TasksLoading.ts

export function loadStories(userId: string) {
  return Task.map2(
    myStories => storiesSharedWithMe =>
      ({
        myStories,
        storiesSharedWithMe,
      }),

    userStories(userId).map(listToLookup),
    userSharedStories(userId).map(listToLookup),
  );
}

function userStories(uid: string) {
  return db.storiesCollection()
    .where("owner", "==", uid)
    .andThen(({ docs }) => docs.map(validateStory).andThen(Task.all));
}

function usersThatShareWithMe(uid: string) {
  return db.usersCollection()
    .where("editors", "array-contains", uid)
    .map(({ docs }) => docs);
}

function userSharedStories(uid: string) {
  return usersThatShareWithMe(uid).andThen(users =>
    users
      .map(({ id }) => userStories(id))
      .andThen(Task.all)
      .map(flatten),
  );
}

function listToLookup<T extends { id: string }>(
  items: T[],
): { [key: string]: T } {
  return items.reduce(
    (sum, story) => {
      sum[story.id] = story;
      return sum;
    },
    {} as {
      [key: string]: T;
    },
  );
}