#include <iostream>
#include <string>
#include <ctime>

class Block {
public:
    int index;
    std::string data;
    std::string previousHash;
    std::string hash;
    time_t timestamp;

    Block(int idx, const std::string& d, const std::string& prevHash) : index(idx), data(d), previousHash(prevHash) {
        timestamp = time(nullptr);
        hash = calculateHash();
    }

    std::string calculateHash() {
        // Calculate hash based on index, data, previousHash, timestamp, etc.
        // You can use cryptographic hash functions like SHA-256 for this purpose
        // For simplicity, we will use a simple hash function here
        return std::to_string(index) + data + previousHash + std::to_string(timestamp);
    }
};

#include <vector>

class Blockchain {
public:
    std::vector<Block> chain;

    Blockchain() {
        chain.emplace_back(Block(0, "Genesis Block", "0"));
    }

    Block getLastBlock() {
        return chain.back();
    }

    void addBlock(const std::string& data) {
        Block newBlock(chain.size(), data, getLastBlock().hash);
        chain.push_back(newBlock);
    }

    bool isChainValid() {
        for (size_t i = 1; i < chain.size(); i++) {
            if (chain[i].previousHash != chain[i - 1].hash) {
                return false;
            }
        }
        return true;
    }
};

int main() {
    Blockchain blockchain;

    blockchain.addBlock("First Block");
    blockchain.addBlock("Second Block");

    for (const Block& block : blockchain.chain) {
        std::cout << "Block " << block.index << " - Data: " << block.data << " - Hash: " << block.hash << std::endl;
    }

    std::cout << "Is the blockchain valid? " << (blockchain.isChainValid() ? "Yes" : "No") << std::endl;

    return 0;
}