Detect remaining chars for a tweet

gistfile1.m

#define TWEET_MAX_LENGTH 140
#define TWEET_URL_HTTP_LENGTH 22
#define TWEET_URL_HTTPS_LENGTH 23
+ (NSInteger) remainingChars:(NSString *)text {
    NSInteger result = TWEET_MAX_LENGTH - [text length];
    
    NSError *error = nil;
    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"https?://(\\S+)"
                                                                           options:0
                                                                             error:&error];
    
    NSArray *matches = [regex matchesInString:text
                                      options:0
                                        range:NSMakeRange(0, text.length)];
    for (NSTextCheckingResult *match in matches) {
        NSRange urlRange = [match rangeAtIndex:1];
        NSString* url = [text substringWithRange:urlRange];
        
        result += urlRange.length;
        
        if ([url hasPrefix:@"https"]) {
            result -= TWEET_URL_HTTPS_LENGTH;
        } else {
            result -= TWEET_URL_HTTP_LENGTH;
        }
    }
    
    return result;
}