anchor.diff:    }
   
     void _onTextPasted(String selectionText, String text) {
  +    // if user selected url and paste new link, we don't process
  +    // it because user just replace it's old link
  +    if (_PURE_LINK_REGEX.hasMatch(selectionText)) {
  +      return;
  +    }
  +
       //detect only pure link text
       var match = _PURE_LINK_REGEX.firstMatch(text);
       if (match == null) {
  
positive.code:       var pastedTextLength = contentInput.value.length - (initialText.length - selectionLength);
        var end = pasteAtIndex + pastedTextLength;
        var pastedText = contentInput.value.substring(pasteAtIndex, end);
        _onTextPasted(selectionText, pastedText);
      });
  
      // clipboardData only support in chrome, give up
  
negative.code:       return;
      }
  
      if (_isLinkOnReferenceAppendix(contentInput.value, link)) {
        return;
      }
  
      _applyAutoLink(selectionText, link);
    }
  
    /**
     * two cases:
     *
     * 1. user manually editing appendix section, when he paste into this section,
     *    we should not process it
     * 2. user paste a link in textarea, but the link already in appendix, we ignore this case too.
     */
    bool _isLinkOnReferenceAppendix(String fullText, String link) {
      var existRefs = ReferenceAppendix.tryParse(fullText);
      return existRefs.any((ref) => ref.url == link);
    }
  
    /**
  