Source: node_modules/mongodb-core/lib/connection/logger.js

"use strict";

var f = require('util').format
  , MongoError = require('../error');

// Filters for classes
var classFilters = {};
var filteredClasses = {};
var level = null;
// Save the process id
var pid = process.pid;
// current logger
var currentLogger = null;

/**
 * Creates a new Logger instance
 * @class
 * @param {string} className The Class name associated with the logging instance
 * @param {object} [options=null] Optional settings.
 * @param {Function} [options.logger=null] Custom logger function;
 * @param {string} [options.loggerLevel=error] Override default global log level.
 * @return {Logger} a Logger instance.
 */
var Logger = function(className, options) {
  if(!(this instanceof Logger)) return new Logger(className, options);
  options = options || {};

  // Current reference
  var self = this;
  this.className = className;

  // Current logger
  if(currentLogger == null && options.logger) {
    currentLogger = options.logger;
  } else if(currentLogger == null) {
    currentLogger = console.log;
  }

  // Set level of logging, default is error
  if(level == null) {
    level = options.loggerLevel || 'error';
  }

  // Add all class names
  if(filteredClasses[this.className] == null) classFilters[this.className] =  true;
}

/**
 * Log a message at the debug level
 * @method
 * @param {string} message The message to log
 * @param {object} object additional meta data to log
 * @return {null}
 */
Logger.prototype.debug = function(message, object) {
  if(this.isDebug()
    && ((Object.keys(filteredClasses).length > 0 && filteredClasses[this.className])
      || (Object.keys(filteredClasses).length == 0 && classFilters[this.className]))) {
    var dateTime = new Date().getTime();
    var msg = f("[%s-%s:%s] %s %s", 'DEBUG', this.className, pid, dateTime, message);        
    var state = {
      type: 'debug', message: message, className: this.className, pid: pid, date: dateTime
    };
    if(object) state.meta = object;
    currentLogger(msg, state);
  }
}

/**
 * Log a message at the info level
 * @method
 * @param {string} message The message to log
 * @param {object} object additional meta data to log
 * @return {null}
 */
Logger.prototype.info = function(message, object) {
  if(this.isInfo()
    && ((Object.keys(filteredClasses).length > 0 && filteredClasses[this.className])
      || (Object.keys(filteredClasses).length == 0 && classFilters[this.className]))) {
    var dateTime = new Date().getTime();
    var msg = f("[%s-%s:%s] %s %s", 'INFO', this.className, pid, dateTime, message);
    var state = {
      type: 'info', message: message, className: this.className, pid: pid, date: dateTime
    };
    if(object) state.meta = object;
    currentLogger(msg, state);
  }
},

/**
 * Log a message at the error level
 * @method
 * @param {string} message The message to log
 * @param {object} object additional meta data to log
 * @return {null}
 */
Logger.prototype.error = function(message, object) {
  if(this.isError()
    && ((Object.keys(filteredClasses).length > 0 && filteredClasses[this.className])
      || (Object.keys(filteredClasses).length == 0 && classFilters[this.className]))) {
    var dateTime = new Date().getTime();
    var msg = f("[%s-%s:%s] %s %s", 'ERROR', this.className, pid, dateTime, message);
    var state = {
      type: 'error', message: message, className: this.className, pid: pid, date: dateTime
    };
    if(object) state.meta = object;
    currentLogger(msg, state);
  }
},

/**
 * Is the logger set at info level
 * @method
 * @return {boolean}
 */
Logger.prototype.isInfo = function() {
  return level == 'info' || level == 'debug';
},

/**
 * Is the logger set at error level
 * @method
 * @return {boolean}
 */
Logger.prototype.isError = function() {
  return level == 'error' || level == 'info' || level == 'debug';
},

/**
 * Is the logger set at debug level
 * @method
 * @return {boolean}
 */
Logger.prototype.isDebug = function() {
  return level == 'debug';
}

/**
 * Resets the logger to default settings, error and no filtered classes
 * @method
 * @return {null}
 */
Logger.reset = function() {
  level = 'error';
  filteredClasses = {};
}

/**
 * Get the current logger function
 * @method
 * @return {function}
 */
Logger.currentLogger = function() {
  return currentLogger;
}

/**
 * Set the current logger function
 * @method
 * @param {function} logger Logger function.
 * @return {null}
 */
Logger.setCurrentLogger = function(logger) {
  if(typeof logger != 'function') throw new MongoError("current logger must be a function");
  currentLogger = logger;
}

/**
 * Set what classes to log.
 * @method
 * @param {string} type The type of filter (currently only class)
 * @param {string[]} values The filters to apply
 * @return {null}
 */
Logger.filter = function(type, values) {
  if(type == 'class' && Array.isArray(values)) {
    filteredClasses = {};

    values.forEach(function(x) {
      filteredClasses[x] = true;
    });
  }
}

/**
 * Set the current log level
 * @method
 * @param {string} level Set current log level (debug, info, error)
 * @return {null}
 */
Logger.setLevel = function(_level) {
  if(_level != 'info' && _level != 'error' && _level != 'debug') throw new Error(f("%s is an illegal logging level", _level));
  level = _level;
}

module.exports = Logger;
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