// Implementing logger class with Winston 3, using custom label and singleton pattern
// logger/index.js
const { createLogger, format, transports } = require("winston");
const { combine, timestamp, colorize, label, printf } = format;

const myFormat = printf(info => {
  return `${info.timestamp} [${info.label}] ${info.level}: ${
    typeof info.message === "string"
      ? info.message
      : JSON.stringify(info.message, null, "\t")
  }`;
});

const logger = (id = "main") => {
  if (this._logger && this._logger.id === id) return this._logger;
  this._logger = createLogger({
    format: combine(label({ label: id }), colorize(), timestamp(), myFormat),
    transports: [new transports.Console()],
    level: "debug"
  });
  this._logger.id = id;
  return this._logger;
};

module.exports = logger;


// usage
const logger = require("../logger")("Custom-Label");
logger.info("Info message");
logger.error("Error message");