import hashlib
import time

def hash256(data):
    """Double-SHA256."""
    return hashlib.sha256(hashlib.sha256(data).digest()).digest()

def mine_block(header_prefix, target_hex):
    target = int(target_hex, 16)
    nonce = 0
    start_time = time.time()

    print(f"--- Mining Started ---")
    print(f"[*] Target: {target_hex}")

    while nonce < 2**32:
        # 1. Append nonce (4-byte little-endian) to header prefix
        # header_prefix is 76 bytes, nonce is 4 bytes = 80 byte header
        header = header_prefix + nonce.to_bytes(4, 'little')

        # 2. Hash
        block_hash = hash256(header)
        hash_val = int.from_bytes(block_hash, 'little')

        # 3. Check against target
        if hash_val < target:
            elapsed = time.time() - start_time
            print(f"\n[SUCCESS] Block Mined!")
            print(f"[*] Nonce: {nonce}")
            print(f"[*] Hash:  {block_hash[::-1].hex()}")
            print(f"[*] Time:  {elapsed:.2f} seconds")
            return nonce, block_hash

        # Status update every 1M hashes
        if nonce % 1000000 == 0 and nonce > 0:
            print(f"[*] Progress: {nonce/1000000:.0f}M hashes...")

        nonce += 1

    return None

# --- Simulation ---

# Mock 76-byte header (Version, PrevHash, Merkle, Time, Bits)
mock_header_prefix = b'\x02\x00\x00\x00' + b'\x00'*32 + b'\x00'*32 + b'\x64\xb0\x11\xc9' + b'\x2a\x6f\x06\x17'

# We will set a VERY EASY target for this simulation (4 leading hex zeroes)
easy_target = "0000ffff" + "f"*56 

mine_block(mock_header_prefix, easy_target)