substrate: asset conversion pallet swaps credits

substrate/frame/asset-conversion/src/fungibles.rs

@@ -0,0 +1,113 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2023 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use super::*;
+
+/// TODO
+pub type NativeCredit<T> =
+	CreditFungible<<T as frame_system::Config>::AccountId, <T as Config>::Currency>;
+
+/// TODO
+pub type AssetCredit<T> =
+	CreditFungibles<<T as frame_system::Config>::AccountId, <T as Config>::Assets>;
+
+/// TODO
+pub enum Credit<T: Config> {
+	/// TODO
+	Native(NativeCredit<T>),
+	/// TODO
+	Asset(AssetCredit<T>),
+}
+
+impl<T: Config> From<NativeCredit<T>> for Credit<T> {
+	fn from(value: NativeCredit<T>) -> Self {
+		Credit::Native(value)
+	}
+}
+
+impl<T: Config> From<AssetCredit<T>> for Credit<T> {
+	fn from(value: AssetCredit<T>) -> Self {
+		Credit::Asset(value)
+	}
+}
+
+impl<T: Config> Credit<T> {
+	/// TODO
+	pub fn peek(&self) -> T::AssetBalance {
+		match self {
+			Credit::Native(c) => c.peek().into(),
+			Credit::Asset(c) => c.peek(),
+		}
+	}
+
+	/// TODO
+	pub fn split(self, amount: T::AssetBalance) -> (Self, Self) {
+		match self {
+			Credit::Native(c) => {
+				let (left, right) = c.split(amount.into());
+				(left.into(), right.into())
+			},
+			Credit::Asset(c) => {
+				let (left, right) = c.split(amount);
+				(left.into(), right.into())
+			},
+		}
+	}
+
+	/// TODO
+	pub fn asset(&self) -> T::MultiAssetId {
+		match self {
+			Credit::Native(_) => T::MultiAssetIdConverter::get_native(),
+			Credit::Asset(c) => c.asset().into(),
+		}
+	}
+}
+
+impl<T: Config> Pallet<T> {
+	/// TODO
+	pub fn resolve(who: &T::AccountId, credit: Credit<T>) -> Result<(), Credit<T>> {
+		match credit {
+			Credit::Native(c) => T::Currency::resolve(who, c).map_err(|c| c.into()),
+			Credit::Asset(c) => T::Assets::resolve(who, c).map_err(|c| c.into()),
+		}
+	}
+
+	/// TODO
+	pub fn withdraw(
+		asset_id: &T::MultiAssetId,
+		who: &T::AccountId,
+		amount: T::AssetBalance,
+		keep_alive: bool,
+	) -> Result<Credit<T>, DispatchError> {
+		let preservation = match keep_alive {
+			true => Preserve,
+			false => Expendable,
+		};
+
+		match T::MultiAssetIdConverter::try_convert(asset_id) {
+			MultiAssetIdConversionResult::Converted(asset_id) =>
+				T::Assets::withdraw(asset_id, who, amount, Exact, preservation, Polite)
+					.map(|c| c.into()),
+			MultiAssetIdConversionResult::Native => {
+				let amount = Self::convert_asset_balance_to_native_balance(amount)?;
+				T::Currency::withdraw(who, amount, Exact, preservation, Polite).map(|c| c.into())
+			},
+			MultiAssetIdConversionResult::Unsupported(_) =>
+				Err(Error::<T>::UnsupportedAsset.into()),
+		}
+	}
+}