From 5a885adc15fb1aeed4ca16b87286719d45893a7a Mon Sep 17 00:00:00 2001
From: Aditya Kulkarni <adityapk@gmail.com>
Date: Wed, 29 Jul 2020 09:59:22 -0700
Subject: [PATCH] Grab sync lock when sending to prevent anchor changes.

Fixes #40
---
 lib/src/lightclient.rs | 14 +++++++++-----
 lib/src/lightwallet.rs | 12 ++++++++++--
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/lib/src/lightclient.rs b/lib/src/lightclient.rs
index 6d440bc..9d5419c 100644
--- a/lib/src/lightclient.rs
+++ b/lib/src/lightclient.rs
@@ -1483,11 +1483,15 @@ impl LightClient {
 
         info!("Creating transaction");
 
-        let rawtx = self.wallet.write().unwrap().send_to_address(
-            u32::from_str_radix(&self.config.consensus_branch_id, 16).unwrap(), 
-            &self.sapling_spend, &self.sapling_output,
-            addrs
-        );
+        let rawtx = {
+            let _lock = self.sync_lock.lock().unwrap();
+        
+            self.wallet.write().unwrap().send_to_address(
+                u32::from_str_radix(&self.config.consensus_branch_id, 16).unwrap(), 
+                &self.sapling_spend, &self.sapling_output,
+                addrs
+            )
+        };
         
         match rawtx {
             Ok(txbytes)   => broadcast_raw_tx(&self.get_server_uri(), txbytes),
diff --git a/lib/src/lightwallet.rs b/lib/src/lightwallet.rs
index 3a8e4b1..d5a957d 100644
--- a/lib/src/lightwallet.rs
+++ b/lib/src/lightwallet.rs
@@ -1946,7 +1946,9 @@ impl LightWallet {
         // Select notes to cover the target value
         println!("{}: Selecting notes", now() - start_time);
         let target_value = Amount::from_u64(total_value).unwrap() + DEFAULT_FEE ;
-        let notes: Vec<_> = self.txs.read().unwrap().iter()
+
+        // Select the candidate notes that are eligible to be spent
+        let mut candidate_notes: Vec<_> = self.txs.read().unwrap().iter()
             .map(|(txid, tx)| tx.notes.iter().map(move |note| (*txid, note)))
             .flatten()
             .filter_map(|(txid, note)| {
@@ -1960,7 +1962,13 @@ impl LightWallet {
                         .and_then(|zk| zk.extsk.clone());
                     SpendableNote::from(txid, note, anchor_offset, &extsk)
                 }
-            })
+            }).collect();
+
+        // Sort by highest value-notes first.
+        candidate_notes.sort_by(|a, b| b.note.value.cmp(&a.note.value));
+
+        // Select the minimum number of notes required to satisfy the target value
+        let notes: Vec<_> = candidate_notes.iter()
             .scan(0, |running_total, spendable| {
                 let value = spendable.note.value;
                 let ret = if *running_total < u64::from(target_value) {