feat(utils): add utils for WeChat MP (#9487)

Motivation:
There are multiple routes that need to fetch articles from WeChat MP.
However, letting them fetch articles by themselves could potentially
lead to cache key collisions. Even if cache key collisions do not occur,
un-normalized URL could potentially lead to duplicated requests.
What's more, articles from WeChat MP have weird formats and need to be
fixed. Creating a universal function to do this work can create some
ease for new route contributors.

Note:
In order to make this PR atomic as much as possible, I did not touch
those broken routes. Once this PR is merged, I will try to fix them.

Signed-off-by: Rongrong <15956627+Rongronggg9@users.noreply.github.com>

test/utils/wechat-mp.js

@@ -0,0 +1,102 @@
+process.env.REQUEST_TIMEOUT = '500';
+const cheerio = require('cheerio');
+const wechatMp = require('../../lib/utils/wechat-mp');
+const nock = require('nock');
+const ctx = require('../../lib/app').context;
+
+afterAll(() => {
+    delete process.env.REQUEST_TIMEOUT;
+});
+
+// date from the cache will be an ISO8601 string, so we need to use this function
+const compareDate = (date1, date2) => {
+    date1 = typeof date1 === 'string' ? new Date(date1) : date1;
+    date2 = typeof date2 === 'string' ? new Date(date2) : date2;
+    return date1.getTime() === date2.getTime();
+};
+
+describe('wechat-mp', () => {
+    it('fixArticleContent', () => {
+        const divHeader = '<div class="rich_media_content " id="js_content">';
+        const divFooter = '</div>';
+
+        const htmlSection =
+            '<section>test</section>' +
+            '<section><p>test</p></section>' +
+            '<section><div>test</div></section>' +
+            '<section><section><section>test</section></section></section>' +
+            '<div><section><p>test</p></section></div>' +
+            '<p>test</p>' +
+            '<div><p>test</p></div>' +
+            '<script>const test = "test"</script>';
+        const expectedHtmlSection = '<p>test</p>' + '<div><p>test</p></div>' + '<div><div>test</div></div>' + '<div><div><p>test</p></div></div>' + '<div><div><p>test</p></div></div>' + '<p>test</p>' + '<div><p>test</p></div>';
+        let $ = cheerio.load(divHeader + htmlSection + divFooter);
+        expect(wechatMp.fixArticleContent(htmlSection)).toBe(expectedHtmlSection);
+        expect(wechatMp.fixArticleContent($('div#js_content.rich_media_content'))).toBe(expectedHtmlSection);
+
+        const htmlImg = '<img alt="test" data-src="http://rsshub.test/test.jpg" src="http://rsshub.test/test.jpg">' + '<img alt="test" data-src="http://rsshub.test/test.jpg">' + '<img alt="test" src="http://rsshub.test/test.jpg">';
+        const expectedHtmlImg = new Array(3 + 1).join('<img alt="test" src="http://rsshub.test/test.jpg">');
+        $ = cheerio.load(divHeader + htmlImg + divFooter);
+        expect(wechatMp.fixArticleContent(htmlImg)).toBe(expectedHtmlImg);
+        expect(wechatMp.fixArticleContent($('div#js_content.rich_media_content'))).toBe(expectedHtmlImg);
+        expect(wechatMp.fixArticleContent(htmlImg, true)).toBe(htmlImg);
+        expect(wechatMp.fixArticleContent($('div#js_content.rich_media_content'), true)).toBe(htmlImg);
+
+        expect(wechatMp.fixArticleContent('')).toBe('');
+        expect(wechatMp.fixArticleContent(null)).toBe('');
+        expect(wechatMp.fixArticleContent(undefined)).toBe('');
+        expect(wechatMp.fixArticleContent($('div#something_not_in.the_document_tree'))).toBe('');
+    });
+
+    it('fetchArticle_&_finishArticleItem', async () => {
+        const ct = 1636626300;
+        const exampleMpArticlePage =
+            '\n' +
+            '<meta name="description" content="summary" />\n' +
+            '<meta name="author" content="author" />\n' +
+            '<meta property="og:title" content="title" />\n' +
+            '<meta property="twitter:card" content="summary" />\n' +
+            '<div class="rich_media_content" id="js_content" style="visibility: hidden;">description</div>\n' +
+            '<div class="profile_inner"><strong class="profile_nickname">mpName</strong></div>\n' +
+            '<script type="text/javascript" nonce="000000000">\n' +
+            'var appmsg_type = "9";\n' +
+            `var ct = "${ct}";\n` +
+            '</script>';
+
+        nock('https://mp.weixin.qq.com')
+            .get('/rsshub_test/wechatMp_fetchArticle')
+            .reply(() => [200, exampleMpArticlePage]);
+        const httpsUrl = 'https://mp.weixin.qq.com/rsshub_test/wechatMp_fetchArticle';
+        const httpUrl = httpsUrl.replace(/^https:\/\//, 'http://');
+
+        let _ret;
+        try {
+            _ret = await wechatMp.fetchArticle(ctx, 'https://im.not.wechat.mp/and/an/error/is/expected');
+        } catch (e) {
+            expect(e.name).toBe('Error');
+        }
+
+        expect(_ret).toBeUndefined();
+
+        const expectedItem = {
+            title: 'title',
+            summary: 'summary',
+            author: 'author',
+            description: 'description',
+            mpName: 'mpName',
+            link: httpsUrl,
+        };
+        const expectedDate = new Date(ct * 1000);
+
+        const fetchArticleItem = await wechatMp.fetchArticle(ctx, httpUrl);
+        expect(compareDate(fetchArticleItem.pubDate, expectedDate)).toBe(true);
+        delete fetchArticleItem.pubDate;
+        expect(fetchArticleItem).toEqual(expectedItem);
+
+        delete expectedItem.mpName;
+        const finishArticleItem = await wechatMp.finishArticleItem(ctx, { link: httpUrl });
+        expect(compareDate(finishArticleItem.pubDate, expectedDate)).toBe(true);
+        delete finishArticleItem.pubDate;
+        expect(finishArticleItem).toEqual(expectedItem);
+    });
+});