Snudown → NSAttributedString

NSString+Markdown.h

@import Foundation;

@interface NSString (Markdown)

@property (nonatomic, readonly) NSAttributedString *attributedStringFromRawMarkdown;
@property (nonatomic, readonly) NSString *HTMLFromRawMarkdown;

@end

NSString+Markdown.m

// From https://github.com/reddit/snudown
// Installation: copy /snudown to your project,
// delete everything but the html and src folders,
// and the html_block_names.txt and snudown.def files.
#include "markdown.h"
#include "html.h"

// DTCoreText is used to convert HTML into an attributed string
#import "DTCoreText.h"
// CCHLinkTextView is favored over UITextView beacuse
// it can be configured to handle the tapping of /r/subreddit autolinks.
// Not necessary, see lines 47-49.
#import "CCHLinkTextView.h"

@implementation NSString (Markdown)

- (NSAttributedString *)attributedStringFromRawMarkdown {
    if (self.isEmpty) {
        return [NSAttributedString new];
    }
    
    // Get HTML
    NSString *html = self.HTMLFromRawMarkdown;
    if (html.isEmpty) {
        return [NSAttributedString new];
    }
    
    // Convert to data, gather conversion options
    NSData *data = [html dataUsingEncoding:NSUTF8StringEncoding];
    NSDictionary *options = @{DTDefaultFontName: @"HelveticaNeue",
                              DTDefaultFontFamily: @"Helvetica Neue",
                              DTUseiOS6Attributes: @YES,
                              DTDefaultFontSize: @([UIFont systemFontSize])};
    
    // Convert to attributed string
    NSMutableAttributedString *htmlToAttributedBody = [[NSMutableAttributedString alloc] initWithHTMLData:data options:options documentAttributes:nil];
    
    // Trim trailing whitespace, set foreground text color
    //
    // You will have to set the foreground color of the text
    // like this if the text color ever needs to change on-screen
    UIColor *foregroundTextColor = [UIColor whateverYouWant];
    CFStringTrimWhitespace((CFMutableStringRef)htmlToAttributedBody.mutableString);
    [htmlToAttributedBody addAttribute:NSForegroundColorAttributeName
                                 value:foregroundTextColor
                                 range:NSMakeRange(0, htmlToAttributedBody.length)];
    
    // Replace NSLinkAttributeName with CCHLinkAttributeName
    // Unnecessary unless you're using CCHLinkTextView (which I reccomend to allow tapping of /r/subreddit autolinks)
    // Remove this method call if you're not using CCHLinkTextView
    [htmlToAttributedBody enumerateAttributesInRange:NSMakeRange(0, htmlToAttributedBody.length) options:NSAttributedStringEnumerationReverse usingBlock:^(NSDictionary *attrs, NSRange range, BOOL *stop) {
        id linkval = attrs[NSLinkAttributeName];
        if (linkval) {
            [htmlToAttributedBody removeAttribute:NSLinkAttributeName range:range];
            [htmlToAttributedBody addAttribute:CCHLinkAttributeName value:linkval range:range];
        }
    }];
    
    return htmlToAttributedBody.copy;
}

- (NSString *)HTMLFromRawMarkdown {
    if (self.isEmpty) {
        return self;
    }
    
    NSData *data = [self dataUsingEncoding:NSUTF8StringEncoding];
    
    struct sd_callbacks callbacks;
    struct html_renderopt options;
    struct sd_markdown *markdown = NULL;
    
    // performing markdown parsing
    struct buf *ob = bufnew(data.length);
    
    sdhtml_renderer(&callbacks, &options, 0);
    markdown = sd_markdown_new(1023, 16, 2, &callbacks, &options);
    sd_markdown_render(ob, data.bytes, data.length, markdown);
    sd_markdown_free(markdown);
    
    NSString *html;
    if (ob->size == 0) {
        html = @"";
    } else {
        html = [[NSString alloc] initWithBytes:ob->data length:ob->size encoding:NSUTF8StringEncoding];
    }
    
    bufrelease(ob);
    return html;
}

@end

YourCCHLinkTextViewDelegate.m

// In the implementation of whatever class implements the CCHLinkTextViewDelegate protocol

- (void)linkTextView:(CCHLinkTextView *)linkTextView didTapLinkWithValue:(id)value {
    if ([value isKindOfClass:[NSURL class]])
        value = [value absoluteString];
    
    NSString urlString = (id)value;
    
    // Handle value as NSString, ie "/r/subreddit" I think
    // ...
}

- (void)linkTextView:(CCHLinkTextView *)linkTextView didLongPressLinkWithValue:(id)value {
    if ([value isKindOfClass:[NSURL class]])
    value = [value absoluteString];
    
    NSString urlString = (id)value;
    
    // Handle value as NSString, ie "/r/subreddit" I think
    // ...
}