path: root/lib/cologne.js

'use strict';

const Utilities = require('./utilities');

const internals = {

  // Maps log levels to their syslog labels

  kLevelStrings: [
    'emerg',
    'alert',
    'crit',
    'error',
    'warning',
    'notice',
    'info',
    'debug'
  ],

  // Version of the Cologne Log Format used

  kLogVersion: '2.0.0'
};

/** TYPE DEFINITIONS **/

/**
 * Main interface for Cologne Loggers
 *
 * @interface ILogger
 */

/**
 * Receives any number of cologne log objects and logs them.
 *
 * @memberof ILogger
 * @function
 * @name log
 */

/**
 * Main interface for Cologne Formatters
 *
 * @interface IFormatter
 */

/**
 * Receives a cologne log object and returns a formatted string.
 *
 * @memberof IFormatter
 * @function
 * @name format
 * @param {tCologneLog} logObject the log to be formatted
 * @returns {string} the formatted log
 */

/**
 * The main cologne log format.
 *
 * @typedef {object} tCologneLog
 * @property {Bigint} _timestamp the timestamp in nanoseconds
 * @property {String} _cologneLog main identifier, encodes the version of the
 * cologne log format being used.
 * @property {String} _from the origin of the log message.
 * @property {String} _level the severity level of the log, uses syslog
 * priorities.
 * @property {String} _levelString the severity level keyword of the log,
 * uses syslog priority keywords.
 */

/**
 * The main logger class. It can be instantiated with loggers in order to
 * send messages to different destinations.
 *
 * @class Cologne
 */
const Cologne = class Cologne {

  constructor(config) {

    /**
     * The name of this logger, useful to distinguish between different
     * loggers.
     *
     * @name from
     * @instance
     * @memberof Cologne
     * @type String
     * @default 'Generic Cologne Logger
     */
    this.from = 'Generic Cologne Logger';

    /**
     * The array containing all the loggers it will call to.
     *
     * @name loggers
     * @instance
     * @memberof Cologne
     * @type ILogger[]
     * @default []
     */
    this.loggers = [];

    Object.assign(this, config);
  }

  /**
   * Adds a logger to the current instance.
   *
   * @function addLogger
   * @instance
   * @memberof Cologne
   * @param {ILogger} logger the logger to add
   */
  addLogger(logger) {

    this.loggers.push(logger);
  }

  /**
   * Removes a logger from the current instance.
   *
   * @function removeLogger
   * @instance
   * @memberof Cologne
   * @param {ILogger} logger the logger to remove
   * @return {ILogger[]} the removed log, inside an array.
   */
  removeLogger(logger) {

    const index = this.loggers.indexOf(logger);
    if (index >= 0) {
      this.loggers.splice(index, 1);
    }
  }

  /**
   * Given a message, it builds a cologne log object without logging it.
   * If you send a cologne log object, it will only update the level.
   *
   * If the message is an object, the log object will be extended with
   * its properties.
   *
   * @function buildLog
   * @instance
   * @memberof Cologne
   * @param {*} message The message to log
   * @param {number} [level=6] The level of the message to log
   * @return {tCologneLog} a cologne log object
   */
  buildLog(rawMessage, level) {

    if (typeof rawMessage === 'undefined' || rawMessage === null || !rawMessage._cologneLog) {

      const message = typeof rawMessage === 'object' ? Utilities.stringify(rawMessage) : rawMessage;

      const logObject = {
        message: String(message),
        _cologneLog: internals.kLogVersion,
        _from: this.from,
        _level: level || 6,
        _timestamp: Utilities.now()
      };

      logObject._levelString = internals.kLevelStrings[logObject._level];

      if (typeof rawMessage === 'object') {
        Object.assign(logObject, rawMessage);
      }

      return logObject;
    }

    rawMessage._level = level || rawMessage._level;
    rawMessage._levelString = internals.kLevelStrings[rawMessage._level];

    return rawMessage;
  }

  /**
   * Default log function. Sends arguments to loggers. If not specified in log
   * object, it will set the severity to 6 - INFO.
   *
   * @function log
   * @instance
   * @memberof Cologne
   */
  log(...logs) {

    this._log(null, ...logs);
  }

  /**
   * Logs with debug level
   *
   * @function debug
   * @instance
   * @memberof Cologne
   */
  debug(...logs) {

    this._log(7, ...logs);
  }

  /**
   * Logs with info level
   *
   * @function info
   * @instance
   * @memberof Cologne
   */
  info(...logs) {

    this._log(6, ...logs);
  }

  /**
   * Logs with notice level
   *
   * @function notice
   * @instance
   * @memberof Cologne
   */
  notice(...logs) {

    this._log(5, ...logs);
  }

  /**
   * Logs with warn level
   *
   * @function warn
   * @instance
   * @memberof Cologne
   */
  warn(...logs) {

    this._log(4, ...logs);
  }

  /**
   * Logs with error level
   *
   * @function error
   * @instance
   * @memberof Cologne
   */
  error(...logs) {

    this._log(3, ...logs);
  }

  // Private method that builds all the logs and sends them to the loggers.

  _log(level, ...logs) {

    const structuredLogs = logs.map((log) => this.buildLog(log, level));

    for (const logger of this.loggers) {
      logger.log(...structuredLogs);
    }
  }
};

/**
 * Namespace that includes the built-in formatters.
 *
 * @namespace Formatters
 */
const Formatters = {};
Formatters.Simple = require('./formatters/simple');
Formatters.Token = require('./formatters/token');

/**
 * Namespace that includes the built-in loggers.
 *
 * @namespace Loggers
 */
const Loggers = {};
Loggers.Console = require('./loggers/console');
Loggers.File = require('./loggers/file');

module.exports = {
  Cologne,
  Formatters,
  Loggers,
  Utilities
};