Core TypeScript SDK (@authsetu/sdk-core)

The @authsetu/sdk-core library provides low-level client architecture, token lifecycle management, event streams, and feature tier enforcement for Node.js, browser, and custom framework environments.

Installation

bash

npm install @authsetu/sdk-core

---

1. Initializing AuthSetuClient

Create a singleton client instance configured with your project's Publishable or Secret Key.

typescript

import { AuthSetuClient } from "@authsetu/sdk-core";

const client = new AuthSetuClient({
  publishableKey: "pk_test_123456789",
  baseUrl: "https://api.authsetu.com",
  autoRefreshTokens: true,
  storage: "localStorage", // 'localStorage' | 'sessionStorage' | 'cookie'
});

await client.initialize();

---

2. Token Lifecycle & Auto Refresh Loop

AuthSetuClient manages JWT access tokens and refresh tokens under the hood:

typescript

// Retrieve valid access token (automatically refreshes if expired)
const accessToken = await client.tokenManager.getValidToken();

// Force token refresh manually
const newTokens = await client.tokenManager.refreshToken();

console.log("Current Access Token:", accessToken);

---

3. Event Emitter & Listener API

Listen to auth lifecycle events across your app:

typescript

// Subscribe to authentication state changes
client.events.on("sessionExpired", () => {
  console.warn("User session expired. Prompting re-login...");
});

client.events.on("tokenRefreshed", ({ accessToken }) => {
  console.log("Access token silently refreshed:", accessToken);
});

client.events.on("organizationSwitched", (org) => {
  console.log("Switched active organization to:", org.name);
});

---

4. Feature Tier & Plan Limit Guards

Check subscription tier features and limits programmatically using checkPlanFeature and checkPlanUsageLimit:

typescript

import { checkPlanFeature, checkPlanUsageLimit, PLAN_LIMITS } from "@authsetu/sdk-core";

const userPlan = "pro"; // 'free' | 'starter' | 'pro' | 'enterprise'

// Check boolean feature permission
const canAccessSAML = checkPlanFeature(userPlan, "samlSso");
console.log("SAML Access:", canAccessSAML);

// Check usage limits (e.g. max team members)
const usageCheck = checkPlanUsageLimit(userPlan, "maxMembers", 15);
if (usageCheck.isExceeded) {
  console.warn(`Limit reached: ${usageCheck.current} / ${usageCheck.limit}`);
}

---

5. PKCE Challenge Generation for OAuth

Generate secure Proof Key for Code Exchange (PKCE) challenges for native or web OAuth flows:

typescript

import { generatePKCEChallenge, generateState } from "@authsetu/sdk-core";

const state = generateState();
const { codeVerifier, codeChallenge, codeChallengeMethod } = await generatePKCEChallenge();

// Store codeVerifier in session storage before redirecting to identity provider
sessionStorage.setItem("pkce_verifier", codeVerifier);

console.log("Code Challenge:", codeChallenge);