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

// 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;
}

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

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

  constructor() {
    super('SkateSpotsCacheDB');
    this.version(1).stores({
      spots: 'id, pubkey, identifier, [pubkey+identifier], cachedAt, viewedAt',
      pendingPosts: 'id, kind, status, createdAt',
      settings: 'key',
    });
  }
}

// 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();

  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();

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

/**
 * 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();
  return db.pendingPosts
    .where('status')
    .equals('pending')
    .sortBy('createdAt');
}

/**
 * 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.where('status').equals('pending').count();
}

// ============ 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;
}