add future transactions to address synchronizer

electrum/address_synchronizer.py

@@ -43,6 +43,7 @@ if TYPE_CHECKING:
     from .json_db import JsonDB
 
 
+TX_HEIGHT_FUTURE = -3
 TX_HEIGHT_LOCAL = -2
 TX_HEIGHT_UNCONF_PARENT = -1
 TX_HEIGHT_UNCONFIRMED = 0
@@ -71,6 +72,7 @@ class AddressSynchronizer(Logger):
         # locks: if you need to take multiple ones, acquire them in the order they are defined here!
         self.lock = threading.RLock()
         self.transaction_lock = threading.RLock()
+        self.future_tx = {} # txid -> blocks remaining
         # Transactions pending verification.  txid -> tx_height. Access with self.lock.
         self.unverified_tx = defaultdict(int)
         # true when synchronized
@@ -556,6 +558,11 @@ class AddressSynchronizer(Logger):
             return cached_local_height
         return self.network.get_local_height() if self.network else self.db.get('stored_height', 0)
 
+    def add_future_tx(self, tx, num_blocks):
+        with self.lock:
+            self.add_transaction(tx.txid(), tx)
+            self.future_tx[tx.txid()] = num_blocks
+
     def get_tx_height(self, tx_hash: str) -> TxMinedInfo:
         with self.lock:
             verified_tx_mined_info = self.db.get_verified_tx(tx_hash)
@@ -565,6 +572,9 @@ class AddressSynchronizer(Logger):
             elif tx_hash in self.unverified_tx:
                 height = self.unverified_tx[tx_hash]
                 return TxMinedInfo(height=height, conf=0)
+            elif tx_hash in self.future_tx:
+                conf = self.future_tx[tx_hash]
+                return TxMinedInfo(height=TX_HEIGHT_FUTURE, conf=conf)
             else:
                 # local transaction
                 return TxMinedInfo(height=TX_HEIGHT_LOCAL, conf=0)