Mine empty block

app/codes/blockchain.py

@@ -5,7 +5,7 @@
 
 import sqlite3
 
-from ..constants import NEWRL_DB
+from ..constants import EMPTY_BLOCK_NONCE, NEWRL_DB
 from .state_updater import update_db_states
 
 
@@ -44,6 +44,14 @@ def get_block(self, block_index):
 
         return block
 
+    def empty_block_hash(self, block):
+        proof = EMPTY_BLOCK_NONCE  # Hardcoded value for empty block
+        block['proof'] = proof
+        block_hash = self.calculate_hash(block)
+        block_hash = '0000' + block_hash[:4]
+
+        return block_hash
+
     def proof_of_work(self, block):
         """Proof of work which takes a block with proof set as 0 as input and 
            returns the proof that makes its hash start with 0000"""
@@ -82,20 +90,27 @@ def mine_block(self, cur, text):
         """Mine a new block"""
         print("Starting the mining step 1")
         last_block_cursor = cur.execute(
-            'SELECT block_index, hash FROM blocks ORDER BY block_index DESC LIMIT 1')
+            'SELECT block_index, hash, timestamp FROM blocks ORDER BY block_index DESC LIMIT 1')
         last_block = last_block_cursor.fetchone()
         last_block_index = last_block[0] if last_block is not None else 0
         last_block_hash = last_block[1] if last_block is not None else 0
+        last_block_timestamp = last_block[2] if last_block is not None else 0
 
         block = {
             'index': last_block_index + 1,
-            'timestamp': str(datetime.datetime.now()),
             'proof': 0,
             'text': text,
             'previous_hash': last_block_hash
         }
 
-        block_hash = self.proof_of_work(block)
+        if len(text['transactions']) == 0:
+            # TODO - Fix the timestamp. Supposed to be real timestamp
+            block['timestamp'] = last_block_timestamp + 1
+            block_hash = self.empty_block_hash(block)
+        else:
+            block['timestamp'] = str(datetime.datetime.now())
+            block_hash = self.proof_of_work(block)
+
         print("New block hash is ", block_hash)
 
         block = self.create_block(cur, block, block_hash)

app/codes/validator.py

@@ -11,7 +11,7 @@
 from app.codes.p2p.transport import send
 from .blockchain import get_last_block_hash
 from .transactionmanager import Transactionmanager
-from ..constants import MEMPOOL_PATH
+from ..constants import EMPTY_BLOCK_NONCE, MEMPOOL_PATH
 
 
 logging.basicConfig(level=logging.INFO)
@@ -125,6 +125,9 @@ def validate_block(block, validate_receipts=True):
 
     # Also check for block index
 
+    if not validate_empty_block(block):
+        return False
+
     sign_valid = validate_signature(
         data=block['data'],
         public_key=block['signature']['public_key'],
@@ -142,3 +145,12 @@ def validate_block(block, validate_receipts=True):
             return False
 
     return True
+
+
+def validate_empty_block(block):
+    data = block['data']
+
+    if len(data['text']['transactions']) == 0 and data['proof'] != EMPTY_BLOCK_NONCE:
+        return False
+
+    return True

app/constants.py

@@ -5,6 +5,7 @@
 if IS_TEST:
     print('Using constants for Test')
 
+EMPTY_BLOCK_NONCE = 42
 DATA_PATH = 'data_test/' if IS_TEST else 'data/'
 MEMPOOL_PATH = DATA_PATH + 'mempool/'
 TMP_PATH = DATA_PATH + 'tmp/'