Verify payment on chain before generating meme (#3)

Part of https://www.notion.so/Implement-payment-gating-188a6b22d472806a9267c2bda72925cc

Co-authored-by: Adw8 <adwaitgharpure@gmail.com>
Reviewed-on: #3
Co-authored-by: adwait <adwait@noreply.git.vdb.to>
Co-committed-by: adwait <adwait@noreply.git.vdb.to>

src/app/api/flux/route.ts

@@ -1,5 +1,8 @@
 import { NextRequest, NextResponse } from 'next/server'
 import { fal } from "@fal-ai/client"
+import { FLUX_MODELS } from '../../../services/fluxService'
+
+import { verifyPayment } from '../../../utils/verifyPayment'
 
 if (!process.env.FAL_AI_KEY) {
   throw new Error('FAL_AI_KEY is not configured in environment variables')
@@ -16,7 +19,7 @@ const IMAGE_HEIGHT: number = 1024
 
 export async function POST(req: NextRequest): Promise<NextResponse> {
   try {
-    const { prompt, modelId } = await req.json()
+    const { prompt, modelId, transactionSignature } = await req.json()
 
     if (!prompt || !modelId) {
       return NextResponse.json(
@@ -25,6 +28,28 @@ export async function POST(req: NextRequest): Promise<NextResponse> {
       )
     }
 
+    if (!transactionSignature) {
+      return NextResponse.json(
+        { error: 'Transaction signature is required' },
+        { status: 400 }
+      )
+    }
+
+    const model = FLUX_MODELS.find((model) => model.modelId === modelId)
+    if (!model) {
+      return NextResponse.json(
+        { error: 'Invalid modelId' },
+        { status: 400 }
+      )
+    }
+
+    const expectedAmount = model.cost;
+    const isPaymentVerified = await verifyPayment(transactionSignature, expectedAmount)
+
+    if (!isPaymentVerified) {
+      throw new Error('Payment verification failed');
+    }
+
     console.log('Generating with Flux model:', modelId)
     console.log('Prompt:', prompt)
 

src/app/page.tsx

@@ -49,8 +49,10 @@ const Page: React.FC = (): React.ReactElement => {
         return { error: paymentResult.error }
       }
 
+      const transactionSignature = paymentResult.transactionSignature;
+
       // Then generate image with specified model
-      return generateWithFlux(prompt, modelId)
+      return generateWithFlux(prompt, modelId, transactionSignature)
     }
   }