src/utils/formatters/single-post-formatter.js from tningjs/sam-and-his-friends

src/utils/formatters/single-post-formatter.js
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/**
 * @module utils/formatters/single-post-formatter
 */
const { JSDOM } = require('jsdom');
const Readability = require('readability');

const { getActiveUserFromCache } = require('../../data/cache/active-users');
const {
    addPostToCache,
    getPostFromCache,
} = require('../../data/cache/single-post');
const {
    commentsFormatter,
} = require('../../utils/formatters/comments-formatter');
const { tagsFormatter } = require('../../utils/formatters/tags-formatter');
const { metaDescription, siteTitle, username } = require('../../utils/config');

function getJsdom(cooked = '') {
    return new JSDOM(`<!DOCTYPE html>${cooked}`);
}

function getImages(jsdom) {
    const imgElements = jsdom.window.document.querySelectorAll('img');
    return Array.from(imgElements).map(imgElement => ({
        srcStr: imgElement.getAttribute('src'),
        altStr: imgElement.getAttribute('alt') || '',
    }));
}

function getExcerpt(jsdom) {
    const article = new Readability(jsdom.window.document).parse();
    const { textContent, excerpt } = article;
    // Readability.js return first p as excerpt
    const extractedContent =
        excerpt && excerpt.startsWith('摘要') ? excerpt : textContent;
    return `${extractedContent.slice(0, 150)}...`;
}

/**
 * Format single post from API data for rendering
 * @param {object} postData - Data from API
 * @returns {object} Formatted post
 */
exports.singlePostFormatter = async function singlePostFormatter(postData) {
    const poster = await getActiveUserFromCache(postData.details.created_by.id);
    // Owner means the website owner who create article in index page
    const isPosterSiteOwner = username === poster.username.slice(1); // poster.username begins with `@`
    const { title, views, like_count: numLikes } = postData;
    const numComments = postData.posts_count + postData.reply_count;
    const comments = await commentsFormatter(postData.post_stream.posts.slice(1));
    const tags = tagsFormatter(postData.category_id);
    const post = postData.post_stream.posts[0];
    const cachedPost = await getPostFromCache(postData.id);

    // Only create JSDOM if the post is not in cache
    if (!cachedPost) {
        const jsdom = getJsdom(post.cooked);

        // Notice: getImages() has to be called before getExcerpt(). Because new Readability().parse() modify jsdom object
        Object.assign(post, {
            heroImage: getImages(jsdom)[0],
            excerpt: getExcerpt(jsdom),
        });

        addPostToCache(post);
    }

    return {
        tags,
        title,
        siteTitle: `${siteTitle} | ${title}`,
        views,
        numLikes,
        numComments,
        comments,
        isPosterSiteOwner,
        metaDescription,
        name: poster.name || poster.username,
        excerpt: post.excerpt,
        content: post.cooked,
        date: post.updated_at,
        reads: post.reads,
        heroImage: cachedPost.heroImage || post.heroImage,
        authorImageUrl: poster.userImageUrl,
        userProfileUrl: poster.userProfileUrl,
    };
};