import AsyncStorage from '@react-native-async-storage/async-storage';
import { Product, Sale, Customer } from '../types';

const KEYS = {
  PRODUCTS: '@offline_products',
  PENDING_SALES: '@pending_sales',
  CUSTOMERS: '@offline_customers',
  LAST_SYNC: '@last_sync',
  OFFLINE_MODE: '@offline_mode',
};

interface PendingSale {
  id: string;
  items: Array<{ productId: string; quantity: number; unitPrice: number }>;
  paymentMethod: string;
  customerId?: string;
  total: number;
  createdAt: string;
  synced: boolean;
}

class OfflineStorage {
  // Products
  async saveProducts(products: Product[]): Promise<void> {
    await AsyncStorage.setItem(KEYS.PRODUCTS, JSON.stringify(products));
  }

  async getProducts(): Promise<Product[]> {
    const data = await AsyncStorage.getItem(KEYS.PRODUCTS);
    return data ? JSON.parse(data) : [];
  }

  async getProductByBarcode(barcode: string): Promise<Product | null> {
    const products = await this.getProducts();
    return products.find((p) => p.barcode === barcode) || null;
  }

  async updateProductStock(productId: string, quantitySold: number): Promise<void> {
    const products = await this.getProducts();
    const updatedProducts = products.map((p) =>
      p.id === productId ? { ...p, stock: Math.max(0, p.stock - quantitySold) } : p
    );
    await this.saveProducts(updatedProducts);
  }

  // Pending Sales (offline sales to sync later)
  async savePendingSale(sale: Omit<PendingSale, 'id' | 'createdAt' | 'synced'>): Promise<string> {
    const pendingSales = await this.getPendingSales();
    const newSale: PendingSale = {
      ...sale,
      id: `offline_${Date.now()}_${Math.random().toString(36).substr(2, 9)}`,
      createdAt: new Date().toISOString(),
      synced: false,
    };
    pendingSales.push(newSale);
    await AsyncStorage.setItem(KEYS.PENDING_SALES, JSON.stringify(pendingSales));

    // Update local stock
    for (const item of sale.items) {
      await this.updateProductStock(item.productId, item.quantity);
    }

    return newSale.id;
  }

  async getPendingSales(): Promise<PendingSale[]> {
    const data = await AsyncStorage.getItem(KEYS.PENDING_SALES);
    return data ? JSON.parse(data) : [];
  }

  async getUnsyncedSales(): Promise<PendingSale[]> {
    const sales = await this.getPendingSales();
    return sales.filter((s) => !s.synced);
  }

  async markSaleAsSynced(saleId: string): Promise<void> {
    const sales = await this.getPendingSales();
    const updatedSales = sales.map((s) =>
      s.id === saleId ? { ...s, synced: true } : s
    );
    await AsyncStorage.setItem(KEYS.PENDING_SALES, JSON.stringify(updatedSales));
  }

  async removeSyncedSales(): Promise<void> {
    const sales = await this.getPendingSales();
    const unsyncedSales = sales.filter((s) => !s.synced);
    await AsyncStorage.setItem(KEYS.PENDING_SALES, JSON.stringify(unsyncedSales));
  }

  // Customers
  async saveCustomers(customers: Customer[]): Promise<void> {
    await AsyncStorage.setItem(KEYS.CUSTOMERS, JSON.stringify(customers));
  }

  async getCustomers(): Promise<Customer[]> {
    const data = await AsyncStorage.getItem(KEYS.CUSTOMERS);
    return data ? JSON.parse(data) : [];
  }

  // Sync metadata
  async setLastSync(timestamp: string): Promise<void> {
    await AsyncStorage.setItem(KEYS.LAST_SYNC, timestamp);
  }

  async getLastSync(): Promise<string | null> {
    return AsyncStorage.getItem(KEYS.LAST_SYNC);
  }

  // Offline mode
  async setOfflineMode(enabled: boolean): Promise<void> {
    await AsyncStorage.setItem(KEYS.OFFLINE_MODE, JSON.stringify(enabled));
  }

  async isOfflineMode(): Promise<boolean> {
    const data = await AsyncStorage.getItem(KEYS.OFFLINE_MODE);
    return data ? JSON.parse(data) : false;
  }

  // Clear all offline data
  async clearAll(): Promise<void> {
    await AsyncStorage.multiRemove([
      KEYS.PRODUCTS,
      KEYS.PENDING_SALES,
      KEYS.CUSTOMERS,
      KEYS.LAST_SYNC,
    ]);
  }

  // Get offline stats
  async getOfflineStats(): Promise<{
    productCount: number;
    pendingSalesCount: number;
    pendingSalesTotal: number;
    lastSync: string | null;
  }> {
    const [products, pendingSales, lastSync] = await Promise.all([
      this.getProducts(),
      this.getUnsyncedSales(),
      this.getLastSync(),
    ]);

    return {
      productCount: products.length,
      pendingSalesCount: pendingSales.length,
      pendingSalesTotal: pendingSales.reduce((sum, s) => sum + s.total, 0),
      lastSync,
    };
  }
}

export const offlineStorage = new OfflineStorage();
export default offlineStorage;