什么是区块链溯源

from flask import Flask, jsonify, request
import hashlib

app = Flask(__name__)

blockchain = []

class Block:
    def __init__(self, index, data, previous_hash):
        self.index = index
        self.data = data
        self.previous_hash = previous_hash
        self.hash = self.calculate_hash()

    def calculate_hash(self):
        value = str(self.index) + str(self.data) + str(self.previous_hash)
        return hashlib.sha256(value.encode('utf-8')).hexdigest()

def create_genesis_block():
    return Block(0, "Genesis Block", "0")

blockchain.append(create_genesis_block())

@app.route('/add_block', methods=['POST'])
def add_block():
    data = request.get_json()['data']
    previous_block = blockchain[-1]
    new_index = previous_block.index + 1
    new_block = Block(new_index, data, previous_block.hash)
    blockchain.append(new_block)
    return jsonify({'message': 'Block added successfully'})

@app.route('/get_chain', methods=['GET'])
def get_chain():
    chain_data = []
    for block in blockchain:
        chain_data.append({'index': block.index, 'data': block.data, 'hash': block.hash})
    return jsonify({'chain': chain_data})

if __name__ == '__main__':
    app.run(port=5000)