package byteblocks;

import java.nio.charset.StandardCharsets;

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

import java.time.Instant;

import java.util.ArrayList;

import java.util.List;

import static byteblocks.DataGenerator.randomName;

public class BlocksSimulator {

private static class Block {

private String hash;

private long blockHeight;

private String prevHash;

private long timestamp;

private String data;

private String nonce;

public String encodedData() {

return String.format("%s|%s|%s|%s|%s", blockHeight, prevHash, timestamp, data, nonce);

}

}

public static void printBlock(Block block, boolean isLast) {

String blockTitle = "Block " + Instant.ofEpochMilli(block.timestamp);

System.out.println(blockTitle + " (Height: " + block.blockHeight + ")");

System.out.println("├─ Hash: " + block.hash + "...");

System.out.println("├─ Previous Hash: \"" + block.prevHash + "\"");

System.out.println("└─ Data: \"" + block.data + "\"");

if (!isLast) {

System.out.println(" │");

System.out.println(" ▼");

}

}

private static Block genesisBlock() {

Block block = new Block();

block.timestamp = System.currentTimeMillis();

block.blockHeight = 0;

block.prevHash = "";

block.data = "Genesis";

return block;

}

private static Block newBlock(Block prev, String data) {

Block block = new Block();

block.timestamp = System.currentTimeMillis();

block.blockHeight = prev.blockHeight + 1;

block.prevHash = prev.hash;

block.data = data;

return block;

}

public static void minerProofOfWork(Block block) throws NoSuchAlgorithmException {

int nonce = 0;

MessageDigest digest = MessageDigest.getInstance("SHA-256");

while (true) {

block.nonce = Long.toString(nonce);

String encodedData = block.encodedData();

byte[] encodedHash = digest.digest(encodedData.getBytes(StandardCharsets.UTF_8));

String hash = bytesToHex(encodedHash);

if (hash.startsWith("00")) {

block.hash = hash;

return;

}

nonce++;

}

}

private static String bytesToHex(byte[] hash) {

StringBuilder hexString = new StringBuilder(2 * hash.length);

for (int i = 0; i < hash.length; i++) {

String hex = Integer.toHexString(0xff & hash[i]);

if (hex.length() == 1) {

hexString.append('0');

}

hexString.append(hex);

}

return hexString.toString();

}

private static void simulateWorld() throws Exception {

Block genesis = genesisBlock();

minerProofOfWork(genesis);

printBlock(genesis, false);

List<Block> blocks = new ArrayList<>();

blocks.add(genesis);

int numberOfBlocks = 3;

for (int i = 0; i < numberOfBlocks; i++) {

Block prev = blocks.getLast();

Block current = newBlock(prev, randomName());

minerProofOfWork(current);

printBlock(current, i + 1 == numberOfBlocks);

blocks.add(current);

Thread.sleep(2_000);

}

}

public static void main(String[] args) throws Exception {

simulateWorld();

}

}