better-auth/STUDY_CHECKLIST.md

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 <T, O>

• 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

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📋 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<Profile> 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)

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📋 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

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📋 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

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📋 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

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🎯 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)

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📊 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)

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📝 Notes Section

Use this space to write down:

• Questions you have
• Aha moments
• Patterns you notice
• Ideas for your implementation

[Your notes here]

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🎓 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! 🚀