appjs25-eas-update-workshop-code/utils/usePersistentDate.ts

import { date1GreaterThanDate2 } from "@/utils/dateUtils";
import AsyncStorage from "@react-native-async-storage/async-storage";
import { useEffect, useState } from "react";

/**
 * Hook that takes a date computed since restart, and persists it if is later than the value already stored.
 * If the date has never been computed, attempt to read the previously saved value from storage.
 *
 * @param dateSinceRestart The date computed since restart
 *
 * @returns the most recently computed date, either computed since restart, or retrieved from storage
 */
export const usePersistentDate = (dateSinceRestart: Date | undefined) => {
  const [localDate, setLocalDate] = useState<Date | undefined>(undefined);

  useEffect(() => {
    if (
      dateSinceRestart &&
      date1GreaterThanDate2(dateSinceRestart, localDate)
    ) {
      // Caller passed in a date, so store it and set the local copy
      storeLastUpdateCheckDateAsync(dateSinceRestart).then(() => {
        setLocalDate(dateSinceRestart);
      });
    }
  }, [dateSinceRestart, localDate]);

  useEffect(() => {
    if (localDate === undefined) {
      // If no date has yet been defined, try reading it from storage
      fetchLastUpdateCheckDateAsync().then((storedDate) => {
        if (storedDate) {
          setLocalDate(storedDate);
        }
      });
    }
  }, [localDate]);

  return localDate;
};

const fetchLastUpdateCheckDateAsync: () => Promise<
  Date | undefined
> = async () => {
  const dateString = await AsyncStorage.getItem("@lastUpdateCheckDate");
  return dateString ? new Date(dateString) : undefined;
};

const storeLastUpdateCheckDateAsync: (date: Date) => Promise<void> = async (
  date,
) => {
  const dateString = date.toISOString();
  return await AsyncStorage.setItem("@lastUpdateCheckDate", dateString);
};