danilobellini/ethereum_note.py

## ethereum_note.py
"""
Application to store a single message note in the Ethereum blockchain.
In order to run this web server, the ethereum node daemon
(e.g. the Geth HTTP RPC on 8545) should be running in the same host.

Input parameters should be on the following environment variables:

  export ETH_CONTRACT_ADDRESS=0xAAAA...          # Enforced
  export ETH_NODE_URL='http://localhost:8545'    # Optional

Command to run the application (it requires Python 3.6+):

  python3 -m sanic --host 0.0.0.0 --port 1337 ethereum_note.app

To install a virtualenv with its requirements (bash):

  python3 -m venv somewhere/with/your/virtualenv
  source somewhere/with/your/virtualenv/bin/activate
  python3 -m pip install sanic web3

By Danilo J. S. Bellini,
software created based on Solange Gueiros' Solidity/JavaScript snippets
available at https://github.com/solangegueiros/DevEthereum-Course
shown during her introductory course to Ethereum given on TDC 2018 SP
(The Developer's Conference @ São Paulo).
"""
import json, os

from sanic import response, Sanic
from web3 import HTTPProvider, Web3
from web3.contract import ConciseContract


ETH_NODE_URL = os.environ.get("ETH_NODE_URL", "http://localhost:8545")
ETH_CONTRACT_ADDRESS = os.environ["ETH_CONTRACT_ADDRESS"]

# Requires Python 3.6+ in order to keep the dict order
# One can store abi directly as a string instead of dumping this,
# e.g. using the JS array from the first "web3Deploy" line in "Details"
# when infonote.sol gets compiled by http://remix.ethereum.org/
abi_list = [
    {
        "constant": False,
        "inputs": [{"name": "i", "type": "string"}],
        "name": "set",
        "outputs": [],
        "payable": False,
        "stateMutability": "nonpayable",
        "type": "function",
    },
    {
        "constant": True,
        "inputs": [],
        "name": "get",
        "outputs": [{"name": "", "type": "string"}],
        "payable": False,
        "stateMutability": "view",
        "type": "function",
    },
]

w3 = Web3(HTTPProvider(ETH_NODE_URL))
contract = w3.eth.contract(
    address=Web3.toChecksumAddress(ETH_CONTRACT_ADDRESS),
    abi=json.dumps(abi_list, separators=(",", ":")),
    ContractFactoryClass=ConciseContract,
)


app = Sanic(__name__)
app.static("/", "index.html")


@app.route("/info")
async def get_info(request):
    return response.text(contract.get())


@app.route("/info", methods=["POST"])
async def post_info(request):
    contract.set(request.body, transact={"from": w3.eth.accounts[0]})
    return response.text("Stored!")

## index.html
<!DOCTYPE html>
<html>

  <head>
    <title>InfoNote</title>
    <meta charset="UTF-8" />

    <script>
      document.addEventListener("DOMContentLoaded", function(){

        document.getElementById("get").addEventListener("click", function (){
          var xhr = new XMLHttpRequest();
          xhr.open("GET", "info", true);
          xhr.addEventListener("load", function(){
            document.getElementById("stored").textContent = this.responseText;
          })
          xhr.send(null);
        });

        document.getElementById("set").addEventListener("click", function (){
          var xhr = new XMLHttpRequest();
          xhr.open("POST", "info", true);
          xhr.setRequestHeader("Content-Type", "text/plain");
          xhr.addEventListener("readystatechange", function(){
            if(this.readyState == XMLHttpRequest.DONE && this.status == 200)
              alert("Stored! Wait a little bit to have this update 'mined'.");
          })
          xhr.send(document.getElementById("typed").value);
        });

      });
    </script>

    <style>
      button {display: block;}
    </style>

  </head>

  <body>
    <input id="typed">
    <button id="set">Set</button>
    <hr>
    <pre id="stored"></pre>
    <button id="get">Get</button>
  </body>

</html>

## infonote.sol
pragma solidity ^0.4.24;

contract InfoNote {
    string private info;
    function set(string i) public { info = i; }
    function get() public view returns (string) { return info; }
}
	"""
	Application to store a single message note in the Ethereum blockchain.
	In order to run this web server, the ethereum node daemon
	(e.g. the Geth HTTP RPC on 8545) should be running in the same host.

	Input parameters should be on the following environment variables:

	export ETH_CONTRACT_ADDRESS=0xAAAA... # Enforced
	export ETH_NODE_URL='http://localhost:8545' # Optional

	Command to run the application (it requires Python 3.6+):

	python3 -m sanic --host 0.0.0.0 --port 1337 ethereum_note.app

	To install a virtualenv with its requirements (bash):

	python3 -m venv somewhere/with/your/virtualenv
	source somewhere/with/your/virtualenv/bin/activate
	python3 -m pip install sanic web3

	By Danilo J. S. Bellini,
	software created based on Solange Gueiros' Solidity/JavaScript snippets
	available at https://github.com/solangegueiros/DevEthereum-Course
	shown during her introductory course to Ethereum given on TDC 2018 SP
	(The Developer's Conference @ São Paulo).
	"""
	import json, os

	from sanic import response, Sanic
	from web3 import HTTPProvider, Web3
	from web3.contract import ConciseContract


	ETH_NODE_URL = os.environ.get("ETH_NODE_URL", "http://localhost:8545")
	ETH_CONTRACT_ADDRESS = os.environ["ETH_CONTRACT_ADDRESS"]

	# Requires Python 3.6+ in order to keep the dict order
	# One can store abi directly as a string instead of dumping this,
	# e.g. using the JS array from the first "web3Deploy" line in "Details"
	# when infonote.sol gets compiled by http://remix.ethereum.org/
	abi_list = [
	{
	"constant": False,
	"inputs": [{"name": "i", "type": "string"}],
	"name": "set",
	"outputs": [],
	"payable": False,
	"stateMutability": "nonpayable",
	"type": "function",
	},
	{
	"constant": True,
	"inputs": [],
	"name": "get",
	"outputs": [{"name": "", "type": "string"}],
	"payable": False,
	"stateMutability": "view",
	"type": "function",
	},
	]

	w3 = Web3(HTTPProvider(ETH_NODE_URL))
	contract = w3.eth.contract(
	address=Web3.toChecksumAddress(ETH_CONTRACT_ADDRESS),
	abi=json.dumps(abi_list, separators=(",", ":")),
	ContractFactoryClass=ConciseContract,
	)


	app = Sanic(__name__)
	app.static("/", "index.html")


	@app.route("/info")
	async def get_info(request):
	return response.text(contract.get())


	@app.route("/info", methods=["POST"])
	async def post_info(request):
	contract.set(request.body, transact={"from": w3.eth.accounts[0]})
	return response.text("Stored!")
	<!DOCTYPE html>
	<html>

	<head>
	<title>InfoNote</title>
	<meta charset="UTF-8" />

	<script>
	document.addEventListener("DOMContentLoaded", function(){

	document.getElementById("get").addEventListener("click", function (){
	var xhr = new XMLHttpRequest();
	xhr.open("GET", "info", true);
	xhr.addEventListener("load", function(){
	document.getElementById("stored").textContent = this.responseText;
	})
	xhr.send(null);
	});

	document.getElementById("set").addEventListener("click", function (){
	var xhr = new XMLHttpRequest();
	xhr.open("POST", "info", true);
	xhr.setRequestHeader("Content-Type", "text/plain");
	xhr.addEventListener("readystatechange", function(){
	if(this.readyState == XMLHttpRequest.DONE && this.status == 200)
	alert("Stored! Wait a little bit to have this update 'mined'.");
	})
	xhr.send(document.getElementById("typed").value);
	});

	});
	</script>

	<style>
	button {display: block;}
	</style>

	</head>

	<body>
	<input id="typed">
	<button id="set">Set</button>
	<hr>
	<pre id="stored"></pre>
	<button id="get">Get</button>
	</body>

	</html>
	pragma solidity ^0.4.24;

	contract InfoNote {
	string private info;
	function set(string i) public { info = i; }
	function get() public view returns (string) { return info; }
	}