import type { ReadonlyJSONObject } from "assistant-stream/utils";

export class CloudResponseError extends Error {
  constructor(message: string) {
    super(message);
    this.name = "CloudResponseError";
  }
}

const invalidCloudResponse = (field: string, expected: string) =>
  new CloudResponseError(
    `Invalid Assistant Cloud response for "${field}": expected ${expected}`,
  );

export const readCloudRecord = (
  value: unknown,
  field: string,
): Record<string, unknown> => {
  if (typeof value !== "object" || value === null || Array.isArray(value)) {
    throw invalidCloudResponse(field, "an object");
  }
  return value as Record<string, unknown>;
};

export const readCloudArray = (value: unknown, field: string): unknown[] => {
  if (!Array.isArray(value)) throw invalidCloudResponse(field, "an array");
  return value;
};

export const readCloudString = (value: unknown, field: string): string => {
  if (typeof value !== "string") throw invalidCloudResponse(field, "a string");
  return value;
};

export const readCloudNullableString = (
  value: unknown,
  field: string,
): string | null => {
  if (value === null) return null;
  return readCloudString(value, field);
};

export const readCloudBoolean = (value: unknown, field: string): boolean => {
  if (typeof value !== "boolean") {
    throw invalidCloudResponse(field, "a boolean");
  }
  return value;
};

export const readCloudInteger = (value: unknown, field: string): number => {
  if (!Number.isInteger(value)) throw invalidCloudResponse(field, "an integer");
  return value as number;
};

export const readCloudTimestamp = (value: unknown, field: string): Date => {
  if (typeof value !== "string") {
    throw invalidCloudResponse(field, "a canonical ISO timestamp");
  }

  const date = new Date(value);
  // The round trip pins the backend DTO's Date#toISOString() wire contract.
  if (Number.isNaN(date.getTime()) || date.toISOString() !== value) {
    throw invalidCloudResponse(field, "a canonical ISO timestamp");
  }

  return date;
};

export const readCloudJSONObject = (
  value: unknown,
  field: string,
): ReadonlyJSONObject => readCloudRecord(value, field) as ReadonlyJSONObject;