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//! Types related to the construction and evaluation of transaction proposals.
use std::{
collections::{BTreeMap, BTreeSet},
fmt::{self, Debug, Display},
};
use nonempty::NonEmpty;
use zcash_primitives::{
consensus::BlockHeight,
transaction::{components::amount::NonNegativeAmount, TxId},
};
use crate::{
fees::TransactionBalance,
wallet::{Note, ReceivedNote, WalletTransparentOutput},
zip321::TransactionRequest,
PoolType, ShieldedProtocol,
};
/// Errors that can occur in construction of a [`Step`].
#[derive(Debug, Clone)]
pub enum ProposalError {
/// The total output value of the transaction request is not a valid Zcash amount.
RequestTotalInvalid,
/// The total of transaction inputs overflows the valid range of Zcash values.
Overflow,
/// The input total and output total of the payment request are not equal to one another. The
/// sum of transaction outputs, change, and fees is required to be exactly equal to the value
/// of provided inputs.
BalanceError {
input_total: NonNegativeAmount,
output_total: NonNegativeAmount,
},
/// The `is_shielding` flag may only be set to `true` under the following conditions:
/// * The total of transparent inputs is nonzero
/// * There exist no Sapling inputs
/// * There provided transaction request is empty; i.e. the only output values specified
/// are change and fee amounts.
ShieldingInvalid,
/// A reference to the output of a prior step is invalid.
ReferenceError(StepOutput),
/// An attempted double-spend of a prior step output was detected.
StepDoubleSpend(StepOutput),
/// An attempted double-spend of an output belonging to the wallet was detected.
ChainDoubleSpend(PoolType, TxId, u32),
/// There was a mismatch between the payments in the proposal's transaction request
/// and the payment pool selection values.
PaymentPoolsMismatch,
}
impl Display for ProposalError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
ProposalError::RequestTotalInvalid => write!(
f,
"The total requested output value is not a valid Zcash amount."
),
ProposalError::Overflow => write!(
f,
"The total of transaction inputs overflows the valid range of Zcash values."
),
ProposalError::BalanceError {
input_total,
output_total,
} => write!(
f,
"Balance error: the output total {} was not equal to the input total {}",
u64::from(*output_total),
u64::from(*input_total)
),
ProposalError::ShieldingInvalid => write!(
f,
"The proposal violates the rules for a shielding transaction."
),
ProposalError::ReferenceError(r) => {
write!(f, "No prior step output found for reference {:?}", r)
}
ProposalError::StepDoubleSpend(r) => write!(
f,
"The proposal uses the output of step {:?} in more than one place.",
r
),
ProposalError::ChainDoubleSpend(pool, txid, index) => write!(
f,
"The proposal attempts to spend the same output twice: {}, {}, {}",
pool, txid, index
),
ProposalError::PaymentPoolsMismatch => write!(
f,
"The chosen payment pools did not match the payments of the transaction request."
),
}
}
}
impl std::error::Error for ProposalError {}
/// The Sapling inputs to a proposed transaction.
#[derive(Clone, PartialEq, Eq)]
pub struct ShieldedInputs<NoteRef> {
anchor_height: BlockHeight,
notes: NonEmpty<ReceivedNote<NoteRef, Note>>,
}
impl<NoteRef> ShieldedInputs<NoteRef> {
/// Constructs a [`ShieldedInputs`] from its constituent parts.
pub fn from_parts(
anchor_height: BlockHeight,
notes: NonEmpty<ReceivedNote<NoteRef, Note>>,
) -> Self {
Self {
anchor_height,
notes,
}
}
/// Returns the anchor height for Sapling inputs that should be used when constructing the
/// proposed transaction.
pub fn anchor_height(&self) -> BlockHeight {
self.anchor_height
}
/// Returns the list of Sapling notes to be used as inputs to the proposed transaction.
pub fn notes(&self) -> &NonEmpty<ReceivedNote<NoteRef, Note>> {
&self.notes
}
}
/// A proposal for a series of transactions to be created.
///
/// Each step of the proposal represents a separate transaction to be created. At present, only
/// transparent outputs of earlier steps may be spent in later steps; the ability to chain shielded
/// transaction steps may be added in a future update.
#[derive(Clone, PartialEq, Eq)]
pub struct Proposal<FeeRuleT, NoteRef> {
fee_rule: FeeRuleT,
min_target_height: BlockHeight,
steps: NonEmpty<Step<NoteRef>>,
}
impl<FeeRuleT, NoteRef> Proposal<FeeRuleT, NoteRef> {
/// Constructs a validated multi-step [`Proposal`].
///
/// This operation validates the proposal for agreement between outputs and inputs
/// in the case of multi-step proposals, and ensures that no double-spends are being
/// proposed.
///
/// Parameters:
/// * `fee_rule`: The fee rule observed by the proposed transaction.
/// * `min_target_height`: The minimum block height at which the transaction may be created.
/// * `steps`: A vector of steps that make up the proposal.
pub fn multi_step(
fee_rule: FeeRuleT,
min_target_height: BlockHeight,
steps: NonEmpty<Step<NoteRef>>,
) -> Result<Self, ProposalError> {
let mut consumed_chain_inputs: BTreeSet<(PoolType, TxId, u32)> = BTreeSet::new();
let mut consumed_prior_inputs: BTreeSet<StepOutput> = BTreeSet::new();
for (i, step) in steps.iter().enumerate() {
for prior_ref in step.prior_step_inputs() {
// check that there are no forward references
if prior_ref.step_index() >= i {
return Err(ProposalError::ReferenceError(*prior_ref));
}
// check that the reference is valid
let prior_step = &steps[prior_ref.step_index()];
match prior_ref.output_index() {
StepOutputIndex::Payment(idx) => {
if prior_step.transaction_request().payments().len() <= idx {
return Err(ProposalError::ReferenceError(*prior_ref));
}
}
StepOutputIndex::Change(idx) => {
if prior_step.balance().proposed_change().len() <= idx {
return Err(ProposalError::ReferenceError(*prior_ref));
}
}
}
// check that there are no double-spends
if !consumed_prior_inputs.insert(*prior_ref) {
return Err(ProposalError::StepDoubleSpend(*prior_ref));
}
}
for t_out in step.transparent_inputs() {
let key = (
PoolType::Transparent,
TxId::from_bytes(*t_out.outpoint().hash()),
t_out.outpoint().n(),
);
if !consumed_chain_inputs.insert(key) {
return Err(ProposalError::ChainDoubleSpend(key.0, key.1, key.2));
}
}
for s_out in step.shielded_inputs().iter().flat_map(|i| i.notes().iter()) {
let key = (
match &s_out.note() {
Note::Sapling(_) => PoolType::Shielded(ShieldedProtocol::Sapling),
#[cfg(feature = "orchard")]
Note::Orchard(_) => PoolType::Shielded(ShieldedProtocol::Orchard),
},
*s_out.txid(),
s_out.output_index().into(),
);
if !consumed_chain_inputs.insert(key) {
return Err(ProposalError::ChainDoubleSpend(key.0, key.1, key.2));
}
}
}
Ok(Self {
fee_rule,
min_target_height,
steps,
})
}
/// Constructs a validated [`Proposal`] having only a single step from its constituent parts.
///
/// This operation validates the proposal for balance consistency and agreement between
/// the `is_shielding` flag and the structure of the proposal.
///
/// Parameters:
/// * `transaction_request`: The ZIP 321 transaction request describing the payments to be
/// made.
/// * `payment_pools`: A map from payment index to pool type.
/// * `transparent_inputs`: The set of previous transparent outputs to be spent.
/// * `shielded_inputs`: The sets of previous shielded outputs to be spent.
/// * `balance`: The change outputs to be added the transaction and the fee to be paid.
/// * `fee_rule`: The fee rule observed by the proposed transaction.
/// * `min_target_height`: The minimum block height at which the transaction may be created.
/// * `is_shielding`: A flag that identifies whether this is a wallet-internal shielding
/// transaction.
#[allow(clippy::too_many_arguments)]
pub fn single_step(
transaction_request: TransactionRequest,
payment_pools: BTreeMap<usize, PoolType>,
transparent_inputs: Vec<WalletTransparentOutput>,
shielded_inputs: Option<ShieldedInputs<NoteRef>>,
balance: TransactionBalance,
fee_rule: FeeRuleT,
min_target_height: BlockHeight,
is_shielding: bool,
) -> Result<Self, ProposalError> {
Ok(Self {
fee_rule,
min_target_height,
steps: NonEmpty::singleton(Step::from_parts(
&[],
transaction_request,
payment_pools,
transparent_inputs,
shielded_inputs,
vec![],
balance,
is_shielding,
)?),
})
}
/// Returns the fee rule to be used by the transaction builder.
pub fn fee_rule(&self) -> &FeeRuleT {
&self.fee_rule
}
/// Returns the target height for which the proposal was prepared.
///
/// The chain must contain at least this many blocks in order for the proposal to
/// be executed.
pub fn min_target_height(&self) -> BlockHeight {
self.min_target_height
}
/// Returns the steps of the proposal. Each step corresponds to an independent transaction to
/// be generated as a result of this proposal.
pub fn steps(&self) -> &NonEmpty<Step<NoteRef>> {
&self.steps
}
}
impl<FeeRuleT: Debug, NoteRef> Debug for Proposal<FeeRuleT, NoteRef> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Proposal")
.field("fee_rule", &self.fee_rule)
.field("min_target_height", &self.min_target_height)
.field("steps", &self.steps)
.finish()
}
}
/// A reference to either a payment or change output within a step.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
pub enum StepOutputIndex {
Payment(usize),
Change(usize),
}
/// A reference to the output of a step in a proposal.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
pub struct StepOutput {
step_index: usize,
output_index: StepOutputIndex,
}
impl StepOutput {
/// Constructs a new [`StepOutput`] from its constituent parts.
pub fn new(step_index: usize, output_index: StepOutputIndex) -> Self {
Self {
step_index,
output_index,
}
}
/// Returns the step index to which this reference refers.
pub fn step_index(&self) -> usize {
self.step_index
}
/// Returns the identifier for the payment or change output within
/// the referenced step.
pub fn output_index(&self) -> StepOutputIndex {
self.output_index
}
}
/// The inputs to be consumed and outputs to be produced in a proposed transaction.
#[derive(Clone, PartialEq, Eq)]
pub struct Step<NoteRef> {
transaction_request: TransactionRequest,
payment_pools: BTreeMap<usize, PoolType>,
transparent_inputs: Vec<WalletTransparentOutput>,
shielded_inputs: Option<ShieldedInputs<NoteRef>>,
prior_step_inputs: Vec<StepOutput>,
balance: TransactionBalance,
is_shielding: bool,
}
impl<NoteRef> Step<NoteRef> {
/// Constructs a validated [`Step`] from its constituent parts.
///
/// This operation validates the proposal for balance consistency and agreement between
/// the `is_shielding` flag and the structure of the proposal.
///
/// Parameters:
/// * `transaction_request`: The ZIP 321 transaction request describing the payments
/// to be made.
/// * `payment_pools`: A map from payment index to pool type. The set of payment indices
/// provided here must exactly match the set of payment indices in the [`TransactionRequest`],
/// and the selected pool for an index must correspond to a valid receiver of the
/// address at that index (or the address itself in the case of bare transparent or Sapling
/// addresses).
/// * `transparent_inputs`: The set of previous transparent outputs to be spent.
/// * `shielded_inputs`: The sets of previous shielded outputs to be spent.
/// * `balance`: The change outputs to be added the transaction and the fee to be paid.
/// * `is_shielding`: A flag that identifies whether this is a wallet-internal shielding
/// transaction.
#[allow(clippy::too_many_arguments)]
pub fn from_parts(
prior_steps: &[Step<NoteRef>],
transaction_request: TransactionRequest,
payment_pools: BTreeMap<usize, PoolType>,
transparent_inputs: Vec<WalletTransparentOutput>,
shielded_inputs: Option<ShieldedInputs<NoteRef>>,
prior_step_inputs: Vec<StepOutput>,
balance: TransactionBalance,
is_shielding: bool,
) -> Result<Self, ProposalError> {
// Verify that the set of payment pools matches exactly a set of valid payment recipients
if transaction_request.payments().len() != payment_pools.len() {
return Err(ProposalError::PaymentPoolsMismatch);
}
for (idx, pool) in &payment_pools {
if !transaction_request
.payments()
.get(idx)
.iter()
.any(|payment| payment.recipient_address.has_receiver(*pool))
{
return Err(ProposalError::PaymentPoolsMismatch);
}
}
let transparent_input_total = transparent_inputs
.iter()
.map(|out| out.txout().value)
.fold(Ok(NonNegativeAmount::ZERO), |acc, a| {
(acc? + a).ok_or(ProposalError::Overflow)
})?;
let shielded_input_total = shielded_inputs
.iter()
.flat_map(|s_in| s_in.notes().iter())
.map(|out| out.note().value())
.fold(Some(NonNegativeAmount::ZERO), |acc, a| (acc? + a))
.ok_or(ProposalError::Overflow)?;
let prior_step_input_total = prior_step_inputs
.iter()
.map(|s_ref| {
let step = prior_steps
.get(s_ref.step_index)
.ok_or(ProposalError::ReferenceError(*s_ref))?;
Ok(match s_ref.output_index {
StepOutputIndex::Payment(i) => {
step.transaction_request
.payments()
.get(&i)
.ok_or(ProposalError::ReferenceError(*s_ref))?
.amount
}
StepOutputIndex::Change(i) => step
.balance
.proposed_change()
.get(i)
.ok_or(ProposalError::ReferenceError(*s_ref))?
.value(),
})
})
.collect::<Result<Vec<_>, _>>()?
.into_iter()
.fold(Some(NonNegativeAmount::ZERO), |acc, a| (acc? + a))
.ok_or(ProposalError::Overflow)?;
let input_total = (transparent_input_total + shielded_input_total + prior_step_input_total)
.ok_or(ProposalError::Overflow)?;
let request_total = transaction_request
.total()
.map_err(|_| ProposalError::RequestTotalInvalid)?;
let output_total = (request_total + balance.total()).ok_or(ProposalError::Overflow)?;
if is_shielding
&& (transparent_input_total == NonNegativeAmount::ZERO
|| shielded_input_total > NonNegativeAmount::ZERO
|| request_total > NonNegativeAmount::ZERO)
{
return Err(ProposalError::ShieldingInvalid);
}
if input_total == output_total {
Ok(Self {
transaction_request,
payment_pools,
transparent_inputs,
shielded_inputs,
prior_step_inputs,
balance,
is_shielding,
})
} else {
Err(ProposalError::BalanceError {
input_total,
output_total,
})
}
}
/// Returns the transaction request that describes the payments to be made.
pub fn transaction_request(&self) -> &TransactionRequest {
&self.transaction_request
}
/// Returns the map from payment index to the pool that has been selected
/// for the output that will fulfill that payment.
pub fn payment_pools(&self) -> &BTreeMap<usize, PoolType> {
&self.payment_pools
}
/// Returns the transparent inputs that have been selected to fund the transaction.
pub fn transparent_inputs(&self) -> &[WalletTransparentOutput] {
&self.transparent_inputs
}
/// Returns the shielded inputs that have been selected to fund the transaction.
pub fn shielded_inputs(&self) -> Option<&ShieldedInputs<NoteRef>> {
self.shielded_inputs.as_ref()
}
/// Returns the inputs that should be obtained from the outputs of the transaction
/// created to satisfy a previous step of the proposal.
pub fn prior_step_inputs(&self) -> &[StepOutput] {
self.prior_step_inputs.as_ref()
}
/// Returns the change outputs to be added to the transaction and the fee to be paid.
pub fn balance(&self) -> &TransactionBalance {
&self.balance
}
/// Returns a flag indicating whether or not the proposed transaction
/// is exclusively wallet-internal (if it does not involve any external
/// recipients).
pub fn is_shielding(&self) -> bool {
self.is_shielding
}
/// Returns whether or not this proposal requires interaction with the specified pool
pub fn involves(&self, pool_type: PoolType) -> bool {
match pool_type {
PoolType::Transparent => {
self.is_shielding
|| !self.transparent_inputs.is_empty()
|| self
.payment_pools()
.values()
.any(|pool| matches!(pool, PoolType::Transparent))
}
PoolType::Shielded(ShieldedProtocol::Sapling) => {
let sapling_in = self.shielded_inputs.iter().any(|s_in| {
s_in.notes()
.iter()
.any(|note| matches!(note.note(), Note::Sapling(_)))
});
let sapling_out = self
.payment_pools()
.values()
.any(|pool| matches!(pool, PoolType::Shielded(ShieldedProtocol::Sapling)));
let sapling_change = self
.balance
.proposed_change()
.iter()
.any(|c| c.output_pool() == ShieldedProtocol::Sapling);
sapling_in || sapling_out || sapling_change
}
PoolType::Shielded(ShieldedProtocol::Orchard) => {
#[cfg(not(feature = "orchard"))]
let orchard_in = false;
#[cfg(feature = "orchard")]
let orchard_in = self.shielded_inputs.iter().any(|s_in| {
s_in.notes()
.iter()
.any(|note| matches!(note.note(), Note::Orchard(_)))
});
let orchard_out = self
.payment_pools()
.values()
.any(|pool| matches!(pool, PoolType::Shielded(ShieldedProtocol::Orchard)));
let orchard_change = self
.balance
.proposed_change()
.iter()
.any(|c| c.output_pool() == ShieldedProtocol::Orchard);
orchard_in || orchard_out || orchard_change
}
}
}
}
impl<NoteRef> Debug for Step<NoteRef> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Step")
.field("transaction_request", &self.transaction_request)
.field("transparent_inputs", &self.transparent_inputs)
.field(
"shielded_inputs",
&self.shielded_inputs().map(|i| i.notes.len()),
)
.field("prior_step_inputs", &self.prior_step_inputs)
.field(
"anchor_height",
&self.shielded_inputs().map(|i| i.anchor_height),
)
.field("balance", &self.balance)
.field("is_shielding", &self.is_shielding)
.finish_non_exhaustive()
}
}