import hashlib
import time

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

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

class Node:
    def __init__(self, name, max_block_size):
        self.name = name
        self.max_block_size = max_block_size  # Consensus Rule
        self.chain = []
        print(f"[*] Node '{self.name}' initialized with {self.max_block_size}MB limit.")

    def add_block(self, new_block):
        # 1. Check if block size exceeds consensus rules
        if new_block.size_mb > self.max_block_size:
            print(f"[!] REJECTED: Block {new_block.index} size ({new_block.size_mb}MB) "
                  f"exceeds limit ({self.max_block_size}MB). Consensus Failure!")
            return False

        # 2. Add to chain
        self.chain.append(new_block)
        print(f"[+] ACCEPTED: Block {new_block.index} added. Hash: {new_block.hash[:16]}...")
        return True

# --- Simulation ---

# 1. Initialize an 'Old Rule' node (1MB limit)
honest_node = Node("Bitcoin Core 0.14", max_block_size=1.0)

# 2. Simulate valid blocks
genesis = Block(0, "Genesis", "0", 0.1)
honest_node.add_block(genesis)

block1 = Block(1, "TX_DATA_1", genesis.hash, 0.8)
honest_node.add_block(block1)

# 3. Simulate a Hard Fork Block (2MB)
print("\n--- ATTACK: A miner attempts a Hard Fork ---")
fork_block = Block(2, "BIG_TX_DATA", block1.hash, 2.0)
success = honest_node.add_block(fork_block)

if not success:
    print("\n[*] RESULT: The node ignored the fork and stayed on the original chain.")
    print(f"[*] Chain Height: {len(honest_node.chain)}")