import chalk from 'chalk';

export interface LoggerOptions {
  /** Whether to prepend a timestamp to each log message */
  showTimestamp?: boolean;
}

export default class Logger {
  private static instance: Logger;
  private showTimestamp: boolean;

  // Private constructor to prevent direct instantiation.
  private constructor(options: LoggerOptions = {}) {
    this.showTimestamp = options.showTimestamp ?? false;
  }

  /**
   * Returns the singleton instance of Logger.
   * The options are applied only on the first call.
   * @param options Logger configuration options.
   */
  public static getInstance(options: LoggerOptions = {}): Logger {
    if (!Logger.instance) {
      Logger.instance = new Logger(options);
    }
    if (options.showTimestamp !== undefined) {
      Logger.instance.showTimestamp = options.showTimestamp;
    }
    return Logger.instance;
  }

  public debug(...args: any[]): void {
    this.log('debug', ...args);
  }

  public info(...args: any[]): void {
    this.log('info', ...args);
  }

  public warn(...args: any[]): void {
    this.log('warn', ...args);
  }

  public error(...args: any[]): void {
    this.log('error', ...args);
  }

  public success(...args: any[]): void {
    this.log('success', ...args);
  }

  public logErrorAndExit(message: string, exitCode = 1): void {
    this.error(message);
    process.exit(exitCode);
  }

  // Returns an ISO formatted timestamp.
  private getTimestamp(): string {
    return new Date().toISOString();
  }

  /**
   * Logs a message with a colored level tag.
   * @param level - The log level (e.g. 'debug', 'info', 'warn', 'error').
   * @param args - One or more values to log.
   */
  private log(level: string, ...args: any[]): void {
    let colorFn: (text: string) => string;

    switch (level) {
      case 'debug':
        colorFn = chalk.gray;
        break;
      case 'info':
        colorFn = chalk.blue;
        break;
      case 'warn':
        colorFn = chalk.yellow;
        break;
      case 'error':
        colorFn = chalk.red;
        break;
      case 'success':
        colorFn = chalk.green;
        break;
      default:
        colorFn = chalk.white;
    }

    const timestamp =
      this?.showTimestamp === true ? `[${this.getTimestamp()}] ` : '';
    const levelTag = colorFn(`[${level.toUpperCase()}]`);
    console.log(`${timestamp}${levelTag}`, ...args);
  }
}

export const logger = Logger.getInstance({ showTimestamp: true });