module.exports = {
    initialiseLogger: function (config, winston, Elasticsearch) {
      const { format } = winston;
      const { combine, timestamp } = format;

      let env = 'dev';
      if (process.env.NODE_ENV === 'production') {
        env = 'prod';
      }

      // Custom format function that will look for an error object and log out the stack and if
      // its not production, the error itself
      const myFormat = format.printf((info) => {
        const { timestamp: tmsmp, level, message, error, ...rest } = info;
        let log = `${tmsmp} - ${level}:\t${message}`;
        // Only if there is an error
        if ( error ) {
          if ( error.stack) log = `${log}\n${error.stack}`;
          if (process.env.NODE_ENV !== 'production') log = `${log}\n${JSON.stringify(error, null, 2)}`;
        }
        // Check if rest is object
        if ( !( Object.keys(rest).length === 0 && rest.constructor === Object ) ) {
          log = `${log}\n${JSON.stringify(rest, null, 2)}`;
        }
        return log;
      });

      const esTransportOpts = {
        level: 'info',
        indexPrefix: 'logs_denbot',
        clientOpts: {
            host: config.elasticsearch.elasticsearch_address,
            log: 'info'
        },
        transformer: logData => {
            return {
              timestamp: new Date().toISOString(),
              severity: logData.level,
              message: logData.message,
              meta: {
                app: 'denbot',
                env: env,
                stack: logData.meta.stack
              }
            }
        }
      };

      const logger = winston.createLogger({
        level: 'info',
        format: combine(
          winston.format.errors({ stack: true }), // <-- use errors format
          winston.format.timestamp(),
          winston.format.prettyPrint(),
          myFormat,
          winston.format.json()
        ),
        defaultMeta: { service: 'user-service' },
        transports: [
          new winston.transports.File({ filename: 'error.log', level: 'error' }),
          new winston.transports.File({ filename: 'combined.log' }),
          new Elasticsearch(esTransportOpts)
        ],
      });

      //
      // If we're not in production then log to the `console` with the format:
      // `${info.level}: ${info.message} JSON.stringify({ ...rest }) `
      //
      //if (process.env.NODE_ENV !== 'production') {
        logger.add(new winston.transports.Console({
          format: winston.format.simple(),
        }));
      //}

      return logger;
    },
  };