cinny/src/app/hooks/useReminders.ts

import { useCallback, useEffect, useState } from 'react';
import { MatrixClient } from 'matrix-js-sdk';
import { useMatrixClient } from './useMatrixClient';
import { useAccountDataCallback } from './useAccountDataCallback';

export type Reminder = {
  roomId: string;
  eventId: string;
  timestamp: number;
  message: string;
};

const REMINDERS_KEY = 'io.lotus.reminders';

type RemindersContent = {
  reminders: Reminder[];
};

function readReminders(mx: MatrixClient): Reminder[] {
  return (
    (mx.getAccountData(REMINDERS_KEY as any)?.getContent() as RemindersContent | undefined)
      ?.reminders ?? []
  );
}

export function useReminders(): {
  reminders: Reminder[];
  addReminder: (r: Reminder) => Promise<void>;
  removeReminder: (eventId: string, timestamp: number) => Promise<void>;
  getReminders: () => Reminder[];
} {
  const mx = useMatrixClient();
  const [reminders, setReminders] = useState<Reminder[]>(() => readReminders(mx));

  useAccountDataCallback(
    mx,
    useCallback(
      (evt) => {
        if (evt.getType() === REMINDERS_KEY) {
          setReminders(evt.getContent<RemindersContent>()?.reminders ?? []);
        }
      },
      [setReminders],
    ),
  );

  // Re-read on mx change
  useEffect(() => {
    setReminders(readReminders(mx));
  }, [mx]);

  const addReminder = useCallback(
    async (r: Reminder) => {
      const current = readReminders(mx);
      const next = [...current, r];
      await (mx as any).setAccountData(REMINDERS_KEY, { reminders: next });
    },
    [mx],
  );

  const removeReminder = useCallback(
    async (eventId: string, timestamp: number) => {
      const current = readReminders(mx);
      const next = current.filter((r) => !(r.eventId === eventId && r.timestamp === timestamp));
      await (mx as any).setAccountData(REMINDERS_KEY, { reminders: next });
    },
    [mx],
  );

  const getReminders = useCallback(() => reminders, [reminders]);

  return { reminders, addReminder, removeReminder, getReminders };
}