import type { PresenceState } from '@chat-app/shared/supabase';
import { useEffect, useState } from 'react';

import { supabase } from './supabase';

// Subscribe to a single peer's presence_state via Supabase realtime.
// Returns null until the first row arrives, or when userId is undefined.
export function usePeerPresence(userId: string | undefined): PresenceState | null {
  const [presence, setPresence] = useState<PresenceState | null>(null);

  useEffect(() => {
    if (!userId) {
      setPresence(null);
      return;
    }
    let cancelled = false;

    void supabase
      .from('profiles')
      .select('presence_state')
      .eq('user_id', userId)
      .maybeSingle()
      .then(({ data }) => {
        if (!cancelled) setPresence(data?.presence_state ?? null);
      });

    const channel = supabase
      .channel('peer-presence:' + userId)
      .on(
        'postgres_changes',
        {
          event: 'UPDATE',
          schema: 'public',
          table: 'profiles',
          filter: 'user_id=eq.' + userId,
        },
        (payload: { new: Record<string, unknown> }) => {
          const next = payload.new['presence_state'];
          if (typeof next === 'string') setPresence(next as PresenceState);
        },
      )
      .subscribe();

    return () => {
      cancelled = true;
      void supabase.removeChannel(channel);
    };
  }, [userId]);

  return presence;
}