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@implementation UITextView (RSExtras)


static BOOL stringCharacterIsAllowedAsPartOfLink(NSString *s) {

    /*[s length] is assumed to be 0 or 1. s may be nil.
     Totally not a strict check.*/

    if (s == nil || [s length] < 1)
        return NO;

    unichar ch = [s characterAtIndex:0];
    if ([[NSCharacterSet whitespaceAndNewlineCharacterSet] characterIsMember:ch])
        return NO;
    return YES;
}


- (NSString *)rs_potentialLinkAtPoint:(CGPoint)point {

    /*Grow a string around the tap until hitting a space, cr, lf, or beginning or end of document.*/

    /*If we don't check for end of document, then you could tap way below end of text, and it would return a link if the last text was a link. This has the unfortunate side effect that you can't tap on the last character of a link if it appears at the end of a document. I can live with shipping that.*/

    UITextRange *textRange = [self characterRangeAtPoint:point];
    UITextPosition *endOfDocumentTextPosition = self.endOfDocument;
    if ([textRange.end isEqual:endOfDocumentTextPosition])
        return nil;

    UITextPosition *tapPosition = [self closestPositionToPoint:point];
    if (tapPosition == nil)
        return nil;

    NSMutableString *s = [NSMutableString stringWithString:@""];

    /*Move right*/

    UITextPosition *textPosition = tapPosition;

    BOOL isFirstCharacter = YES;
    
    while (true) {
        UITextRange *rangeOfCharacter = [self.tokenizer rangeEnclosingPosition:textPosition withGranularity:UITextGranularityCharacter inDirection:UITextWritingDirectionNatural];
        NSString *oneCharacter = [self textInRange:rangeOfCharacter];

        if (isFirstCharacter) {
            /*If first character is cr or lf, then we're off the right hand side of the link. Maybe way outside.*/
            if ([oneCharacter isEqualToString:@"\n"] || [oneCharacter isEqualToString:@"\r"])
                return nil;
        }

        isFirstCharacter = NO;
        
        if (!stringCharacterIsAllowedAsPartOfLink(oneCharacter))
            break;
        [s appendString:oneCharacter];

        textPosition = [self positionFromPosition:textPosition offset:1];
        if (textPosition == nil)
            break;
    }

    /*Move left*/

    textPosition = [self positionFromPosition:tapPosition offset:-1];
    if (textPosition != nil) {

        while (true) {
            UITextRange *rangeOfCharacter = [self.tokenizer rangeEnclosingPosition:textPosition withGranularity:UITextGranularityCharacter inDirection:UITextWritingDirectionNatural];
            NSString *oneCharacter = [self textInRange:rangeOfCharacter];

            if (!stringCharacterIsAllowedAsPartOfLink(oneCharacter))
                break;
            [s insertString:oneCharacter atIndex:0];

            textPosition = [self positionFromPosition:textPosition offset:-1];
            if (textPosition == nil)
                break;
        }
    }

    return s;
}


- (NSString *)rs_linkAtPoint:(CGPoint)point {

    NSString *potentialLink = [self rs_potentialLinkAtPoint:point];
    if (potentialLink == nil || [potentialLink length] < 1)
        return nil;

    NSArray *links = [potentialLink rs_links];
    if (links == nil || [links count] < 1)
        return nil;
    
    NSString *firstLink = links[0];
    return firstLink;
}


@end