findBook() をコールする Custom Hook

use-find-book.ts

import { useContext, useEffect, useRef, useState } from 'react';

import { Book } from 'domains/mangarel/models/book';
import findBook from 'domains/mangarel/services/find-book';
import { FirebaseContext } from 'contexts';

const useFindBook = (id: string) => {
  const [book, setBook] = useState<Book>();
  const [isLoading, setIsLoading] = useState(false);
  const [error, setError] = useState<Error | null>(null);
  const firebaseRef = useRef(useContext(FirebaseContext));

  useEffect(() => {
    const { db } = firebaseRef.current;
    if (!db) throw new Error('Firestore is not initialized');

    const load = async () => {
      setIsLoading(true);
      try {
        const bookData = await findBook(db, id);

        if (bookData) {
          setBook(bookData);
          setError(null);
        } else {
          setError(new Error('404 book not found'));
        }
      } catch (err) {
        setError(err);
      } finally {
        setIsLoading(false);
      }
    };

    load();
  }, [id]);

  return { book, isLoading, error };
};

export default useFindBook;

findBook() のほうはこんな感じ↓

import firebase from 'firebase/app';

import { Book } from '../models/book';
import { collectionName } from '../constants';

const findBook = async (
  db: firebase.firestore.Firestore,
  id: string | null,
) => {
  if (!id) return null;

  const doc = await db
    .collection(collectionName.books)
    .doc(id)
    .get();

  return doc.exists ? ({ ...doc.data(), id: doc.id } as Book) : null;
};

export default findBook;