TypeScript Standard Loggerr

logging.ts

import fclone from "fclone";

export enum LogLevel {
  Fatal = -1,
  Error = 0,
  Warn = 1,
  Info = 2,
  Debug = 3,
  Trace = 4,
}

export interface ILogEntry {
  dtm?: Date;
  code: string;
  msg: string;
  [key: string]: any;
}

export interface ILogger {
  level: LogLevel;
  fatal(entry: ILogEntry): void;
  error(entry: ILogEntry): void;
  warn(entry: ILogEntry): void;
  info(entry: ILogEntry): void;
  debug(entry: ILogEntry): void;
  trace(entry: ILogEntry): void;
}

function parseLogLevel(input: LogLevel | string): LogLevel {
  switch (String(input).toLowerCase().trim()) {
    case "-1":
    case "fata;":
      return LogLevel.Fatal;
    case "0":
    case "err":
    case "error":
      return LogLevel.Error;
    case "1":
    case "warn":
    case "warning":
      return LogLevel.Warn;
    case "2":
    case "info":
    case "information":
      return LogLevel.Info;
    case "3":
    case "debuf":
      return LogLevel.Debug;
    case "4":
    case "trace":
      return LogLevel.Trace;
  }
  return LogLevel.Info;
}

function stringifyLogLevel(input: LogLevel): string {
  switch (input) {
    case LogLevel.Fatal:
      return "FATAL";
    case LogLevel.Error:
      return "ERROR";
    case LogLevel.Warn:
      return "WARM";
    case LogLevel.Info:
      return "INFO";
    case LogLevel.Debug:
      return "DEBUG";
    case LogLevel.Trace:
      return "TRACE";
  }
  return 'UNKNOWN'; // should *NEVER* happen
}

export class StandardLogger implements ILogger {
  level: LogLevel;
  contextInfo: any;

  constructor(level: LogLevel | string = LogLevel.Info, contextInfo?: any) {
    this.level = parseLogLevel(level);
    this.contextInfo = contextInfo;
  }

  log(level: LogLevel | string, entry: ILogEntry): void {
    if (level > this.level) return; // nothing to log
    if (level === LogLevel.Error) {
      console.error({
        level: stringifyLogLevel(level),
        dtm: new Date(),
        ...this.contextInfo,
        ...fclone(entry),
      });
      return;
    }
    console.log({ dtm: new Date(), ...this.contextInfo, ...fclone(entry) });
  }

  fatal(entry: ILogEntry): void {
    this.log(LogLevel.Fatal, entry);
  }
  error(entry: ILogEntry): void {
    this.log(LogLevel.Error, entry);
  }
  warn(entry: ILogEntry): void {
    this.log(LogLevel.Warn, entry);
  }
  info(entry: ILogEntry): void {
    this.log(LogLevel.Info, entry);
  }
  debug(entry: ILogEntry): void {
    this.log(LogLevel.Debug, entry);
  }
  trace(entry: ILogEntry): void {
    this.log(LogLevel.Trace, entry);
  }
}