How to add runtime type safety using zod when using external api's

zod-external-api-example-no-validation.ts

interface User {
  id: number;
  name: string;
  email: string;
  address?: string;
}

interface GetUserByIdParams {
  id: User["id"];
  filter: { [k in keyof User]: User[k] };
}

interface Weather {
  summary: string;
  max: number;
  min: number;
  chanceOfRain: number;
}

interface UserWeatherResponse {
  user: User;
  weather: Weather;
}

function getUserService() {
  return {
    getUserById: (id: User["id"]) => ({
      id,
      name: "John Doe",
      email: "[email protected]",
    }),
  };
}

function getWeatherFromGoogleApi(address: string): Weather {
  const responseFromGoogle = {
    summary: "It will be a nice sunny day",
    max: 20,
    min: 20,
    chanceOfRain: 0,
    humidity: 10,
  };

  return {
    summary: responseFromGoogle.summary,
    max: responseFromGoogle.max,
    min: responseFromGoogle.min,
    chanceOfRain: responseFromGoogle.chanceOfRain,
  };
}

function getWeatherService() {
  return {
    getWeatherForUser: (user: User) =>
      getWeatherFromGoogleApi(user.address ?? ""),
  };
}

const userService = getUserService();
const weatherService = getWeatherService();

export const getUserWeather = (
  params: GetUserByIdParams
): UserWeatherResponse => {
  const user = userService.getUserById(params.id);
  const weather = weatherService.getWeatherForUser(user);

  return {
    user,
    weather,
  };
};