firestoreをfunctionsで使う時のあれ

helper.ts

import admin from 'firebase-admin'
const db = admin.firestore()

export type Document<T> = {
  readonly id: string
  readonly ref: admin.firestore.DocumentReference<admin.firestore.DocumentData>
  readonly exists: boolean
  data: () => T
}

export const findDoc = async <T>(path: string): Promise<Document<T>> => {
  const doc = await db.doc(path).get()
  return {
    id: doc.id,
    ref: doc.ref,
    exists: doc.exists,
    data: (): T => {
      if (!doc.exists) {
        throw Error('data not found.')
      }
      return ({ ...doc.data(), id: doc.id } as unknown) as T
    },
  }
}