAppend appendString:@"\n"];
            }
            if (!listItem&&!listItemFollows) {
                if (paraSpace) {
                    paragraphStyle.paragraphSpacing = baseFont.pointSize;
                }
                else if (!lastBlock) {
                    [newlineAppend appendString:@"\n"];
                }
            }
            
            [mas insertAttributedString:[[NSAttributedString alloc] initWithString:newlineAppend attributes:@{NSFontAttributeName: baseFont}] atIndex:outRange.location+outRange.length];
            outRange.length+=newlineAppend.length;
            [mas addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:outRange];
            lastBlock=NO;
        }];
                
        NMLogTemp(@"Done AddFormattingWithBaseFont:\n%@", mas);
        return [mas copy];
    }
    else {
        return nil;
    }
}

@end

Hi @pilotmoon
Is it working on iOS? I've never got any intentKind except NSPresentationIntentKindHeader or NSPresentationIntentKindHeader

I have only tested it on Mac