src/Blockchain.java - master - skirill/blockchain

src/Blockchain.java
134 строки6 KB
K. S
Added Wallet and TransactionInput and -Output
18 июл 2024, 16:03
18 июл 2024, 16:037604be7
import java.awt.font.TransformAttribute;
import java.security.Security;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Optional;

import com.google.gson.GsonBuilder;

public class Blockchain {
    public static ArrayList<Block> blockchain = new ArrayList<Block>();
    public static HashMap<String, TransactionOutput> UTXOs = new HashMap<String, TransactionOutput>();

    public static int difficulty = 5;
    public static float minimumTransaction = 0.1f;
    public static Wallet walletA;
    public static Wallet walletB;
    public static Transaction genesisTransaction;

    public static void main(String[] args) {
        Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());

        walletA = new Wallet();
        walletB = new Wallet();
        Wallet coinbase = new Wallet();

        genesisTransaction = new Transaction(coinbase.publicKey, walletA.publicKey, 100f, null);
        genesisTransaction.generateSignature(coinbase.privateKey);
        genesisTransaction.transactionId = "0";
        genesisTransaction.outputs.add(new TransactionOutput(genesisTransaction.recipient, genesisTransaction.value, genesisTransaction.transactionId));
        UTXOs.put(genesisTransaction.outputs.get(0).id, genesisTransaction.outputs.get(0));

        System.out.println("Creating and Mining Genesis block...");
        Block genesis = new Block("0");
        genesis.addTransaction(genesisTransaction);
        addBlock(genesis);

        Block block1 = new Block(genesis.hash);
        System.out.println("\nWalletA's balance is: " + walletA.getBalance());
        System.out.println("\nWalletA is Attempting to send funds (40) to WalletB...");
        block1.addTransaction(walletA.sendFunds(walletB.publicKey, 40f));
        addBlock(block1);
        System.out.println("\nWalletA's balance is: " + walletA.getBalance());
        System.out.println("WalletB's balance is: " + walletB.getBalance());

        Block block2 = new Block(block1.hash);
        System.out.println("\nWalletA Attempting to send more funds (1000) than is has...");
        block2.addTransaction(walletA.sendFunds(walletB.publicKey, 1000f));
        addBlock(block2);
        System.out.println("\nWalletA's balance is: " + walletA.getBalance());
        System.out.println("WalletB's balance is: " + walletB.getBalance());

        Block block3 = new Block(block2.hash);
        System.out.println("\nWalletB is Attempting to send funds (20) to WalletA...");
        block3.addTransaction(walletB.sendFunds(walletA.publicKey, 20f));
        System.out.println("\nWalletA's balance is: " + walletA.getBalance());
        System.out.println("WalletB's balance is: " + walletB.getBalance());

        isChainValid();
    }

    public static void addBlock(Block newBlock) {
        newBlock.mineBlock(difficulty);
        blockchain.add(newBlock);
    }

    public static Boolean isChainValid()  {
        Block currentBlock;
        Block previousBlock;
        String hashTarget = new String(new char[difficulty]).replace('\0', '0');
        HashMap<String, TransactionOutput> tempUTXOs = new HashMap<String, TransactionOutput>();
        tempUTXOs.put(genesisTransaction.outputs.get(0).id, genesisTransaction.outputs.get(0));

        for(int i = 1; i < blockchain.size(); i++) {
            currentBlock = blockchain.get(i);
            previousBlock = blockchain.get(i-1);
            if(!currentBlock.hash.equals(currentBlock.calculateHash())) {
                System.out.println("#Prev hashes not equal");
                return false;
            }
            if(!previousBlock.hash.equals(currentBlock.previousHash)) {
                System.out.println("#Prev hashes not equal");
                return false;
            }
            if(!currentBlock.hash.substring(0, difficulty).equals(hashTarget)) {
                System.out.println("#This block hasn't been mined");
                return false;
            }
            
            TransactionOutput tempOutput;
            for(int t = 0; t < currentBlock.transactions.size(); t++) {
                Transaction currentTransaction = currentBlock.transactions.get(t);

                if(!currentTransaction.verifySignature()) {
                    System.out.println("#Signature on Transaction("+t+") is Invalid");
                    return false;
                }

                if(currentTransaction.getInputsValue() != currentTransaction.getOutputsValue()) {
                    System.out.println("#Inputs are not equal to output on Transaction("+t+")");
                    return false;
                }

                for(TransactionInput input: currentTransaction.inputs) {
                    tempOutput = tempUTXOs.get(input.transactionOutputId);
                    if(tempOutput == null) {
                        System.out.println("#Referenced input on Transaction("+t+") is Missing");
                        return false;
                    }
                    if(input.UTXO.value != tempOutput.value) {
                        System.out.println("#Referenced input on Transaction("+t+") value is Invalid");
                        return false;
                    }

                    tempUTXOs.remove(input.transactionOutputId);
                }

                for(TransactionOutput output: currentTransaction.outputs) {
                    tempUTXOs.put(output.id, output);
                }

                if(currentTransaction.outputs.get(0).reciepient != currentTransaction.recipient) {
                    System.out.println("#Trasaction(" + t + ") output reciepient is not who it should be");
                    return false;
                }
                if(currentTransaction.outputs.get(1).reciepient != currentTransaction.recipient) {
                    System.out.println("#Trasaction(" + t + ") output 'change' is not sender.");
                    return false;
                }
            }
        }
        System.out.println("Blockchain is valid");
        return true;
    }
}