Custom Authentication Adapters Guide

Overview
Server-Side Adapters
Client-Side Adapters
Common Patterns
Testing Adapters
Complete Examples

Overview

SolvaPay SDK uses authentication adapters to extract user IDs from requests. There are two types of adapters:

Server-Side Adapters (@solvapay/auth) - Extract user IDs from HTTP requests in API routes
Client-Side Adapters (@solvapay/react) - Extract user IDs and tokens from client-side auth state

Server-Side Adapters

Server-side adapters are used with @solvapay/server to extract user IDs from HTTP requests in API routes, Express endpoints, and other server-side contexts.

Interface

import type { AuthAdapter } from '@solvapay/auth'

interface AuthAdapter {
  /**
   * Extract the authenticated user ID from a request.
   * Should never throw - return null if authentication fails or is missing.
   */
  getUserIdFromRequest(req: Request | RequestLike): Promise<string | null>
}

Basic Example: JWT Token Adapter

import type { AuthAdapter } from '@solvapay/auth'
import jwt from 'jsonwebtoken'

class JWTAuthAdapter implements AuthAdapter {
  constructor(private secret: string) {}

  async getUserIdFromRequest(req: Request | RequestLike): Promise<string | null> {
    try {
      // Extract token from Authorization header
      const authHeader = req.headers.get?.('authorization') || (req.headers as any).authorization

      if (!authHeader || !authHeader.startsWith('Bearer ')) {
        return null
      }

      const token = authHeader.replace('Bearer ', '')

      // Verify and decode token
      const decoded = jwt.verify(token, this.secret) as { userId: string }

      return decoded.userId || null
    } catch (error) {
      // Never throw - return null on error
      return null
    }
  }
}

// Usage
const authAdapter = new JWTAuthAdapter(process.env.JWT_SECRET!)
const userId = await authAdapter.getUserIdFromRequest(request)

Example: Session-Based Adapter

import type { AuthAdapter } from '@solvapay/auth'
import { getSession } from 'your-session-library'

class SessionAuthAdapter implements AuthAdapter {
  async getUserIdFromRequest(req: Request | RequestLike): Promise<string | null> {
    try {
      // Extract session from request
      const session = await getSession(req)

      if (!session || !session.userId) {
        return null
      }

      return session.userId
    } catch (error) {
      return null
    }
  }
}

Example: Custom Header Adapter

import type { AuthAdapter } from '@solvapay/auth'

class HeaderAuthAdapter implements AuthAdapter {
  constructor(private headerName: string = 'x-user-id') {}

  async getUserIdFromRequest(req: Request | RequestLike): Promise<string | null> {
    const userId = req.headers.get?.(this.headerName) || (req.headers as any)[this.headerName]

    return userId || null
  }
}

// Usage
const authAdapter = new HeaderAuthAdapter('x-customer-id')

Using with SolvaPay Server SDK

import { createSolvaPay } from '@solvapay/server'
import type { AuthAdapter } from '@solvapay/auth'

const authAdapter: AuthAdapter = {
  async getUserIdFromRequest(req) {
    // Your custom logic
    return userId || null
  },
}

const solvaPay = createSolvaPay({ apiKey: process.env.SOLVAPAY_SECRET_KEY })
const payable = solvaPay.payable({ product: 'prd_myapi', plan: 'pln_premium' })

// Use with Express
app.post(
  '/api/tasks',
  payable.http(createTask, {
    getCustomerRef: async req => {
      const userId = await authAdapter.getUserIdFromRequest(req)
      if (!userId) throw new Error('Unauthorized')
      return userId
    },
  }),
)

// Use with Next.js
export const POST = payable.next(createTask, {
  getCustomerRef: async req => {
    const userId = await authAdapter.getUserIdFromRequest(req)
    if (!userId) throw new Error('Unauthorized')
    return userId
  },
})

Client-Side Adapters

Client-side adapters are used with @solvapay/react to extract user IDs and tokens from client-side authentication state.

Interface

import type { AuthAdapter } from '@solvapay/react'

interface AuthAdapter {
  /**
   * Get the authentication token
   */
  getToken(): Promise<string | null>

  /**
   * Get the user ID (for cache key)
   */
  getUserId(): Promise<string | null>
}

Basic Example: LocalStorage Adapter

import type { AuthAdapter } from '@solvapay/react';

class LocalStorageAuthAdapter implements AuthAdapter {
  async getToken(): Promise<string | null> {
    return localStorage.getItem('auth-token');
  }

  async getUserId(): Promise<string | null> {
    const token = await this.getToken();
    if (!token) return null;

    try {
      // Decode JWT token (client-side)
      const payload = JSON.parse(atob(token.split('.')[1]));
      return payload.userId || null;
    } catch {
      return null;
    }
  }
}

// Usage with SolvaPayProvider
import { SolvaPayProvider } from '@solvapay/react';

function App() {
  const adapter = new LocalStorageAuthAdapter();

  return (
    <SolvaPayProvider config={{ auth: { adapter } }}>
      <YourApp />
    </SolvaPayProvider>
  );
}

Example: Context-Based Adapter

import type { AuthAdapter } from '@solvapay/react';
import { useContext } from 'react';
import { AuthContext } from './AuthContext';

function createContextAuthAdapter(): AuthAdapter {
  return {
    async getToken() {
      // Access auth context
      const { token } = useContext(AuthContext);
      return token || null;
    },

    async getUserId() {
      const { user } = useContext(AuthContext);
      return user?.id || null;
    },
  };
}

// Usage
function App() {
  const adapter = createContextAuthAdapter();

  return (
    <SolvaPayProvider config={{ auth: { adapter } }}>
      <YourApp />
    </SolvaPayProvider>
  );
}

Example: Async Storage Adapter (React Native)

import type { AuthAdapter } from '@solvapay/react'
import AsyncStorage from '@react-native-async-storage/async-storage'

class AsyncStorageAuthAdapter implements AuthAdapter {
  async getToken(): Promise<string | null> {
    return await AsyncStorage.getItem('auth-token')
  }

  async getUserId(): Promise<string | null> {
    const token = await this.getToken()
    if (!token) return null

    try {
      const payload = JSON.parse(atob(token.split('.')[1]))
      return payload.userId || null
    } catch {
      return null
    }
  }
}

Common Patterns

Pattern 1: JWT Token with User ID Extraction

// Server-side
class JWTAdapter implements AuthAdapter {
  constructor(private secret: string) {}

  async getUserIdFromRequest(req: Request | RequestLike): Promise<string | null> {
    const token = this.extractToken(req)
    if (!token) return null

    try {
      const decoded = jwt.verify(token, this.secret) as { userId: string }
      return decoded.userId
    } catch {
      return null
    }
  }

  private extractToken(req: Request | RequestLike): string | null {
    const authHeader = req.headers.get?.('authorization') || (req.headers as any).authorization
    return authHeader?.replace('Bearer ', '') || null
  }
}

// Server-side
class CookieAuthAdapter implements AuthAdapter {
  async getUserIdFromRequest(req: Request | RequestLike): Promise<string | null> {
    // Extract from cookies
    const cookies = this.parseCookies(req)
    const sessionId = cookies['session-id']

    if (!sessionId) return null

    // Look up session in database/cache
    const session = await this.getSession(sessionId)
    return session?.userId || null
  }

  private parseCookies(req: Request | RequestLike): Record<string, string> {
    const cookieHeader = req.headers.get?.('cookie') || (req.headers as any).cookie
    if (!cookieHeader) return {}

    return cookieHeader.split(';').reduce(
      (acc, cookie) => {
        const [key, value] = cookie.trim().split('=')
        acc[key] = value
        return acc
      },
      {} as Record<string, string>,
    )
  }

  private async getSession(sessionId: string): Promise<{ userId: string } | null> {
    // Your session lookup logic
    return null
  }
}

Pattern 3: API Key with User Mapping

// Server-side
class APIKeyAuthAdapter implements AuthAdapter {
  constructor(private keyToUserId: Map<string, string>) {}

  async getUserIdFromRequest(req: Request | RequestLike): Promise<string | null> {
    const apiKey = req.headers.get?.('x-api-key') || (req.headers as any)['x-api-key']

    if (!apiKey) return null

    return this.keyToUserId.get(apiKey) || null
  }
}

Testing Adapters

Mock Adapter for Testing

// Server-side mock
class MockAuthAdapter implements AuthAdapter {
  constructor(private mockUserId: string | null = 'test-user-123') {}

  async getUserIdFromRequest(req: Request | RequestLike): Promise<string | null> {
    // Allow override via header
    const headerUserId =
      req.headers.get?.('x-mock-user-id') || (req.headers as any)['x-mock-user-id']

    return headerUserId || this.mockUserId
  }
}

// Client-side mock
class MockClientAuthAdapter implements AuthAdapter {
  constructor(private mockUserId: string | null = 'test-user-123') {}

  async getToken(): Promise<string | null> {
    return 'mock-token'
  }

  async getUserId(): Promise<string | null> {
    return this.mockUserId
  }
}

Testing with Adapters

import { describe, it, expect } from 'vitest'
import { MockAuthAdapter } from './MockAuthAdapter'

describe('AuthAdapter', () => {
  it('should extract user ID from request', async () => {
    const adapter = new MockAuthAdapter('user-123')
    const request = new Request('http://localhost', {
      headers: { 'x-mock-user-id': 'user-123' },
    })

    const userId = await adapter.getUserIdFromRequest(request)
    expect(userId).toBe('user-123')
  })

  it('should return null for missing auth', async () => {
    const adapter = new MockAuthAdapter(null)
    const request = new Request('http://localhost')

    const userId = await adapter.getUserIdFromRequest(request)
    expect(userId).toBeNull()
  })
})

Complete Examples

Example 1: Firebase Auth Adapter (Client-Side)

import type { AuthAdapter } from '@solvapay/react';
import { getAuth } from 'firebase/auth';

class FirebaseAuthAdapter implements AuthAdapter {
  async getToken(): Promise<string | null> {
    const auth = getAuth();
    const user = auth.currentUser;

    if (!user) return null;

    return await user.getIdToken();
  }

  async getUserId(): Promise<string | null> {
    const auth = getAuth();
    return auth.currentUser?.uid || null;
  }
}

// Usage
function App() {
  const adapter = new FirebaseAuthAdapter();

  return (
    <SolvaPayProvider config={{ auth: { adapter } }}>
      <YourApp />
    </SolvaPayProvider>
  );
}

Example 2: Auth0 Adapter (Server-Side)

import type { AuthAdapter } from '@solvapay/auth'
import { initAuth0 } from '@auth0/nextjs-auth0'

class Auth0Adapter implements AuthAdapter {
  private auth0: any

  constructor() {
    this.auth0 = initAuth0({
      secret: process.env.AUTH0_SECRET,
      baseURL: process.env.AUTH0_BASE_URL,
      clientID: process.env.AUTH0_CLIENT_ID,
      clientSecret: process.env.AUTH0_CLIENT_SECRET,
    })
  }

  async getUserIdFromRequest(req: Request | RequestLike): Promise<string | null> {
    try {
      const session = await this.auth0.getSession(req)
      return session?.user?.sub || null
    } catch {
      return null
    }
  }
}

Example 3: Custom OAuth Adapter

import type { AuthAdapter } from '@solvapay/auth'

class OAuthAdapter implements AuthAdapter {
  constructor(
    private tokenEndpoint: string,
    private clientId: string,
    private clientSecret: string,
  ) {}

  async getUserIdFromRequest(req: Request | RequestLike): Promise<string | null> {
    const token = this.extractToken(req)
    if (!token) return null

    try {
      // Verify token with OAuth provider
      const response = await fetch(this.tokenEndpoint, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/x-www-form-urlencoded',
        },
        body: new URLSearchParams({
          client_id: this.clientId,
          client_secret: this.clientSecret,
          token,
        }),
      })

      const data = await response.json()
      return data.user_id || null
    } catch {
      return null
    }
  }

  private extractToken(req: Request | RequestLike): string | null {
    const authHeader = req.headers.get?.('authorization') || (req.headers as any).authorization
    return authHeader?.replace('Bearer ', '') || null
  }
}

Best Practices

Never Throw: Adapters should never throw exceptions. Return null if authentication fails.
Handle Errors Gracefully: Catch all errors and return null instead of throwing.
Cache When Possible: Cache expensive operations (like token verification) when appropriate.
Type Safety: Use TypeScript for better type safety and developer experience.
Test Thoroughly: Write tests for your adapters, including edge cases.
Documentation: Document your adapter’s behavior and requirements.

Next Steps

Express.js Integration Guide - Use adapters with Express
Next.js Integration Guide - Use adapters with Next.js
React Integration Guide - Use adapters with React
Webhooks - Handle auth-related purchase events
API Reference - Full API documentation

TypeScript SDK

Table of Contents

Overview

Server-Side Adapters

Interface

Basic Example: JWT Token Adapter

Example: Session-Based Adapter

Example: Custom Header Adapter

Using with SolvaPay Server SDK

Client-Side Adapters

Interface

Basic Example: LocalStorage Adapter

Example: Context-Based Adapter

Example: Async Storage Adapter (React Native)

Common Patterns

Pattern 1: JWT Token with User ID Extraction

Pattern 3: API Key with User Mapping

Testing Adapters

Mock Adapter for Testing

Testing with Adapters

Complete Examples

Example 1: Firebase Auth Adapter (Client-Side)

Example 2: Auth0 Adapter (Server-Side)

Example 3: Custom OAuth Adapter

Best Practices

Next Steps

TypeScript SDK

​Table of Contents

​Overview

​Server-Side Adapters

​Interface

​Basic Example: JWT Token Adapter

​Example: Session-Based Adapter

​Example: Custom Header Adapter

​Using with SolvaPay Server SDK

​Client-Side Adapters

​Interface

​Basic Example: LocalStorage Adapter

​Example: Context-Based Adapter

​Example: Async Storage Adapter (React Native)

​Common Patterns

​Pattern 1: JWT Token with User ID Extraction

​Pattern 2: Cookie-Based Authentication

​Pattern 3: API Key with User Mapping

​Testing Adapters

​Mock Adapter for Testing

​Testing with Adapters

​Complete Examples

​Example 1: Firebase Auth Adapter (Client-Side)

​Example 2: Auth0 Adapter (Server-Side)

​Example 3: Custom OAuth Adapter

​Best Practices

​Next Steps

Table of Contents

Overview

Server-Side Adapters

Interface

Basic Example: JWT Token Adapter

Example: Session-Based Adapter

Example: Custom Header Adapter

Using with SolvaPay Server SDK

Client-Side Adapters

Interface

Basic Example: LocalStorage Adapter

Example: Context-Based Adapter

Example: Async Storage Adapter (React Native)

Common Patterns

Pattern 1: JWT Token with User ID Extraction

Pattern 2: Cookie-Based Authentication

Pattern 3: API Key with User Mapping

Testing Adapters

Mock Adapter for Testing

Testing with Adapters

Complete Examples

Example 1: Firebase Auth Adapter (Client-Side)

Example 2: Auth0 Adapter (Server-Side)

Example 3: Custom OAuth Adapter

Best Practices

Next Steps