logger.js

var chalk = require('chalk');
var util = require('util');

'use strict';

module.exports = {
  Logger: Logger,
  setDebugEnabled: setDebugEnabled,
  _system: new Logger() // system logger, for internal use only
}

var DEBUG_ENABLED = false;

// Turns on debug level logging
function setDebugEnabled(enabled) {
  DEBUG_ENABLED = enabled;
}

// global cache of logger instances by plugin name
var loggerCache = {};

/**
 * Logger class
 */

function Logger(prefix) {
  this.prefix = prefix;
}

Logger.prototype.debug = function(msg) {
  if (DEBUG_ENABLED)
    this.log.apply(this, ['debug'].concat(Array.prototype.slice.call(arguments)));
}
  
Logger.prototype.info = function(msg) {
  this.log.apply(this, ['info'].concat(Array.prototype.slice.call(arguments)));
}

Logger.prototype.warn = function(msg) {
  this.log.apply(this, ['warn'].concat(Array.prototype.slice.call(arguments)));
}

Logger.prototype.error = function(msg) {
  this.log.apply(this, ['error'].concat(Array.prototype.slice.call(arguments)));
}
  
Logger.prototype.log = function(level, msg) {
  
  msg = util.format.apply(util, Array.prototype.slice.call(arguments, 1));
  func = console.log;
  
  if (level == 'debug') {
    msg = chalk.gray(msg);
  }
  else if (level == 'warn') {
    msg = chalk.yellow(msg);
    func = console.error;    
  }
  else if (level == 'error') {
    msg = chalk.bold.red(msg);
    func = console.error;
  }
  
  // prepend prefix if applicable
  if (this.prefix)
    msg = chalk.cyan("[" + this.prefix +  "]") + " " + msg;
  
  // prepend timestamp
  var date = new Date();
  msg = "[" + date.toLocaleString() + "]" + " " + msg;

  func(msg);
}
  
Logger.withPrefix = function(prefix) {

  if (!loggerCache[prefix]) {
    // create a class-like logger thing that acts as a function as well
    // as an instance of Logger.
    var logger = new Logger(prefix);
    var log = logger.info.bind(logger);
    log.debug = logger.debug;
    log.info = logger.info;
    log.warn = logger.warn;
    log.error = logger.error;
    log.log = logger.log;
    log.prefix = logger.prefix;
    loggerCache[prefix] = log;
  }
  
  return loggerCache[prefix];
}