feat: add chain sync protocol for block history synchronization

main.py

@@ -156,6 +156,50 @@ async def handler(data):
             else:
                 logger.warning("📥 Received Block #%s — rejected", block.index)
 
+        elif msg_type == "status":
+            import json as _json
+            peer_height = payload["height"]
+            my_height = chain.height
+
+            if peer_height > my_height:
+                writer = data.get("_writer")
+                if writer:
+                    request = _json.dumps({
+                        "type": "get_blocks",
+                        "data": {
+                            "from_height": my_height + 1,
+                            "to_height": peer_height
+                        }
+                    }) + "\n"
+                    writer.write(request.encode())
+                    await writer.drain()
+                    logger.info("📡 Requesting blocks %d~%d from %s",
+                               my_height + 1, peer_height, peer_addr)
+        elif msg_type == "get_blocks":
+            import json as _json
+            from_h = payload["from_height"]
+            to_h = payload["to_height"]
+            blocks = chain.get_blocks_range(from_h, to_h)
+
+            writer = data.get("_writer")
+            if writer and blocks:
+                response = _json.dumps({
+                    "type": "blocks",
+                    "data": {"blocks": blocks}
+                }) + "\n"
+                writer.write(response.encode())
+                await writer.drain()
+                logger.info("📤 Sent %d blocks to %s", len(blocks), peer_addr)
+
+        elif msg_type == "blocks":
+            received = payload["blocks"]
+            success, count = chain.add_blocks_bulk(received)
+
+            if success:
+                logger.info("✅ Chain synced: added %d blocks", count)
+            else:
+                logger.warning("❌ Chain sync failed after %d blocks", count)
+
     return handler
 
 
@@ -324,7 +368,14 @@ async def on_peer_connected(writer):
         }) + "\n"
         writer.write(sync_msg.encode())
         await writer.drain()
-        logger.info("🔄 Sent state sync to new peer")
+
+        status_msg = _json.dumps({
+            "type": "status",
+            "data": {"height": chain.height}
+        }) + "\n"
+        writer.write(status_msg.encode())
+        await writer.drain()
+        logger.info("🔄 Sent state sync and status to new peer")
 
     network.register_on_peer_connected(on_peer_connected)
 

minichain/chain.py

@@ -54,6 +54,12 @@ def last_block(self):
         with self._lock: # Acquire lock for thread-safe access
             return self.chain[-1]
 
+    @property
+    def height(self) -> int:
+        """Returns the current chain height (genesis = 0)"""
+        with self._lock:
+            return len(self.chain) - 1
+
     def add_block(self, block):
         """
         Validates and adds a block to the chain if all transactions succeed.
@@ -82,3 +88,26 @@ def add_block(self, block):
             self.state = temp_state
             self.chain.append(block)
             return True
+
+    def get_blocks_range(self, from_height: int, to_height: int) -> list:
+        """Return serialized blocks from from_height to to_height inclusive."""
+        with self._lock:
+            to_height = min(to_height, len(self.chain) - 1)
+            if from_height > to_height or from_height < 0:
+                return []
+            return [b.to_dict() for b in self.chain[from_height:to_height + 1]]
+
+    def add_blocks_bulk(self, block_dicts: list) -> tuple:
+        """Add blocks validating chain linkage only. State relies on sync message."""
+        added = 0
+        for block_dict in block_dicts:
+            block = Block.from_dict(block_dict)
+            with self._lock:
+                try:
+                    validate_block_link_and_hash(self.last_block, block)
+                except ValueError as exc:
+                    logger.warning("Block %s rejected: %s", block.index, exc)
+                    return False, added
+                self.chain.append(block)
+                added += 1
+        return True, added

minichain/p2p.py

@@ -15,7 +15,7 @@
 logger = logging.getLogger(__name__)
 
 TOPIC = "minichain-global"
-SUPPORTED_MESSAGE_TYPES = {"sync", "tx", "block"}
+SUPPORTED_MESSAGE_TYPES = {"sync", "tx", "block", "status", "get_blocks", "blocks"}
 
 
 class P2PNetwork:
@@ -207,6 +207,37 @@ def _validate_block_payload(self, payload):
             for tx_payload in payload["transactions"]
         )
 
+    def _validate_status_payload(self, payload):
+        if not isinstance(payload, dict):
+            return False
+        if set(payload) != {"height"}:
+            return False
+        if not isinstance(payload["height"], int) or payload["height"] < 0:
+            return False
+        return True
+
+    def _validate_get_blocks_payload(self, payload):
+        if not isinstance(payload, dict):
+            return False
+        if set(payload) != {"from_height", "to_height"}:
+            return False
+        fh, th = payload.get("from_height"), payload.get("to_height")
+        if not isinstance(fh, int) or not isinstance(th, int):
+            return False
+        if fh < 0 or fh > th:
+            return False
+        return True
+
+    def _validate_blocks_payload(self, payload):
+        if not isinstance(payload, dict):
+            return False
+        if set(payload) != {"blocks"}:
+            return False
+        blocks = payload.get("blocks")
+        if not isinstance(blocks, list):
+            return False
+        return all(isinstance(b, dict) for b in blocks)
+
     def _validate_message(self, message):
         if not isinstance(message, dict):
             return False
@@ -226,6 +257,9 @@ def _validate_message(self, message):
             "sync": self._validate_sync_payload,
             "tx": self._validate_transaction_payload,
             "block": self._validate_block_payload,
+            "status": self._validate_status_payload,
+            "get_blocks": self._validate_get_blocks_payload,
+            "blocks": self._validate_blocks_payload,
         }
         return validators[msg_type](payload)
 
@@ -283,6 +317,7 @@ async def _listen_to_peer(
                     continue
                 self._mark_seen(msg_type, payload)
                 data["_peer_addr"] = addr
+                data["_writer"] = writer
 
                 if self._handler_callback:
                     try: