Client

The FastAuthClient is the main entry point for interacting with the FastAuth system in browser environments. It provides a high-level interface for authentication operations and transaction signing through various providers.

Overview

The FastAuthClient is a generic TypeScript class that orchestrates authentication and signing operations by delegating to a configurable provider. It serves as an abstraction layer that standardizes the interface for different authentication providers while maintaining type safety.

Dependencies

Configuration Types

type FastAuthClientOptions = {
    mpcContractId: string; // MPC contract address
    fastAuthContractId: string; // FastAuth contract address
};

Constructor

constructor(
    provider: P,
    connection: Connection,
    options: FastAuthClientOptions
)

• provider: An instance implementing IFastAuthProvider interface
• connection: NEAR network connection from near-api-js
• options: Configuration object containing contract IDs

Methods

login

Initiates the authentication process using the configured provider.

• Parameters: Variable arguments that are passed directly to the provider's login method
• Returns: Result from the provider's login implementation (typically void)
• Usage: Delegates to provider.login() with all provided arguments

logout

Terminates the user session.

• Returns: Result from the provider's logout implementation (typically void)
• Usage: Delegates to provider.logout()

getSigner

Creates and returns a configured signer instance for transaction operations.

• Returns: Promise resolving to a FastAuthSigner instance
• Throws: FastAuthClientError with code USER_NOT_LOGGED_IN if user is not authenticated
• Behavior:
  1. Checks authentication status via provider.isLoggedIn()
  2. Creates a new FastAuthSigner instance if authenticated
  3. Initializes the signer before returning

Provider Interface

interface IFastAuthProvider {
    // Authentication methods
    login(...args: any[]): void | Promise<void>;
    logout(): void | Promise<void>;
    isLoggedIn(): Promise<boolean>;

    // Transaction signing methods
    requestTransactionSignature(...args: any[]): Promise<void>;
    requestDelegateActionSignature(...args: any[]): Promise<void>;

    // Utility methods
    getSignatureRequest(): Promise<SignatureRequest>;
    getPath(): Promise<string>;
}

Usage

Client instantiation

import { FastAuthClient } from "@fast-auth-near/browser-sdk";
import { Connection } from "near-api-js";

// 1. Set up NEAR connection
const connection = new Connection({
    networkId: "testnet",
    provider: { type: "JsonRpcProvider", args: { url: "https://rpc.testnet.near.org" } },
});

// 2. Create provider instance
const provider = new SomeAuthProvider(config);

// 3. Initialize client
const client = new FastAuthClient(provider, connection, {
    mpcContractId: "v1.signer-prod.testnet",
    fastAuthContractId: "fast-auth-beta-001.testnet",
});

// 4. Authenticate
await client.login(/* provider-specific args */);

// 5. Get signer for transactions
const signer = await client.getSigner();

Error Handling

try {
    const signer = await client.getSigner();
    // Use signer for transactions
} catch (error) {
    if (error instanceof FastAuthClientError) {
        // Handle authentication errors
        console.error("Authentication required:", error.message);
    }
}