logger.ts

import winston, { format } from "winston";
import DailyRotateFile from "winston-daily-rotate-file";

const winstonLogger = winston.createLogger({
	format: winston.format.combine(
		format.errors({ stack: true }),
		format.timestamp({
			format: "YYYY-MM-DD HH:mm:ss+ms",
		}),
		format.json()
	),
});
/**
 * This sets up a logger that automatically rotates based on the date, a max size, and has max of 30d of files
 */
const fileLog = new DailyRotateFile({
	createSymlink: true,
	filename: "log-%DATE%.log",
	dirname: "logs",
	datePattern: "YYYY-MM-DD",
	zippedArchive: true,
	maxSize: "20m",
	maxFiles: "30d",
});
winstonLogger.add(fileLog);

const errorLog = new DailyRotateFile({
	createSymlink: true,
	frequency: "1h",
	filename: "error-%DATE%.log",
	dirname: "logs",
	zippedArchive: true,
	datePattern: "YYYY-MM-DD-HH",
	maxSize: "20m",
	maxFiles: "30d",
	level: "error",
});
winstonLogger.add(errorLog);

const consoleLog = new winston.transports.Console({
	level: process.env.LOG_LEVEL || "debug",
});
winstonLogger.add(consoleLog);

type LogOptions = string | JSON | Error;
type LogMessage = (message: LogOptions) => void;
/**
 * Winston does not nicely log Error objects (the resulting entry is empty). This method handles that translation
 * @param message Error or regular LogMessage
 */
const winstonDecorator =
	(log: winston.LeveledLogMethod) => (msg: LogOptions) => {
		if (typeof msg === "string") {
			log(msg);
		} else if (msg instanceof Error) {
			const { message, stack, name } = msg;
			log({ message, stack, name });
		} else {
			log(JSON.stringify(msg));
		}
	};
/**
 * This is a defined interface for logging that closely resembles the winston logging methods. It is unlikely we will want the
 * interface itself to change (ie calling static logger.info/error/debug/etc methods) but we may want to be able
 * to swap out winston should we decide we want a different framework. With this we will
 * not depend on exposed details of the winston interface when using our logger elsewhere in the application,
 * and if we swap it out in the future it will be as simple as calling the underlying logger via the static method
 * declarations
 */
class logger {
	static info: LogMessage = winstonDecorator(
		winstonLogger.info
	);
	static error: LogMessage = winstonDecorator(
		winstonLogger.error
	);
	static debug: LogMessage = winstonDecorator(
		winstonLogger.debug
	);
}

export default logger;