persist blockchain across sessions via save/load

.gitignore

@@ -12,6 +12,7 @@
 *.cb2
 .*.lb
 
+
 ## Intermediate documents:
 *.dvi
 *.xdv
@@ -332,3 +333,4 @@ __pycache__/
 *.so
 *bore.zip
 *bore_bin
+node_data/

main.py

@@ -19,18 +19,22 @@
 import argparse
 import asyncio
 import logging
+import os
+import re
 import sys
 
 from nacl.signing import SigningKey
 from nacl.encoding import HexEncoder
 
 from minichain import Transaction, Blockchain, Block, State, Mempool, P2PNetwork, mine_block
+from minichain.persistence import save, load
 from minichain.validators import is_valid_receiver
 
 
 logger = logging.getLogger(__name__)
 
 BURN_ADDRESS = "0" * 40
+DATA_DIR = "node_data"
 
 
 # ──────────────────────────────────────────────
@@ -82,12 +86,14 @@ def mine_and_process_block(chain, mempool, miner_pk):
     mined_block = mine_block(block)
 
     if chain.add_block(mined_block):
-        logger.info("✅ Block #%d mined and added (%d txs)", mined_block.index, len(mineable_txs))
+     if chain.add_block(mined_block):
+         logger.info("✅ Block #%d mined and added (%d txs)", mined_block.index, len(mineable_txs))
+         mempool.remove_transactions(mineable_txs)
         mempool.remove_transactions(mineable_txs)
         chain.state.credit_mining_reward(miner_pk)
         return mined_block
     else:
-        logger.error("❌ Block rejected by chain")
+        logger.error("Block rejected by chain")
         return None
 
 
@@ -108,13 +114,13 @@ async def handler(data):
             for addr, acc in remote_accounts.items():
                 if addr not in chain.state.accounts:
                     chain.state.accounts[addr] = acc
-                    logger.info("🔄 Synced account %s... (balance=%d)", addr[:12], acc.get("balance", 0))
-            logger.info("🔄 State sync complete — %d accounts", len(chain.state.accounts))
+                    logger.info("Synced account %s... (balance=%d)", addr[:12], acc.get("balance", 0))
+            logger.info("State sync complete — %d accounts", len(chain.state.accounts))
 
         elif msg_type == "tx":
             tx = Transaction(**payload)
             if mempool.add_transaction(tx):
-                logger.info("📥 Received tx from %s... (amount=%s)", tx.sender[:8], tx.amount)
+                logger.info("Received tx from %s... (amount=%s)", tx.sender[:8], tx.amount)
 
         elif msg_type == "block":
             txs_raw = payload.get("transactions", [])
@@ -132,7 +138,7 @@ async def handler(data):
             block.hash = block_hash
 
             if chain.add_block(block):
-                logger.info("📥 Received Block #%d — added to chain", block.index)
+                logger.info("Received Block #%d — added to chain", block.index)
 
                 # Apply mining reward for the remote miner (burn address as placeholder)
                 miner = payload.get("miner", BURN_ADDRESS)
@@ -141,7 +147,7 @@ async def handler(data):
                 # Drop only confirmed transactions so higher nonces can remain queued.
                 mempool.remove_transactions(block.transactions)
             else:
-                logger.warning("📥 Received Block #%s — rejected", block.index)
+                logger.warning("Received Block #%s — rejected", block.index)
 
     return handler
 
@@ -217,9 +223,9 @@ async def cli_loop(sk, pk, chain, mempool, network):
 
             if mempool.add_transaction(tx):
                 await network.broadcast_transaction(tx)
-                print(f"  ✅ Tx sent: {amount} coins → {receiver[:12]}...")
+                print(f"  Tx sent: {amount} coins -> {receiver[:12]}...")
             else:
-                print("  ❌ Transaction rejected (invalid sig, duplicate, or mempool full).")
+                print("  Transaction rejected (invalid sig, duplicate, or mempool full).")
 
         # ── mine ──
         elif cmd == "mine":
@@ -275,7 +281,19 @@ async def run_node(port: int, connect_to: str | None, fund: int):
     """Boot the node, optionally connect to a peer, then enter the CLI."""
     sk, pk = create_wallet()
 
-    chain = Blockchain()
+    # ── Load existing chain or start fresh ──────────────────────────────────
+    chain_file = os.path.join(DATA_DIR, "blockchain.json")
+    if os.path.exists(chain_file):
+        try:
+            chain = load(path=DATA_DIR)
+            logger.info("Loaded existing chain (%d blocks) from '%s'", len(chain.chain), DATA_DIR)
+        except Exception as e:
+            logger.warning("Could not load chain: %s — starting fresh.", e)
+            chain = Blockchain()
+    else:
+        chain = Blockchain()
+        logger.info("No saved chain found — starting fresh.")
+
     mempool = Mempool()
     network = P2PNetwork()
 
@@ -291,7 +309,7 @@ async def on_peer_connected(writer):
         }) + "\n"
         writer.write(sync_msg.encode())
         await writer.drain()
-        logger.info("🔄 Sent state sync to new peer")
+        logger.info("Sent state sync to new peer")
 
     network._on_peer_connected = on_peer_connected
 
@@ -300,7 +318,7 @@ async def on_peer_connected(writer):
     # Fund this node's wallet so it can transact in the demo
     if fund > 0:
         chain.state.credit_mining_reward(pk, reward=fund)
-        logger.info("💰 Funded %s... with %d coins", pk[:12], fund)
+        logger.info("Funded %s... with %d coins", pk[:12], fund)
 
     # Connect to a seed peer if requested
     if connect_to:
@@ -313,6 +331,12 @@ async def on_peer_connected(writer):
     try:
         await cli_loop(sk, pk, chain, mempool, network)
     finally:
+        try:
+            os.makedirs(DATA_DIR, exist_ok=True)
+            save(chain, path=DATA_DIR)
+            logger.info("Chain saved to '%s' (%d blocks)", DATA_DIR, len(chain.chain))
+        except Exception as e:
+            logger.error("Failed to save chain: %s", e)
         await network.stop()
 
 

minichain/__init__.py

@@ -6,6 +6,7 @@
 from .contract import ContractMachine
 from .p2p import P2PNetwork
 from .mempool import Mempool
+from .persistence import save, load
 
 __all__ = [
     "mine_block",
@@ -18,4 +19,6 @@
     "ContractMachine",
     "P2PNetwork",
     "Mempool",
+    "save",
+    "load",
 ]

minichain/persistence.py

@@ -0,0 +1,145 @@
+"""
+Chain persistence: save and load the blockchain and state to/from JSON.
+
+Design:
+  - blockchain.json  holds the full list of serialized blocks
+  - state.json       holds the accounts dict
+
+Usage:
+    from minichain.persistence import save, load
+
+    save(blockchain, path="data/")
+    blockchain = load(path="data/")
+"""
+
+import json
+import os
+import logging
+from .block import Block
+from .transaction import Transaction
+from .chain import Blockchain
+
+logger = logging.getLogger(__name__)
+
+_CHAIN_FILE = "blockchain.json"
+_STATE_FILE = "state.json"
+
+
+# Public API
+
+def save(blockchain: Blockchain, path: str = ".") -> None:
+    """
+    Persist the blockchain and account state to two JSON files inside `path`.
+
+    Args:
+        blockchain: The live Blockchain instance to save.
+        path:       Directory to write blockchain.json and state.json into.
+    """
+    os.makedirs(path, exist_ok=True)
+
+    _write_json(
+        os.path.join(path, _CHAIN_FILE),
+        [block.to_dict() for block in blockchain.chain],
+    )
+
+    _write_json(
+        os.path.join(path, _STATE_FILE),
+        blockchain.state.accounts,
+    )
+
+    logger.info(
+        "Saved %d blocks and %d accounts to '%s'",
+        len(blockchain.chain),
+        len(blockchain.state.accounts),
+        path,
+    )
+
+
+def load(path: str = ".") -> Blockchain:
+    """
+    Restore a Blockchain from JSON files inside `path`.
+
+    Returns a fully initialised Blockchain whose chain and state match
+    what was previously saved with save().
+
+    Raises:
+        FileNotFoundError: if blockchain.json or state.json are missing.
+        ValueError:        if the data is structurally invalid.
+    """
+    chain_path = os.path.join(path, _CHAIN_FILE)
+    state_path = os.path.join(path, _STATE_FILE)
+
+    raw_blocks = _read_json(chain_path)
+    raw_accounts = _read_json(state_path)
+
+    if not isinstance(raw_blocks, list) or not raw_blocks:
+        raise ValueError(f"Invalid or empty chain data in '{chain_path}'")
+
+    # FIX: validate raw_accounts is a dict before use
+    if not isinstance(raw_accounts, dict):
+        raise ValueError(f"Invalid accounts data in '{state_path}'")
+
+    blockchain = Blockchain.__new__(Blockchain)   # skip __init__ (no genesis)
+    import threading
+    from .state import State
+    from .contract import ContractMachine
+
+    blockchain._lock = threading.RLock()
+    blockchain.chain = [_deserialize_block(b) for b in raw_blocks]
+
+    blockchain.state = State.__new__(State)
+    blockchain.state.accounts = raw_accounts
+    blockchain.state.contract_machine = ContractMachine(blockchain.state)
+
+    logger.info(
+        "Loaded %d blocks and %d accounts from '%s'",
+        len(blockchain.chain),
+        len(blockchain.state.accounts),
+        path,
+    )
+    return blockchain
+
+
+# Helpers
+
+def _write_json(filepath: str, data) -> None:
+    with open(filepath, "w", encoding="utf-8") as f:
+        json.dump(data, f, indent=2)
+
+
+def _read_json(filepath: str):
+    if not os.path.exists(filepath):
+        raise FileNotFoundError(f"Persistence file not found: '{filepath}'")
+    with open(filepath, "r", encoding="utf-8") as f:
+        return json.load(f)
+
+
+def _deserialize_block(data: dict) -> Block:
+    """Reconstruct a Block (including its transactions) from a plain dict."""
+    transactions = [
+        Transaction(
+            sender=tx["sender"],
+            receiver=tx["receiver"],
+            amount=tx["amount"],
+            nonce=tx["nonce"],
+            data=tx.get("data"),
+            signature=tx.get("signature"),
+            timestamp=tx["timestamp"],
+        )
+        for tx in data.get("transactions", [])
+    ]
+
+    block = Block(
+        index=data["index"],
+        previous_hash=data["previous_hash"],
+        transactions=transactions,
+        timestamp=data["timestamp"],
+        difficulty=data.get("difficulty"),
+    )
+    block.nonce = data["nonce"]
+    block.hash = data["hash"]
+    # Preserve the stored merkle root rather than recomputing to guard against
+    # any future change in the hash algorithm.
+    block.merkle_root = data.get("merkle_root")
+    return block
+