Initial commit

src/modules/webhooks/service.ts

@@ -0,0 +1,47 @@
+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();