export const LOG_LEVELS = {
  TRACE: "0",
  DEBUG: "1",
  INFO: "2",
  WARN: "3",
  ERROR: "4",
  FATAL: "5",
  OFF: "6",
} as const;
export type LogLevel = (typeof LOG_LEVELS)[keyof typeof LOG_LEVELS];

/**
 * Converts the FAUNA_DEBUG environment variable (string) into a LogLevel.
 *   The intended use is to set FAUNA_DEBUG=0|1|2|3|4.
 *
 *   This function will convert null, undefined, empty, or or any non matching
 *   string to a LogLevel of ERROR.
 *
 * @param debug_level - The String value of FAUNA_DEBUG.
 */
export function parseDebugLevel(debug_level: string | undefined): LogLevel {
  switch (debug_level) {
    case "0":
    case "1":
    case "2":
    case "3":
    case "4":
    case "5":
    case "6":
      return debug_level;
    default:
      return LOG_LEVELS.OFF;
  }
}

export interface LogHandler {
  trace(msg: string, ...args: any[]): void;
  debug(msg: string, ...args: any[]): void;
  info(msg: string, ...args: any[]): void;
  warn(msg: string, ...args: any[]): void;
  error(msg: string, ...args: any[]): void;
  fatal(msg: string, ...args: any[]): void;
}

export class ConsoleLogHandler implements LogHandler {
  readonly #level: LogLevel;
  constructor(level: LogLevel) {
    this.#level = level;
  }

  trace(msg: string, ...args: any[]): void {
    if (this.#level <= LOG_LEVELS.TRACE) {
      console.trace(msg, ...args);
    }
  }

  debug(msg: string, ...args: any[]): void {
    if (this.#level <= LOG_LEVELS.DEBUG) {
      console.debug(msg, ...args);
    }
  }

  info(msg: string, ...args: any[]): void {
    if (this.#level <= LOG_LEVELS.INFO) {
      console.info(msg, ...args);
    }
  }

  warn(msg: string, ...args: any[]): void {
    if (this.#level <= LOG_LEVELS.WARN) {
      console.warn(msg, ...args);
    }
  }

  error(msg: string, ...args: any[]): void {
    if (this.#level <= LOG_LEVELS.ERROR) {
      console.error(msg, ...args);
    }
  }

  fatal(msg: string, ...args: any[]): void {
    if (this.#level <= LOG_LEVELS.FATAL) {
      console.error(msg, ...args);
    }
  }
}

export function defaultLogHandler(): LogHandler {
  return new ConsoleLogHandler(LOG_LEVELS.FATAL);
}