Koa Logger

'use strict';

// Example Usage:
// const logger: any = require("./logger.js");
// const app = new Koa();
// app.use(logger());


const chalk = require('chalk');
const winston = require("winston");

const STATUS_COLORS = {
  error: 'red',
  warn: 'yellow',
  info: 'green'
};


const winstonInstance = winston.createLogger({
  level: 'info',
  format: winston.format.json(),
  defaultMeta: { service: 'user-service' },
  transports: [
    new winston.transports.File({ filename: 'error.log', level: 'error' }),
    new winston.transports.File({ filename: 'combined.log' })
  ]
});


function logger(winstonInstance) {
  return async (ctx, next) => {
    const start = new Date();
    await next();
    const ms = new Date() - start;

    let logLevel;
    if (ctx.status >= 500) {
      logLevel = 'error';
    }
    if (ctx.status >= 400) {
      logLevel = 'warn';
    }
    if (ctx.status >= 100) {
      logLevel = 'info';
    }

    let msg = (chalk.gray(`${ctx.method} ${ctx.originalUrl}`) +
      chalk[STATUS_COLORS[logLevel]](` ${ctx.status} `) +
      chalk.gray(`${ms}ms`));

    winstonInstance.log(logLevel, msg);
  };
}

module.exports = () => logger(winstonInstance);