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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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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/>. | ||
|
|
||
| //! Adapters for the AssetExchanger config item. | ||
| //! | ||
| //! E.g. types that implement the [`xcm_executor::traits::AssetExchange`] trait. | ||
| mod single_asset_adapter; | ||
| pub use single_asset_adapter::SingleAssetExchangeAdapter; |
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polkadot/xcm/xcm-builder/src/asset_exchange/single_asset_adapter/adapter.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,210 @@ | ||
| // 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/>. | ||
|
|
||
| //! Single asset exchange adapter. | ||
| extern crate alloc; | ||
| use alloc::vec; | ||
| use core::marker::PhantomData; | ||
| use frame_support::{ensure, traits::tokens::fungibles}; | ||
| use pallet_asset_conversion::{QuotePrice, SwapCredit}; | ||
| use xcm::prelude::*; | ||
| use xcm_executor::{ | ||
| traits::{AssetExchange, MatchesFungibles}, | ||
| AssetsInHolding, | ||
| }; | ||
|
|
||
| /// An adapter from [`pallet_asset_conversion::SwapCredit`] and | ||
| /// [`pallet_asset_conversion::QuotePrice`] to [`xcm_executor::traits::AssetExchange`]. | ||
| /// | ||
| /// This adapter takes just one fungible asset in `give` and allows only one fungible asset in | ||
| /// `want`. If you need to handle more assets in either `give` or `want`, then you should use | ||
| /// another type that implements [`xcm_executor::traits::AssetExchange`] or build your own. | ||
| /// | ||
| /// This adapter also only works for fungible assets. | ||
| /// | ||
| /// `exchange_asset` and `quote_exchange_price` will both return an error if there's | ||
| /// more than one asset in `give` or `want`. | ||
| pub struct SingleAssetExchangeAdapter<AssetConversion, Fungibles, Matcher, AccountId>( | ||
| PhantomData<(AssetConversion, Fungibles, Matcher, AccountId)>, | ||
| ); | ||
| impl<AssetConversion, Fungibles, Matcher, AccountId> AssetExchange | ||
| for SingleAssetExchangeAdapter<AssetConversion, Fungibles, Matcher, AccountId> | ||
| where | ||
| AssetConversion: SwapCredit< | ||
| AccountId, | ||
| Balance = u128, | ||
| AssetKind = Fungibles::AssetId, | ||
| Credit = fungibles::Credit<AccountId, Fungibles>, | ||
| > + QuotePrice<Balance = u128, AssetKind = Fungibles::AssetId>, | ||
| Fungibles: fungibles::Balanced<AccountId, Balance = u128>, | ||
| Matcher: MatchesFungibles<Fungibles::AssetId, Fungibles::Balance>, | ||
| { | ||
| fn exchange_asset( | ||
| _: Option<&Location>, | ||
| give: AssetsInHolding, | ||
| want: &Assets, | ||
| maximal: bool, | ||
| ) -> Result<AssetsInHolding, AssetsInHolding> { | ||
| let mut give_iter = give.fungible_assets_iter(); | ||
| let give_asset = give_iter.next().ok_or_else(|| { | ||
| log::trace!( | ||
| target: "xcm::SingleAssetExchangeAdapter::exchange_asset", | ||
| "No fungible asset was in `give`.", | ||
| ); | ||
| give.clone() | ||
| })?; | ||
| ensure!(give_iter.next().is_none(), give.clone()); // We only support 1 asset in `give`. | ||
| ensure!(give.non_fungible_assets_iter().next().is_none(), give.clone()); // We don't allow non-fungible assets. | ||
| ensure!(want.len() == 1, give.clone()); // We only support 1 asset in `want`. | ||
| let want_asset = want.get(0).ok_or_else(|| give.clone())?; | ||
| let (give_asset_id, give_amount) = | ||
| Matcher::matches_fungibles(&give_asset).map_err(|error| { | ||
| log::trace!( | ||
| target: "xcm::SingleAssetExchangeAdapter::exchange_asset", | ||
| "Could not map XCM asset give {:?} to FRAME asset. Error: {:?}", | ||
| give_asset, | ||
| error, | ||
| ); | ||
| give.clone() | ||
| })?; | ||
| let (want_asset_id, want_amount) = | ||
| Matcher::matches_fungibles(&want_asset).map_err(|error| { | ||
| log::trace!( | ||
| target: "xcm::SingleAssetExchangeAdapter::exchange_asset", | ||
| "Could not map XCM asset want {:?} to FRAME asset. Error: {:?}", | ||
| want_asset, | ||
| error, | ||
| ); | ||
| give.clone() | ||
| })?; | ||
|
|
||
| // We have to do this to convert the XCM assets into credit the pool can use. | ||
| let swap_asset = give_asset_id.clone().into(); | ||
| let credit_in = Fungibles::issue(give_asset_id, give_amount); | ||
|
|
||
| // Do the swap. | ||
| let (credit_out, maybe_credit_change) = if maximal { | ||
| // If `maximal`, then we swap exactly `credit_in` to get as much of `want_asset_id` as | ||
| // we can, with a minimum of `want_amount`. | ||
| let credit_out = <AssetConversion as SwapCredit<_>>::swap_exact_tokens_for_tokens( | ||
| vec![swap_asset, want_asset_id], | ||
| credit_in, | ||
| Some(want_amount), | ||
| ) | ||
| .map_err(|(credit_in, error)| { | ||
| log::error!( | ||
| target: "xcm::SingleAssetExchangeAdapter::exchange_asset", | ||
| "Could not perform the swap, error: {:?}.", | ||
| error | ||
| ); | ||
| drop(credit_in); | ||
| give.clone() | ||
| })?; | ||
|
|
||
| // We don't have leftover assets if exchange was maximal. | ||
| (credit_out, None) | ||
| } else { | ||
| // If `minimal`, then we swap as little of `credit_in` as we can to get exactly | ||
| // `want_amount` of `want_asset_id`. | ||
| let (credit_out, credit_change) = | ||
| <AssetConversion as SwapCredit<_>>::swap_tokens_for_exact_tokens( | ||
| vec![swap_asset, want_asset_id], | ||
| credit_in, | ||
| want_amount, | ||
| ) | ||
| .map_err(|(credit_in, error)| { | ||
| log::error!( | ||
| target: "xcm::SingleAssetExchangeAdapter::exchange_asset", | ||
| "Could not perform the swap, error: {:?}.", | ||
| error | ||
| ); | ||
| drop(credit_in); | ||
| give.clone() | ||
| })?; | ||
|
|
||
| (credit_out, Some(credit_change)) | ||
| }; | ||
|
|
||
| // We create an `AssetsInHolding` instance by putting in the resulting asset | ||
| // of the exchange. | ||
| let resulting_asset: Asset = (want_asset.id.clone(), credit_out.peek()).into(); | ||
| let mut result: AssetsInHolding = resulting_asset.into(); | ||
|
|
||
| // If we have some leftover assets from the exchange, also put them in the result. | ||
| if let Some(credit_change) = maybe_credit_change { | ||
| let leftover_asset: Asset = (give_asset.id.clone(), credit_change.peek()).into(); | ||
| result.subsume(leftover_asset); | ||
| } | ||
|
|
||
| Ok(result.into()) | ||
| } | ||
|
|
||
| fn quote_exchange_price(give: &Assets, want: &Assets, maximal: bool) -> Option<Assets> { | ||
| if give.len() != 1 || want.len() != 1 { | ||
| return None; | ||
| } // We only support 1 asset in `give` or `want`. | ||
| let give_asset = give.get(0)?; | ||
| let want_asset = want.get(0)?; | ||
| // We first match both XCM assets to the asset ID types `AssetConversion` can handle. | ||
| let (give_asset_id, give_amount) = Matcher::matches_fungibles(give_asset) | ||
| .map_err(|error| { | ||
| log::trace!( | ||
| target: "xcm::SingleAssetExchangeAdapter::quote_exchange_price", | ||
| "Could not map XCM asset {:?} to FRAME asset. Error: {:?}.", | ||
| give_asset, | ||
| error, | ||
| ); | ||
| () | ||
| }) | ||
| .ok()?; | ||
| let (want_asset_id, want_amount) = Matcher::matches_fungibles(want_asset) | ||
| .map_err(|error| { | ||
| log::trace!( | ||
| target: "xcm::SingleAssetExchangeAdapter::quote_exchange_price", | ||
| "Could not map XCM asset {:?} to FRAME asset. Error: {:?}.", | ||
| want_asset, | ||
| error, | ||
| ); | ||
| () | ||
| }) | ||
| .ok()?; | ||
| // We quote the price. | ||
| if maximal { | ||
| // The amount of `want` resulting from swapping `give`. | ||
| let resulting_want = | ||
| <AssetConversion as QuotePrice>::quote_price_exact_tokens_for_tokens( | ||
| give_asset_id, | ||
| want_asset_id, | ||
| give_amount, | ||
| true, // Include fee. | ||
| )?; | ||
|
|
||
| Some((want_asset.id.clone(), resulting_want).into()) | ||
| } else { | ||
| // The `give` amount required to obtain `want`. | ||
| let necessary_give = | ||
| <AssetConversion as QuotePrice>::quote_price_tokens_for_exact_tokens( | ||
| give_asset_id, | ||
| want_asset_id, | ||
| want_amount, | ||
| true, // Include fee. | ||
| )?; | ||
|
|
||
| Some((give_asset.id.clone(), necessary_give).into()) | ||
| } | ||
| } | ||
| } |
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