@dynacom/blaze/lib/logger.js

const path = require('path');
const fs = require('fs-extra');

module.exports = function (options) {
	let config = {
		path: path.join(process.env.BLAZE_INSTANCE, 'logs'),
		maxLogSize: 2000000, // Max size of the log file - falsy for infinite
		logInterval: 86400000 // Interval before creating a new log file - falsy for infinite
	}

	Object.assign(config, options);

	fs.ensureDirSync(config.path);

	return function (logObject) {
		logObject.timestamp = Date.now();

		let upper = Date.now() + config.logInterval;
		let lower = Date.now() - config.logInterval;

		// OpenLogStream
		let existingLog = fs.readdirSync(config.path)
			.sort((a, b) => a < b)
			.find(fileName => {
				let fileNumber = Number(fileName.replace('.log', ''));
				if (fileNumber > upper || fileNumber < lower) {
					return false;
				}
				const stats = fs.statSync(path.join(config.path, fileName));
				return stats.size < config.maxLogSize;
			});

		let logName = existingLog || (Date.now() + '.log');

		let cache = [];
		let jsLine = JSON.stringify(logObject, function (key, value) {
			if (typeof value === 'object' && value !== null) {
				if (cache.indexOf(value) !== -1) {
					// Circular reference found, discard key
					return;
				}
				// Store value in our collection
				cache.push(value);
			}
			return value;
		}) + ',';

		if (null == existingLog) {
			let increment = 1;
			while (fs.existsSync(path.join(config.path, logName))) {
				logName = logName.replace('.log', '').split('-')[0] + '-' + increment + '.log';
				increment++;
			}
			fs.writeFileSync(path.join(config.path, logName), jsLine);
		}
		fs.appendFile(path.join(config.path, logName), jsLine, error => {
			if (error) { throw err };
		});
	}
}