// ==UserScript==
// @name 	Multi Tags Search for ?B
// @include	http://b.hatena.ne.jp/*
// @namespace	http://fg-180.katamayu.net/userscripts
// ==/UserScript==


(function(){
  query = GM_getValue('search_tag', '');
  tag = location.pathname.split('/')[2];

  if(tag && !tag.match(/^\d{8}$/) && query.indexOf(tag) < 0 && !tag.match(/^https?:/)){  // tag page
    query = tag + ' ' + query;
    GM_setValue('search_tag', query);
  }else if(!tag && location.search == ''){   // top page
    query = '';
    GM_setValue('search_tag', '');
  }

  textField = document.getElementsByName('word')[0];
  textField.value = decodeURI(query);

  clearButton = document.createElement('input');
  clearButton.type = 'button';
  clearButton.value = 'Clear';
  clearButton.addEventListener('click', 
                               function(){
                                 textField.value = '';
                                 GM_setValue('search_tag', '');
                               }, true);
  textField.parentNode.appendChild(clearButton);
})();