Implemented transactions record

build.gradle

@@ -0,0 +1,18 @@
+apply plugin: 'idea'
+apply plugin: 'java'
+
+repositories {
+    maven {
+        url 'https://repo.maven.apache.org/maven2'
+        name 'Maven Central'
+    }
+}
+
+test {
+    useJUnitPlatform()
+}
+
+dependencies {
+    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.7.2'
+    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.7.2'
+}

src/main/java/Main.java

@@ -4,7 +4,7 @@ import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
 import java.util.stream.IntStream;
 import model.BlockChain;
-import util.ChatClient;
+import util.TransactionsGenerator;
 import model.Miner;
 import util.FileManagement;
 import util.Security;
@@ -24,15 +24,15 @@ public final class Main {
             Security.generateKeys();
         }
 
-        final var chatExecutor = Executors.newScheduledThreadPool(nThreads);
+        final var transactionsExecutor = Executors.newScheduledThreadPool(nThreads);
 
-        // Mocks a chat client who send messages to the blockchain
-        chatExecutor.scheduleAtFixedRate(new ChatClient(blockChain), 0, 200, TimeUnit.MILLISECONDS);
+        // Mocks a generator to send transactions into the blockchain
+        transactionsExecutor.scheduleAtFixedRate(new TransactionsGenerator(blockChain), 0, 200, TimeUnit.MILLISECONDS);
 
         final var minerExecutor = Executors.newFixedThreadPool(nThreads);
 
-        // Creation of 5 miners
-        IntStream.range(0, 5)
+        // Creation of 15 miners
+        IntStream.range(0, 15)
             .mapToObj(minerId -> new Miner(minerId, blockChain))
             .forEach(minerExecutor::submit);
 
@@ -42,10 +42,10 @@ public final class Main {
             minerExecutor.shutdownNow();
         }
 
-        chatExecutor.shutdown();
+        transactionsExecutor.shutdown();
 
-        if (!chatExecutor.awaitTermination(60, TimeUnit.SECONDS)) {
-            chatExecutor.shutdownNow();
+        if (!transactionsExecutor.awaitTermination(60, TimeUnit.SECONDS)) {
+            transactionsExecutor.shutdownNow();
         }
 
         FileManagement.saveBlockChain(blockChain);

src/main/java/exceptions/NotEnoughCoinsException.java

@@ -0,0 +1,9 @@
+package exceptions;
+
+public class NotEnoughCoinsException extends RuntimeException {
+
+  public NotEnoughCoinsException(final String username) {
+    super(username + " has not enough coins to perform the transaction");
+  }
+
+}

src/main/java/model/Block.java

@@ -15,7 +15,7 @@ public class Block implements Serializable {
   private final int id;
   private final int magicNumber;
   private final float generationSecs;
-  private final List<Message> chatMessages;
+  private final List<Transaction> transactions;
   private final long timeStamp;
 
   public Block(
@@ -25,7 +25,7 @@ public class Block implements Serializable {
       final int id,
       final int magicNumber,
       final float generationSecs,
-      final List<Message> blockMessages
+      final List<Transaction> blockTransactions
   ) {
     this.previousBlockHash = previousBlockHash;
     this.blockHash = blockHash;
@@ -33,7 +33,7 @@ public class Block implements Serializable {
     this.id = id;
     this.magicNumber = magicNumber;
     this.generationSecs = generationSecs;
-    this.chatMessages = blockMessages;
+    this.transactions = blockTransactions;
     this.timeStamp = new Date().getTime();
   }
 
@@ -48,6 +48,7 @@ public class Block implements Serializable {
   public String toString() {
     return "Block: " + "\n"
         + "Created by miner #" + this.minerId + "\n"
+        + "miner #" + this.minerId + " gets 100 VC\n"
         + "Id: " + this.id + "\n"
         + "Timestamp: " + this.timeStamp + "\n"
         + "Magic number: " + this.magicNumber + "\n"
@@ -59,13 +60,13 @@ public class Block implements Serializable {
   }
 
   public String messagesToString() {
-    return chatMessages.isEmpty() ? "Empty block\n" : chatMessages.stream()
-        .map(m -> String.valueOf(m.getId()).concat(" - ").concat(m.getText()).concat("\n"))
+    return transactions.isEmpty() ? "No transactions\n" : transactions.stream()
+        .map(m -> "ID: ".concat(String.valueOf(m.getId()).concat(" - ").concat(m.getText()).concat("\n")))
         .collect(Collectors.joining());
   }
 
-  public List<Message> getMessages() {
-    return chatMessages;
+  public List<Transaction> getMessages() {
+    return transactions;
   }
 
 }

src/main/java/model/BlockChain.java

@@ -10,6 +10,7 @@ import java.util.concurrent.atomic.AtomicInteger;
 import util.FileManagement;
 import util.HashFunction;
 import util.Security;
+import exceptions.NotEnoughCoinsException;
 
 import java.util.*;
 import java.util.stream.Collectors;
@@ -24,8 +25,10 @@ public class BlockChain implements Serializable {
 
   private final Random random = new Random();
   private final List<Block> blockList = new LinkedList<>();
-  private final List<Message> incomingChatMessages = new ArrayList<>();
-  private final AtomicInteger lastMessageId = new AtomicInteger(1);
+  private final List<Transaction> incomingTransactions = new ArrayList<>();
+  private final AtomicInteger lastTransactionId = new AtomicInteger(1);
+  private final Map<Integer,Integer> minersCoins = new HashMap<>();
+  private final Map<String,Integer> usersCoins = new HashMap<>();
 
   private int hashZeroes;
   private int magicNumber;
@@ -50,7 +53,7 @@ public class BlockChain implements Serializable {
     final String previousBlockHash = (nextId > 0) ? blockList.get(nextId - 1).getBlockHash() : "0";
     final String blockHash = calculateBlockHash(minerId);
 
-    incomingChatMessages.sort(Comparator.comparingInt(Message::getId));
+    incomingTransactions.sort(Comparator.comparingInt(Transaction::getId));
 
     final var block = new Block(
         previousBlockHash,
@@ -59,11 +62,12 @@ public class BlockChain implements Serializable {
         nextId,
         magicNumber,
         generationSecs,
-        incomingChatMessages
+        incomingTransactions
     );
     blockList.add(block);
+    minersCoins.put(minerId, 100);
     System.out.println(block);
-    incomingChatMessages.clear();
+    incomingTransactions.clear();
 
     if (generationSecs < LOWER_LIMIT_SECS) {
       hashZeroes += 1;
@@ -77,19 +81,52 @@ public class BlockChain implements Serializable {
 
   }
 
-  public int getNextMessageId() {
-    return lastMessageId.getAndIncrement();
+  public void acceptTransaction(
+      final int nextTransactionId,
+      final String sender,
+      final int amount,
+      final String receiver
+  ) throws
+      NoSuchAlgorithmException,
+      SignatureException,
+      InvalidKeyException,
+      IOException,
+      InvalidKeySpecException,
+      NotEnoughCoinsException
+  {
+    if (usersCoins.get(sender) <= 0 || usersCoins.get(sender) < amount) {
+      throw new NotEnoughCoinsException(sender);
+    } else {
+      transferCoins(sender, amount, receiver);
+      incomingTransactions.add(new Transaction(
+          nextTransactionId,
+          sender,
+          amount,
+          receiver,
+          Security.getPrivate(),
+          Security.getPublic()
+      ));
+    }
   }
 
-  public void acceptText(final int nextMessageId, final String name, final String text)
-      throws NoSuchAlgorithmException, SignatureException, InvalidKeyException, IOException, InvalidKeySpecException {
-    incomingChatMessages.add(new Message(
-        nextMessageId,
-        name,
-        text,
-        Security.getPrivate(),
-        Security.getPublic()
-    ));
+  public void acceptUser(final String username, final int coins){
+    usersCoins.put(username, coins);
+  }
+
+  public void transferCoins(final String sender, final int amount, final String receiver) {
+    final int prevSenderCoins = usersCoins.get(sender);
+    final int prevReceiverCoins = usersCoins.get(receiver);
+
+    usersCoins.put(sender, prevSenderCoins - amount);
+    usersCoins.put(receiver, prevReceiverCoins + amount);
+  }
+
+  public Map<String, Integer> getUsersCoins() {
+    return usersCoins;
+  }
+
+  public int getNextTransactionId() {
+    return lastTransactionId.getAndIncrement();
   }
 
   public boolean validateBlockchain() {
@@ -109,13 +146,13 @@ public class BlockChain implements Serializable {
     if (!blockList.stream()
         .map(Block::getMessages)
         .flatMap(Collection::stream)
-        .map(Message::getId)
+        .map(Transaction::getId)
         .sorted()
         .collect(Collectors.toList())
         .equals(blockList.stream()
             .map(Block::getMessages)
             .flatMap(Collection::stream)
-            .map(Message::getId)
+            .map(Transaction::getId)
             .collect(Collectors.toList())
         )
     ) {

src/main/java/model/Transaction.java

@@ -5,7 +5,7 @@ import util.Security;
 import java.io.Serializable;
 import java.security.*;
 
-public class Message implements Serializable  {
+public class Transaction implements Serializable  {
 
     private static final long serialVersionUID = 1L;
 
@@ -14,10 +14,16 @@ public class Message implements Serializable  {
     private final byte[] signature;
     private final PublicKey publicKey;
 
-    public Message(final int id, final String name, final String text, final PrivateKey privateKey, final PublicKey publicKey)
-        throws NoSuchAlgorithmException, InvalidKeyException, SignatureException {
+    public Transaction(
+        final int id,
+        final String sender,
+        final int amount,
+        final String receiver,
+        final PrivateKey privateKey,
+        final PublicKey publicKey
+    ) throws NoSuchAlgorithmException, InvalidKeyException, SignatureException {
         this.id = id;
-        this.text = "Chatter " + name + " says: " + text;
+        this.text = sender + " sent " + amount + " VC to " + receiver;
         this.signature = Security.sign(text, privateKey);
         this.publicKey = publicKey;
     }

src/main/java/util/Security.java

@@ -7,7 +7,7 @@ import java.security.*;
 import java.security.spec.InvalidKeySpecException;
 import java.security.spec.PKCS8EncodedKeySpec;
 import java.security.spec.X509EncodedKeySpec;
-import model.Message;
+import model.Transaction;
 
 public final class Security {
 
@@ -42,7 +42,7 @@ public final class Security {
         return rsa.sign();
     }
 
-    public static boolean messageIsValid(final Message msg) {
+    public static boolean messageIsValid(final Transaction msg) {
         return Security.verifySignature(msg.getId() + msg.getText(), msg.getSignature(), msg.getPublicKey());
     }
 

src/main/java/util/TransactionsGenerator.java

@@ -0,0 +1,67 @@
+package util;
+
+import java.util.Arrays;
+import java.util.stream.Stream;
+import model.BlockChain;
+import exceptions.NotEnoughCoinsException;
+
+import java.io.IOException;
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.SignatureException;
+import java.security.spec.InvalidKeySpecException;
+import java.util.Random;
+
+public class TransactionsGenerator implements Runnable {
+
+    private static final Random random = new Random();
+    private static final int INITIAL_COINS = 100;
+    private static final String[] userNames = Stream.of(
+        "Thom", "Jonny", "Ed", "Colin", "Phil"
+    ).toArray(String[]::new);
+
+    private final BlockChain blockChain;
+
+    public TransactionsGenerator(final BlockChain blockChain) {
+        this.blockChain = blockChain;
+        if (blockChain.getUsersCoins().isEmpty()) {
+            setInitialUserCoins();
+        }
+    }
+
+    @Override
+    public void run() {
+        try {
+            blockChain.acceptTransaction(
+                blockChain.getNextTransactionId(),
+                getRandomUserName(),
+                getRandomAmount(),
+                getRandomUserName()
+            );
+        } catch (final NoSuchAlgorithmException |
+            SignatureException |
+            InvalidKeyException |
+            IOException |
+            InvalidKeySpecException |
+            NotEnoughCoinsException e)
+        {
+            e.printStackTrace();
+        }
+    }
+
+    private String getRandomUserName() {
+        return userNames[random.nextInt(userNames.length)];
+    }
+
+    private int getRandomAmount(){
+        final int MIN_AMOUNT = 1;
+        final int MAX_AMOUNT = 100;
+
+        return random.nextInt((MAX_AMOUNT - MIN_AMOUNT) + 1) + MIN_AMOUNT;
+    }
+
+    private void setInitialUserCoins() {
+        Arrays.stream(userNames).forEach(userName -> blockChain.acceptUser(userName, INITIAL_COINS));
+    }
+
+}

src/util/ChatClient.java

@@ -1,53 +0,0 @@
-package util;
-
-import model.BlockChain;
-
-import java.io.IOException;
-import java.security.InvalidKeyException;
-import java.security.NoSuchAlgorithmException;
-import java.security.SignatureException;
-import java.security.spec.InvalidKeySpecException;
-import java.util.Random;
-
-public class ChatClient implements Runnable {
-
-    private static final Random random = new Random();
-
-    private final BlockChain blockChain;
-
-    public ChatClient(final BlockChain blockChain) {
-        this.blockChain = blockChain;
-    }
-
-    @Override
-    public void run() {
-        try {
-            blockChain.acceptText(blockChain.getNextMessageId(), generateRandomName(), generateRandomText());
-        } catch (final NoSuchAlgorithmException | SignatureException | InvalidKeyException | IOException | InvalidKeySpecException e) {
-            e.printStackTrace();
-        }
-    }
-
-    private String generateRandomName() {
-        final int leftLimit = 97; // letter 'a'
-        final int rightLimit = 122; // letter 'z'
-        final int targetStringLength = 5;
-
-        return random.ints(leftLimit, rightLimit + 1)
-            .limit(targetStringLength)
-            .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
-            .toString();
-    }
-
-    private String generateRandomText() {
-        final int leftLimit = 97; // letter 'a'
-        final int rightLimit = 122; // letter 'z'
-        final int targetStringLength = 20;
-
-        return random.ints(leftLimit, rightLimit + 1)
-            .limit(targetStringLength)
-            .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
-            .toString();
-    }
-
-}