HTTP + Ethereum example

app.py

  
'''
Important docs
https://web3py.readthedocs.io/en/stable/web3.eth.html#web3.eth.Eth.getTransaction
https://web3py.readthedocs.io/en/stable/web3.eth.html#web3.eth.Eth.getTransactionReceipt
'''
import hashlib
import json
import os

from flask import Flask, request, jsonify
from hexbytes import HexBytes
from web3 import Web3, HTTPProvider
from eth_typing.ethpm import URI
from web3.datastructures import AttributeDict


ETH_PROVIDER_ADDRESS: URI = URI('http://127.0.0.1:7545')  # I'm using Ganache as my blockchain provider
contract_json_path = os.environ.get('DEPLOYED_CONTRACT_BUILD')  # path to the compile contract (JSON)
contract_address = os.environ.get('DEPLOYED_CONTRACT_ADDRESS')  # address on the blockchain of deployed smart contract (hex)
with open(contract_json_path) as f:
    info_json = json.load(f)
    contract_abi = info_json["abi"]  # necessary to load the contract in the app.py

app = Flask(__name__)
w3 = Web3(HTTPProvider(ETH_PROVIDER_ADDRESS))
payer_account = w3.eth.accounts[0]
w3.eth.defaultAccount = w3.eth.accounts[0]
contract = w3.eth.contract(address=contract_address, abi=contract_abi)


def add_to_blockchain(hashed_data):
    tx_hash = contract.functions.saveTransaction(hashed_data, w3.eth.defaultAccount).transact()
    tx_receipt = w3.eth.waitForTransactionReceipt(tx_hash)
    return tx_receipt


@app.route('/add-transaction', methods=['POST'])
def add_transaction():
    if not request.data:
        return jsonify({'error': 'Data must be passed in payload'}), 400
    payload = request.json.get('payload', None)
    if not payload:
        return jsonify({'error': 'payload cannot be empty'}), 400

    hashed_data = hashlib.sha256(payload.encode()).hexdigest()
    wpc_response = add_to_blockchain(hashed_data)
    
    return 'success'


@app.route('/list-transactions', methods=['GET'])
def list_transactions():
    # TODO: not sure we will need it.
    return jsonify([])