from hashlib import sha256
import time

class AdBlockchain:
    def __init__(self):
        self.chain = []
        self.create_block(proof=1, previous_hash='0')
        
    def create_block(self, proof, previous_hash, ad_data=None):
        block = {
            'index': len(self.chain) + 1,
            'timestamp': str(time.time()),
            'proof': proof,
            'previous_hash': previous_hash,
            'ad_hash': self.hash_ad(ad_data)
        }
        self.chain.append(block)
        return block
    
    def hash_ad(self, ad_data):
        return sha256(str(ad_data).encode()).hexdigest()

    def is_chain_valid(self):
        for i in range(1, len(self.chain)):
            current_block = self.chain[i]
            previous_block = self.chain[i - 1]
            if current_block['previous_hash'] != self.hash_ad(previous_block):
                return False
        return True