gurubot2/app/modules/logger.js

const winston = require('winston');

const { splat, colorize, combine, timestamp, printf } = winston.format;

function getLogLevel(config) {
    if (process.env.LOG_LEVEL) {
        return process.env.LOG_LEVEL;
    }

    if (config.__DEV__) {
        return 'debug';
    }
    if (config.__PROD__) {
        return 'error';
    }

    return 'verbose';
}

function getLogger(config) {
    const logLevel = getLogLevel(config);

    return winston.createLogger({
        transports: [
            new (winston.transports.Console)({
                name: 'info-console',
                colorize: !config.__PROD__,
                format: combine(
                    timestamp(),
                    colorize(),
                    splat(),
                    printf(({ timestamp: time, level, message, meta }) => {
                        let metaString = '';
                        if (meta) {
                            metaString = JSON.stringify(meta);
                        }

                        return `[${time}] ${level}: ${message} ${metaString}`;
                    })
                ),
                timestamp: true,
                level: logLevel
            })
        ]
    });
}

module.exports = { getLogger };