zcash_client_backend: Add serialization & parsing for protobuf Propos…

…al representation.

zcash_primitives
================

Added
-----
- `impl {Clone, PartialEq, Eq} for zcash_primitives::memo::Error`
- `impl {PartialEq, Eq} for zcash_primitives::sapling::note::Rseed`
- `impl From<TxId> for [u8; 32]`

zcash_client_backend
====================

Added
-----
- `zcash_client_backend::data_api::SaplingInputSource::get_spendable_sapling_note`
- `zcash_client_backend::data_api::TransparentInputSource::get_unspent_transparent_output`
- `zcash_client_backend::data_api::input_selection::Proposal::from_parts`
- `zcash_client_backend::data_api::input_selection::SaplingInputs::from_parts`
- `zcash_client_backend::zip321::TransactionRequest::total`
- `zcash_client_backend::proto::`
  - `PROPOSAL_SER_V1`
  - `ProposalError`
  - `proposal::Proposal::{from_standard_proposal, try_into_standard_proposal}`
  - `proposal::ProposedInput::parse_txid`
- `impl Clone for zcash_client_backend::{
     zip321::{Payment, TransactionRequest, Zip321Error, parse::Param, parse::IndexedParam},
     wallet::{ReceivedSaplingNote, WalletTransparentOutput},
     wallet::input_selection::{Proposal, SaplingInputs},
   }`
- `impl {PartialEq, Eq} for zcash_client_backend::{
     zip321::{Zip321Error, parse::Param, parse::IndexedParam},
     wallet::{ReceivedSaplingNote, WalletTransparentOutput},
     wallet::input_selection::{Proposal, SaplingInputs},
   }`

zcash_client_backend/CHANGELOG.md

@@ -26,11 +26,11 @@ and this library adheres to Rust's notion of
       backend-specific note identifier. The related `NoteRef` type parameter has
       been removed from `error::Error`.
     - A new variant `UnsupportedPoolType` has been added.
-  - `wallet::shield_transparent_funds` no longer
-    takes a `memo` argument; instead, memos to be associated with the shielded
-    outputs should be specified in the construction of the value of the
-    `input_selector` argument, which is used to construct the proposed shielded
-    values as internal "change" outputs.
+  - `wallet::shield_transparent_funds` no longer takes a `memo` argument;
+    instead, memos to be associated with the shielded outputs should be
+    specified in the construction of the value of the `input_selector`
+    argument, which is used to construct the proposed shielded values as
+    internal "change" outputs.
   - `wallet::create_proposed_transaction` no longer takes a
     `change_memo` argument; instead, change memos are represented in the
     individual values of the `proposed_change` field of the `Proposal`'s

zcash_client_backend/src/data_api.rs

@@ -220,6 +220,14 @@ pub trait SaplingInputSource {
     /// or a UUID.
     type NoteRef: Copy + Debug + Eq + Ord;
 
+    /// Returns a received Sapling note, or Ok(None) if the note is not known to belong to the
+    /// wallet or if the note is not spendable.
+    fn get_spendable_sapling_note(
+        &self,
+        txid: &TxId,
+        index: u32,
+    ) -> Result<Option<ReceivedSaplingNote<Self::NoteRef>>, Self::Error>;
+
     /// Returns a list of spendable Sapling notes sufficient to cover the specified target value,
     /// if possible.
     fn select_spendable_sapling_notes(
@@ -236,6 +244,13 @@ pub trait TransparentInputSource {
     /// The type of errors produced by a wallet backend.
     type Error;
 
+    /// Returns a received transparent UTXO, or Ok(None) if the UTXO is not known to belong to the
+    /// wallet or is not spendable.
+    fn get_unspent_transparent_output(
+        &self,
+        outpoint: &OutPoint,
+    ) -> Result<Option<WalletTransparentOutput>, Self::Error>;
+
     /// Returns a list of unspent transparent UTXOs that appear in the chain at heights up to and
     /// including `max_height`.
     fn get_unspent_transparent_outputs(
@@ -974,6 +989,14 @@ pub mod testing {
         type Error = ();
         type NoteRef = u32;
 
+        fn get_spendable_sapling_note(
+            &self,
+            _txid: &TxId,
+            _index: u32,
+        ) -> Result<Option<ReceivedSaplingNote<Self::NoteRef>>, Self::Error> {
+            Ok(None)
+        }
+
         fn select_spendable_sapling_notes(
             &self,
             _account: AccountId,
@@ -989,6 +1012,13 @@ pub mod testing {
     impl TransparentInputSource for MockWalletDb {
         type Error = ();
 
+        fn get_unspent_transparent_output(
+            &self,
+            _outpoint: &OutPoint,
+        ) -> Result<Option<WalletTransparentOutput>, Self::Error> {
+            Ok(None)
+        }
+
         fn get_unspent_transparent_outputs(
             &self,
             _address: &TransparentAddress,

zcash_client_backend/src/data_api/wallet/input_selection.rs

@@ -79,6 +79,7 @@ impl<DE: fmt::Display, SE: fmt::Display> fmt::Display for InputSelectorError<DE,
 }
 
 /// The inputs to be consumed and outputs to be produced in a proposed transaction.
+#[derive(Clone, PartialEq, Eq)]
 pub struct Proposal<FeeRuleT, NoteRef> {
     transaction_request: TransactionRequest,
     transparent_inputs: Vec<WalletTransparentOutput>,
@@ -90,6 +91,45 @@ pub struct Proposal<FeeRuleT, NoteRef> {
 }
 
 impl<FeeRuleT, NoteRef> Proposal<FeeRuleT, NoteRef> {
+    /// Constructs a [`Proposal`] from its constituent parts.
+    #[allow(clippy::too_many_arguments)]
+    pub(crate) fn from_parts(
+        transaction_request: TransactionRequest,
+        transparent_inputs: Vec<WalletTransparentOutput>,
+        sapling_inputs: Option<SaplingInputs<NoteRef>>,
+        balance: TransactionBalance,
+        fee_rule: FeeRuleT,
+        min_target_height: BlockHeight,
+        is_shielding: bool,
+    ) -> Result<Self, ()> {
+        let transparent_total = transparent_inputs
+            .iter()
+            .map(|out| out.txout().value)
+            .fold(Ok(NonNegativeAmount::ZERO), |acc, a| (acc? + a).ok_or(()))?;
+        let sapling_total = sapling_inputs
+            .iter()
+            .flat_map(|s_in| s_in.notes().iter())
+            .map(|out| out.value())
+            .fold(Ok(NonNegativeAmount::ZERO), |acc, a| (acc? + a).ok_or(()))?;
+        let input_total = (transparent_total + sapling_total).ok_or(())?;
+
+        let output_total = (transaction_request.total()? + balance.total()).ok_or(())?;
+
+        if input_total == output_total {
+            Ok(Self {
+                transaction_request,
+                transparent_inputs,
+                sapling_inputs,
+                balance,
+                fee_rule,
+                min_target_height,
+                is_shielding,
+            })
+        } else {
+            Err(())
+        }
+    }
+
     /// Returns the transaction request that describes the payments to be made.
     pub fn transaction_request(&self) -> &TransactionRequest {
         &self.transaction_request
@@ -147,12 +187,23 @@ impl<FeeRuleT, NoteRef> Debug for Proposal<FeeRuleT, NoteRef> {
 }
 
 /// The Sapling component of a proposed transaction.
+#[derive(Clone, PartialEq, Eq)]
 pub struct SaplingInputs<NoteRef> {
     anchor_height: BlockHeight,
     notes: NonEmpty<ReceivedSaplingNote<NoteRef>>,
 }
 
 impl<NoteRef> SaplingInputs<NoteRef> {
+    pub fn from_parts(
+        anchor_height: BlockHeight,
+        notes: NonEmpty<ReceivedSaplingNote<NoteRef>>,
+    ) -> Self {
+        Self {
+            anchor_height,
+            notes,
+        }
+    }
+
     pub fn anchor_height(&self) -> BlockHeight {
         self.anchor_height
     }

zcash_client_backend/src/fees.rs

@@ -54,6 +54,9 @@ impl ChangeValue {
 pub struct TransactionBalance {
     proposed_change: Vec<ChangeValue>,
     fee_required: NonNegativeAmount,
+
+    // A cache for the sum of proposed change and fee; we compute it on construction anyway, so we
+    // cache the resulting value.
     total: NonNegativeAmount,
 }