Fix undesired rollback

Rocket.toml

@@ -3,4 +3,5 @@ allow_backup = true
 allow_send = true
 
 yec = { db_path = "./yec.db", lwd_url = "https://lite.ycash.xyz:9067" }
-zec = { db_path = "./zec.db", lwd_url = "https://mainnet.lightwalletd.com:9067" }
+zec = { db_path = "./zec.db", lwd_url = "https://lwdv3.zecwallet.co:443" }
+# zec = { db_path = "./zec.db", lwd_url = "https://zuul.free2z.cash:9067" }

src/chain.rs

@@ -121,6 +121,11 @@ pub async fn download_chain(
         .into_inner();
     while let Some(mut block) = block_stream.message().await? {
         if prev_hash.is_some() && block.prev_hash.as_slice() != prev_hash.unwrap() {
+            log::warn!(
+                "Reorg: {} != {}",
+                hex::encode(block.prev_hash.as_slice()),
+                hex::encode(prev_hash.unwrap())
+            );
             anyhow::bail!(ChainError::Reorg);
         }
         let mut ph = [0u8; 32];

src/scan.rs

@@ -116,6 +116,9 @@ pub async fn sync_async(
     };
     let end_height = get_latest_height(&mut client).await?;
     let end_height = (end_height - target_height_offset).max(start_height);
+    if start_height >= end_height {
+        return Ok(());
+    }
 
     let decrypter = DecryptNode::new(vks);