Better Auth Fayda Plugin

Better Auth plugin for Fayda.

Installation

You can install the plugin using pnpm, npm, or yarn.

pnpm add fayda

Auth Configuration

To use the plugin, you need to add it to your better-auth plugin list. Ensure you set the accountLinking options to link the user's Fayda identity with their local account.

The clientId and privateKey should be loaded from your environment variables.

import { fayda } from 'fayda';
import { betterAuth } from 'better-auth';

export const auth = betterAuth({
	// ...
	plugins: [
		// ...
		await fayda({
			clientId: env.CLIENT_ID,
			privateKey: env.PRIVATE_KEY,
		})
	],
	account: {
		accountLinking: {
			enabled: true,
			trustedProviders: ['fayda']
		}
	}
});

Redirect Configuration

IMPORTANT: The clientId you receive from Fayda must have its redirectURL configured to <baseUrl>/api/auth/oauth2/callback/fayda where <baseUrl> is the address of your application like https://example.com.

If you are using a development clientId and need to use a different callbackUrl (e.g., http://localhost:3000/callback), you will need to set up a redirector. This redirector will accept the request and forward it to the correct better-auth callback handler.

Below is a SvelteKit example of how to implement this redirect. In this example, if your callbackURL is http://localhost:3000/callback, you would place this code in src/routes/callback/+page.server.ts.

import { redirect } from '@sveltejs/kit';
import type { PageServerLoad } from './$types';

export const load: PageServerLoad = async (req) => {
	const originalUrl = new URL(req.url, `http://localhost:3000`);
	const target = new URL('http://localhost:3000/api/auth/oauth2/callback/fayda');
	target.search = originalUrl.search;

	redirect(302, target);
};

Auth Configuration

Next, you need to add the generic OAuth client plugin to your client-side authentication configuration. This will enable the client to initiate the OAuth flow with the Fayda provider.

import { createAuthClient } from 'better-auth/svelte';
import { genericOAuthClient } from 'better-auth/client/plugins';

export const authClient = createAuthClient({
	baseURL: 'http://localhost:3000',
	plugins: [genericOAuthClient()]
});

Once the client is configured, you can use the signIn.oauth2 method to start the authentication flow.

authClient.signIn.oauth2({
	providerId: 'fayda',
});