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Client

The FastAuthClient is the main entry point for interacting with the FastAuth system in React applications. It provides a high-level interface for authentication operations and transaction signing through various providers, with automatic contract configuration based on network selection.

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. The React SDK version automatically configures contract addresses based on the selected network.

Dependencies​

Configuration Types​

type FastAuthClientNetwork = "mainnet" | "testnet";

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

Constructor​

constructor(
    provider: P,
    connection: Connection,
    network: FastAuthClientNetwork,
    relayerURL: string
)
  • provider: An instance implementing IFastAuthProvider interface
  • connection: NEAR network connection from near-api-js
  • network: Network identifier ("mainnet" or "testnet") - automatically configures contract addresses
  • relayerURL: URL of the FastAuth relayer service for transaction relaying

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()

isLoggedIn​

Checks if the user is currently authenticated.

  • Returns: Promise resolving to a boolean indicating authentication status
  • Usage: Delegates to provider.isLoggedIn()
  • Behavior: Checks authentication status through the configured provider

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 (with relayer support)
    3. Initializes the signer before returning

Provider Interface​

interface IFastAuthProvider {
    // Base signer provider methods
    isLoggedIn(): Promise<boolean>;
    requestTransactionSignature(...args: any[]): Promise<void>;
    requestDelegateActionSignature(...args: any[]): Promise<void>;
    getSignatureRequest(): Promise<SignatureRequest>;
    getPath(): Promise<string>;

    // Client-specific methods
    login(...args: any[]): void;
    logout(): void;
}

Usage​

Client instantiation​

import { FastAuthClient } from "@fast-auth-near/react-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 with network and relayer URL
const client = new FastAuthClient(
    provider,
    connection,
    "testnet", // Network automatically configures contract addresses
    "https://relayer.example.com/api/relayer/fast-auth" // Relayer URL
);

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

// 5. Check login status
const isLoggedIn = await client.isLoggedIn();

// 6. Get signer for transactions
const signer = await client.getSigner();

Network Configuration​

The React SDK automatically configures contract addresses based on the network:

  • testnet:
    • mpcContractId: "v1.signer-prod.testnet"
    • fastAuthContractId: "fast-auth-beta-001.testnet"
  • mainnet:
    • mpcContractId: "v1.signer"
    • fastAuthContractId: "fast-auth.near"

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);
    }
}