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// Copyright (C) Parity Technologies (UK) Ltd.
// This file is part of Polkadot.
// Polkadot is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Polkadot is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Polkadot. If not, see <http://www.gnu.org/licenses/>.
//! `PayOverXcm` struct for paying through XCM and getting the status back.
use alloc::vec;
use core::marker::PhantomData;
use frame_support::traits::{
tokens::{Pay, PaymentStatus},
Get,
};
use sp_runtime::traits::TryConvert;
use xcm::{opaque::lts::Weight, prelude::*};
use xcm_executor::traits::{QueryHandler, QueryResponseStatus};
/// Implementation of the `frame_support::traits::tokens::Pay` trait, to allow
/// for XCM-based payments of a given `Balance` of some asset ID existing on some chain under
/// ownership of some `Interior` location of the local chain to a particular `Beneficiary`. The
/// `AssetKind` value is not itself bounded (to avoid the issue of needing to wrap some preexisting
/// datatype), however a converter type `AssetKindToLocatableAsset` must be provided in order to
/// translate it into a `LocatableAsset`, which comprises both an XCM `Location` describing
/// the XCM endpoint on which the asset to be paid resides and an XCM `AssetId` to identify the
/// specific asset at that endpoint.
///
/// This relies on the XCM `TransferAsset` instruction. A trait `BeneficiaryRefToLocation` must be
/// provided in order to convert the `Beneficiary` reference into a location usable by
/// `TransferAsset`.
///
/// `PayOverXcm::pay` is asynchronous, and returns a `QueryId` which can then be used in
/// `check_payment` to check the status of the XCM transaction.
///
/// See also `PayAccountId32OverXcm` which is similar to this except that `BeneficiaryRefToLocation`
/// need not be supplied and `Beneficiary` must implement `Into<[u8; 32]>`.
pub struct PayOverXcm<
Interior,
Router,
Querier,
Timeout,
Beneficiary,
AssetKind,
AssetKindToLocatableAsset,
BeneficiaryRefToLocation,
>(
PhantomData<(
Interior,
Router,
Querier,
Timeout,
Beneficiary,
AssetKind,
AssetKindToLocatableAsset,
BeneficiaryRefToLocation,
)>,
);
impl<
Interior: Get<InteriorLocation>,
Router: SendXcm,
Querier: QueryHandler,
Timeout: Get<Querier::BlockNumber>,
Beneficiary: Clone,
AssetKind,
AssetKindToLocatableAsset: TryConvert<AssetKind, LocatableAssetId>,
BeneficiaryRefToLocation: for<'a> TryConvert<&'a Beneficiary, Location>,
> Pay
for PayOverXcm<
Interior,
Router,
Querier,
Timeout,
Beneficiary,
AssetKind,
AssetKindToLocatableAsset,
BeneficiaryRefToLocation,
>
{
type Beneficiary = Beneficiary;
type AssetKind = AssetKind;
type Balance = u128;
type Id = QueryId;
type Error = xcm::latest::Error;
fn pay(
who: &Self::Beneficiary,
asset_kind: Self::AssetKind,
amount: Self::Balance,
) -> Result<Self::Id, Self::Error> {
let locatable = AssetKindToLocatableAsset::try_convert(asset_kind)
.map_err(|_| xcm::latest::Error::InvalidLocation)?;
let LocatableAssetId { asset_id, location: asset_location } = locatable;
let destination = Querier::UniversalLocation::get()
.invert_target(&asset_location)
.map_err(|()| Self::Error::LocationNotInvertible)?;
let beneficiary = BeneficiaryRefToLocation::try_convert(&who)
.map_err(|_| xcm::latest::Error::InvalidLocation)?;
let query_id = Querier::new_query(asset_location.clone(), Timeout::get(), Interior::get());
let message = Xcm(vec![
DescendOrigin(Interior::get()),
UnpaidExecution { weight_limit: Unlimited, check_origin: None },
SetAppendix(Xcm(vec![
SetFeesMode { jit_withdraw: true },
ReportError(QueryResponseInfo {
destination,
query_id,
max_weight: Weight::zero(),
}),
])),
TransferAsset {
beneficiary,
assets: vec![Asset { id: asset_id, fun: Fungibility::Fungible(amount) }].into(),
},
]);
let (ticket, _) = Router::validate(&mut Some(asset_location), &mut Some(message))?;
Router::deliver(ticket)?;
Ok(query_id.into())
}
fn check_payment(id: Self::Id) -> PaymentStatus {
use QueryResponseStatus::*;
match Querier::take_response(id) {
Ready { response, .. } => match response {
Response::ExecutionResult(None) => PaymentStatus::Success,
Response::ExecutionResult(Some(_)) => PaymentStatus::Failure,
_ => PaymentStatus::Unknown,
},
Pending { .. } => PaymentStatus::InProgress,
NotFound | UnexpectedVersion => PaymentStatus::Unknown,
}
}
#[cfg(feature = "runtime-benchmarks")]
fn ensure_successful(_: &Self::Beneficiary, _: Self::AssetKind, _: Self::Balance) {
// We cannot generally guarantee this will go through successfully since we don't have any
// control over the XCM transport layers. We just assume that the benchmark environment
// will be sending it somewhere sensible.
}
#[cfg(feature = "runtime-benchmarks")]
fn ensure_concluded(id: Self::Id) {
Querier::expect_response(id, Response::ExecutionResult(None));
}
}
/// Specialization of the [`PayOverXcm`] trait to allow `[u8; 32]`-based `AccountId` values to be
/// paid on a remote chain.
///
/// Implementation of the [`frame_support::traits::tokens::Pay`] trait, to allow
/// for XCM payments of a given `Balance` of `AssetKind` existing on a `DestinationChain` under
/// ownership of some `Interior` location of the local chain to a particular `Beneficiary`.
///
/// This relies on the XCM `TransferAsset` instruction. `Beneficiary` must implement
/// `Into<[u8; 32]>` (as 32-byte `AccountId`s generally do), and the actual XCM beneficiary will be
/// the location consisting of a single `AccountId32` junction with an appropriate account and no
/// specific network.
///
/// `PayOverXcm::pay` is asynchronous, and returns a `QueryId` which can then be used in
/// `check_payment` to check the status of the XCM transaction.
pub type PayAccountId32OnChainOverXcm<
DestinationChain,
Interior,
Router,
Querier,
Timeout,
Beneficiary,
AssetKind,
> = PayOverXcm<
Interior,
Router,
Querier,
Timeout,
Beneficiary,
AssetKind,
crate::AliasesIntoAccountId32<(), Beneficiary>,
FixedLocation<DestinationChain>,
>;
/// Simple struct which contains both an XCM `location` and `asset_id` to identify an asset which
/// exists on some chain.
pub struct LocatableAssetId {
/// The asset's ID.
pub asset_id: AssetId,
/// The (relative) location in which the asset ID is meaningful.
pub location: Location,
}
/// Adapter `struct` which implements a conversion from any `AssetKind` into a [`LocatableAssetId`]
/// value using a fixed `Location` for the `location` field.
pub struct FixedLocation<FixedLocationValue>(core::marker::PhantomData<FixedLocationValue>);
impl<FixedLocationValue: Get<Location>, AssetKind: Into<AssetId>>
TryConvert<AssetKind, LocatableAssetId> for FixedLocation<FixedLocationValue>
{
fn try_convert(value: AssetKind) -> Result<LocatableAssetId, AssetKind> {
Ok(LocatableAssetId { asset_id: value.into(), location: FixedLocationValue::get() })
}
}