wip: add backtrack conditions

src/lib.rs

@@ -151,8 +151,8 @@ pub fn select_coins_bnb(
     _fee_rate: FeeRate,
     weighted_utxos: &mut [WeightedUtxo],
 ) -> Option<Vec<WeightedUtxo>> {
-    let _value = Amount::ZERO;
-    let selection: Vec<WeightedUtxo> = vec![];
+    let mut value = Amount::ZERO;
+    let mut selection: Vec<WeightedUtxo> = vec![];
     let available_value: Amount = weighted_utxos.iter().map(|u| u.utxo.value).sum();
 
     if available_value < target {
@@ -161,14 +161,26 @@ pub fn select_coins_bnb(
 
     weighted_utxos.sort_by(|a, b| b.utxo.value.cmp(&a.utxo.value));
 
-    for (_i, _utxo) in weighted_utxos.iter().enumerate() {
+    for (_i, utxo) in weighted_utxos.iter().enumerate() {
         // backtrack
         //
         // There are three conditions for backtracking:
         //
         // * value meets or exceeded target
         // * leaf node (nothing left to explorer)
         // * not enough value to make it to target
+        if value >= target
+            || available_value + value < target
+            || utxo == weighted_utxos.last().unwrap()
+        {
+            // backtrack
+        }
+
+        // proceed with depth first search.
+        else {
+            selection.push(utxo.clone());
+            value += utxo.utxo.value;
+        }
     }
 
     Some(selection)