LocalHtmlDataTest/nostr/src/nostr-transport.ts

import type { SyncEvent } from './types.js';

/**
 * Nostr relay transport layer.
 *
 * Implements the same event I/O interface as FolderStore so the SyncEngine
 * can treat it as just another transport.
 *
 * Uses raw WebSocket + minimal Nostr protocol (NIP-01) to avoid
 * heavy dependencies.  Works from file:// origins.
 */

const NOSTR_EVENT_KIND = 4078; // custom regular kind (stored by relays)

// ── Minimal Nostr crypto (secp256k1 via nostr-tools) ─────────

import { generateSecretKey, getPublicKey, finalizeEvent } from 'nostr-tools/pure';
import { SimplePool, type SubCloser } from 'nostr-tools/pool';
import type { Filter } from 'nostr-tools/filter';

export class NostrTransport {
  private relays: string[];
  private pool: SimplePool;
  private roomKey: string | null = null;
  private secretKey: Uint8Array | null = null;

  /** Cached events keyed by our standard filename. */
  private eventCache = new Map<string, SyncEvent>();

  /** Active relay subscription (closeable). */
  private sub: SubCloser | null = null;

  /** Callback fired when a new event arrives in real time. */
  private _onNewEvent?: () => void;

  constructor(relays: string[]) {
    this.relays = relays;
    this.pool = new SimplePool();
  }

  // ── Key management ──────────────────────────────────────────

  /**
   * Set the keypair.  Called by FolderSyncDB after loading from IDB
   * (or generating a new one on first run).
   */
  setKeypair(sk: Uint8Array): void {
    this.secretKey = sk;
    // Derive pubkey (used internally by finalizeEvent)
    getPublicKey(sk);
  }

  generateKeypair(): Uint8Array {
    const sk = generateSecretKey();
    this.setKeypair(sk);
    return sk;
  }

  // ── Room management ─────────────────────────────────────────

  async joinRoom(roomKey: string): Promise<void> {
    if (this.roomKey === roomKey && this.sub) return; // already joined
    this.leaveRoom();
    this.roomKey = roomKey;

    // Fetch existing events from relays
    const fetchFilter: Filter = {
      kinds: [NOSTR_EVENT_KIND],
      '#channel': [roomKey],
      limit: 5000,
    };
    try {
      const events = await this.pool.querySync(this.relays, fetchFilter as Filter);
      for (const ev of events) {
        this.cacheNostrEvent(ev);
      }
    } catch {
      // relay might be unreachable — continue with empty cache
    }

    // Subscribe for new real-time events
    const subFilter: Filter = {
      kinds: [NOSTR_EVENT_KIND],
      '#channel': [roomKey],
      since: Math.floor(Date.now() / 1000),
    };
    this.sub = this.pool.subscribeMany(this.relays, subFilter, {
      onevent: (ev) => {
        const isNew = this.cacheNostrEvent(ev);
        if (isNew) this._onNewEvent?.();
      },
    });
  }

  leaveRoom(): void {
    if (this.sub) {
      this.sub.close();
      this.sub = null;
    }
    this.roomKey = null;
    this.eventCache.clear();
  }

  get isConnected(): boolean {
    return this.roomKey !== null && this.sub !== null;
  }

  get currentRoom(): string | null {
    return this.roomKey;
  }

  // ── Callback for real-time push ─────────────────────────────

  onNewEvent(cb: () => void): void {
    this._onNewEvent = cb;
  }

  // ── Event I/O (same interface as FolderStore) ───────────────

  async writeEvent(filename: string, event: SyncEvent): Promise<void> {
    if (!this.roomKey || !this.secretKey) return;

    this.eventCache.set(filename, event);

    const nostrEvent = finalizeEvent({
      kind: NOSTR_EVENT_KIND,
      created_at: Math.floor(Date.now() / 1000),
      tags: [
        ['channel', this.roomKey],
        ['filename', filename],
      ],
      content: JSON.stringify(event),
    }, this.secretKey);

    // Publish to all relays, don't wait for all to confirm
    try {
      await Promise.any(this.pool.publish(this.relays, nostrEvent as any));
    } catch {
      // All relays failed — event is still in local cache
    }
  }

  async scanEventFilenames(): Promise<string[]> {
    return Array.from(this.eventCache.keys()).sort();
  }

  async readEventFile(filename: string): Promise<SyncEvent | null> {
    return this.eventCache.get(filename) ?? null;
  }

  // ── Cleanup ─────────────────────────────────────────────────

  close(): void {
    this.leaveRoom();
    this.pool.close(this.relays);
  }

  // ── Internals ───────────────────────────────────────────────

  /**
   * Parse a Nostr event and cache it.  Returns true if the event
   * was new (not already cached).
   */
  private cacheNostrEvent(nostrEvent: any): boolean {
    try {
      const filename = nostrEvent.tags?.find(
        (t: string[]) => t[0] === 'filename',
      )?.[1];
      if (!filename) return false;
      if (this.eventCache.has(filename)) return false;

      const syncEvent = JSON.parse(nostrEvent.content) as SyncEvent;
      this.eventCache.set(filename, syncEvent);
      return true;
    } catch {
      return false;
    }
  }
}