First pricing implementation (#27)

* first implementation of elasticity demand computation

* chor: fixing test :(

* feature: rudemantary defintition of pricing pipeline

* chor: fixing cross product missing data

* add warning

* feature: e2e pricing pipeline with inference

web/src/app/api/pricing/route.ts

@@ -13,17 +13,6 @@ export async function GET(req: NextRequest) {
     const experimentId = searchParams.get('experimentId');
     const storeMode = process.env.NEXT_PUBLIC_STORE_MODE || 'shop';
 
-    // log in dev
-    if (process.env.NODE_ENV === 'development') {
-        console.log('[pricing-api]', {
-            productId,
-            sessionId,
-            experimentId,
-            storeMode,
-            timestamp: new Date().toISOString(),
-        });
-    }
-
     if (!productId) {
         return NextResponse.json(
             { error: 'productId is required' },
@@ -34,11 +23,46 @@ export async function GET(req: NextRequest) {
     // stub: call external pricing provider (random for now)
     const basePrice = 100 + Math.random() * 900; // 100-1000 range
     const price = Math.round(basePrice * 100) / 100;
+    const timestamp = new Date().toISOString();
+
+    // log price to kafka for elasticity computation
+    if (sessionId) {
+        const backendUrl = process.env.BACKEND_URL || 'http://localhost:5000';
+        try {
+            await fetch(`${backendUrl}/api/kafka/price-log`, {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({
+                    productId,
+                    price,
+                    sessionId,
+                    experimentId: experimentId || undefined,
+                    storeMode,
+                    ts: timestamp,
+                }),
+            });
+        } catch (err) {
+            console.error('[price-log-error]', err);
+            // don't fail the pricing request if logging fails
+        }
+    }
+
+    // log in dev
+    if (process.env.NODE_ENV === 'development') {
+        console.log('[pricing-api]', {
+            productId,
+            sessionId,
+            experimentId,
+            storeMode,
+            price,
+            timestamp,
+        });
+    }
 
     const response: PricingResponse = {
         price,
         currency: 'EUR',
-        cachedAt: new Date().toISOString(),
+        cachedAt: timestamp,
     };
 
     return NextResponse.json(response);