Metalsmith plugin to transform one JSON array to multiple "files" in the metalsmith chain

jsonToFiles.js

const _ = require('lodash');
const path = require('path');

/**
 * metalsmith plugin that transforms one JSON array to multiple "files" in the metalsmith chain
 *
 * A JSON file is taken by the plugin if a ".json" extension is detected + it has a "type: collection" metadata.
 * Each object in the JSON array must at least have a "path" key to generate the fake file path.
 * All other properties are set on the file object.
 *
 * for example, if you have a "examples.json" file containing:
 *
 * ---
 * type: collection
 * ---
 * [
 *   {"contents": "This is some content", "path": "example-1.html"},
 *   {"contents": "This is some other content with meta data", "date": "2016-01-01", "path": "example-2"}
 * ]
 *
 * the metalsmith files object will be filled with:
 *
 * {
 *  "examples/example-1.html": {
 *    "contents": "This is some content"
 *  },
 *  "examples/example-2.txt": {
 *    "contents": "This is some other content with meta data",
 *    "date": "2016-01-01"
 *  }
 * }
 */
module.exports = () => (files, metalsmith, done) => {
	setImmediate(done);

	let cylonFiles = {}; // these look like files. But they aren't.

	Object.keys(files).forEach((file) => {
		const data = files[file];

		// only check json file that are set as "collection"
		if (path.extname(file) !== '.json' || data.type !== 'collection') {
			return true;
		}

		const collectionName = path.basename(file, '.json');
		const json = JSON.parse(data.contents);

		// add our data to a temporary object to prevent loop issues
		_.extend(cylonFiles, getFilesObjectForCollection(json, collectionName));

		// do not keep the original JSON in the metalsmith chain
		delete files[file];
	});

	_.extend(files, cylonFiles);
};

function getFilesObjectForCollection(json, collectionName) {
	const result = {};
	_.forEach(json, (line) => {
		const extension = path.extname(line.path) ? '' : '.txt';
		const filepath = path.join(collectionName, line.path + extension);
		delete line.path;
		result[filepath] = line;
	});
	return result;
}