API - First x402 endpoint

[sweetmantech]

Summary by CodeRabbit

• New Features

  • Added payment processing middleware integration to the application.
  • Added new /image/generate endpoint.

• Dependencies

  • Added Coinbase x402 and x402-express libraries for payment handling.

• Configuration

  • Updated TypeScript module resolution settings for improved compatibility.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

This pull request integrates x402-express payment middleware into an Express application to enable payment-protected API routes. A new payment middleware factory is created, configured with wallet and facilitator details, and registered in the app. A /api/image/generate route is added and protected via the middleware. Dependencies and TypeScript configuration are updated accordingly.

Changes

Cohort / File(s)	Change Summary
Payment Middleware Integration src/app.ts, lib/x402/paymentMiddleware.ts	New middleware module exports createPaymentMiddleware() factory that configures x402-express with wallet address, facilitator URL, and route pricing/schemas; middleware is imported and registered in Express app setup
API Route Addition routes.ts	Adds new GET route /api/image/generate with inline handler returning static weather report; positioned before default export and subject to payment middleware
Dependency Management package.json	Adds @coinbase/x402 and x402-express packages for payment processing functionality
Build Configuration tsconfig.json	Updates compiler options: module from "commonjs" to "NodeNext", moduleResolution from "node" to "nodenext" for enhanced module handling

Sequence Diagram

sequenceDiagram
    participant Client
    participant PaymentMiddleware
    participant Route Handler

    Client->>PaymentMiddleware: GET /api/image/generate
    Note over PaymentMiddleware: Validate payment headers<br/>(wallet, price, network)
    alt Payment Valid
        PaymentMiddleware->>Route Handler: Forward request
        Route Handler->>Client: 200 JSON (weather report)
    else Payment Invalid
        PaymentMiddleware->>Client: 402 Payment Required
    end

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Areas requiring extra attention:

• JSON schema definitions and pricing configuration in paymentMiddleware.ts for correctness
• x402-express integration behavior and error handling patterns
• Interaction between new middleware and existing Express middleware stack
• Verification that /api/image/generate route is properly protected by the middleware

Poem

🐰 A hop through payments, x402 style,
Middleware guards the route with flair,
NodeNext resolves the paths compile-time sweet,
Image generation now pays its way,
Security wrapped in schemas neat! 🎉

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'API - First x402 endpoint' accurately reflects the main change: adding a new x402 payment middleware integration with a first endpoint for payment processing.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch sweetmantech/myc-3502-api-first-x402-endpoint

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[coderabbitai]

Actionable comments posted: 3

🧹 Nitpick comments (1)

lib/x402/paymentMiddleware.ts (1)

32-36: Add validation for middleware configuration.

Consider adding runtime validation to ensure the middleware is configured correctly before returning it. This helps catch configuration issues early.

 export const createPaymentMiddleware = (): RequestHandler => {
+  if (!RECEIVING_WALLET_ADDRESS) {
+    throw new Error("Payment middleware requires RECEIVING_WALLET_ADDRESS");
+  }
+  if (!FACILITATOR_URL) {
+    throw new Error("Payment middleware requires FACILITATOR_URL");
+  }
   return paymentMiddleware(RECEIVING_WALLET_ADDRESS, routeConfig, {
     url: FACILITATOR_URL,
   });
 };

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between b10ef96 and c20909e.

⛔ Files ignored due to path filters (1)

• pnpm-lock.yaml is excluded by !**/pnpm-lock.yaml

📒 Files selected for processing (5)

• app.ts (2 hunks)
• lib/x402/paymentMiddleware.ts (1 hunks)
• package.json (2 hunks)
• routes.ts (1 hunks)
• tsconfig.json (1 hunks)

🧰 Additional context used

🧬 Code graph analysis (1)

app.ts (1)

lib/x402/paymentMiddleware.ts (1)

• createPaymentMiddleware (32-36)

🔇 Additional comments (3)

tsconfig.json (1)

28-31: LGTM! Module resolution update is appropriate.

The change to NodeNext module and nodenext moduleResolution is a standard configuration that provides better interoperability with modern ES modules while still outputting CommonJS (as noted in the comment). This aligns well with the new x402 dependencies being added.

app.ts (1)

19-20: No action required—the middleware and route handler work correctly together.

The original review mischaracterizes the code. The payment middleware validates payment and then calls next() so your route handler runs. If the request is unpaid/invalid the middleware responds with the 402 paywall response (does not call next()). This is exactly what the code does:

1. Payment middleware validates the request to GET /api/image/generate
2. On valid payment: calls next() and the route handler at routes.ts:140 executes
3. On invalid payment: returns 402 response directly

There is no conflict. This is standard Express middleware chaining behavior and the implementation is correct.

Likely an incorrect or invalid review comment.

package.json (1)

21-21: No action required—library versions are current and secure.

Verification confirms that both @coinbase/x402 and x402-express at version 0.7.3 are the latest available releases and are free from known vulnerabilities. The high-severity advisory for x402-express affects only versions < 0.5.2, and the current version 0.7.3 is well beyond that threshold.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Response shape mismatched to advertised schema

The payment middleware publishes an outputSchema with top-level weather and temperature fields for GET /api/image/generate (lib/x402/paymentMiddleware.ts lines 21-26), but the new handler returns them nested inside report, so paid callers receive a different shape than promised and any client validating against the advertised schema will fail on every call.

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