From e49fc2b9fc3dfdcebd2e61f34e1d698dce505c76 Mon Sep 17 00:00:00 2001 From: Claude Date: Sat, 15 Nov 2025 16:22:57 +0000 Subject: [PATCH] docs: add comprehensive learning guides for payment gateway abstraction Created four detailed guides to help understand better-auth patterns and apply them to building a payment gateway abstraction library: - LEARNING_GUIDE.md: 17-file study roadmap organized in 5 phases - OAUTH_TO_PAYMENT_MAPPING.md: Mental model showing OAuth-to-Payment parallels - QUICK_START_IMPLEMENTATION.md: Complete implementation guide with code - STUDY_CHECKLIST.md: Interactive checklist to track learning progress These guides show how to learn from better-auth's provider abstraction, plugin system, and configuration patterns to build a "better-payments" library that makes integrating Stripe, Flutterwave, PayStack, and other payment gateways as simple as better-auth makes OAuth providers. --- LEARNING_GUIDE.md | 490 ++++++++++++++++++++ OAUTH_TO_PAYMENT_MAPPING.md | 455 ++++++++++++++++++ QUICK_START_IMPLEMENTATION.md | 837 ++++++++++++++++++++++++++++++++++ STUDY_CHECKLIST.md | 206 +++++++++ 4 files changed, 1988 insertions(+) create mode 100644 LEARNING_GUIDE.md create mode 100644 OAUTH_TO_PAYMENT_MAPPING.md create mode 100644 QUICK_START_IMPLEMENTATION.md create mode 100644 STUDY_CHECKLIST.md diff --git a/LEARNING_GUIDE.md b/LEARNING_GUIDE.md new file mode 100644 index 0000000000..38b9acb745 --- /dev/null +++ b/LEARNING_GUIDE.md @@ -0,0 +1,490 @@ +# Better-Auth Learning Guide for Payment Gateway Project + +This guide will help you understand the better-auth codebase to build your payment gateway abstraction library. + +## 📚 Learning Path - Study These Files in Order + +### **PHASE 1: Understanding Provider Abstraction** (START HERE) + +#### 1. Provider Interface Definition +**File:** `packages/core/src/oauth2/oauth-provider.ts` +**Lines to focus on:** 14-83 +**What to learn:** +- How a provider interface is structured +- What methods every provider must implement +- How TypeScript generics are used for type safety +- The difference between required and optional methods + +**Key concepts:** +```typescript +- OAuthProvider interface +- createAuthorizationURL() - how providers start flows +- validateAuthorizationCode() - how providers verify results +- getUserInfo() - how providers fetch data +- Optional methods (refreshAccessToken, revokeToken) +``` + +**Your equivalent:** +```typescript +PaymentProvider +- createPaymentIntent() +- verifyPayment() +- handleWebhook() +- Optional: refundPayment(), createSubscription() +``` + +--- + +#### 2. Simple Provider Implementation +**File:** `packages/core/src/social-providers/github.ts` +**Lines to focus on:** 1-200 +**What to learn:** +- How to implement the provider interface +- How to define provider-specific options +- How to make API calls to external services +- How to transform external data to standard format + +**Key concepts:** +```typescript +- GithubProfile interface (provider-specific data) +- GithubOptions interface (extends ProviderOptions) +- github() factory function +- API endpoint configuration +- Error handling +``` + +**Why GitHub first:** Simpler than Google (no OIDC), shows basic patterns clearly + +--- + +#### 3. Complex Provider Implementation +**File:** `packages/core/src/social-providers/google.ts` +**Lines to focus on:** 1-250 +**What to learn:** +- Advanced provider features (ID token verification) +- Provider-specific options (accessType, display, hd) +- How to handle different authentication flows +- Token refresh implementation + +**Key concepts:** +```typescript +- GoogleProfile interface +- GoogleOptions with provider-specific fields +- verifyIdToken() for OIDC +- refreshAccessToken() implementation +- Using helper functions (createAuthorizationURL, validateAuthorizationCode) +``` + +--- + +#### 4. Provider with Environment Handling +**File:** `packages/core/src/social-providers/paypal.ts` +**Lines to focus on:** 1-150 +**What to learn:** +- How to handle sandbox vs production environments +- Dynamic endpoint configuration +- Environment-based API URLs + +**Key concepts:** +```typescript +- PayPalOptions with environment field +- Conditional endpoint URLs (sandbox vs live) +- Environment-aware token endpoints +``` + +**Why this matters for you:** Payment gateways also have sandbox/production modes! + +--- + +#### 5. Provider Registry and Exports +**File:** `packages/core/src/social-providers/index.ts` +**Lines to focus on:** 1-100 +**What to learn:** +- How to organize multiple providers +- Type-safe provider registration +- Creating enums from provider names +- Configuration type generation + +**Key concepts:** +```typescript +- socialProviders object (registry) +- socialProviderList array +- SocialProviders type (for configuration) +- Type-safe provider keys +``` + +--- + +### **PHASE 2: Understanding Configuration System** + +#### 6. Main Configuration Interface +**File:** `packages/core/src/types/init-options.ts` +**Lines to focus on:** 1-300 +**What to learn:** +- How to structure main configuration +- Nested configuration objects +- Optional vs required fields +- Default values and documentation + +**Key concepts:** +```typescript +- BetterAuthOptions interface +- socialProviders configuration +- emailAndPassword configuration +- plugins array +- advanced options +``` + +**Your equivalent:** +```typescript +PaymentGatewayOptions +- providers: PaymentProviders +- defaultCurrency +- webhooks +- plugins +- advanced +``` + +--- + +#### 7. Provider Options Type +**File:** `packages/core/src/oauth2/oauth-provider.ts` +**Lines to focus on:** 85-120 +**What to learn:** +- Base options that all providers share +- How to allow provider-specific extensions +- Generic type parameters for flexibility + +**Key concepts:** +```typescript +- ProviderOptions interface +- clientId, clientSecret (common to all) +- getUserInfo override option +- mapProfileToUser customization +``` + +--- + +### **PHASE 3: Understanding the Core Factory** + +#### 8. Main Entry Point +**File:** `packages/better-auth/src/auth/auth.ts` +**Lines to focus on:** 1-50 +**What to learn:** +- How the public API is exposed +- Simple wrapper pattern +- Type inference from options + +**Key concepts:** +```typescript +- betterAuth() function +- Generic type parameter +- Delegation to createBetterAuth +- Return type: Auth +``` + +**Your equivalent:** +```typescript +export const betterPayments = ( + options: Options +) => { + return createPaymentGateway(options); +}; +``` + +--- + +#### 9. Core Factory Function +**File:** `packages/better-auth/src/auth/base.ts` +**Lines to focus on:** 1-150 +**What to learn:** +- How to initialize the system +- Request handler creation +- Plugin aggregation +- Error code collection + +**Key concepts:** +```typescript +- createBetterAuth() factory +- initFn for async initialization +- handler: async (request: Request) +- Plugin error code aggregation +- Context management +``` + +--- + +#### 10. Context Creation +**File:** `packages/better-auth/src/context/create-context.ts` +**Lines to focus on:** 1-300 +**What to learn:** +- How to instantiate providers from config +- Provider validation +- Context object structure + +**Key concepts:** +```typescript +- Provider instantiation loop +- Config validation (checking clientId, clientSecret) +- Filtering disabled providers +- Creating provider instances from registry +``` + +**This is where:** +```typescript +socialProviders: { + google: { clientId: "...", clientSecret: "..." } +} +// Becomes: +const provider = socialProviders["google"](config); +``` + +--- + +### **PHASE 4: Understanding Plugin System** + +#### 11. Plugin Interface +**File:** `packages/core/src/types/plugin.ts` +**Lines to focus on:** 1-200 +**What to learn:** +- Plugin lifecycle hooks +- How plugins extend functionality +- Database schema definition +- Custom endpoints + +**Key concepts:** +```typescript +- BetterAuthPlugin interface +- init() lifecycle hook +- endpoints object +- schema definition +- hooks (before/after) +- $ERROR_CODES +``` + +--- + +#### 12. Simple Plugin Example +**File:** `packages/better-auth/src/plugins/bearer/index.ts` +**Lines to focus on:** 1-200 +**What to learn:** +- How to create a simple plugin +- Request/response transformation +- Middleware pattern + +**Key concepts:** +```typescript +- bearer() plugin factory +- hooks.before and hooks.after +- matcher() function +- handler() implementation +- Header manipulation +``` + +**Why bearer:** Simple, focused plugin that shows core patterns + +--- + +#### 13. Complex Plugin Example +**File:** `packages/stripe/src/index.ts` +**Lines to focus on:** 1-500 +**What to learn:** +- How to integrate external services +- Database schema in plugins +- Custom endpoints +- Error handling + +**Key concepts:** +```typescript +- stripe() plugin factory with options +- schema.subscription definition +- Multiple endpoints (get-plans, subscribe, cancel) +- External API integration (Stripe SDK) +- Error codes definition +``` + +**This is EXACTLY what you're building!** A Stripe plugin but as the core concept. + +--- + +#### 14. Plugin Initialization +**File:** `packages/better-auth/src/context/helpers.ts` +**Lines to focus on:** 1-150 (runPluginInit function) +**What to learn:** +- How plugins are initialized +- How plugins can modify context and options +- Plugin composition + +**Key concepts:** +```typescript +- runPluginInit() function +- Iterating through plugins +- Calling plugin.init() +- Merging options from plugins +- Deep merging with defu +``` + +--- + +### **PHASE 5: Understanding Package Structure** + +#### 15. Monorepo Workspace Config +**File:** `pnpm-workspace.yaml` +**What to learn:** +- How to structure a monorepo +- Package organization + +--- + +#### 16. Core Package Structure +**File:** `packages/core/package.json` +**What to learn:** +- How to define exports +- Dependencies vs peerDependencies +- Package naming + +--- + +#### 17. Main Package Structure +**File:** `packages/better-auth/package.json` +**What to learn:** +- How to export plugins +- Subpath exports pattern +- Build configuration + +--- + +## 🎯 Quick Reference by Concept + +### **Want to learn:** Provider Abstraction +**Read:** Files 1, 2, 3, 4, 5 (in order) + +### **Want to learn:** Configuration System +**Read:** Files 6, 7, 10 + +### **Want to learn:** Main Entry Point +**Read:** Files 8, 9 + +### **Want to learn:** Plugin System +**Read:** Files 11, 12, 13, 14 + +### **Want to learn:** Project Structure +**Read:** Files 15, 16, 17 + +--- + +## 📝 Study Notes Template + +For each file, take notes using this template: + +```markdown +### File: [filename] + +**Main Purpose:** +[What does this file do?] + +**Key Interfaces/Types:** +- [Type name]: [What it represents] +- [Type name]: [What it represents] + +**Key Functions:** +- [Function name]: [What it does] +- [Function name]: [What it does] + +**How I'll use this pattern:** +[Your notes on how to apply this to payment gateways] + +**Questions:** +[Anything you don't understand] +``` + +--- + +## 🚀 Practical Exercise + +After studying files 1-5, try this: + +**Exercise 1:** Design your `PaymentProvider` interface +- Model it after `OAuthProvider` +- Define required methods (create, verify, webhook) +- Define optional methods (refund, subscription) + +**Exercise 2:** Implement a Stripe provider +- Model it after `google.ts` +- Use the Stripe SDK +- Follow the same pattern + +**Exercise 3:** Implement a Flutterwave provider +- Model it after `github.ts` +- Use fetch for API calls +- Transform Flutterwave responses to your standard format + +**Exercise 4:** Create a provider registry +- Model it after `social-providers/index.ts` +- Export all your providers +- Create type-safe configuration + +--- + +## ⏱️ Estimated Time + +- **Phase 1 (Provider Abstraction):** 3-4 hours +- **Phase 2 (Configuration):** 1-2 hours +- **Phase 3 (Core Factory):** 2-3 hours +- **Phase 4 (Plugin System):** 3-4 hours +- **Phase 5 (Package Structure):** 1 hour + +**Total:** ~10-14 hours of focused study + +--- + +## 💡 Pro Tips + +1. **Don't read everything at once** - Follow the phases +2. **Try implementing as you learn** - Build your version alongside +3. **Focus on patterns, not details** - You don't need to understand every line +4. **Skip complex parts initially** - Come back to advanced features later +5. **Compare OAuth flow to Payment flow** - They're similar: + - OAuth: redirect → callback → get token → get user + - Payment: create intent → redirect → webhook → verify payment + +--- + +## 🎓 What You'll Understand + +After studying these files, you'll know: + +✅ How to create a provider abstraction +✅ How to make providers pluggable +✅ How to create type-safe configuration +✅ How to build a factory function +✅ How to create a plugin system +✅ How to structure a monorepo +✅ How to make your library framework-agnostic + +--- + +## 🤔 Common Questions + +**Q: Do I need to understand everything in better-auth?** +A: No! Focus on the provider pattern and plugin system. Skip auth-specific logic. + +**Q: Should I copy the code?** +A: Copy the **patterns**, not the code. Adapt it for payments. + +**Q: What about the database stuff?** +A: Optional for MVP. Start with just payment provider abstraction. + +**Q: How similar should my library be?** +A: Very similar in architecture, different in domain (payments vs auth). + +--- + +## 📞 Next Steps + +1. Read Phase 1 files (1-5) +2. Take notes using the template above +3. Try Exercise 1-2 +4. Share your progress and ask questions! + +Good luck! 🚀 diff --git a/OAUTH_TO_PAYMENT_MAPPING.md b/OAUTH_TO_PAYMENT_MAPPING.md new file mode 100644 index 0000000000..c3161c5535 --- /dev/null +++ b/OAUTH_TO_PAYMENT_MAPPING.md @@ -0,0 +1,455 @@ +# OAuth to Payment Gateway Mapping + +This document shows how OAuth concepts in better-auth map to Payment Gateway concepts in your library. + +## 🔄 Core Concept Mapping + +| OAuth Concept (better-auth) | Payment Concept (your library) | Why It's Similar | +|----------------------------|--------------------------------|------------------| +| **OAuth Provider** (Google, GitHub) | **Payment Gateway** (Stripe, Flutterwave) | Both are external services with different APIs | +| **Authorization URL** | **Payment Intent / Checkout URL** | Both redirect user to external service | +| **OAuth Callback** | **Payment Webhook** | Both receive confirmation from external service | +| **Access Token** | **Payment ID / Transaction ID** | Both are identifiers for the session/transaction | +| **User Profile** | **Payment Details** | Both are data returned from the service | +| **Refresh Token** | **Subscription Renewal** | Both handle recurring/long-term access | + +--- + +## 📋 Interface Comparison + +### Better-Auth: OAuthProvider Interface + +```typescript +export interface OAuthProvider { + id: string; // "google", "github" + name: string; // "Google", "GitHub" + + // Start the OAuth flow + createAuthorizationURL: (data: { + state: string; + codeVerifier: string; + scopes?: string[]; + redirectURI: string; + }) => Promise; + + // Verify the callback + validateAuthorizationCode: (data: { + code: string; + redirectURI: string; + }) => Promise; + + // Get user data + getUserInfo: (token: OAuth2Tokens) => Promise<{ + user: OAuth2UserInfo; + data: T; + }>; + + // Optional: refresh access + refreshAccessToken?: (refreshToken: string) => Promise; +} +``` + +### Your Library: PaymentProvider Interface + +```typescript +export interface PaymentProvider { + id: string; // "stripe", "flutterwave" + name: string; // "Stripe", "Flutterwave" + + // Start the payment flow + createPaymentIntent: (data: { + amount: number; + currency: string; + customerId?: string; + metadata?: Record; + }) => Promise; + + // Verify the payment + verifyPayment: (paymentId: string) => Promise; + + // Handle provider callback + handleWebhook: (payload: unknown, signature: string) => Promise; + + // Optional: handle refunds + refundPayment?: (paymentId: string, amount?: number) => Promise; +} +``` + +**See the parallel?** Both follow the same pattern: +1. **Initiate** (create URL / create intent) +2. **Verify** (validate code / verify payment) +3. **Get Data** (get user info / handle webhook) +4. **Optional Features** (refresh token / refund) + +--- + +## 🔄 Flow Comparison + +### OAuth Flow (better-auth) + +``` +1. User clicks "Login with Google" + ↓ +2. createAuthorizationURL() generates redirect URL + ↓ +3. User redirects to Google + ↓ +4. User approves on Google's site + ↓ +5. Google redirects back with code + ↓ +6. validateAuthorizationCode() exchanges code for tokens + ↓ +7. getUserInfo() fetches user profile + ↓ +8. User is logged in +``` + +### Payment Flow (your library) + +``` +1. User clicks "Pay with Stripe" + ↓ +2. createPaymentIntent() generates checkout session + ↓ +3. User redirects to Stripe checkout + ↓ +4. User pays on Stripe's site + ↓ +5. Stripe sends webhook to your server + ↓ +6. handleWebhook() verifies webhook signature + ↓ +7. verifyPayment() confirms payment status + ↓ +8. Payment is complete +``` + +**Same flow, different domain!** + +--- + +## 📦 Provider Implementation Comparison + +### Better-Auth: Google Provider + +```typescript +export const google = (options: GoogleOptions) => { + return { + id: "google", + name: "Google", + + async createAuthorizationURL({ state, scopes, redirectURI }) { + const url = new URL("https://accounts.google.com/o/oauth2/auth"); + url.searchParams.set("client_id", options.clientId); + url.searchParams.set("redirect_uri", redirectURI); + url.searchParams.set("scope", scopes.join(" ")); + url.searchParams.set("state", state); + return url; + }, + + async validateAuthorizationCode({ code, redirectURI }) { + const response = await fetch("https://oauth2.googleapis.com/token", { + method: "POST", + body: new URLSearchParams({ + code, + client_id: options.clientId, + client_secret: options.clientSecret, + redirect_uri: redirectURI, + grant_type: "authorization_code", + }), + }); + return await response.json(); + }, + + async getUserInfo(token) { + const user = decodeJwt(token.idToken); + return { + user: { + id: user.sub, + email: user.email, + name: user.name, + }, + data: user, + }; + }, + }; +}; +``` + +### Your Library: Stripe Provider + +```typescript +export const stripe = (options: StripeOptions) => { + const stripeClient = new Stripe(options.apiKey); + + return { + id: "stripe", + name: "Stripe", + + async createPaymentIntent({ amount, currency, customerId, metadata }) { + const paymentIntent = await stripeClient.paymentIntents.create({ + amount, + currency, + customer: customerId, + metadata, + }); + + return { + id: paymentIntent.id, + clientSecret: paymentIntent.client_secret, + amount: paymentIntent.amount, + status: paymentIntent.status, + }; + }, + + async verifyPayment(paymentId) { + const paymentIntent = await stripeClient.paymentIntents.retrieve(paymentId); + + return { + id: paymentIntent.id, + status: paymentIntent.status, + paid: paymentIntent.status === "succeeded", + amount: paymentIntent.amount, + }; + }, + + async handleWebhook(payload, signature) { + const event = stripeClient.webhooks.constructEvent( + payload, + signature, + options.webhookSecret + ); + + return { + type: event.type, + data: event.data.object, + }; + }, + }; +}; +``` + +**Notice:** Same structure, different API calls! + +--- + +## 🔌 Plugin Comparison + +### Better-Auth: Stripe Plugin (for subscriptions) + +```typescript +export const stripe = (options: StripeOptions) => { + return { + id: "stripe", + + schema: { + subscription: { + fields: { + stripeSubscriptionId: { type: "string" }, + stripeCustomerId: { type: "string" }, + plan: { type: "string" }, + status: { type: "string" }, + }, + }, + }, + + endpoints: { + "subscription/subscribe": createAuthEndpoint(...), + "subscription/cancel": createAuthEndpoint(...), + }, + }; +}; +``` + +### Your Library: Subscription Plugin + +```typescript +export const subscriptions = (options: SubscriptionOptions) => { + return { + id: "subscriptions", + + schema: { + subscription: { + fields: { + paymentProviderId: { type: "string" }, + subscriptionId: { type: "string" }, + plan: { type: "string" }, + status: { type: "string" }, + currentPeriodEnd: { type: "date" }, + }, + }, + }, + + endpoints: { + "subscription/create": createPaymentEndpoint(...), + "subscription/cancel": createPaymentEndpoint(...), + "subscription/upgrade": createPaymentEndpoint(...), + }, + }; +}; +``` + +**Same plugin architecture!** + +--- + +## ⚙️ Configuration Comparison + +### Better-Auth Configuration + +```typescript +const auth = betterAuth({ + // Configure multiple OAuth providers + socialProviders: { + google: { + clientId: process.env.GOOGLE_CLIENT_ID, + clientSecret: process.env.GOOGLE_CLIENT_SECRET, + scopes: ["email", "profile"], + }, + github: { + clientId: process.env.GITHUB_CLIENT_ID, + clientSecret: process.env.GITHUB_CLIENT_SECRET, + }, + }, + + // Add plugins + plugins: [ + bearer(), + organization(), + ], +}); +``` + +### Your Library Configuration + +```typescript +const payments = betterPayments({ + // Configure multiple payment providers + providers: { + stripe: { + apiKey: process.env.STRIPE_SECRET_KEY, + webhookSecret: process.env.STRIPE_WEBHOOK_SECRET, + }, + flutterwave: { + secretKey: process.env.FLUTTERWAVE_SECRET_KEY, + publicKey: process.env.FLUTTERWAVE_PUBLIC_KEY, + }, + }, + + // Add plugins + plugins: [ + subscriptions(), + invoicing(), + ], +}); +``` + +**Identical configuration pattern!** + +--- + +## 🎯 Usage Comparison + +### Better-Auth Usage + +```typescript +// Redirect to Google login +const url = await auth.api.signInSocial({ + provider: "google", + callbackURL: "/auth/callback", +}); + +// Verify callback +const session = await auth.api.verifyCallback({ + code: request.query.code, +}); + +// Get user +const user = await auth.api.getSession({ + token: session.token, +}); +``` + +### Your Library Usage + +```typescript +// Create Stripe payment +const intent = await payments.payment.create("stripe", { + amount: 5000, + currency: "USD", +}); + +// Redirect user to intent.clientSecret or payment URL + +// Verify webhook +const event = await payments.payment.handleWebhook("stripe", { + payload: request.body, + signature: request.headers["stripe-signature"], +}); + +// Get payment status +const status = await payments.payment.verify("stripe", event.paymentId); +``` + +**Same API design!** + +--- + +## 🔑 Key Takeaways + +| Better-Auth Does | Your Library Does | Same Pattern | +|------------------|-------------------|--------------| +| Abstracts OAuth providers | Abstracts payment gateways | ✅ Provider abstraction | +| Supports Google, GitHub, etc. | Supports Stripe, Flutterwave, etc. | ✅ Multiple providers | +| Plugins add features (SSO, passkey) | Plugins add features (subscriptions, invoicing) | ✅ Plugin system | +| Type-safe configuration | Type-safe configuration | ✅ TypeScript generics | +| Framework agnostic | Framework agnostic | ✅ Works anywhere | +| Monorepo structure | Monorepo structure | ✅ Package organization | + +--- + +## 💡 Aha Moments + +### 1. **Provider = Service Abstraction** +Better-auth abstracts OAuth providers (Google, GitHub) +→ You abstract payment providers (Stripe, Flutterwave) + +### 2. **Same Flow, Different Domain** +OAuth: redirect → callback → get user +→ Payment: checkout → webhook → verify payment + +### 3. **Plugins = Features** +Better-auth plugins: SSO, organizations, passkeys +→ Your plugins: subscriptions, invoicing, split payments + +### 4. **Configuration = Developer Experience** +Better-auth makes OAuth simple +→ You make payments simple + +--- + +## 📚 Study Strategy + +When reading better-auth code, mentally replace: + +- `OAuthProvider` → `PaymentProvider` +- `createAuthorizationURL` → `createPaymentIntent` +- `validateAuthorizationCode` → `verifyPayment` +- `getUserInfo` → `handleWebhook` +- `google()` → `stripe()` +- `github()` → `flutterwave()` + +The patterns are **identical**, only the domain changes! + +--- + +## 🎓 Next Steps + +1. ✅ Read this mapping document +2. ✅ Study the files in LEARNING_GUIDE.md +3. ✅ Keep this mental mapping in mind +4. ✅ When you see OAuth code, think "How does this apply to payments?" +5. ✅ Start implementing your own providers + +**You've got this!** 🚀 diff --git a/QUICK_START_IMPLEMENTATION.md b/QUICK_START_IMPLEMENTATION.md new file mode 100644 index 0000000000..c80cfde884 --- /dev/null +++ b/QUICK_START_IMPLEMENTATION.md @@ -0,0 +1,837 @@ +# Quick Start: Building Your Payment Gateway Library + +After studying better-auth, here's how to start building your payment gateway abstraction library. + +## 🚀 Project Setup + +### Step 1: Create Monorepo Structure + +```bash +mkdir better-payments +cd better-payments + +# Initialize pnpm workspace +pnpm init + +# Create packages +mkdir -p packages/core/src/providers +mkdir -p packages/core/src/types +mkdir -p packages/better-payments/src +mkdir -p packages/stripe-plugin/src +mkdir -p examples/nextjs +``` + +### Step 2: Create `pnpm-workspace.yaml` + +```yaml +packages: + - 'packages/*' + - 'examples/*' +``` + +### Step 3: Create Root `package.json` + +```json +{ + "name": "better-payments-workspace", + "version": "0.0.1", + "private": true, + "scripts": { + "build": "pnpm -r build", + "dev": "pnpm -r --parallel dev", + "test": "pnpm -r test" + }, + "devDependencies": { + "typescript": "^5.3.0", + "tsup": "^8.0.0" + } +} +``` + +--- + +## 📝 Step-by-Step Implementation + +### Phase 1: Core Types + +**File:** `packages/core/src/types/provider.ts` + +```typescript +/** + * Core payment provider interface + * Inspired by better-auth's OAuthProvider + */ + +export interface PaymentIntent { + id: string; + amount: number; + currency: string; + status: 'pending' | 'processing' | 'succeeded' | 'failed' | 'canceled'; + clientSecret?: string; + paymentUrl?: string; + metadata?: Record; +} + +export interface PaymentStatus { + id: string; + status: 'pending' | 'processing' | 'succeeded' | 'failed' | 'canceled'; + amount: number; + currency: string; + paid: boolean; + metadata?: Record; +} + +export interface WebhookEvent { + type: string; + paymentId: string; + status: PaymentStatus['status']; + data: any; +} + +export interface Refund { + id: string; + paymentId: string; + amount: number; + status: 'pending' | 'succeeded' | 'failed'; + reason?: string; +} + +export interface CreatePaymentData { + amount: number; + currency: string; + customerId?: string; + customerEmail?: string; + description?: string; + metadata?: Record; + returnUrl?: string; +} + +// Base options that all providers share +export interface ProviderOptions { + // Provider credentials + apiKey?: string; + secretKey?: string; + publicKey?: string; + webhookSecret?: string; + + // Environment + environment?: 'sandbox' | 'production' | 'test'; + + // Customization + onPaymentSuccess?: (payment: PaymentStatus) => Promise | void; + onPaymentFailure?: (payment: PaymentStatus) => Promise | void; + mapPaymentData?: (data: TProfile) => Partial; +} + +// Main provider interface +export interface PaymentProvider< + TProviderData extends Record = Record, + TOptions extends Record = Partial +> { + id: string; // "stripe", "flutterwave", "paystack" + name: string; // "Stripe", "Flutterwave", "PayStack" + + // Required methods + createPaymentIntent: (data: CreatePaymentData) => Promise; + + verifyPayment: (paymentId: string) => Promise; + + handleWebhook: (payload: any, signature: string) => Promise; + + // Optional methods + refundPayment?: (paymentId: string, amount?: number, reason?: string) => Promise; + + cancelPayment?: (paymentId: string) => Promise; + + getPayment?: (paymentId: string) => Promise; + + // Configuration + options?: TOptions; +} + +export type LiteralString = string & {}; +``` + +--- + +### Phase 2: First Provider (Stripe) + +**File:** `packages/core/src/providers/stripe.ts` + +```typescript +import Stripe from 'stripe'; +import type { PaymentProvider, ProviderOptions, CreatePaymentData } from '../types/provider.js'; + +export interface StripeProfile { + id: string; + object: string; + amount: number; + currency: string; + status: string; + // ... add more Stripe-specific fields +} + +export interface StripeOptions extends ProviderOptions { + apiKey: string; + webhookSecret: string; + apiVersion?: string; +} + +export const stripe = (options: StripeOptions) => { + // Initialize Stripe client + const stripeClient = new Stripe(options.apiKey, { + apiVersion: options.apiVersion || '2023-10-16', + }); + + return { + id: 'stripe' as const, + name: 'Stripe', + + async createPaymentIntent(data: CreatePaymentData) { + const paymentIntent = await stripeClient.paymentIntents.create({ + amount: data.amount, + currency: data.currency, + customer: data.customerId, + description: data.description, + metadata: data.metadata || {}, + // Enable automatic payment methods + automatic_payment_methods: { + enabled: true, + }, + }); + + return { + id: paymentIntent.id, + amount: paymentIntent.amount, + currency: paymentIntent.currency, + status: mapStripeStatus(paymentIntent.status), + clientSecret: paymentIntent.client_secret || undefined, + metadata: paymentIntent.metadata, + }; + }, + + async verifyPayment(paymentId: string) { + const paymentIntent = await stripeClient.paymentIntents.retrieve(paymentId); + + const status: PaymentStatus = { + id: paymentIntent.id, + status: mapStripeStatus(paymentIntent.status), + amount: paymentIntent.amount, + currency: paymentIntent.currency, + paid: paymentIntent.status === 'succeeded', + metadata: paymentIntent.metadata, + }; + + // Call custom handler if provided + if (status.paid && options.onPaymentSuccess) { + await options.onPaymentSuccess(status); + } + + return status; + }, + + async handleWebhook(payload: any, signature: string) { + let event: Stripe.Event; + + try { + event = stripeClient.webhooks.constructEvent( + payload, + signature, + options.webhookSecret + ); + } catch (err) { + throw new Error(`Webhook signature verification failed: ${err.message}`); + } + + const paymentIntent = event.data.object as Stripe.PaymentIntent; + + return { + type: event.type, + paymentId: paymentIntent.id, + status: mapStripeStatus(paymentIntent.status), + data: event.data.object, + }; + }, + + async refundPayment(paymentId: string, amount?: number, reason?: string) { + const refund = await stripeClient.refunds.create({ + payment_intent: paymentId, + amount, + reason: reason as Stripe.RefundCreateParams.Reason, + }); + + return { + id: refund.id, + paymentId: paymentId, + amount: refund.amount, + status: refund.status === 'succeeded' ? 'succeeded' : + refund.status === 'pending' ? 'pending' : 'failed', + reason, + }; + }, + + async cancelPayment(paymentId: string) { + const paymentIntent = await stripeClient.paymentIntents.cancel(paymentId); + + return { + id: paymentIntent.id, + status: mapStripeStatus(paymentIntent.status), + amount: paymentIntent.amount, + currency: paymentIntent.currency, + paid: false, + }; + }, + + async getPayment(paymentId: string) { + return this.verifyPayment(paymentId); + }, + + options, + } satisfies PaymentProvider; +}; + +// Helper function to map Stripe statuses to our standard statuses +function mapStripeStatus(status: string): PaymentStatus['status'] { + switch (status) { + case 'requires_payment_method': + case 'requires_confirmation': + case 'requires_action': + return 'pending'; + case 'processing': + return 'processing'; + case 'succeeded': + return 'succeeded'; + case 'canceled': + return 'canceled'; + default: + return 'failed'; + } +} +``` + +--- + +### Phase 3: Second Provider (Flutterwave) + +**File:** `packages/core/src/providers/flutterwave.ts` + +```typescript +import type { PaymentProvider, ProviderOptions, CreatePaymentData } from '../types/provider.js'; + +export interface FlutterwaveProfile { + id: number; + tx_ref: string; + flw_ref: string; + amount: number; + currency: string; + status: string; + // ... add more Flutterwave-specific fields +} + +export interface FlutterwaveOptions extends ProviderOptions { + publicKey: string; + secretKey: string; + encryptionKey: string; + environment?: 'sandbox' | 'production'; +} + +export const flutterwave = (options: FlutterwaveOptions) => { + const baseURL = options.environment === 'production' + ? 'https://api.flutterwave.com/v3' + : 'https://api.flutterwave.com/v3'; // Same for both + + return { + id: 'flutterwave' as const, + name: 'Flutterwave', + + async createPaymentIntent(data: CreatePaymentData) { + const txRef = `tx-${Date.now()}-${Math.random().toString(36).substr(2, 9)}`; + + const response = await fetch(`${baseURL}/payments`, { + method: 'POST', + headers: { + 'Authorization': `Bearer ${options.secretKey}`, + 'Content-Type': 'application/json', + }, + body: JSON.stringify({ + tx_ref: txRef, + amount: data.amount, + currency: data.currency, + redirect_url: data.returnUrl, + customer: { + email: data.customerEmail, + ...(data.customerId && { customer_id: data.customerId }), + }, + customizations: { + title: data.description || 'Payment', + }, + meta: data.metadata, + }), + }); + + if (!response.ok) { + throw new Error(`Flutterwave API error: ${response.statusText}`); + } + + const result = await response.json(); + + return { + id: result.data.id.toString(), + amount: data.amount, + currency: data.currency, + status: 'pending', + paymentUrl: result.data.link, + metadata: { tx_ref: txRef, ...data.metadata }, + }; + }, + + async verifyPayment(paymentId: string) { + const response = await fetch( + `${baseURL}/transactions/${paymentId}/verify`, + { + headers: { + 'Authorization': `Bearer ${options.secretKey}`, + }, + } + ); + + if (!response.ok) { + throw new Error(`Flutterwave verification error: ${response.statusText}`); + } + + const result = await response.json(); + const data = result.data; + + const status: PaymentStatus = { + id: data.id.toString(), + status: mapFlutterwaveStatus(data.status), + amount: data.amount, + currency: data.currency, + paid: data.status === 'successful', + metadata: data.meta, + }; + + if (status.paid && options.onPaymentSuccess) { + await options.onPaymentSuccess(status); + } + + return status; + }, + + async handleWebhook(payload: any, signature: string) { + // Verify webhook signature + const crypto = await import('crypto'); + const hash = crypto + .createHmac('sha256', options.encryptionKey) + .update(JSON.stringify(payload)) + .digest('hex'); + + if (hash !== signature) { + throw new Error('Invalid webhook signature'); + } + + return { + type: payload.event, + paymentId: payload.data.id.toString(), + status: mapFlutterwaveStatus(payload.data.status), + data: payload.data, + }; + }, + + async refundPayment(paymentId: string, amount?: number) { + const response = await fetch(`${baseURL}/transactions/${paymentId}/refund`, { + method: 'POST', + headers: { + 'Authorization': `Bearer ${options.secretKey}`, + 'Content-Type': 'application/json', + }, + body: JSON.stringify({ + amount, + }), + }); + + if (!response.ok) { + throw new Error(`Flutterwave refund error: ${response.statusText}`); + } + + const result = await response.json(); + + return { + id: result.data.id.toString(), + paymentId, + amount: result.data.amount, + status: 'succeeded', + }; + }, + + options, + } satisfies PaymentProvider; +}; + +function mapFlutterwaveStatus(status: string): PaymentStatus['status'] { + switch (status) { + case 'successful': + return 'succeeded'; + case 'failed': + return 'failed'; + case 'pending': + return 'pending'; + default: + return 'processing'; + } +} +``` + +--- + +### Phase 4: Provider Registry + +**File:** `packages/core/src/providers/index.ts` + +```typescript +import { stripe } from './stripe.js'; +import { flutterwave } from './flutterwave.js'; + +export const paymentProviders = { + stripe, + flutterwave, + // Add more providers here +} as const; + +export const paymentProviderList = Object.keys(paymentProviders) as [ + 'stripe', + ...(keyof typeof paymentProviders)[], +]; + +export type PaymentProviderList = typeof paymentProviderList; + +export type PaymentProviders = { + [K in PaymentProviderList[number]]?: Parameters< + (typeof paymentProviders)[K] + >[0] & { + enabled?: boolean; + }; +}; + +// Re-export providers +export { stripe } from './stripe.js'; +export { flutterwave } from './flutterwave.js'; +export type { StripeOptions } from './stripe.js'; +export type { FlutterwaveOptions } from './flutterwave.js'; +``` + +--- + +### Phase 5: Main Configuration + +**File:** `packages/core/src/types/options.ts` + +```typescript +import type { PaymentProviders } from '../providers/index.js'; + +export interface PaymentGatewayOptions { + /** + * Payment providers configuration + */ + providers: PaymentProviders; + + /** + * Default currency for payments + * @default "USD" + */ + defaultCurrency?: string; + + /** + * Webhook configuration + */ + webhooks?: { + /** + * Path for webhook endpoint + * @default "/api/payments/webhook" + */ + path?: string; + + /** + * Handle webhook events + */ + onEvent?: (event: WebhookEvent) => Promise | void; + }; + + /** + * Plugins + */ + plugins?: PaymentPlugin[]; + + /** + * Advanced options + */ + advanced?: { + /** + * Retry failed payments automatically + */ + retryFailedPayments?: boolean; + + /** + * Auto refund on cancellation + */ + autoRefundOnCancel?: boolean; + + /** + * Enable logging + */ + logging?: boolean; + }; +} + +export interface PaymentPlugin { + id: string; + init?: (context: any) => Promise | void; + endpoints?: Record; +} +``` + +--- + +### Phase 6: Main Factory Function + +**File:** `packages/better-payments/src/index.ts` + +```typescript +import type { PaymentGatewayOptions } from '@better-payments/core/types/options'; +import { paymentProviders } from '@better-payments/core/providers'; +import type { PaymentProvider } from '@better-payments/core/types/provider'; + +export const betterPayments = ( + options: Options +) => { + // Instantiate providers from configuration + const providers = Object.entries(options.providers || {}) + .map(([key, config]) => { + if (!config || config.enabled === false) { + return null; + } + + const providerFactory = paymentProviders[key as keyof typeof paymentProviders]; + if (!providerFactory) { + console.warn(`Provider ${key} not found`); + return null; + } + + return providerFactory(config as any); + }) + .filter((p): p is PaymentProvider => p !== null); + + // Helper to find provider + const findProvider = (providerId: string) => { + const provider = providers.find(p => p.id === providerId); + if (!provider) { + throw new Error(`Provider ${providerId} not found or not enabled`); + } + return provider; + }; + + return { + /** + * Payment operations + */ + payment: { + /** + * Create a new payment + */ + create: async (providerId: string, data: CreatePaymentData) => { + const provider = findProvider(providerId); + return provider.createPaymentIntent({ + ...data, + currency: data.currency || options.defaultCurrency || 'USD', + }); + }, + + /** + * Verify a payment + */ + verify: async (providerId: string, paymentId: string) => { + const provider = findProvider(providerId); + return provider.verifyPayment(paymentId); + }, + + /** + * Refund a payment + */ + refund: async (providerId: string, paymentId: string, amount?: number, reason?: string) => { + const provider = findProvider(providerId); + if (!provider.refundPayment) { + throw new Error(`Provider ${providerId} does not support refunds`); + } + return provider.refundPayment(paymentId, amount, reason); + }, + + /** + * Cancel a payment + */ + cancel: async (providerId: string, paymentId: string) => { + const provider = findProvider(providerId); + if (!provider.cancelPayment) { + throw new Error(`Provider ${providerId} does not support cancellation`); + } + return provider.cancelPayment(paymentId); + }, + + /** + * Get payment details + */ + get: async (providerId: string, paymentId: string) => { + const provider = findProvider(providerId); + if (provider.getPayment) { + return provider.getPayment(paymentId); + } + return provider.verifyPayment(paymentId); + }, + }, + + /** + * HTTP handler for webhooks + */ + handler: async (request: Request) => { + const url = new URL(request.url); + const webhookPath = options.webhooks?.path || '/api/payments/webhook'; + + if (!url.pathname.endsWith(webhookPath)) { + return new Response('Not found', { status: 404 }); + } + + // Extract provider from query or header + const providerId = url.searchParams.get('provider') || + request.headers.get('x-payment-provider'); + + if (!providerId) { + return new Response('Provider not specified', { status: 400 }); + } + + const provider = findProvider(providerId); + + // Get signature from headers + const signature = request.headers.get(`${providerId}-signature`) || + request.headers.get('stripe-signature') || + request.headers.get('verif-hash') || ''; + + try { + const payload = await request.text(); + const event = await provider.handleWebhook(JSON.parse(payload), signature); + + // Call webhook handler + if (options.webhooks?.onEvent) { + await options.webhooks.onEvent(event); + } + + return new Response(JSON.stringify({ received: true }), { + status: 200, + headers: { 'Content-Type': 'application/json' }, + }); + } catch (error) { + console.error('Webhook error:', error); + return new Response( + JSON.stringify({ error: error.message }), + { status: 400, headers: { 'Content-Type': 'application/json' } } + ); + } + }, + + /** + * Configuration + */ + options, + + /** + * List of enabled providers + */ + providers: providers.map(p => ({ id: p.id, name: p.name })), + }; +}; + +// Re-export types +export type { PaymentGatewayOptions } from '@better-payments/core/types/options'; +export type { PaymentProvider, CreatePaymentData, PaymentIntent, PaymentStatus } from '@better-payments/core/types/provider'; +``` + +--- + +## 🎯 Usage Example + +**File:** `examples/nextjs/app/api/payments/route.ts` + +```typescript +import { betterPayments } from 'better-payments'; + +const payments = betterPayments({ + providers: { + stripe: { + apiKey: process.env.STRIPE_SECRET_KEY!, + webhookSecret: process.env.STRIPE_WEBHOOK_SECRET!, + onPaymentSuccess: async (payment) => { + console.log('Payment succeeded:', payment.id); + // Send email, update database, etc. + }, + }, + flutterwave: { + publicKey: process.env.FLUTTERWAVE_PUBLIC_KEY!, + secretKey: process.env.FLUTTERWAVE_SECRET_KEY!, + encryptionKey: process.env.FLUTTERWAVE_ENCRYPTION_KEY!, + }, + }, + defaultCurrency: 'USD', +}); + +// Create payment endpoint +export async function POST(request: Request) { + const { provider, amount, currency } = await request.json(); + + try { + const payment = await payments.payment.create(provider, { + amount, + currency, + customerEmail: 'customer@example.com', + description: 'Test payment', + }); + + return Response.json(payment); + } catch (error) { + return Response.json({ error: error.message }, { status: 500 }); + } +} + +// Webhook endpoint +export async function POST_WEBHOOK(request: Request) { + return payments.handler(request); +} +``` + +--- + +## ✅ What You've Built + +After following this guide, you have: + +- ✅ Core provider interface +- ✅ Stripe provider implementation +- ✅ Flutterwave provider implementation +- ✅ Provider registry system +- ✅ Type-safe configuration +- ✅ Main factory function +- ✅ Webhook handling +- ✅ Framework-agnostic API + +--- + +## 🎓 Next Steps + +1. **Add more providers** (PayStack, PayPal, Square) +2. **Add plugins** (subscriptions, invoicing, split payments) +3. **Add database support** (save payment records) +4. **Add React hooks** (usePayment, useSubscription) +5. **Add documentation** (README, API reference) +6. **Add tests** (unit tests, integration tests) +7. **Publish to npm** (better-payments) + +--- + +**You've got the foundation! Start building!** 🚀 diff --git a/STUDY_CHECKLIST.md b/STUDY_CHECKLIST.md new file mode 100644 index 0000000000..c447fc1d4b --- /dev/null +++ b/STUDY_CHECKLIST.md @@ -0,0 +1,206 @@ +# Better-Auth Study Checklist + +Use this checklist to track your progress as you study the better-auth codebase. + +## 📋 Phase 1: Provider Abstraction + +- [ ] **File 1:** `packages/core/src/oauth2/oauth-provider.ts` (Lines 14-83) + - [ ] Understand `OAuthProvider` interface + - [ ] Note required methods + - [ ] Note optional methods + - [ ] Understand generic types `` + +- [ ] **File 2:** `packages/core/src/social-providers/github.ts` (Lines 1-200) + - [ ] Understand `GithubProfile` interface + - [ ] Understand `GithubOptions` interface + - [ ] See how `github()` factory works + - [ ] Note API endpoint patterns + +- [ ] **File 3:** `packages/core/src/social-providers/google.ts` (Lines 1-250) + - [ ] Compare with GitHub provider + - [ ] Understand additional features (verifyIdToken) + - [ ] Note token refresh pattern + - [ ] See helper function usage + +- [ ] **File 4:** `packages/core/src/social-providers/paypal.ts` (Lines 1-150) + - [ ] Understand environment handling (sandbox/production) + - [ ] Note conditional endpoint URLs + - [ ] See how it differs from GitHub/Google + +- [ ] **File 5:** `packages/core/src/social-providers/index.ts` (Lines 1-100) + - [ ] Understand `socialProviders` registry + - [ ] Understand `socialProviderList` enum + - [ ] Understand `SocialProviders` type + - [ ] Note how types are generated + +**Exercise after Phase 1:** +- [ ] Design your `PaymentProvider` interface (on paper or in code) +- [ ] List required methods for payment providers +- [ ] List optional methods for payment providers + +--- + +## 📋 Phase 2: Configuration System + +- [ ] **File 6:** `packages/core/src/types/init-options.ts` (Lines 1-300) + - [ ] Understand `BetterAuthOptions` structure + - [ ] Note how `socialProviders` is configured + - [ ] Note how plugins array works + - [ ] See `emailAndPassword` config pattern + +- [ ] **File 7:** `packages/core/src/oauth2/oauth-provider.ts` (Lines 85-120) + - [ ] Understand `ProviderOptions` interface + - [ ] Note common fields (clientId, clientSecret) + - [ ] Note customization options (getUserInfo, mapProfileToUser) + +**Exercise after Phase 2:** +- [ ] Design your `PaymentGatewayOptions` interface +- [ ] Design your `ProviderOptions` base interface +- [ ] Design provider-specific options (StripeOptions, FlutterwaveOptions) + +--- + +## 📋 Phase 3: Core Factory + +- [ ] **File 8:** `packages/better-auth/src/auth/auth.ts` (Lines 1-50) + - [ ] Understand `betterAuth()` function + - [ ] Note how generics are used + - [ ] See delegation to `createBetterAuth` + +- [ ] **File 9:** `packages/better-auth/src/auth/base.ts` (Lines 1-150) + - [ ] Understand `createBetterAuth()` factory + - [ ] Note the `handler` function + - [ ] See plugin aggregation pattern + - [ ] Understand error code collection + +- [ ] **File 10:** `packages/better-auth/src/context/create-context.ts` (Lines 1-300) + - [ ] See how providers are instantiated from config + - [ ] Note provider validation + - [ ] Understand context object structure + +**Exercise after Phase 3:** +- [ ] Sketch out your `betterPayments()` function +- [ ] Sketch out your `createPaymentGateway()` factory +- [ ] Design your context object structure + +--- + +## 📋 Phase 4: Plugin System + +- [ ] **File 11:** `packages/core/src/types/plugin.ts` (Lines 1-200) + - [ ] Understand `BetterAuthPlugin` interface + - [ ] Note lifecycle hooks (init, before, after) + - [ ] Understand schema definition + - [ ] Note endpoints pattern + +- [ ] **File 12:** `packages/better-auth/src/plugins/bearer/index.ts` (Lines 1-200) + - [ ] Understand bearer plugin pattern + - [ ] See hooks.before and hooks.after + - [ ] Note matcher function + - [ ] Understand header manipulation + +- [ ] **File 13:** `packages/stripe/src/index.ts` (Lines 1-500) + - [ ] See complex plugin example + - [ ] Note schema definition for subscriptions + - [ ] Note multiple endpoints pattern + - [ ] See Stripe SDK integration + - [ ] Note error codes definition + +- [ ] **File 14:** `packages/better-auth/src/context/helpers.ts` (Lines 1-150) + - [ ] Understand `runPluginInit()` function + - [ ] See how plugins modify options + - [ ] Note deep merge pattern + +**Exercise after Phase 4:** +- [ ] Design your `PaymentPlugin` interface +- [ ] Sketch a subscriptions plugin +- [ ] Sketch an invoicing plugin + +--- + +## 📋 Phase 5: Package Structure + +- [ ] **File 15:** `pnpm-workspace.yaml` + - [ ] Understand monorepo structure + - [ ] Note package organization + +- [ ] **File 16:** `packages/core/package.json` + - [ ] See exports configuration + - [ ] Note dependencies structure + +- [ ] **File 17:** `packages/better-auth/package.json` + - [ ] See subpath exports + - [ ] Note plugin export pattern + +**Exercise after Phase 5:** +- [ ] Design your monorepo structure +- [ ] Plan your package names +- [ ] Decide on export strategy + +--- + +## 🎯 Final Exercises + +- [ ] **Exercise 1:** Implement a basic Stripe provider + - [ ] Create `StripeOptions` interface + - [ ] Create `stripe()` factory function + - [ ] Implement `createPaymentIntent()` + - [ ] Implement `verifyPayment()` + - [ ] Implement `handleWebhook()` + +- [ ] **Exercise 2:** Implement a basic Flutterwave provider + - [ ] Create `FlutterwaveOptions` interface + - [ ] Create `flutterwave()` factory function + - [ ] Implement core methods + - [ ] Handle sandbox/production environments + +- [ ] **Exercise 3:** Create provider registry + - [ ] Create `paymentProviders` object + - [ ] Create `PaymentProviders` type + - [ ] Test type safety + +- [ ] **Exercise 4:** Build minimal working version + - [ ] Create `betterPayments()` function + - [ ] Support 2 providers (Stripe + Flutterwave) + - [ ] Test with actual API calls (sandbox mode) + +--- + +## 📊 Progress Tracker + +**Phase 1:** ☐☐☐☐☐ (0/5 files) +**Phase 2:** ☐☐ (0/2 files) +**Phase 3:** ☐☐☐ (0/3 files) +**Phase 4:** ☐☐☐☐ (0/4 files) +**Phase 5:** ☐☐☐ (0/3 files) + +**Exercises:** ☐☐☐☐ (0/4 completed) + +**Overall Progress:** 0% (0/21 total tasks) + +--- + +## 📝 Notes Section + +Use this space to write down: +- Questions you have +- Aha moments +- Patterns you notice +- Ideas for your implementation + +``` +[Your notes here] +``` + +--- + +## 🎓 Completion + +When you check all boxes above, you'll be ready to: +✅ Build your payment gateway abstraction library +✅ Support multiple payment providers +✅ Create a plugin system +✅ Structure a professional monorepo +✅ Provide excellent TypeScript types + +**Good luck!** 🚀