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// ==UserScript==
// @name        Qiita filter by updated_at
// @description Add "filter by updated_at" links to Qiita's search page
// @namespace   https://gist.github.com/tkrkt
// @include     http://qiita.com/search?*
// @version     5
// @require     https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.13.0/moment.min.js
// @require     https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.13.0/locale/ja.js
// @require     https://cdnjs.cloudflare.com/ajax/libs/URI.js/1.18.1/URI.min.js
// @grant       none
// ==/UserScript==

const filters = [
  [7, 'd'],
  [1, 'M'],
  [3, 'M'],
  [1, 'y'],
  [3, 'y']
];

const search = URI(location.href).search(true); // e.g. search.q = 'tag:JavaScript updated:>2016-05-30'
const [dateParam, date] = search.q.match(/\s?updated:>([\d-]*)/) || []; // e.g. ['+updated:>2016-05-30', '2016-05-30']
const currentFilter = date ? moment(date, 'YYYY-MM-DD').from(moment().startOf('day')) : '期間指定なし'; // e.g. '一ヶ月前'
const query = search.q.replace(dateParam, ''); // e.g. 'tag:JavaScript'

const span = document.createElement('span');
span.style.padding = '6px 12px';
span.style.display = 'block';

const links = filters.map(([time, amount]) => {
  const m = moment().startOf('day').subtract(time, amount);
  return [' updated:>' + m.format('YYYY-MM-DD'), m.from(moment().startOf('day'))]; // e.g. ['+updated:>2016-05-30', '一ヶ月前']
});

const html = [['', '期間指定なし'], ...links].map(([filterParam, text]) => {
  if (currentFilter === text) {
    return `<span>${text.replace('前', '以内')}</span>`;
  } else {
    return `<a href="${URI(location.href).removeQuery('q').addQuery({q: query + filterParam})}">${text.replace('前', '以内')}</a>`;
  }
}).join(' / ');

span.innerHTML = html;

const container = document.querySelector('form.searchResultContainer_form');
container.appendChild(span);