From 5fa8bbf2b73df402d227f66f5ef8714718e1b6b0 Mon Sep 17 00:00:00 2001
From: Christian Baltzer <christian@baltzer.de>
Date: Sun, 14 Jul 2019 16:52:56 +0200
Subject: [PATCH] Blockchain Logik fertig

---
 .../java/ugsbo/com/buchhaltung/Block.java     | 41 +++++++++++++------
 .../ugsbo/com/buchhaltung/Blockchain.java     |  9 ++--
 2 files changed, 33 insertions(+), 17 deletions(-)

diff --git a/src/main/java/ugsbo/com/buchhaltung/Block.java b/src/main/java/ugsbo/com/buchhaltung/Block.java
index 3904106..b315519 100644
--- a/src/main/java/ugsbo/com/buchhaltung/Block.java
+++ b/src/main/java/ugsbo/com/buchhaltung/Block.java
@@ -12,19 +12,11 @@ public class Block {
   String ownHash;
   String previousHash;
   
-  public Block(int data, Block vorher, String previousHash, int konto) {
-    this.data = data;
-    ownHash = createNewHash();
-    
-    kontostand = konto + this.data;
-    
-    this.vorher = vorher;
-    this.previousHash = previousHash;
-  }
   
+  //erste Block
   public Block(int data) {
     this.data = data;
-    ownHash = createNewHash();
+    ownHash = createNewHash(Integer.toString(data));
     
     kontostand = this.data;
     
@@ -32,8 +24,33 @@ public class Block {
     this.previousHash = null;
   }
 
-  private String createNewHash() {
-    return null;
+  //Alle anderen Blöcke
+  public Block(int data, Block vorher, String previousHash, int konto) {
+    this.data = data;
+    ownHash = createNewHash(Integer.toString(data)+previousHash);
+    
+    kontostand = konto + this.data;
+    
+    this.vorher = vorher;
+    this.previousHash = previousHash;
+  }
+  
+  private String createNewHash(String input) {
+    try {
+      MessageDigest digest = MessageDigest.getInstance("SHA-256");            
+      //Applies sha256 to our input, 
+      byte[] hash = digest.digest(input.getBytes("UTF-8"));           
+      StringBuffer hexString = new StringBuffer(); // This will contain hash as hexidecimal
+      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();
+  }
+  catch(Exception e) {
+      throw new RuntimeException(e);
+  }
   }
   
   public int getKontostand() {
diff --git a/src/main/java/ugsbo/com/buchhaltung/Blockchain.java b/src/main/java/ugsbo/com/buchhaltung/Blockchain.java
index 4f323bf..987b2b1 100644
--- a/src/main/java/ugsbo/com/buchhaltung/Blockchain.java
+++ b/src/main/java/ugsbo/com/buchhaltung/Blockchain.java
@@ -1,5 +1,7 @@
 package ugsbo.com.buchhaltung;
 
+import com.google.gson.*;
+
 public class Blockchain {
  
   Block Workingobjekt;
@@ -11,7 +13,6 @@ public class Blockchain {
 
 
   public void add(int eingabe) {
-    // TODO Auto-generated method stub
     Block newWorkingobjekt = new Block(eingabe, Workingobjekt, Workingobjekt.getHash(), Workingobjekt.getKontostand());
     
     Workingobjekt = newWorkingobjekt;
@@ -19,14 +20,12 @@ public class Blockchain {
 
 
   public int kontostand() {
-    // TODO Auto-generated method stub
     return Workingobjekt.getKontostand();
   }
   
   public String toString() {
-    
-    
-    return null;
+    String JSON = new GsonBuilder().setPrettyPrinting().create().toJson(Workingobjekt);      
+    return JSON;
   }