metalsmith_feed.js

module.exports = function(options) {
  if (options == null) {
    options = {};
  }
  const RSS = require('rss');
  const url = require('url');

  const limit = options.limit != null ? options.limit : 20;
  const destination = options.destination || 'rss.xml';
  const collectionName = options.collection;

  if (!collectionName) {
    throw new Error('collection option is required');
  }

  return function(files, metalsmith, done) {
    const metadata = metalsmith.metadata();

    if (!metadata.collections) {
      return done(
        new Error('no collections configured - see metalsmith-collections')
      );
    }

    let collection = metadata.collections[collectionName];

    const feedOptions = {
      ...metadata.site,
      ...options,
      site_url: metadata.site != null ? metadata.site.url : undefined,
      generator: 'metalsmith-feed'
    };

    const siteUrl = feedOptions.site_url;
    if (!siteUrl) {
      return done(
        new Error('either site_url or metadata.site.url must be configured')
      );
    }

    if (feedOptions.feed_url == null) {
      feedOptions.feed_url = url.resolve(siteUrl, destination);
    }

    const feed = new RSS(feedOptions);
    if (limit) {
      collection = collection.slice(0, limit);
    }
    const preprocess = options.preprocess || (file => file);
    for (let file of collection) {
      const itemData = {
        ...file,
        description: file.less || file.excerpt || file.contents
      };
      if (!itemData.url && itemData.path) {
        itemData.url = url.resolve(siteUrl, itemData.path);
      }
      if (itemData.link) {
        itemData.guid = itemData.url;
        itemData.url = itemData.link;
      }
      feed.item(preprocess(itemData));
    }

    files[destination] = {contents: new Buffer(feed.xml(), 'utf8')};
    return done();
  };
};