// ==UserScript==
// @name         RSS 订阅链接查找器
// @namespace    https://greasyfork.org/users/1171320
// @version      0.1
// @description  打开网页时，查询可能的 RSS 链接并验证可用性，在网页右下角列举出来。
// @author       Lama AI 辅助
// @match        *://*/*
// @grant        GM_xmlhttpRequest
// @grant        GM_addStyle
// @license MIT
// @downloadURL none
// ==/UserScript==

(function() {
    'use strict';

    const rssLinks = new Set();
    const possibleRssPaths = [
        '/rss',
        '/feed',
        '/atom.xml',
        '/rss.xml',
        '/feed.xml'
        // 可添加其他常见的 RSS 路径
    ];
    const xmlRegex = /<\?xml.*?<rss|<feed/; // 用于检测返回内容是否为 XML/RSS/Atom

     function addStyle() {
         GM_addStyle(`
        #rss-finder-container {
            position: fixed;
            bottom: 20px;
            right: 20px;
            background: #fff;
            border: 1px solid #ccc;
            padding: 10px;
            max-height: 300px;
            overflow-y: auto;
            z-index: 9999;
        }
        #rss-finder-container h4{
           margin:0px;
           margin-bottom:5px;
        }
        #rss-finder-list {
            list-style: none;
            padding: 0;
        }
        #rss-finder-list li {
            margin-bottom: 5px;
        }
        #rss-finder-list a {
            color: blue;
            text-decoration: none;
        }
       `);
    }


    function findRssLinks() {
        // 查找 link 标签
        const linkTags = document.querySelectorAll('link[type="application/rss+xml"], link[type="application/atom+xml"]');
        linkTags.forEach(link => {
            if (link.href) {
                addRssLink(link.href);
            }
        });

         // 尝试猜测 RSS 路径
        possibleRssPaths.forEach(path => {
            const guessedUrl = window.location.origin + path;
            addRssLink(guessedUrl);
        });


    }



    function addRssLink(url) {
        if(rssLinks.has(url)) return;

        GM_xmlhttpRequest({
             method: 'GET',
            url: url,
            onload: function(response) {
                if (response.status === 200 && xmlRegex.test(response.responseText)) {
                        rssLinks.add(url);
                        updateRssList();
                 }
           },
               onerror: function(error){
            //  预加载失败，打印错误信息
                console.log(`加载失败: ${url}`, error);
         }
       });
   }

    function updateRssList() {
          let container = document.getElementById('rss-finder-container');
          if(!container){
             container = document.createElement('div');
             container.id = 'rss-finder-container';
              container.innerHTML = '<h4>可用RSS订阅:</h4><ul id="rss-finder-list"></ul>';
             document.body.appendChild(container);
          }

         const list = container.querySelector('#rss-finder-list');
         list.innerHTML = '';

        rssLinks.forEach(url => {
            const li = document.createElement('li');
            const a = document.createElement('a');
            a.href = url;
            a.target = '_blank';
            a.rel = 'noopener noreferrer';
            a.textContent = url;
            li.appendChild(a);
            list.appendChild(li);
        });
    }

    addStyle();
    findRssLinks();

})();