ChatApp/apps/desktop/src/lib/usePeerPresence.ts

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

import { supabase } from './supabase';

export interface PeerPresence {
  state: PresenceState;
  statusMessage: string | null;
}

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

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

    void supabase
      .from('profiles')
      .select('presence_state, status_message')
      .eq('user_id', userId)
      .maybeSingle()
      .then(({ data }) => {
        if (cancelled || !data) return;
        setPresence({
          state: (data.presence_state as PresenceState | null) ?? 'offline',
          statusMessage: data.status_message ?? 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 nextState = payload.new['presence_state'];
          const nextMsg = payload.new['status_message'];
          setPresence((prev) => {
            const state =
              typeof nextState === 'string'
                ? (nextState as PresenceState)
                : prev?.state ?? 'offline';
            const statusMessage =
              nextMsg === null
                ? null
                : typeof nextMsg === 'string'
                  ? nextMsg
                  : prev?.statusMessage ?? null;
            return { state, statusMessage };
          });
        },
      )
      .subscribe();

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

  return presence;
}