zcash_client_backend: Allow change strategies to act based on wallet …

…balance.

zcash_client_backend/src/data_api.rs

@@ -804,20 +804,28 @@ impl<NoteRef> SpendableNotes<NoteRef> {
 /// the wallet.
 pub struct WalletMeta {
     sapling_note_count: usize,
+    sapling_total_value: NonNegativeAmount,
     #[cfg(feature = "orchard")]
     orchard_note_count: usize,
+    #[cfg(feature = "orchard")]
+    orchard_total_value: NonNegativeAmount,
 }
 
 impl WalletMeta {
     /// Constructs a new [`WalletMeta`] value from its constituent parts.
     pub fn new(
         sapling_note_count: usize,
+        sapling_total_value: NonNegativeAmount,
         #[cfg(feature = "orchard")] orchard_note_count: usize,
+        #[cfg(feature = "orchard")] orchard_total_value: NonNegativeAmount,
     ) -> Self {
         Self {
             sapling_note_count,
+            sapling_total_value,
             #[cfg(feature = "orchard")]
             orchard_note_count,
+            #[cfg(feature = "orchard")]
+            orchard_total_value,
         }
     }
 
@@ -838,13 +846,24 @@ impl WalletMeta {
         self.sapling_note_count
     }
 
+    /// Returns the total value of Sapling notes represented by [`Self::sapling_note_count`].
+    pub fn sapling_total_value(&self) -> NonNegativeAmount {
+        self.sapling_total_value
+    }
+
     /// Returns the number of unspent Orchard notes belonging to the account for which this was
     /// generated.
     #[cfg(feature = "orchard")]
     pub fn orchard_note_count(&self) -> usize {
         self.orchard_note_count
     }
 
+    /// Returns the total value of Orchard notes represented by [`Self::orchard_note_count`].
+    #[cfg(feature = "orchard")]
+    pub fn orchard_total_value(&self) -> NonNegativeAmount {
+        self.orchard_total_value
+    }
+
     /// Returns the total number of unspent shielded notes belonging to the account for which this
     /// was generated.
     pub fn total_note_count(&self) -> usize {
@@ -855,6 +874,16 @@ impl WalletMeta {
 
         self.sapling_note_count + orchard_note_count
     }
+
+    /// Returns the total value of shielded notes represented by [`Self::total_note_count`]
+    pub fn total_value(&self) -> NonNegativeAmount {
+        #[cfg(feature = "orchard")]
+        let orchard_value = self.orchard_total_value;
+        #[cfg(not(feature = "orchard"))]
+        let orchard_value = NonNegativeAmount::ZERO;
+
+        (self.sapling_total_value + orchard_value).expect("Does not overflow Zcash maximum value.")
+    }
 }
 
 /// A trait representing the capability to query a data store for unspent transaction outputs

zcash_client_backend/src/fees/zip317.rs

@@ -303,7 +303,7 @@ mod tests {
 
         {
             // spend a single Sapling note and produce 5 outputs
-            let balance = |existing_notes| {
+            let balance = |existing_notes, total| {
                 change_strategy.compute_balance(
                     &Network::TestNetwork,
                     Network::TestNetwork
@@ -326,14 +326,17 @@ mod tests {
                     None,
                     Some(&WalletMeta::new(
                         existing_notes,
+                        total,
                         #[cfg(feature = "orchard")]
                         0,
+                        #[cfg(feature = "orchard")]
+                        NonNegativeAmount::ZERO,
                     )),
                 )
             };
 
             assert_matches!(
-                balance(0),
+                balance(0, NonNegativeAmount::ZERO),
                 Ok(balance) if
                     balance.proposed_change() == [
                         ChangeValue::sapling(NonNegativeAmount::const_from_u64(129_4000), None),
@@ -346,7 +349,7 @@ mod tests {
             );
 
             assert_matches!(
-                balance(2),
+                balance(2, NonNegativeAmount::const_from_u64(100_0000)),
                 Ok(balance) if
                     balance.proposed_change() == [
                         ChangeValue::sapling(NonNegativeAmount::const_from_u64(216_0000), None),
@@ -382,8 +385,11 @@ mod tests {
                 None,
                 Some(&WalletMeta::new(
                     0,
+                    NonNegativeAmount::ZERO,
                     #[cfg(feature = "orchard")]
                     0,
+                    #[cfg(feature = "orchard")]
+                    NonNegativeAmount::ZERO,
                 )),
             );
 

zcash_client_sqlite/src/lib.rs

@@ -128,7 +128,7 @@ pub mod error;
 pub mod wallet;
 use wallet::{
     commitment_tree::{self, put_shard_roots},
-    common::count_outputs,
+    common::spendable_notes_meta,
     SubtreeProgressEstimator,
 };
 
@@ -354,7 +354,7 @@ impl<C: Borrow<rusqlite::Connection>, P: consensus::Parameters> InputSource for
         min_value: NonNegativeAmount,
         exclude: &[Self::NoteRef],
     ) -> Result<WalletMeta, Self::Error> {
-        let sapling_note_count = count_outputs(
+        let sapling_pool_meta = spendable_notes_meta(
             self.conn.borrow(),
             account_id,
             min_value,
@@ -363,7 +363,7 @@ impl<C: Borrow<rusqlite::Connection>, P: consensus::Parameters> InputSource for
         )?;
 
         #[cfg(feature = "orchard")]
-        let orchard_note_count = count_outputs(
+        let orchard_pool_meta = spendable_notes_meta(
             self.conn.borrow(),
             account_id,
             min_value,
@@ -372,9 +372,12 @@ impl<C: Borrow<rusqlite::Connection>, P: consensus::Parameters> InputSource for
         )?;
 
         Ok(WalletMeta::new(
-            sapling_note_count,
+            sapling_pool_meta.note_count,
+            sapling_pool_meta.total_value,
             #[cfg(feature = "orchard")]
-            orchard_note_count,
+            orchard_pool_meta.note_count,
+            #[cfg(feature = "orchard")]
+            orchard_pool_meta.total_value,
         ))
     }
 }

zcash_client_sqlite/src/wallet/common.rs

@@ -226,13 +226,18 @@ where
         .collect::<Result<_, _>>()
 }
 
-pub(crate) fn count_outputs(
+pub(crate) struct PoolMeta {
+    pub(crate) note_count: usize,
+    pub(crate) total_value: NonNegativeAmount,
+}
+
+pub(crate) fn spendable_notes_meta(
     conn: &rusqlite::Connection,
     account: AccountId,
     min_value: NonNegativeAmount,
     exclude: &[ReceivedNoteId],
     protocol: ShieldedProtocol,
-) -> Result<usize, rusqlite::Error> {
+) -> Result<PoolMeta, SqliteClientError> {
     let (table_prefix, _, _) = per_protocol_names(protocol);
 
     let excluded: Vec<Value> = exclude
@@ -247,9 +252,9 @@ pub(crate) fn count_outputs(
         .collect();
     let excluded_ptr = Rc::new(excluded);
 
-    conn.query_row(
+    let (note_count, total_value) = conn.query_row(
         &format!(
-            "SELECT COUNT(*)
+            "SELECT COUNT(*), SUM(value)
              FROM {table_prefix}_received_notes
              INNER JOIN accounts
                ON accounts.id = {table_prefix}_received_notes.account_id
@@ -274,6 +279,13 @@ pub(crate) fn count_outputs(
             ":min_value": u64::from(min_value),
             ":exclude": &excluded_ptr
         ],
-        |row| row.get(0),
-    )
+        |row| Ok((row.get::<_, usize>(0)?, row.get::<_, Option<i64>>(1)?)),
+    )?;
+
+    Ok(PoolMeta {
+        note_count,
+        total_value: total_value.map_or(Ok(NonNegativeAmount::ZERO), |v| {
+            NonNegativeAmount::from_nonnegative_i64(v).map_err(SqliteClientError::BalanceError)
+        })?,
+    })
 }