Last June I took a loan from celsius.network because of some financial aid for my family. Previously I never bothered about Bitcoin price as I was HODLER of it, but as soon as I took the loan I was more scared even there was a small price hiccup.

REFERAL ALERT
If you would like to take the loan against your crypto give celsius a chance, use this signup promo https://celsiusnetwork.app.link/149806af89 you get $40 and I get $40, more about it here

As a result, I googled for the online alerts for bitcoin price, then I found cryptocurrencyalerting.com, but there is a catch I don't get a free phone call alert service, instead got the email only. For outside of the US and Canada, you need to have a pro plan to get either a call or SMS.So I thought why not create a cron job and make a call when the price met the conditions.

The Tech Stack

• I chose NodeJS to work as a cron job, which will constantly query the bitcoin price from an API and check whether the conditions are met.
• For the price of bitcoin I chose the Coingecko API.
• To make a phone call programmatically, I chose twillo . You can have a trial account without a credit card and they provide you some free credits with which you can buy a number and spend minutes/calls made, more about here

DEPLOYMENT STACK

Deta.sh is a free cloud provider where we run our cron job. There is no paid plan yet in deta.sh, so you can have your code run free of cost. Feel free to explore more free hosting and service providers from Free-for-dev

LET'S START CODING YOUR CRYPTO_ALERT

1. Creating an account

First, create a free account at deta.sh, once you had the account it will be directed automatically to this web.deta.sh endpoint.

2. Setting up local Development

Follow the instruction provided at deta.sh, docs here for installing and setting up based on your OS.Once you setup the CLI then login to your deta.sh account from the terminal, more about that is here

3. Deploy a sample CRON job

Now go through the documentation provided here to simply create a cron job running in your dashboard. This basic flow will give you an overview of the platform, till now we haven't gone through our code yet, feel comfortable using deta.sh as it's a great platform for the prototypes like this.

name your sample app as BITCOIN_ALERT while creating, because we later change this sample code given at index.js to our logic

minimum time interval is 1 min while running the cron job

4. Make a Twilio account

REFERAL ALERT
use this referral link www.twilio.com/referral/eES7kf during sign up to get $10 and I get $10

Go through this link, for the limits and description about your free trail account and how to make one if not created yet.

In the trial account you need to verify your phone number if you would like to receive a call or SMS.once you verify you will be able to receive calls that are made from code.

After your signup, you will be redirected to the twilio console .

5. Create a new Twilio project

learn how to make one here.

6. Get your Account SID and Auth token

In your dashboard, you will get Account SID and auth token which are needed to make a call/ send SMS from the code.

7. Setting up Envoirment variable [.env]

All the values that are required in the code are provided from the file called .env.This file holds your API keys and Auth tokens and other data needed for the program. Please make you keep this file sensitive, and do not upload files to a public GitHub repo. You can get this file here. More about env variables here.

.env

PROJECT_KEY=<Deta project key>
DETABASE=<Database name, provide what ever name you like>
MARGIN_CALL=<Your bitcoin margin call price in USD>
LIQUIDATION_CALL=<Your bitcoin liq call price in USD>
TWILIO_SID=<your Twilio sid>
TWILIO_AUTH_TOKEN=<your Twilio auth token>
TWILIO_PHONE_NUMBER=<Twillo phone number with country code>
TWILIO_MESSAGE_LIQ=Bitcoin price is at liquidation call
TWILIO_MESSAGE_MARGIN=Bitcoin price is at margin call
PHONE_NUMBER_WITH_COUNTRY_CODE=<Phone number to which you want to receive a call, with Countrycode>

There should not be space after the equals sign
SECRET=123 //no space after equals
SECRET= 123 //space after equals, not accepted

Once you replace the placeholder text with the actual values in the .env files, apply the following command to reflect these values in the code while executing. If you update any value in future without that command will not be reflected in the code.

deta update -e .env

8.Applying our logic

In the previous step [3] you made a deta project which has a sample code at the index.js file. Now all you need to do is to replace the entire source code/content of the file with the node.js code below. I made comments in the code itself to give you an idea of what that piece of logic is trying to do.

8.1 Updating index.js file

const { app, Deta } = require("deta");
const axios = require("axios");


// add your Project Key
const deta = Deta(process.env.PROJECT_KEY);
// 
// Envorment Varaibles
const db = deta.Base(process.env.DETABASE);
const accountSid = process.env.TWILIO_SID;
const authToken = process.env.TWILIO_AUTH_TOKEN;
const client = require("twilio")(accountSid, authToken);
const marginCall = process.env.MARGIN_CALL;
const liquidationCall = process.env.LIQUIDATION_CALL;
const PhoneNumber=process.env.PHONE_NUMBER_WITH_COUNTRY_CODE;

let btcprice = 0;

// define a function to run on a schedule
// the function must take an event as an argument
app.lib.cron(async (event) => {
  console.log("CRON running @ " + new Date().toLocaleTimeString());
  const resp = await getBitcoinPrice();
  const data = resp.data;
  console.log("Current BTC price ===>", data.bitcoin.usd);
  btcprice = parseInt(data.bitcoin.usd);
  //btcprice = 23000; this variable holds the btc price at that moment

  // hascalled is the key in the database, which stores if phone call made for liquidation/Margin conditions when the predefined criteria met.
  // Suppose if BTC price met Margin condition then a call will be made , once its made,the code is not going 
  // to make a another call in the very next run even the condition satisfied.

// querying the DB for the key `hascalled`
  let hasCalled = await db.get("hascalled");

  console.log("values from db for the key named hascalled is  -->", hasCalled);
  if (hasCalled == null) {
    // Runs for the very first time

    // initally set margin and liq to false for the key 'hascalled' in db
    const insertedkey = await db.put(
      { margin: false, liq: false },
      "hascalled"
    );

    hasCalled = insertedkey;
  }

  //_BTCValidation_Block_Margin
  if (hasCalled.margin == false) {
     
    // This block will get executed only if there was no liquidation call not made yet
    await _BTCValidationMargin();
  }

  //_BTCValidation_Block_Liquidation
  if (hasCalled.liq == false) {
     // This block will get executed only if there was no liquidation call not made yet
    await _BTCValidationliquid();
  }


});

 
const _BTCValidationMargin = async () => {
  if (btcprice < marginCall && btcprice > liquidationCall) {
 
    await getCallfromTwillo(process.env.TWILIO_MESSAGE_MARGIN, PhoneNumber);

    const updateState = await db.update({ margin: true }, "hascalled");
    console.log("DB UPDATED For Margin --->", updateState);
  }
};

const _BTCValidationliquid = async () => {
  if (btcprice < liquidationCall) {
    
    await getCallfromTwillo(process.env.TWILIO_MESSAGE_LIQ, PhoneNumber);

    const updateState = await db.update({ liq: true }, "hascalled");
    console.log("DB UPDATED For Liquid --->", updateState);
  }
};

const getCallfromTwillo = async (msg, _to) => {
  const call = await client.calls.create({
    twiml: `${msg}`,
    to: _to,
    from: process.env.TWILIO_PHONE_NUMBER,
  });
  console.log(call.sid);
 
};

const getBitcoinPrice = async () => {
  try {
    return await axios.get(
      "https://api.coingecko.com/api/v3/simple/price?ids=bitcoin&vs_currencies=USD"
    );
  } catch (error) {
    console.error(error);
  }
};

module.exports = app;

8.2 Updating Project dependencies

Our Logic code depends on the two NPM dependencies , AXIOS and TWILIO.In order to install apply the following commands in the terminal.

npm i axios twilio

9.Finally deploying our logic

open the terminal at the root directory and apply the following command to deploy the local source code to the remote

deta deploy

learn more about deploy here.

10. Check Visor for logs

Deta.sh provides the Visor functionality which is a logger kind for the production code.Learn more about visor here

11. Project Structure

📦BITCOIN_ALERT
┣ 📂.deta
┃ ┣ 📜prog_info
┃ ┗ 📜state
┣ node_modules
┣ 📜.env
┣ 📜index.js
┣ 📜package-lock.json
┗ 📜package.json

12. Deta Base reset

If you would like to reset the key in the DB you can do so by selecting Base section in your detabase dashboard. You would see something like the following image

You can uncheck/check the values of that key as they are the Booleans.The very next execution will read the updated values

Use this github repo for the further reference

⭐⭐⭐ Have fun CODING! ⭐⭐⭐

Thank you for the time. 🐸