import { extractFrames, Frame, isCommonFrame } from "./stack";

export interface Runtime {
  objToStderr(obj: unknown): void;
}

class defaultRuntime implements Runtime {
  objToStderr(obj: unknown): void {
    console.log(obj);
  }
}

export default {
  TimestampFieldName: "time",
  TimestampFieldFormatter: (time: Date): string => time.toISOString(),

  LevelFieldName: "level",
  LevelTraceValue: "trace",
  LevelDebugValue: "debug",
  LevelInfoValue: "info",
  LevelWarnValue: "warn",
  LevelErrorValue: "error",
  LevelFatalValue: "fatal",

  MessageFieldName: "message",

  ErrorFieldName: "error",
  ErrorFieldFormatter: (err: unknown): string | undefined => {
    if (err === null || err === undefined) {
      return undefined;
    } else if (isError(err)) {
      return `${err.name}: ${err.message}`;
    } else if (isErrorLike(err)) {
      return err.message;
    } else if (typeof err === "object") {
      return JSON.stringify(err);
    } else {
      return String(err);
    }
  },

  CallerFieldName: "caller",

  StackFieldName: "stack",
  StackFieldFormatter: (err: unknown): Frame[] | undefined =>
    isError(err)
      ? extractFrames(err.stack)?.filter((frame) => !isCommonFrame(frame))
      : undefined,

  Runtime: new defaultRuntime() as Runtime,

  /** The ParamHook allows us to pass a function in which can populate additional fields into all log messages */
  ParamHook: (): Record<string, string | number | boolean> => {
    return {};
  },
};

function isError(err: unknown): err is Error {
  return err instanceof Error;
}

function isErrorLike(err: unknown): err is { message: string } {
  return typeof err === "object" && err !== null && "message" in err;
}