import crypto from 'crypto';

const WEBHOOK_SECRET = process.env.WEBHOOK_SECRET || 'test_secret_for_webhooks';
// For demo purposes, we log it or hit a dummy URL.
const WEBHOOK_URL = process.env.WEBHOOK_URL || 'http://localhost:8081/webhooks/pharmacy'; 

export class WebhookService {
  async dispatchEvent(event: string, idempotencyKey: string, payload: any) {
    const timestamp = Math.floor(Date.now() / 1000);
    const bodyString = JSON.stringify(payload);
    const dataToSign = `${timestamp}.${bodyString}`;
    
    const signature = crypto
      .createHmac('sha256', WEBHOOK_SECRET)
      .update(dataToSign)
      .digest('hex');

    const signatureHeader = `t=${timestamp},v1=${signature}`;

    console.log(`[WEBHOOK] Dispatching event: ${event} (Idempotency: ${idempotencyKey})`);
    
    try {
      // Assuming Node 20+, native fetch is available
      const response = await fetch(WEBHOOK_URL, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'X-Pharmacy-Event': event,
          'X-Pharmacy-Signature': signatureHeader,
          'Idempotency-Key': idempotencyKey,
        },
        body: bodyString,
      });

      if (!response.ok) {
        console.error(`[WEBHOOK] Dispatch failed with status: ${response.status}`);
      } else {
        console.log(`[WEBHOOK] Successfully dispatched event: ${event}`);
      }
    } catch (error: any) {
      console.error(`[WEBHOOK] Failed to dispatch webhook: ${error.message}`);
      // In a real system, this would queue for retry with exponential backoff.
    }
  }
}

export const webhookService = new WebhookService();