refactor(wallet): make filter_utxos return just optional utxos

Manually selected utxos are already available. We don't need a method to
hand them out.

Author: nymius

crates/wallet/src/wallet/mod.rs

@@ -1417,8 +1417,44 @@ impl Wallet {
 
         fee_amount += fee_rate * tx.weight();
 
-        let (required_utxos, optional_utxos) =
-            self.filter_utxos(&params, current_height.to_consensus_u32());
+        let optional_utxos = self.filter_utxos(&params, current_height.to_consensus_u32());
+
+        let local_weighted_utxos = optional_utxos
+            // combine optional UTxOs with manually selected UTxOs
+            // NOTE: if manually_selected_only is true, then the previous iterator in the chain is
+            // empty and only manually selected UTxOs will be considered
+            // NOTE: manual selection overrides unspendable
+            .chain(params.utxos.clone())
+            // transform every UTxO into a WeightedUtxo
+            .map(|utxo| {
+                let keychain = utxo.keychain;
+                WeightedUtxo {
+                    satisfaction_weight: self
+                        .public_descriptor(keychain)
+                        .max_weight_to_satisfy()
+                        .unwrap(),
+                    utxo: Utxo::Local(utxo),
+                }
+            });
+
+        // include foreign UTxOs
+        let all_weighted_utxos = local_weighted_utxos.chain(params.foreign_utxos.clone());
+
+        let (required_utxos, optional_utxos) = all_weighted_utxos
+            // split UTxOs in required and optional
+            // if drain_wallet is true, all UTxOs are required, if false, only manually selected
+            // and foreign are required
+            // TODO: collection could be kept separate from selection
+            .partition::<Vec<WeightedUtxo>, _>(|x| {
+                params.drain_wallet
+                    // keep UTxO in required UTxOs if
+                    || match x.utxo {
+                        // it is in manually selected group
+                        Utxo::Local(ref lo) => params.utxos.contains(lo),
+                        // it is foreign
+                        Utxo::Foreign {..} => true,
+                    }
+            });
 
         // get drain script
         let mut drain_index = Option::<(KeychainKind, u32)>::None;
@@ -1970,11 +2006,11 @@ impl Wallet {
 
     /// Given the options returns the list of utxos that must be used to form the
     /// transaction and any further that may be used if needed.
-    fn filter_utxos(
-        &self,
-        params: &TxParams,
+    fn filter_utxos<'a>(
+        &'a self,
+        params: &'a TxParams,
         current_height: u32,
-    ) -> (Vec<WeightedUtxo>, Vec<WeightedUtxo>) {
+    ) -> impl Iterator<Item = LocalOutput> + 'a {
         self
             // get all unspent UTxOs from wallet
             .list_unspent()
@@ -2010,41 +2046,6 @@ impl Wallet {
                                     }))
                     })
             })
-            // combine optional UTxOs with manually selected UTxOs
-            // NOTE: if manually_selected_only is true, then the previous iterator in the chain is
-            // empty and only manually selected UTxOs will be considered
-            // NOTE: manual selection overrides unspendable
-            .chain(params.utxos.clone())
-            // transform every UTxO into a WeightedUtxo
-            .map(|utxo| {
-                let keychain = utxo.keychain;
-                WeightedUtxo {
-                    satisfaction_weight: self
-                        .public_descriptor(keychain)
-                        .max_weight_to_satisfy()
-                        .unwrap(),
-                    utxo: Utxo::Local(utxo),
-                }
-            })
-            // include foreign UTxOs
-            .chain(params.foreign_utxos.clone())
-            // TODO: here filter_utxos could be splitted further into two functions to allow the
-            // addition of extra filters for inputs based on properties of the WeightedUtxos
-            //
-            // split UTxOs in required and optional
-            // if drain_wallet is true, all UTxOs are required, if false, only manually selected
-            // and foreign are required
-            // TODO: collection could be kept separate from selection
-            .partition::<Vec<WeightedUtxo>, _>(|x| {
-                params.drain_wallet
-                    // keep UTxO in required UTxOs if
-                    || match x.utxo {
-                        // it is in manually selected group
-                        Utxo::Local(ref lo) => params.utxos.contains(lo),
-                        // it is foreign
-                        Utxo::Foreign {..} => true,
-                    }
-            })
     }
 
     fn complete_transaction(