Smol project we were forced to make during class

blockchain.cpp

  ////////////////////////////////////
 //  WORTHLESS BLOCKCHAIN PROJECT  //
////////////////////////////////////

// The most basic imitation/implementation of how a Blockchain would work
// Still has lots of flaws (╯°□°）╯︵ ┻━┻

#include <ctime>
#include <cstring>
#include <iostream>
#include <string>
#include <vector>

using namespace std;

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

  Block(string data, string previousHash, int index) {
    this->data = data;
    this->previousHash = previousHash;
    this->index = index;
    this->timestamp = time(nullptr);
    this->currentHash = calculateHash();
  }

  string calculateHash() {
    string hashStr =
        previousHash + to_string(timestamp) + data + to_string(index);

    hash<string> str_hash;
    return to_string(str_hash(hashStr));
  }
};

class Blockchain {
public:
  int blockHeight;
  vector<Block> blocks;

  Blockchain() {
    blockHeight = 0;
    blocks.push_back(generateGenesisBlock());
  }

  Block generateGenesisBlock() { return Block("Genesis Block", "0", 0); }

  void addBlock(string data) {
    string previousHash = blocks[blockHeight].currentHash;
    Block blockToAdd = Block(data, previousHash, blockHeight + 1);
    blockHeight++;
    blocks.push_back(blockToAdd);
  }

  void printBlocks() {
    for (int i = 0; i < blocks.size(); i++) {
      cout << "Block " << blocks[i].index << endl;
      cout << "Data\t\t" << blocks[i].data << endl;
      cout << "Timestamp\t\t" << blocks[i].timestamp << endl;
      cout << "Previous Hash\t\t" << blocks[i].previousHash << endl;
      cout << "Current Hash\t\t" << blocks[i].currentHash << endl;
      cout << endl;
    }
  }

  void validateBlockchain() {
    for (int i = blocks.size() - 1; i > 1; i--) {
      if (strcmp(blocks[i].previousHash.c_str(),
                 blocks[i - 1].calculateHash().c_str()) != 0) {
        cout << "Blockchain is invalid" << endl;
        return;
      }
    }
    cout << "Blockchain is valid" << endl;
  }
};

int main() {
  Blockchain blockchain = Blockchain();
  cout << "\nAdding BLocks\n";

  int blocksToAdd = 5;
  for (int i = 0; i < blocksToAdd; i++) {
    blockchain.addBlock("Block Data " + to_string(i));
  }

  blockchain.printBlocks();
  blockchain.validateBlockchain();

  cout << "\nModifying Blockchain\n";

  cout << "\nold hash: " + blockchain.blocks[2].calculateHash() << endl;
  blockchain.blocks[2].data = "Modified Block Data 69";
  cout << "hash after change: " + blockchain.blocks[2].calculateHash() << endl
       << endl;
  blockchain.printBlocks();

  cout << "\nValidating Blockchain\n";
  blockchain.validateBlockchain();

  return 0;
}