import { useEffect, useRef, useState, useCallback } from 'react';
import { supabase } from '../lib/supabase';
import type { RealtimeChannel } from '@supabase/supabase-js';

/**
 * Typing-Indicator für eine DM-Konversation via Supabase-Broadcast (ephemer,
 * KEIN DB-Write — Tipp-Status muss nicht persistiert werden).
 *
 * Beide Peers joinen denselben deterministischen Channel (sortiertes ID-Paar),
 * damit `send()` von A bei B ankommt. `self:false` filtert die eigenen Events.
 *
 *  - `sendTyping()`     → throttled-Broadcast „ich tippe" (max 1×/1.5s)
 *  - `sendStopTyping()` → sofortiger „Stop" (beim Senden / Leeren des Inputs)
 *  - `partnerTyping`    → true solange Partner-Events reinkommen (Auto-Clear 4s)
 */
export function useDmTyping(myUserId: string | undefined, partnerId: string | undefined) {
  const [partnerTyping, setPartnerTyping] = useState(false);
  const channelRef = useRef<RealtimeChannel | null>(null);
  const clearTimer = useRef<ReturnType<typeof setTimeout> | null>(null);
  const lastSent = useRef(0);

  useEffect(() => {
    if (!myUserId || !partnerId) return;
    const pair = [myUserId, partnerId].sort().join('_');
    const channel = supabase.channel(`dm-typing:${pair}`, {
      config: { broadcast: { self: false } },
    });
    channel
      .on('broadcast', { event: 'typing' }, (msg: any) => {
        if (msg?.payload?.userId !== partnerId) return;
        setPartnerTyping(true);
        if (clearTimer.current) clearTimeout(clearTimer.current);
        clearTimer.current = setTimeout(() => setPartnerTyping(false), 4000);
      })
      .on('broadcast', { event: 'stop_typing' }, (msg: any) => {
        if (msg?.payload?.userId !== partnerId) return;
        if (clearTimer.current) clearTimeout(clearTimer.current);
        setPartnerTyping(false);
      })
      .subscribe();
    channelRef.current = channel;

    return () => {
      if (clearTimer.current) clearTimeout(clearTimer.current);
      supabase.removeChannel(channel);
      channelRef.current = null;
      setPartnerTyping(false);
    };
  }, [myUserId, partnerId]);

  const sendTyping = useCallback(() => {
    const now = Date.now();
    if (now - lastSent.current < 1500) return; // Throttle
    lastSent.current = now;
    channelRef.current?.send({
      type: 'broadcast',
      event: 'typing',
      payload: { userId: myUserId },
    });
  }, [myUserId]);

  const sendStopTyping = useCallback(() => {
    lastSent.current = 0;
    channelRef.current?.send({
      type: 'broadcast',
      event: 'stop_typing',
      payload: { userId: myUserId },
    });
  }, [myUserId]);

  return { partnerTyping, sendTyping, sendStopTyping };
}