Create blockchain.py

blockchain/blockchain.py

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+import hashlib
+import time
+from flask import Flask, jsonify, request
+from flask_restful import Api, Resource
+from flask_sqlalchemy import SQLAlchemy
+
+app = Flask(__name__)
+api = Api(app)
+app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite:///blockchain.db"
+db = SQLAlchemy(app)
+
+class Block(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    index = db.Column(db.Integer)
+    timestamp = db.Column(db.Float)
+    data = db.Column(db.String(100))
+    previous_hash = db.Column(db.String(100))
+    hash = db.Column(db.String(100))
+
+class Blockchain(object):
+    def __init__(self):
+        self.chain = []
+        self.create_block(proof=1, previous_hash="0")
+
+    def create_block(self, proof, previous_hash):
+        block = {
+            "index": len(self.chain) + 1,
+            "timestamp": time.time(),
+            "data": "",
+            "previous_hash": previous_hash,
+            "hash": "",
+        }
+
+        block["hash"] = self.calculate_hash(block)
+        self.chain.append(block)
+
+        return block
+
+    def calculate_hash(self, block):
+        block_string = json.dumps(block, sort_keys=True).encode()
+        return hashlib.sha256(block_string).hexdigest()
+
+    def is_valid_chain(self, chain):
+        for i in range(1, len(chain)):
+            current_block = chain[i]
+            previous_block = chain[i - 1]
+
+            if current_block["previous_hash"]!= self.calculate_hash(previous_block):
+                return False
+
+            if current_block["hash"]!= self.calculate_hash(current_block):
+                return False
+
+        return True
+
+    def replace_chain(self, chain):
+        if self.is_valid_chain(chain) and len(chain) > len(self.chain):
+            self.chain = chain
+
+@app.before_first_request
+def setup_blockchain():
+    blockchain = Blockchain()
+    db.create_all()
+    db.session.add(blockchain)
+    db.session.commit()
+
+class BlockchainAPI(Resource):
+    def get(self):
+        return jsonify({"chain": self.blockchain.chain})
+
+    def post(self):
+        data = request.get_json()
+        new_block = self.blockchain.create_block(data["proof"], data["previous_hash"])
+        db.session.add(new_block)
+        db.session.commit()
+        return jsonify({"message": "New block added to the chain"})
+
+api.add_resource(BlockchainAPI, "/blockchain")
+
+if __name__ == "__main__":
+    app.run(debug=True)