import { Injectable, Logger, NotFoundException } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import * as crypto from 'crypto';
import {
  PosIntegration,
  PosProvider,
} from '../../entities/pos-integration.entity';
import { InventorySyncService } from './inventory-sync.service';
import {
  IPosWebhookHandler,
  PosWebhookEventType,
  SaleWebhookData,
  InventoryWebhookData,
  ProductWebhookData,
} from '../interfaces/pos-webhook.interface';

@Injectable()
export class PosWebhookService implements IPosWebhookHandler {
  private readonly logger = new Logger(PosWebhookService.name);

  constructor(
    @InjectRepository(PosIntegration)
    private integrationRepository: Repository<PosIntegration>,
    private inventorySyncService: InventorySyncService,
  ) {}

  private verifyWebhookSignature(
    payload: string,
    signature: string,
    secret: string,
  ): boolean {
    try {
      const expectedSignature = crypto
        .createHmac('sha256', secret)
        .update(payload)
        .digest('hex');

      return crypto.timingSafeEqual(
        Buffer.from(signature),
        Buffer.from(expectedSignature),
      );
    } catch {
      return false;
    }
  }

  async handleWebhook(
    storeId: string,
    provider: PosProvider,
    rawPayload: string,
    signature: string,
  ): Promise<{ success: boolean; message: string }> {
    this.logger.log(
      `Received webhook from ${provider} for store ${storeId}`,
    );

    // Find integration
    const integration = await this.integrationRepository.findOne({
      where: { storeId, provider, isActive: true },
    });

    if (!integration) {
      throw new NotFoundException(
        `No active integration found for provider ${provider}`,
      );
    }

    // Verify signature
    if (integration.webhookSecret && signature) {
      const isValid = this.verifyWebhookSignature(
        rawPayload,
        signature,
        integration.webhookSecret,
      );

      if (!isValid) {
        this.logger.warn(
          `Invalid webhook signature for integration ${integration.id}`,
        );
        return { success: false, message: 'Invalid signature' };
      }
    }

    try {
      const payload = JSON.parse(rawPayload);
      await this.processWebhookPayload(integration, payload);

      return { success: true, message: 'Webhook processed successfully' };
    } catch (error) {
      this.logger.error(`Failed to process webhook: ${error.message}`);
      return { success: false, message: error.message };
    }
  }

  private async processWebhookPayload(
    integration: PosIntegration,
    payload: {
      eventType: PosWebhookEventType;
      eventId?: string;
      data: unknown;
    },
  ): Promise<void> {
    const { eventType, data } = payload;

    switch (eventType) {
      case PosWebhookEventType.SALE_CREATED:
      case PosWebhookEventType.SALE_UPDATED:
        await this.processSaleEvent(
          integration.storeId,
          integration.id,
          data as SaleWebhookData,
        );
        break;

      case PosWebhookEventType.SALE_REFUNDED:
        // Handle refunds - increase inventory
        await this.processSaleRefund(
          integration.storeId,
          integration.id,
          data as SaleWebhookData,
        );
        break;

      case PosWebhookEventType.INVENTORY_UPDATED:
        await this.processInventoryEvent(
          integration.storeId,
          integration.id,
          data as InventoryWebhookData,
        );
        break;

      case PosWebhookEventType.PRODUCT_CREATED:
      case PosWebhookEventType.PRODUCT_UPDATED:
      case PosWebhookEventType.PRODUCT_DELETED:
        await this.processProductEvent(
          integration.storeId,
          integration.id,
          eventType,
          data as ProductWebhookData,
        );
        break;

      default:
        this.logger.warn(`Unknown event type: ${eventType}`);
    }
  }

  async processSaleEvent(
    storeId: string,
    integrationId: string,
    data: SaleWebhookData,
  ): Promise<void> {
    const integration = await this.integrationRepository.findOneOrFail({
      where: { id: integrationId },
    });

    if (!integration.syncConfig?.syncOnSale) {
      this.logger.log('Sale sync disabled for this integration, skipping');
      return;
    }

    const saleItems = data.items.map((item) => ({
      productId: item.productId,
      quantity: item.quantity,
    }));

    await this.inventorySyncService.processSale(
      integration,
      saleItems,
      data.saleId,
    );

    this.logger.log(
      `Processed sale ${data.saleId} with ${saleItems.length} items`,
    );
  }

  private async processSaleRefund(
    storeId: string,
    integrationId: string,
    data: SaleWebhookData,
  ): Promise<void> {
    // For refunds, we add the quantity back
    const integration = await this.integrationRepository.findOneOrFail({
      where: { id: integrationId },
    });

    // Convert refund to inventory updates (positive quantities)
    const products = data.items.map((item) => ({
      externalId: item.productId,
      name: item.productName || `Product ${item.productId}`,
      quantity: item.quantity, // This will be added back
    }));

    await this.inventorySyncService.syncFromPos(integration, products);

    this.logger.log(
      `Processed refund for sale ${data.saleId} with ${products.length} items`,
    );
  }

  async processInventoryEvent(
    storeId: string,
    integrationId: string,
    data: InventoryWebhookData,
  ): Promise<void> {
    const integration = await this.integrationRepository.findOneOrFail({
      where: { id: integrationId },
    });

    const products = [
      {
        externalId: data.productId,
        name: data.productName || `Product ${data.productId}`,
        quantity: data.newQuantity,
      },
    ];

    await this.inventorySyncService.syncFromPos(integration, products);

    this.logger.log(
      `Processed inventory update for product ${data.productId}: ${data.newQuantity}`,
    );
  }

  async processProductEvent(
    storeId: string,
    integrationId: string,
    eventType: PosWebhookEventType,
    data: ProductWebhookData,
  ): Promise<void> {
    const integration = await this.integrationRepository.findOneOrFail({
      where: { id: integrationId },
    });

    if (eventType === PosWebhookEventType.PRODUCT_DELETED) {
      // We don't delete items from our inventory when deleted from POS
      // Just log it
      this.logger.log(`Product ${data.productId} deleted in POS, skipping`);
      return;
    }

    const products = [
      {
        externalId: data.productId,
        name: data.name,
        sku: data.sku,
        barcode: data.barcode,
        category: data.category,
        quantity: data.quantity || 0,
        price: data.price,
        cost: data.cost,
      },
    ];

    await this.inventorySyncService.syncFromPos(integration, products);

    this.logger.log(
      `Processed product ${eventType} for ${data.productId}: ${data.name}`,
    );
  }
}