Introduce BaseAccount

env.example

@@ -1,7 +1,11 @@
 NODE_ENV=development
+ATXP_AUTH_CLIENT_TOKEN=
 
+# For dev scripts
 SOLANA_ENDPOINT=
 SOLANA_PRIVATE_KEY=
 ATXP_DESTINATION=
-ATXP_AUTH_CLIENT_TOKEN=
 ATXP_CONNECTION_STRING=
+BASE_RPC=
+BASE_PRIVATE_KEY=
+

packages/atxp-client/package.json

@@ -30,7 +30,8 @@
     "bignumber.js": "^9.3.0",
     "bs58": "^6.0.0",
     "oauth4webapi": "^3.5.0",
-    "react-native-url-polyfill": "^2.0.0"
+    "react-native-url-polyfill": "^2.0.0",
+    "viem": "^2.34.0"
   },
   "peerDependencies": {
     "expo-crypto": ">=14.0.0",

packages/atxp-client/src/baseAccount.ts

@@ -0,0 +1,24 @@
+import type { Account, PaymentMaker } from './types.js';
+import { privateKeyToAccount } from 'viem/accounts';
+import { BasePaymentMaker } from './basePaymentMaker.js';
+
+export class BaseAccount implements Account {
+  accountId: string;
+  paymentMakers: { [key: string]: PaymentMaker };
+
+  constructor(baseRPCUrl: string, sourceSecretKey: `0x${string}`) {
+    if (!baseRPCUrl) {
+      throw new Error('Base RPC URL is required');
+    }
+    if (!sourceSecretKey) {
+      throw new Error('Source secret key is required');
+    }
+
+    const account = privateKeyToAccount(sourceSecretKey);
+
+    this.accountId = account.address;
+    this.paymentMakers = {
+      'base': new BasePaymentMaker(baseRPCUrl, sourceSecretKey),
+    }
+  }
+}

packages/atxp-client/src/basePaymentMaker.test.ts

@@ -0,0 +1,62 @@
+import { describe, it, expect } from 'vitest';
+import { generatePrivateKey, privateKeyToAccount } from 'viem/accounts';
+import { BasePaymentMaker } from './basePaymentMaker.js';
+
+describe('basePaymentMaker.generateJWT', () => {
+  it('should generate a valid JWT with default payload', async () => {
+    const privateKey = generatePrivateKey();
+    const account = privateKeyToAccount(privateKey);
+    const paymentMaker = new BasePaymentMaker('https://example.com', privateKey);
+    const jwt = await paymentMaker.generateJWT({paymentRequestId: '', codeChallenge: 'testCodeChallenge'});
+
+    // JWT format: header.payload.signature (all base64url)
+    const [headerB64, payloadB64, signatureB64] = jwt.split('.');
+    expect(headerB64).toBeDefined();
+    expect(payloadB64).toBeDefined();
+    expect(signatureB64).toBeDefined();
+
+    // Decode header and payload
+    const decodeB64Url = (str: string) => {
+      // Pad string for base64 decoding
+      let b64 = str.replace(/-/g, '+').replace(/_/g, '/');
+      while (b64.length % 4) b64 += '=';
+      return JSON.parse(Buffer.from(b64, 'base64').toString('utf-8'));
+    };
+    const header = decodeB64Url(headerB64);
+    const payload = decodeB64Url(payloadB64);
+
+    expect(header.alg).toBe('ES256K');
+    expect(header.typ).toBeUndefined(); // BasePaymentMaker doesn't set typ
+    expect(payload.sub).toBe(account.address);
+    expect(payload.iss).toBe('accounts.atxp.ai');
+    expect(payload.aud).toBe('https://auth.atxp.ai');
+    expect(typeof payload.iat).toBe('number');
+    expect(payload.paymentIds).toBeUndefined();
+
+    // Signature verification would require ES256K (secp256k1) verification
+    // which is different from the EdDSA verification used in SolanaPaymentMaker
+    // For now, we just verify the signature is present and properly formatted
+    expect(signatureB64).toBeDefined();
+    expect(signatureB64.length).toBeGreaterThan(0);
+
+    // Decode the signature to verify it's a hex string with 0x prefix
+    const decodedSig = Buffer.from(signatureB64, 'base64url').toString('utf8');
+    expect(decodedSig).toMatch(/^0x[a-fA-F0-9]+$/);
+  });
+
+  it('should include payment request id if provided', async () => {
+    const privateKey = generatePrivateKey();
+    const paymentMaker = new BasePaymentMaker('https://example.com', privateKey);
+    const paymentRequestId = 'id1';
+    const jwt = await paymentMaker.generateJWT({paymentRequestId, codeChallenge: ''});
+    const [, payloadB64] = jwt.split('.');
+    const decodeB64Url = (str: string) => {
+      let b64 = str.replace(/-/g, '+').replace(/_/g, '/');
+      while (b64.length % 4) b64 += '=';
+      return JSON.parse(Buffer.from(b64, 'base64').toString('utf-8'));
+    };
+    const payload = decodeB64Url(payloadB64);
+    expect(payload.payment_request_id).toEqual(paymentRequestId);
+  });
+});
+