bitcoin: make tip_time return an Option

In preparation of making get_block_stats() fallible.

src/bitcoin/mod.rs

@@ -51,7 +51,7 @@ pub trait BitcoinInterface: Send {
     fn chain_tip(&self) -> BlockChainTip;
 
     /// Get the timestamp set in the best block's header.
-    fn tip_time(&self) -> u32;
+    fn tip_time(&self) -> Option<u32>;
 
     /// Check whether this former tip is part of the current best chain.
     fn is_in_chain(&self, tip: &BlockChainTip) -> bool;
@@ -316,9 +316,9 @@ impl BitcoinInterface for d::BitcoinD {
         self.tip_before_timestamp(timestamp)
     }
 
-    fn tip_time(&self) -> u32 {
+    fn tip_time(&self) -> Option<u32> {
         let tip = self.chain_tip();
-        self.get_block_stats(tip.hash).time
+        Some(self.get_block_stats(tip.hash).time)
     }
 
     fn wallet_transaction(
@@ -400,7 +400,7 @@ impl BitcoinInterface for sync::Arc<sync::Mutex<dyn BitcoinInterface + 'static>>
         self.lock().unwrap().block_before_date(timestamp)
     }
 
-    fn tip_time(&self) -> u32 {
+    fn tip_time(&self) -> Option<u32> {
         self.lock().unwrap().tip_time()
     }
 

src/commands/mod.rs

@@ -694,7 +694,12 @@ impl DaemonControl {
     pub fn start_rescan(&self, timestamp: u32) -> Result<(), CommandError> {
         let mut db_conn = self.db.connection();
 
-        if timestamp < MAINNET_GENESIS_TIME || timestamp >= self.bitcoin.tip_time() {
+        let future_timestamp = self
+            .bitcoin
+            .tip_time()
+            .map(|t| timestamp >= t)
+            .unwrap_or(false);
+        if timestamp < MAINNET_GENESIS_TIME || future_timestamp {
             return Err(CommandError::InsaneRescanTimestamp(timestamp));
         }
         if db_conn.rescan_timestamp().is_some() || self.bitcoin.rescan_progress().is_some() {

src/testutils.rs

@@ -106,7 +106,7 @@ impl BitcoinInterface for DummyBitcoind {
         todo!()
     }
 
-    fn tip_time(&self) -> u32 {
+    fn tip_time(&self) -> Option<u32> {
         todo!()
     }