import os import time import json import hashlib import uuid from typing import List

-------------------- BLOCK --------------------

class Block: def init(self, index, timestamp, data, prev_hash): self.index = index self.timestamp = timestamp self.data = data self.prev_hash = prev_hash self.hash = self.calculate_hash()

def calculate_hash(self):
    block_string = json.dumps({
        "index": self.index,
        "timestamp": self.timestamp,
        "data": self.data,
        "prev_hash": self.prev_hash
    }, sort_keys=True).encode()

    return hashlib.sha256(block_string).hexdigest()

-------------------- BLOCKCHAIN --------------------

class Blockchain: def init(self): self.chain = [self.create_genesis_block()]

def create_genesis_block(self):
    return Block(0, time.time(), {"msg": "Genesis Block"}, "0")

def get_latest_block(self):
    return self.chain[-1]

def add_block(self, data):
    prev_block = self.get_latest_block()
    new_block = Block(
        prev_block.index + 1,
        time.time(),
        data,
        prev_block.hash
    )
    self.chain.append(new_block)

def is_valid(self):
    for i in range(1, len(self.chain)):
        curr = self.chain[i]
        prev = self.chain[i - 1]

        if curr.hash != curr.calculate_hash():
            return False
        if curr.prev_hash != prev.hash:
            return False

    return True

-------------------- RESILIENT STORAGE --------------------

class ResilientStorage: def init(self, nodes: List[str], chunk_size=1024): self.nodes = nodes self.chunk_size = chunk_size self.blockchain = Blockchain()

    # Create node directories
    for node in nodes:
        os.makedirs(node, exist_ok=True)

def store_file(self, file_path):
    file_id = str(uuid.uuid4())
    chunk_index = 0

    with open(file_path, "rb") as f:
        while True:
            chunk = f.read(self.chunk_size)
            if not chunk:
                break

            node = self.nodes[chunk_index % len(self.nodes)]
            chunk_name = f"{file_id}_{chunk_index}"

            with open(os.path.join(node, chunk_name), "wb") as cf:
                cf.write(chunk)

            chunk_index += 1

    # Record in blockchain
    self.blockchain.add_block({
        "action": "store",
        "file_id": file_id,
        "file_name": os.path.basename(file_path),
        "chunks": chunk_index,
        "time": time.time()
    })

    return file_id

def retrieve_file(self, file_id, output_path):
    chunks = []

    # Collect chunks from nodes
    for node in self.nodes:
        for file in os.listdir(node):
            if file.startswith(file_id):
                chunks.append(file)

    if not chunks:
        print("File not found!")
        return

    # Sort chunks
    chunks.sort(key=lambda x: int(x.split("_")[-1]))

    with open(output_path, "wb") as out:
        for chunk in chunks:
            for node in self.nodes:
                path = os.path.join(node, chunk)
                if os.path.exists(path):
                    with open(path, "rb") as cf:
                        out.write(cf.read())
                    break

    print("File retrieved successfully!")

def verify_integrity(self):
    return self.blockchain.is_valid()

-------------------- MAIN PROGRAM --------------------

def main(): nodes = ["node1", "node2", "node3"] storage = ResilientStorage(nodes)

while True:
    print("\n--- Blockchain Resilient Storage ---")
    print("1. Store File")
    print("2. Retrieve File")
    print("3. Verify Blockchain")
    print("4. Exit")

    choice = input("Enter choice: ")

    if choice == "1":
        path = input("Enter file path: ")
        if os.path.exists(path):
            file_id = storage.store_file(path)
            print("Stored! File ID:", file_id)
        else:
            print("File not found")

    elif choice == "2":
        file_id = input("Enter file ID: ")
        output = input("Enter output file path: ")
        storage.retrieve_file(file_id, output)

    elif choice == "3":
        if storage.verify_integrity():
            print("Blockchain is VALID")
        else:
            print("Blockchain is CORRUPTED")

    elif choice == "4":
        break

    else:
        print("Invalid choice")

if name == "main": main()

-------------------- OUTPUT --------------------

Enter choice: 1 Enter file path: c:\Users\sarath kumar M\Documents\demo.txt
Stored! File ID: d13b45ad-48b2-484d-9250-21ffbd3a4e32

--- Blockchain Resilient Storage ---

1. Store File
2. Retrieve File
3. Verify Blockchain
4. Exit Enter choice: 2 Enter file ID: d13b45ad-48b2-484d-9250-21ffbd3a4e32 Enter output file path: c:\Users\sarath kumar M\Documents\demo.txt File retrieved successfully!

--- Blockchain Resilient Storage ---

1. Store File
2. Retrieve File
3. Verify Blockchain
4. Exit Enter choice: 3 Blockchain is VALID

--- Blockchain Resilient Storage ---

1. Store File
2. Retrieve File
3. Verify Blockchain
4. Exit Enter choice: 4 PS C:\Users\sarath kumar M\Desktop\blockchain\program>