Setting up a firebase cloud function call

Question

I am trying to set up cloud functions with firebase and I am having a slightly difficult time getting it set up. I want to set up a function that gets called by an HTTP request. The function would take the information provided, double-check if those values are indeed the same values as the ones found in my firestorm and then execute some Javascript code before responding; this is my code:

// The Cloud Functions for Firebase SDK to create Cloud Functions and setup triggers.
const functions = require("firebase-functions");
// The Firebase Admin SDK to access Firestore.
const admin = require('firebase-admin');
admin.initializeApp();


// [START trigger]
exports.buyCrypto = functions.https.onRequest((request, res) => 
{
  // [END trigger]
  // [START sendError]
  // Forbidding PUT requests.
  if (request.method === 'PUT') {
    return res.status(403).send('Forbidden!');
  }
  // [END sendError]
  
    // [START readQueryParam]
    const uid = request.body.uid
    const crypto = request.body.crypto
    const amount = request.body.amount
    
    const docRef = admin.firestore().collection("users").doc(uid);
    docRef.get().then((doc) => {
        if (doc.exists) {
            if(crypto === "BTC")
            {
                if(doc.data.btc <= amount)
                {
                    //execute buy
                    return res.status(200).send("Sucess");
                }
            }
            if(crypto === "ETH")
            {
                if(doc.data.btc <= amount)
                {
                    //execute buy
                    return res.status(200).send("Sucess");
                }
            }
        } else {
            // doc.data() will be undefined in this case
            console.log("No such document!");
        }
    }).catch((error) => {
        console.log("Error getting document:", error);
    });
    
    // Push the new message into Firestore using the Firebase Admin SDK.
    //const writeResult = await admin.firestore().collection('messages').add({original: original});
    // Send back a message that we've successfully written the message
    
    // [START sendResponse]
    const formattedResponse =  "IDK"
    return res.status(403).send("Failed");
    // [END sendResponse]
});

Unfortunatly I cannot seem to find a great deal of documentation for firebase functions and when I try to test it with the emulator through a web browser it goes into infinite loading and does not display an error message so I am finding it impossible to debug anything. Thank you for your time

Answer 1

You are calling return res.status(403).send("Failed"); outside of the then() block, so this line will be called before the asynchronous call to the get() method is completed and the Promise returned by this method is fulfilled. Result: your Cloud Function always sends back an error to its caller.

In addition, you do doc.data.btc instead of doc.data().btc. See the doc for the DocumentSnapshot, data() is a method.

Also, note that you don't need to use return in an HTTPS Cloud Function. Just send back a response with res.redirect(), res.send(), or res.end(). You may watch this video: https://www.youtube.com/watch?v=7IkUgCLr5oA.

The following should therefore do the trick:

exports.buyCrypto = functions.https.onRequest((request, res) => {
    if (request.method === 'PUT') {
        return res.status(403).send('Forbidden!');
    }
    const uid = request.body.uid
    const crypto = request.body.crypto
    const amount = request.body.amount

    const docRef = admin.firestore().collection("users").doc(uid);
    docRef.get().then((doc) => {
        if (doc.exists) {
            if (crypto === "BTC") {
                if (doc.data().btc <= amount) {
                    //execute buy
                    res.status(200).send("Success");
                } else {
                    // send a 200 response or throw an error  res.status(200).send("....");
                    // Depends on your functional requirements
                }
            } else if (crypto === "ETH") {
                if (doc.data.btc <= amount) {
                    //execute buy
                    return res.status(200).send("Success");
                } else {
                    // send a 200 response or throw an error  res.status(200).send("....");
                    // Depends on your functional requirements
                }
            } else {
                // send a 200 response or throw an error  res.status(200).send("....");
                // Depends on your functional requirements
            }
        } else {
            console.log("No such document!");
            // send a 200 response or throw an error  res.status(200).send("....");
        }
    }).catch((error) => {
        console.log("Error getting document:", error);
        res.status(500).send(error);
    });

});