SkateSpots/src/lib/offlineCache.ts

import Dexie, { type Table } from 'dexie';
import type { NostrEvent } from '@nostrify/nostrify';
import { SKATE_SPOT_KIND, type SkateSpot } from '@/lib/types';
import { getLocalDeletions } from '@/lib/localDeletions';

// Define the database schema
interface CachedSpot {
  id: string; // event id
  pubkey: string;
  identifier: string;
  event: NostrEvent;
  spot: SkateSpot;
  cachedAt: number;
  viewedAt: number;
}

interface PendingPost {
  id: string; // local uuid
  kind: number;
  content: string;
  tags: string[][];
  createdAt: number;
  status: 'pending' | 'publishing' | 'failed';
  retries: number;
  /**
   * The ALREADY-SIGNED event, when we have it. Signing happens at the moment of
   * the action (so an interactive signer like Amber is NOT re-prompted at sync
   * time — the signature is just delivered later).
   */
  signedEvent?: NostrEvent;
  lastError?: string;
}

/**
 * Kinds that are only true "now" — a queued one is worse than none (e.g. a
 * spot-status "I'm here" delivered 3 hours later). Dropped once stale.
 */
const EPHEMERAL_KINDS = new Set<number>([2259, 24899]);
const EPHEMERAL_TTL_MS = 15 * 60 * 1000;
/** Hard cap so a long offline stretch can't grow the queue without bound. */
const MAX_PENDING = 100;

interface OfflineSettings {
  key: string;
  value: string;
}

/**
 * The encrypted stash event, kept on device so the stash is still readable
 * offline (and during a relay outage). We deliberately cache the CIPHERTEXT —
 * exactly what relays already hold — never the decrypted list.
 */
interface CachedStashEvent {
  pubkey: string;
  event: NostrEvent;
  cachedAt: number;
}

// Create the Dexie database
class SkateSpotsCacheDB extends Dexie {
  spots!: Table<CachedSpot, string>;
  pendingPosts!: Table<PendingPost, string>;
  settings!: Table<OfflineSettings, string>;
  stash!: Table<CachedStashEvent, string>;

  constructor() {
    super('SkateSpotsCacheDB');
    this.version(1).stores({
      spots: 'id, pubkey, identifier, [pubkey+identifier], cachedAt, viewedAt',
      pendingPosts: 'id, kind, status, createdAt',
      settings: 'key',
    });
    // v2 adds the encrypted-stash cache (see CachedStashEvent).
    this.version(2).stores({
      stash: 'pubkey, cachedAt',
    });
  }
}

// Singleton database instance
let db: SkateSpotsCacheDB | null = null;

function getDB(): SkateSpotsCacheDB {
  if (!db) {
    db = new SkateSpotsCacheDB();
  }
  return db;
}

// ============ Spot Caching ============

/**
 * Cache a spot for offline viewing
 */
export async function cacheSpot(event: NostrEvent, spot: SkateSpot): Promise<void> {
  const db = getDB();
  const now = Date.now();

  // Never re-cache a locally-deleted spot, and evict a stale cached copy.
  const deleted = getLocalDeletions();
  if (
    deleted.has(`${SKATE_SPOT_KIND}:${spot.pubkey}:${spot.identifier}`) ||
    deleted.has(`e:${event.id}`)
  ) {
    await db.spots.delete(event.id);
    return;
  }

  await db.spots.put({
    id: event.id,
    pubkey: spot.pubkey,
    identifier: spot.identifier,
    event,
    spot,
    cachedAt: now,
    viewedAt: now,
  });
}

/**
 * Cache multiple spots at once
 */
export async function cacheSpots(spotsWithEvents: Array<{ event: NostrEvent; spot: SkateSpot }>): Promise<void> {
  const db = getDB();
  const now = Date.now();
  const deleted = getLocalDeletions();

  const isTombstoned = (event: NostrEvent, spot: SkateSpot) =>
    deleted.has(`${SKATE_SPOT_KIND}:${spot.pubkey}:${spot.identifier}`) ||
    deleted.has(`e:${event.id}`);

  const keep =
    deleted.size > 0
      ? spotsWithEvents.filter(({ event, spot }) => !isTombstoned(event, spot))
      : spotsWithEvents;

  if (keep.length > 0) {
    await db.spots.bulkPut(
      keep.map(({ event, spot }) => ({
        id: event.id,
        pubkey: spot.pubkey,
        identifier: spot.identifier,
        event,
        spot,
        cachedAt: now,
        viewedAt: now,
      }))
    );
  }

  // Evict previously-cached rows that now carry a tombstone (deleted after they
  // were cached), so the offline map can never resurrect a deleted spot.
  if (deleted.size > 0) {
    const stale = (await db.spots.toArray())
      .filter(
        (c) =>
          deleted.has(`${SKATE_SPOT_KIND}:${c.pubkey}:${c.identifier}`) ||
          deleted.has(`e:${c.id}`),
      )
      .map((c) => c.id);
    if (stale.length > 0) await db.spots.bulkDelete(stale);
  }
}

/**
 * Get a cached spot by pubkey and identifier
 */
export async function getCachedSpot(pubkey: string, identifier: string): Promise<SkateSpot | null> {
  const db = getDB();
  const cached = await db.spots
    .where('[pubkey+identifier]')
    .equals([pubkey, identifier])
    .first();

  if (cached) {
    // Update viewedAt
    await db.spots.update(cached.id, { viewedAt: Date.now() });
    return cached.spot;
  }

  return null;
}

/**
 * Get all cached spots
 */
export async function getAllCachedSpots(): Promise<SkateSpot[]> {
  const db = getDB();
  const cached = await db.spots.toArray();
  return cached.map(c => c.spot);
}

/**
 * Get recently viewed spots (for offline browsing)
 */
export async function getRecentlyViewedSpots(limit: number = 50): Promise<SkateSpot[]> {
  const db = getDB();
  const cached = await db.spots
    .orderBy('viewedAt')
    .reverse()
    .limit(limit)
    .toArray();
  return cached.map(c => c.spot);
}

/**
 * Get cache statistics
 */
export async function getCacheStats(): Promise<{
  spotCount: number;
  oldestCachedAt: number | null;
  newestCachedAt: number | null;
  totalSizeEstimate: number;
}> {
  const db = getDB();
  const spots = await db.spots.toArray();
  
  if (spots.length === 0) {
    return {
      spotCount: 0,
      oldestCachedAt: null,
      newestCachedAt: null,
      totalSizeEstimate: 0,
    };
  }

  const cachedTimes = spots.map(s => s.cachedAt);
  const totalSize = spots.reduce((acc, s) => acc + JSON.stringify(s).length, 0);

  return {
    spotCount: spots.length,
    oldestCachedAt: Math.min(...cachedTimes),
    newestCachedAt: Math.max(...cachedTimes),
    totalSizeEstimate: totalSize,
  };
}

/**
 * Clear old cached spots (older than maxAge in milliseconds)
 */
export async function clearOldCache(maxAgeMs: number = 7 * 24 * 60 * 60 * 1000): Promise<number> {
  const db = getDB();
  const cutoff = Date.now() - maxAgeMs;
  
  const oldSpots = await db.spots
    .where('cachedAt')
    .below(cutoff)
    .primaryKeys();

  await db.spots.bulkDelete(oldSpots);
  return oldSpots.length;
}

/**
 * Clear all cached spots
 */
export async function clearAllCache(): Promise<void> {
  const db = getDB();
  await db.spots.clear();
}

// ============ Pending Posts Queue ============

/**
 * Add a post to the pending queue (for posting when back online)
 */
export async function queuePost(kind: number, content: string, tags: string[][]): Promise<string> {
  const db = getDB();
  const id = crypto.randomUUID();

  await db.pendingPosts.add({
    id,
    kind,
    content,
    tags,
    createdAt: Date.now(),
    status: 'pending',
    retries: 0,
  });

  return id;
}

/**
 * Get all pending posts
 */
export async function getPendingPosts(): Promise<PendingPost[]> {
  const db = getDB();
  // Anything not currently mid-publish: 'pending' AND retryable 'failed' items
  // (a single failed attempt must not strand an action forever).
  const all = await db.pendingPosts.toArray();
  return all.filter((p) => p.status !== 'publishing').sort((a, b) => a.createdAt - b.createdAt);
}

/**
 * Queue an ALREADY-SIGNED event (the offline path for `useNostrPublish`).
 *
 * Before adding we:
 *  • drop queued events this one SUPERSEDES — for a replaceable (kind 0/3/10000+)
 *    or addressable (30000+) event, only the newest version is worth delivering;
 *  • drop stale ephemeral events;
 *  • cap the queue.
 * so a long offline stretch leaves the newest, still-meaningful actions.
 */
export async function queueSignedEvent(event: NostrEvent): Promise<string> {
  const db = getDB();

  const replaceable = event.kind === 0 || event.kind === 3 || (event.kind >= 10000 && event.kind < 20000);
  const addressable = event.kind >= 30000 && event.kind < 40000;
  if (replaceable || addressable) {
    const d = event.tags.find(([n]) => n === 'd')?.[1] ?? '';
    const existing = await db.pendingPosts.toArray();
    const superseded = existing
      .filter((p) => {
        if (p.kind !== event.kind) return false;
        if (p.signedEvent && p.signedEvent.pubkey !== event.pubkey) return false;
        if (!addressable) return true;
        return (p.tags.find(([n]) => n === 'd')?.[1] ?? '') === d;
      })
      .map((p) => p.id);
    if (superseded.length > 0) await db.pendingPosts.bulkDelete(superseded);
  }

  const id = crypto.randomUUID();
  await db.pendingPosts.add({
    id,
    kind: event.kind,
    content: event.content,
    tags: event.tags,
    createdAt: Date.now(),
    status: 'pending',
    retries: 0,
    signedEvent: event,
  });

  // Keep only the newest MAX_PENDING.
  const count = await db.pendingPosts.count();
  if (count > MAX_PENDING) {
    const oldest = await db.pendingPosts.orderBy('createdAt').limit(count - MAX_PENDING).toArray();
    await db.pendingPosts.bulkDelete(oldest.map((p) => p.id));
  }

  return id;
}

/** Drop queued ephemeral events that are past their useful life. */
export async function prunePendingPosts(): Promise<number> {
  const db = getDB();
  const now = Date.now();
  const stale = (await db.pendingPosts.toArray()).filter(
    (p) => EPHEMERAL_KINDS.has(p.kind) && now - p.createdAt > EPHEMERAL_TTL_MS,
  );
  if (stale.length > 0) await db.pendingPosts.bulkDelete(stale.map((p) => p.id));
  return stale.length;
}

/**
 * Update a pending post's status
 */
export async function updatePendingPostStatus(
  id: string,
  status: 'pending' | 'publishing' | 'failed',
  retries?: number
): Promise<void> {
  const db = getDB();
  const update: Partial<PendingPost> = { status };
  if (retries !== undefined) {
    update.retries = retries;
  }
  await db.pendingPosts.update(id, update);
}

/**
 * Remove a pending post (after successful publish)
 */
export async function removePendingPost(id: string): Promise<void> {
  const db = getDB();
  await db.pendingPosts.delete(id);
}

/**
 * Get pending posts count
 */
export async function getPendingPostsCount(): Promise<number> {
  const db = getDB();
  return db.pendingPosts.count();
}

/**
 * Requeue posts left in `publishing` by a crash/reload. Without this they are
 * never retried (`getPendingPosts` skips `publishing`) yet still counted, so the
 * action silently disappears while the badge claims it is still pending.
 */
export async function reconcileStalePendingPosts(): Promise<void> {
  const db = getDB();
  const all = await db.pendingPosts.toArray();
  const stuck = all.filter((p) => p.status === 'publishing');
  await Promise.all(stuck.map((p) => db.pendingPosts.update(p.id, { status: 'pending' })));
}

// ============ Encrypted Stash Cache (offline readability) ============

/**
 * Remember the encrypted stash event so it can be decrypted offline. Stores the
 * CIPHERTEXT only — never the decrypted list.
 */
export async function cacheStashEvent(pubkey: string, event: NostrEvent): Promise<void> {
  const db = getDB();
  await db.stash.put({ pubkey, event, cachedAt: Date.now() });
}

/** The last encrypted stash event we saw for this pubkey, if any. */
export async function getCachedStashEvent(pubkey: string): Promise<NostrEvent | undefined> {
  const db = getDB();
  try {
    const row = await db.stash.get(pubkey);
    return row?.event;
  } catch {
    return undefined;
  }
}

export async function clearCachedStash(pubkey: string): Promise<void> {
  const db = getDB();
  await db.stash.delete(pubkey);
}

// ============ Offline Detection ============
/**
 * Check if the app is currently offline
 */
export function isOffline(): boolean {
  return !navigator.onLine;
}

/**
 * Listen for online/offline status changes
 */
export function onConnectionChange(callback: (isOnline: boolean) => void): () => void {
  const handleOnline = () => callback(true);
  const handleOffline = () => callback(false);

  window.addEventListener('online', handleOnline);
  window.addEventListener('offline', handleOffline);

  return () => {
    window.removeEventListener('online', handleOnline);
    window.removeEventListener('offline', handleOffline);
  };
}

// ============ Settings ============

/**
 * Store a setting in the offline cache
 */
export async function setSetting(key: string, value: string): Promise<void> {
  const db = getDB();
  await db.settings.put({ key, value });
}

/**
 * Get a setting from the offline cache
 */
export async function getSetting(key: string): Promise<string | null> {
  const db = getDB();
  const setting = await db.settings.get(key);
  return setting?.value ?? null;
}