dchain/client-app/hooks/useMessages.ts

/**
 * Subscribe to the relay inbox via WebSocket and decrypt incoming envelopes
 * for the active chat. Falls back to 30-second polling whenever the WS is
 * not connected — preserves correctness on older nodes or flaky networks.
 *
 * Flow:
 *   1. On mount: one HTTP fetch so we have whatever is already in the inbox
 *   2. Subscribe to topic `inbox:<my_x25519>` — the node pushes a summary
 *      for each fresh envelope as soon as mailbox.Store() succeeds
 *   3. On each push, pull the full envelope list (cheap — bounded by
 *      MailboxPerRecipientCap) and decrypt anything we haven't seen yet
 *   4. If WS disconnects for > 15 seconds, start a 30 s HTTP poll until it
 *      reconnects
 */

import { useEffect, useCallback, useRef } from 'react';
import { fetchInbox } from '@/lib/api';
import { getWSClient } from '@/lib/ws';
import { decryptMessage } from '@/lib/crypto';
import { appendMessage, loadMessages } from '@/lib/storage';
import { useStore } from '@/lib/store';
import { tryParsePostRef } from '@/lib/forwardPost';

const FALLBACK_POLL_INTERVAL  = 30_000;  // HTTP poll when WS is down
const WS_GRACE_BEFORE_POLLING = 15_000;  // don't start polling immediately on disconnect

/**
 * useMessages — mounts per-chat inbox consumption. Accepts:
 *   - contactX25519: the legacy/primary X25519 for the contact.
 *   - contactMasterEd25519 (optional, v2.2.0+): the contact's master
 *     identity so we can attribute envelopes from any of their
 *     linked devices to this conversation.
 *
 * Matching rule: an envelope belongs to this chat when
 *     env.sender_ed25519_pub === contactMasterEd25519  (v2.2.0 path)
 *  OR env.sender_pub         === contactX25519         (legacy path)
 */
export function useMessages(contactX25519: string, contactMasterEd25519?: string) {
  const keyFile   = useStore(s => s.keyFile);
  const appendMsg = useStore(s => s.appendMessage);

  const matchesChat = useCallback((env: { sender_pub: string; sender_ed25519_pub: string }): boolean => {
    if (contactMasterEd25519 && env.sender_ed25519_pub === contactMasterEd25519) return true;
    return env.sender_pub === contactX25519;
  }, [contactX25519, contactMasterEd25519]);

  // Подгружаем кэш сообщений из AsyncStorage при открытии чата.
  // Релей держит envelope'ы всего 7 дней, поэтому без чтения кэша
  // история старше недели пропадает при каждом рестарте приложения.
  // appendMsg в store идемпотентен по id, поэтому безопасно гонять его
  // для каждого кэшированного сообщения.
  useEffect(() => {
    if (!contactX25519) return;
    let cancelled = false;
    loadMessages(contactX25519).then(cached => {
      if (cancelled) return;
      for (const m of cached) appendMsg(contactX25519, m);
    }).catch(() => { /* cache miss / JSON error — not fatal */ });
    return () => { cancelled = true; };
  }, [contactX25519, appendMsg]);

  const pullAndDecrypt = useCallback(async () => {
    if (!keyFile || !contactX25519) return;
    try {
      const envelopes = await fetchInbox(keyFile.x25519_pub);
      for (const env of envelopes) {
        // Only process messages that belong to this chat (see matchesChat).
        if (!matchesChat(env)) continue;

        const text = decryptMessage(
          env.ciphertext,
          env.nonce,
          env.sender_pub,
          keyFile.x25519_priv,
        );
        if (!text) continue;

        // Detect forwarded feed posts — plaintext is a tiny JSON
        // envelope (see lib/forwardPost.ts). Regular text messages
        // stay as-is.
        const postRef = tryParsePostRef(text);

        const msg = {
          id:        env.id || `${env.sender_pub}_${env.nonce.slice(0, 16)}`,
          from:      env.sender_pub,
          text:      postRef ? '' : text,
          timestamp: env.timestamp,
          mine:      false,
          ...(postRef && {
            postRef: {
              postID:   postRef.post_id,
              author:   postRef.author,
              excerpt:  postRef.excerpt,
              hasImage: postRef.has_image,
            },
          }),
        };
        appendMsg(contactX25519, msg);
        await appendMessage(contactX25519, msg);
      }
    } catch (e: any) {
      // Шумные ошибки (404 = нет mailbox'а, Network request failed =
      // нода недоступна) — ожидаемы в dev-среде и при offline-режиме,
      // не спамим console. Остальное — логируем.
      const msg = String(e?.message ?? e ?? '');
      if (/→\s*404\b/.test(msg)) return;
      if (/ 404\b/.test(msg))    return;
      if (/Network request failed/i.test(msg)) return;
      if (/Failed to fetch/i.test(msg))         return;
      console.warn('[useMessages] pull error:', e);
    }
  }, [keyFile, contactX25519, appendMsg]);

  // ── Fallback polling state ────────────────────────────────────────────
  const pollTimerRef       = useRef<ReturnType<typeof setInterval> | null>(null);
  const disconnectTORef    = useRef<ReturnType<typeof setTimeout>  | null>(null);

  const startPolling = useCallback(() => {
    if (pollTimerRef.current) return;
    console.log('[useMessages] WS down — starting HTTP poll fallback');
    pullAndDecrypt();
    pollTimerRef.current = setInterval(pullAndDecrypt, FALLBACK_POLL_INTERVAL);
  }, [pullAndDecrypt]);

  const stopPolling = useCallback(() => {
    if (pollTimerRef.current) {
      clearInterval(pollTimerRef.current);
      pollTimerRef.current = null;
    }
    if (disconnectTORef.current) {
      clearTimeout(disconnectTORef.current);
      disconnectTORef.current = null;
    }
  }, []);

  useEffect(() => {
    if (!keyFile || !contactX25519) return;

    const ws = getWSClient();

    // Initial fetch — populate whatever landed before we mounted.
    pullAndDecrypt();

    // Subscribe to our x25519 inbox — the node emits on mailbox.Store.
    // Topic filter: only envelopes for ME; we then filter by sender inside
    // the handler so we only render messages in THIS chat.
    const offInbox = ws.subscribe('inbox:' + keyFile.x25519_pub, (frame) => {
      if (frame.event !== 'inbox') return;
      const d = frame.data as {
        sender_pub?: string; sender_ed25519_pub?: string;
      } | undefined;
      // Optimisation: if the envelope definitely isn't for this chat,
      // skip the whole refetch. Multi-device aware — the peer may be
      // writing from any of their linked devices (different X25519
      // pubs), so we check against their master Ed25519 too.
      if (d && !matchesChat({
        sender_pub:         d.sender_pub ?? '',
        sender_ed25519_pub: d.sender_ed25519_pub ?? '',
      })) return;
      pullAndDecrypt();
    });

    // Manage fallback polling based on WS connection state.
    const offConn = ws.onConnectionChange((ok) => {
      if (ok) {
        stopPolling();
        // Catch up anything we missed while disconnected.
        pullAndDecrypt();
      } else if (disconnectTORef.current === null) {
        disconnectTORef.current = setTimeout(startPolling, WS_GRACE_BEFORE_POLLING);
      }
    });

    ws.connect();

    return () => {
      offInbox();
      offConn();
      stopPolling();
    };
  }, [keyFile, contactX25519, pullAndDecrypt, startPolling, stopPolling]);
}