Ozan/merkle snapshot

src/main/java/model/codec/EntityType.java

@@ -9,4 +9,6 @@ public class EntityType {
   public static final String TYPE_VALIDATED_TRANSACTION = "type-lightchain-validated-transaction";
   public static final String TYPE_VALIDATED_BLOCK = "type-lightchain-validated-block";
   public static final String TYPE_ECDSA_SIGNATURE = "type-lightchain-ecdsa-signature";
+  public static final String TYPE_ACCOUNT = "type-lightchain-account";
+
 }

src/main/java/model/lightchain/Account.java

@@ -1,11 +1,13 @@
 package model.lightchain;
 
+import model.Entity;
+import model.codec.EntityType;
 import model.crypto.PublicKey;
 
 /**
  * Represents a LightChain account which is the constituent of the SnapShot.
  */
-public class Account {
+public class Account extends Entity {
   /**
    * Unique identifier of the account.
    */
@@ -72,4 +74,24 @@ public Identifier getLastBlockId() {
   public int getStake() {
     return this.stake;
   }
+
+  /**
+   * Type of this entity.
+   *
+   * @return type of this entity.
+   */
+  @Override
+  public String type() {
+    return EntityType.TYPE_ACCOUNT;
+  }
+
+  /**
+   * Identifier of this account.
+   *
+   * @return identifier of this Account
+   */
+  @Override
+  public Identifier id() {
+    return this.identifier;
+  }
 }

src/main/java/modules/ads/merkletree/MerkleTree.java

@@ -133,4 +133,17 @@ private void buildMerkleTree() {
   public int size() {
     return this.size;
   }
+
+  /**
+   * returns all entities in the merkle tree.
+   *
+   * @return all entities in the merkle tree.
+   */
+  public ArrayList<Entity> all() {
+    ArrayList<Entity> entities = new ArrayList<>();
+    for (Entity e : entityHashTable.values()) {
+      entities.add(e);
+    }
+    return entities;
+  }
 }

src/main/java/state/merkle/MerkleSnapshot.java

@@ -0,0 +1,85 @@
+package state.merkle;
+
+import java.util.ArrayList;
+
+import model.Entity;
+import model.lightchain.Account;
+import model.lightchain.Identifier;
+import modules.ads.merkletree.MerkleTree;
+
+/**
+ * Implements a simplified merkle tree based model of the protocol snapshot at a given block.
+ */
+public class MerkleSnapshot implements state.Snapshot {
+  private final Identifier rootBlockId;
+  private final long rootBlockHeight;
+  private MerkleTree merkleTree;
+
+  /**
+   * Constructor of MerkleSnapShot.
+   *
+   * @param rootBlockId     root block id representing this snapshot.
+   * @param rootBlockHeight root block height of this snapshot.
+   */
+  public MerkleSnapshot(Identifier rootBlockId, long rootBlockHeight) {
+    this.rootBlockId = rootBlockId;
+    this.rootBlockHeight = rootBlockHeight;
+    this.merkleTree = new MerkleTree();
+  }
+
+  /**
+   * The identifier of finalized block that this snapshot represents.
+   *
+   * @return the identifier of finalized block that this snapshot represents.
+   */
+  @Override
+  public Identifier getReferenceBlockId() {
+    return rootBlockId;
+  }
+
+  /**
+   * The height of the reference block that this snapshot represents.
+   *
+   * @return height of the reference block that this snapshot represents.
+   */
+  @Override
+  public long getReferenceBlockHeight() {
+    return rootBlockHeight;
+  }
+
+  /**
+   * Fetches account corresponding to an identifier at the given snapshot.
+   *
+   * @param identifier identifier of an account of interest.
+   * @return account corresponding to the given identifier at this snapshot, or null if such an account
+   * does not exist.
+   */
+  @Override
+  public Account getAccount(Identifier identifier) {
+    return (Account) merkleTree.get(identifier).getEntity();
+  }
+
+  /**
+   * Adds an account to the snapshot.
+   *
+   * @param identifier Identifier of the account to add.
+   * @param account Account to add.
+   */
+  public void addAccount(Identifier identifier, Account account) {
+    this.merkleTree.put(account);
+  }
+
+  /**
+   * The list of accounts in this snapshot.
+   *
+   * @return the list of accounts in this snapshot.
+   */
+  @Override
+  public ArrayList<Account> all() {
+    ArrayList<Account> accounts = new ArrayList<>();
+    for (Entity entity : merkleTree.all()) {
+      accounts.add((Account) entity);
+    }
+    return accounts;
+  }
+}