gatsby-theme-advanced/gatsby/utils/getRelatedPosts.js

GatsbyJS theme equipped with advanced features.

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
const categoryMappingCache = new Map();
// Get posts of the same category
const getCategoryPosts = (category, listing) => {
    const cachedCategory = categoryMappingCache.get(category);
    if (cachedCategory)
        return cachedCategory;
    listing.forEach((post) => {
        if (post.category === category) {
            const mappedPosts = categoryMappingCache.get(category) || [];
            mappedPosts.push(post);
            categoryMappingCache.set(category, mappedPosts);
        }
    });
    return categoryMappingCache.get(category) || [];
};
// Get post listing ranked by tag matches
const getRankedMatches = (targetPost, listing) => {
    // If the post doesn't have tags, just return the main listing
    if (!targetPost.tags)
        return listing;
    const rankList = [];
    // Add 1 to the ranking value for each tag match
    listing.forEach((post) => {
        let rank = 0;
        if (post.tags) {
            post.tags.forEach((tag) => {
                var _a;
                if ((_a = targetPost.tags) === null || _a === void 0 ? void 0 : _a.includes(tag)) {
                    rank += 1;
                }
            });
        }
        rankList.push({
            rank,
            post,
        });
    });
    // Sort posts by rank
    rankList.sort((a, b) => {
        if (a.rank > b.rank)
            return -1;
        if (a.rank < b.rank)
            return 1;
        return 0;
    });
    // Map ranking to a post list
    return rankList.map((rankedPost) => rankedPost.post);
};
// Get 2 related posts to a target post
const getRelatedPosts = (targetPost, listing) => {
    // Exclude the target post from the listing
    const filteredListing = listing.filter((post) => post.slug !== targetPost.slug);
    const relatedPosts = [];
    if (targetPost.category) {
        // Filter by category
        const categoryPosts = getCategoryPosts(targetPost.category, filteredListing);
        // Rank the matches by tags
        const rankedMatches = getRankedMatches(targetPost, categoryPosts);
        // Select top 2 posts
        relatedPosts.push(...rankedMatches.slice(0, 2));
    }
    // If we have enough posts, return them
    if (relatedPosts.length > 1)
        return relatedPosts;
    // If we have only one category match, add one more tag match
    if (relatedPosts.length === 1) {
        // Get the ranked tag matches
        const rankedTagMatches = getRankedMatches(targetPost, filteredListing);
        // Filter out existing related post
        const filteredTagMatches = rankedTagMatches.filter((tagMatch) => { var _a; return tagMatch.slug !== ((_a = relatedPosts[0]) === null || _a === void 0 ? void 0 : _a.slug); });
        // And return the highest ranked match
        const highestRankedMatch = filteredTagMatches[0];
        if (highestRankedMatch) {
            relatedPosts.push(highestRankedMatch);
            return relatedPosts;
        }
    }
    // If we don't have any category matches,
    // perform a tag ranking on the whole listing and return the top 2 posts
    return getRankedMatches(targetPost, filteredListing).slice(0, 2);
};
exports.default = getRelatedPosts;