import Expo from "expo";
import { Auth } from "aws-amplify";

...

class SignInScreen extends React.Component {
  
  ...

  loginWithFacebook = async () => {
    const {
      type,
      token,
      expires
    } = await Expo.Facebook.logInWithReadPermissionsAsync("1112222333444555", {
      permissions: ["public_profile", "email"]
    });
    if (type === "success") {
      // Get the user's information with the Facebook Graph api.
      const response = await fetch(
        `https://graph.facebook.com/me?access_token=${token}&fields=id,name,email,first_name,last_name,picture`
      );
      const user = await response.json();
      return {
        user,
        token,
        expires_at: expires
      };
    }
    return null;
  }

  amplifyFacebookSignIn = async () => {
    // Use Expo to login with facebook and get user info.
    const { user, token, expires_at } = await this.loginWithFacebook();
    
    // Use the token to authenticated Amplify.
    await Auth.federatedSignIn("facebook", { token, expires_at }, user);
    
    // At any point you can get the user's information using Auth.currentUserInfo()
    const userDetails = await Auth.currentUserInfo();
    console.log("Current user info:", userDetails);
    
    // Navigate away or do something...
    this.props.navigation.navigate({ routeName: "Main" });
  }

  ...
}