Chat.js

import React from "react";
import { GiftedChat } from "react-native-gifted-chat";
import { getAccessTokenFromStorage } from '../utils/Auth'
import firebaseSvc from "../utils/FirebaseSvc";

export default class Chat extends React.Component {

  state = {
    messages: []
  };

  async componentWillMount() {
     // hit api /chat_token to trade stored wrdup
     // access token for firebase custom token
     let firebaseToken;
     const accessToken = await getAccessTokenFromStorage();
     try {
       const checkResp = await axiosClient.get('/chat_token', {
         headers: {
           Authorization: `Bearer ${accessToken}`,
         },
       });
       firebaseToken = checkResp.data.firebaseToken;
     } catch ({ response, message }) {
       if (response.status === 401) {
         console.log('Error getting firebase ID token', response.status, message);
         return;
       }
     }
     // use token for login into firebase
     const success_callback = (stuff) => console.log("[FIREBASE AUTH] SUCCESS");
     const failed_callback = (stuff) => console.log('[FIREBASE AUTH] FAILURE: ', stuff);
     firebaseSvc.login(firebaseToken,success_callback, failed_callback);
   }

  render() {
    return (
      <GiftedChat
        messages={this.state.messages}
        onSend={message => {
          firebaseSvc.sendMessage(message);
        }}
        user={{
          _id: firebaseSvc.getUid(),
          name: firebaseSvc.getUid() // FIXME: this.props.username
        }}
      />
    );
  }

  // MOUNTED: load messages on each new message
  componentDidMount() {
    firebaseSvc.loadMessages(message => {
      this.setState(previousState => {
        return {
          messages: GiftedChat.append(previousState.messages, message)
        };
      });
    });
  }

  // UNMOUNT: Call the firebase service closer
  componentWillUnmount() {
    firebaseSvc.closeChat();
  }
}

FirebaseSvc.js

import firebase from "firebase";

class FirebaseSvc {

  uid = "";
  messagesRef = null;

  // initialize Firebase Backend
  constructor() {
      if (!firebase.apps.length) { //avoid re-initializing
        firebase.initializeApp({
          apiKey: "AIzaSyB-WtxcyGmf0wiF4Zgr7G37UiE6yzl4Rzs",
          authDomain: "wrdupapp-d4be5.firebaseapp.com",
          databaseURL: "https://wrdupapp-d4be5.firebaseio.com",
          projectId: "wrdupapp-d4be5",
          storageBucket: "wrdupapp-d4be5.appspot.com",
          messagingSenderId: "6614415512"
        });
        this.state = {
          user: {}
        }
      }
    }

  login = async(token, success_callback, failed_callback) => {
    await firebase.auth().signInWithCustomToken(token).then(success_callback, failed_callback);
    this.state = {user: firebase.auth().currentUser};
    this.setUid(user.uid);
    console.log("Firebase User:", this.state.user)
  }

  setUid(value) {
    this.uid = value;
  }

  getUid() {
    return this.uid;
  }

  // retrieve the messages from the Backend
  loadMessages(callback) {
    this.messagesRef = firebase.database().ref("messages");
    this.messagesRef.off(); //Detaches a callback previously attached with on()
    const onReceive = data => {
      const message = data.val();
      callback({
        _id: data.key,
        text: message.text,
        //createdAt: new Date(message.createdAt),
        createdAt: message.createdAt,
        user: {
          _id: message.user._id,
          name: message.user.name
        }
      });
    };

    var d = this.getLimit();
    console.log(d);
    //Generates a new Query object limited to the last specific number of children.
    //this.messagesRef.limitToLast(10).on("child_added", onReceive);
    this.messagesRef
      .orderByChild("createdAt")
      //.startAt(d)
      //.endAt("2017-11-27T06:51:47.851Z")
      .on("child_added", onReceive);
  }

  // send a given message
  sendMessage(message) {
    //console.log(new Date(firebase.database.ServerValue.TIMESTAMP));
    var today = new Date();
    /* today.setDate(today.getDate() - 30);
    var timestamp = new Date(today).toISOString(); */
    var timestamp = today.toISOString();
    for (let i = 0; i < message.length; i++) {
      this.messagesRef.push({
        text: message[i].text,
        user: message[i].user,
        createdAt: timestamp
      });
    }
  }

  // close the connection
  closeChat() {
    if (this.messagesRef) {
      this.messagesRef.off();
    }
  }

  getLimit() {
    var today = new Date();
    //var milliseconds = Date.parse(today);
    //var changed = milliseconds - 86400000; //10 minutes (- 900000) -  86400000 1 day
    today.setDate(today.getDate() - 31); // last 30 Days
    //console.log(today);
    var changedISODate = new Date(today).toISOString();
    //var changedISODate = today.toISOString();
    console.log(changedISODate);
    return changedISODate;
  }
}

// Export instance, not class
const firebaseSvc = new FirebaseSvc();
export default firebaseSvc;