[en] An IFTTT applet to upload my Facebook posts to a blockchain network

contract Posts {
    mapping (uint256 => string) public allPosts;
    uint256 public numPosts;
    address public owner;
    
    function Posts () {
        owner = msg.sender;
    }
    
    function newPost (string content) {
        require(msg.sender == owner);
        allPosts[numPosts] = content;
        numPosts++;
    }
}

// requirements
// web3@0.20.3
// ethereumjs-tx@1.3.3
// express@4.16.2
// body-parser@1.18.2

// credentials information
const address = "<< ADDRESS OF THE ACCOUNT WHICH CREATED THE CONTRACT >>"
const key = "<< PRIVATE KEY OF ABOVE ADDRESS >>"
const accessToken = "<< RONDOMLY GENERATED TOKEN TO ACCESS THIS SERVER >>"

// contract information
const contractAddress = "<< ADDRESS OF THE CONTRACT >>"
const contractABI = [
	{
		"constant": true,
		"inputs": [],
		"name": "owner",
		"outputs": [
			{
				"name": "",
				"type": "address"
			}
		],
		"payable": false,
		"stateMutability": "view",
		"type": "function"
	},
	{
		"constant": true,
		"inputs": [],
		"name": "numPosts",
		"outputs": [
			{
				"name": "",
				"type": "uint256"
			}
		],
		"payable": false,
		"stateMutability": "view",
		"type": "function"
	},
	{
		"constant": true,
		"inputs": [
			{
				"name": "",
				"type": "uint256"
			}
		],
		"name": "allPosts",
		"outputs": [
			{
				"name": "",
				"type": "string"
			}
		],
		"payable": false,
		"stateMutability": "view",
		"type": "function"
	},
	{
		"constant": false,
		"inputs": [
			{
				"name": "content",
				"type": "string"
			}
		],
		"name": "newPost",
		"outputs": [],
		"payable": false,
		"stateMutability": "nonpayable",
		"type": "function"
	},
	{
		"inputs": [],
		"payable": false,
		"stateMutability": "nonpayable",
		"type": "constructor"
	}
]

// requires
const express = require('express');
const Web3 = require('web3');
const tx = require('ethereumjs-tx');
const bodyParser = require('body-parser');

const web3 = new Web3(
  new Web3.providers.HttpProvider('https://rinkeby.infura.io/')
);

// functions
const sendRaw = (rawTx) => {
  var privateKey = new Buffer(key, 'hex');
  var transaction = new tx(rawTx);
  transaction.sign(privateKey);
  var serializedTx = transaction.serialize().toString('hex');
  web3.eth.sendRawTransaction('0x' + serializedTx, (err, result) => {
      if(err) {
          console.log(err);
      } else {
          console.log(result);
      }
  });
}

// main
const app = express();
const posts = new web3.eth.contract(contractABI).at(contractAddress);

app.use(bodyParser.json());

app.post('/', (req, res) => {
	if (req.body.token === undefined || req.body.content === undefined) {
		res.status(500).send("INVALID ARGUMENTS");
		return;
	}
	if (req.body.token != accessToken) {
		res.status(500).send("INVALID TOKEN");
		return;
	}
	try {
		sendRaw({
			nonce: web3.toHex(web3.eth.getTransactionCount(address)),
			gasLimit: web3.toHex(800000),
			gasPrice: web3.toHex(20000000000),
			to: contractAddress,
			data: posts.newPost.getData(req.body.content)
		});
	} catch (e) {
		res.status(500).send("FAIL");
		return;
	}
	res.status(200).send("SUCCEED");
});

app.listen(process.env.PORT || 5000);

{
  "name": "rinkeby-post",
  "version": "1.0.0",
  "main": "index.js",
  "dependencies": {
    "body-parser": "^1.18.2",
    "ethereumjs-tx": "1.3.3",
    "express": "^4.16.2",
    "web3": "0.20.3"
  },
  "scripts": {
    "start": "node ./index.js"
  }
}