Currency swap precompile

crates/precompile-currency-swap/Cargo.toml

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+[package]
+name = "precompile-currency-swap"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[dependencies]
+precompile-utils = { path = "../precompile-utils", default-features = false }
+primitives-currency-swap = { path = "../primitives-currency-swap", default-features = false }
+
+codec = { package = "parity-scale-codec", version = "3.2.2", default-features = false, features = ["derive"] }
+fp-evm = { git = "https://github.com/humanode-network/frontier", branch = "locked/polkadot-v0.9.38", default-features = false }
+frame-support = { default-features = false, git = "https://github.com/humanode-network/substrate", branch = "locked/polkadot-v0.9.38" }
+frame-system = { default-features = false, git = "https://github.com/humanode-network/substrate", branch = "locked/polkadot-v0.9.38" }
+getrandom = { version = "0.2", features = ["js"] }
+num_enum = { version = "0.6.0", default-features = false }
+pallet-evm = { git = "https://github.com/humanode-network/frontier", branch = "locked/polkadot-v0.9.38", default-features = false }
+scale-info = { version = "2.5.0", default-features = false, features = ["derive"] }
+serde = { version = "1", features = ["derive"], optional = true }
+sp-core = { default-features = false, git = "https://github.com/humanode-network/substrate", branch = "locked/polkadot-v0.9.38" }
+sp-runtime = { default-features = false, git = "https://github.com/humanode-network/substrate", branch = "locked/polkadot-v0.9.38" }
+sp-std = { default-features = false, git = "https://github.com/humanode-network/substrate", branch = "locked/polkadot-v0.9.38" }
+
+[dev-dependencies]
+hex-literal = "0.4"
+mockall = "0.11"
+pallet-balances = { default-features = false, git = "https://github.com/humanode-network/substrate", branch = "locked/polkadot-v0.9.38" }
+pallet-evm = { default-features = false, git = "https://github.com/humanode-network/frontier", branch = "locked/polkadot-v0.9.38" }
+pallet-evm-balances = { default-features = false, git = "https://github.com/humanode-network/frontier", branch = "locked/polkadot-v0.9.38" }
+pallet-evm-system = { default-features = false, git = "https://github.com/humanode-network/frontier", branch = "locked/polkadot-v0.9.38" }
+pallet-timestamp = { default-features = false, git = "https://github.com/humanode-network/substrate", branch = "locked/polkadot-v0.9.38" }
+sp-io = { default-features = false, git = "https://github.com/humanode-network/substrate", branch = "locked/polkadot-v0.9.38" }
+
+[features]
+default = ["std"]
+std = [
+  "codec/std",
+  "fp-evm/std",
+  "frame-support/std",
+  "frame-system/std",
+  "getrandom/std",
+  "num_enum/std",
+  "pallet-balances/std",
+  "pallet-evm-balances/std",
+  "pallet-evm-system/std",
+  "pallet-evm/std",
+  "pallet-timestamp/std",
+  "precompile-utils/std",
+  "primitives-currency-swap/std",
+  "scale-info/std",
+  "serde",
+  "sp-core/std",
+  "sp-io/std",
+  "sp-runtime/std",
+  "sp-std/std",
+]

crates/precompile-currency-swap/CurrencySwap.sol

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+// SPDX-License-Identifier: UNLICENSED
+
+pragma solidity >=0.7.0 <0.9.0;
+
+/**
+ * @title Currency Swap Interface
+ *
+ * An interface enabling swapping the funds from EVM accounts to
+ * native Substrate accounts.
+ *
+ * Address: 0x0000000000000000000000000000000000000900
+ */
+interface CurrencySwap {
+  /**
+   * Transfer the funds from an EVM account to native substrate account.
+   * Selector: 76467cbd
+   *
+   * @param nativeAddress The native address to send the funds to.
+   * @return success Whether or not the swap was successful.
+   */
+  function swap(bytes32 nativeAddress) external payable returns (bool success);
+}

crates/precompile-currency-swap/src/lib.rs

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+//! A precompile to swap EVM tokens with native chain tokens.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use frame_support::traits::tokens::currency::Currency;
+use pallet_evm::{
+    ExitError, ExitRevert, Precompile, PrecompileFailure, PrecompileHandle, PrecompileOutput,
+    PrecompileResult,
+};
+use precompile_utils::{succeed, EvmDataWriter, EvmResult, PrecompileHandleExt};
+use sp_core::{Get, H160, H256, U256};
+use sp_std::marker::PhantomData;
+use sp_std::prelude::*;
+
+#[cfg(test)]
+mod mock;
+
+#[cfg(test)]
+mod tests;
+
+/// Possible actions for this interface.
+#[precompile_utils::generate_function_selector]
+#[derive(Debug, PartialEq)]
+pub enum Action {
+    /// Swap EVM tokens to native tokens.
+    Swap = "swap(bytes32)",
+}
+
+/// Exposes the currency swap interface to EVM.
+pub struct CurrencySwap<CurrencySwapT, AccountIdFrom, AccountIdTo, GasCost>(
+    PhantomData<(CurrencySwapT, AccountIdFrom, AccountIdTo, GasCost)>,
+)
+where
+    AccountIdFrom: From<H160>,
+    AccountIdTo: From<[u8; 32]>,
+    CurrencySwapT: primitives_currency_swap::CurrencySwap<AccountIdFrom, AccountIdTo>,
+    FromBalanceFor<CurrencySwapT, AccountIdFrom, AccountIdTo>: TryFrom<U256>,
+    GasCost: Get<u64>;
+
+impl<CurrencySwapT, AccountIdFrom, AccountIdTo, GasCost> Precompile
+    for CurrencySwap<CurrencySwapT, AccountIdFrom, AccountIdTo, GasCost>
+where
+    AccountIdFrom: From<H160>,
+    AccountIdTo: From<[u8; 32]>,
+    CurrencySwapT: primitives_currency_swap::CurrencySwap<AccountIdFrom, AccountIdTo>,
+    FromBalanceFor<CurrencySwapT, AccountIdFrom, AccountIdTo>: TryFrom<U256>,
+    GasCost: Get<u64>,
+{
+    fn execute(handle: &mut impl PrecompileHandle) -> PrecompileResult {
+        handle.record_cost(GasCost::get())?;
+
+        let selector = handle
+            .read_selector()
+            .map_err(|_| PrecompileFailure::Error {
+                exit_status: ExitError::Other("invalid function selector".into()),
+            })?;
+
+        match selector {
+            Action::Swap => Self::swap(handle),
+        }
+    }
+}
+
+/// Utility alias for easy access to [`primitives_currency_swap::CurrencySwap::From::Balance`] type.
+type FromBalanceFor<T, AccountIdFrom, AccountIdTo> =
+    <FromCurrencyFor<T, AccountIdFrom, AccountIdTo> as Currency<AccountIdFrom>>::Balance;
+
+/// Utility alias for easy access to [`primitives_currency_swap::CurrencySwap::From`] type.
+type FromCurrencyFor<T, AccountIdFrom, AccountIdTo> =
+    <T as primitives_currency_swap::CurrencySwap<AccountIdFrom, AccountIdTo>>::From;
+
+impl<CurrencySwapT, AccountIdFrom, AccountIdTo, GasCost>
+    CurrencySwap<CurrencySwapT, AccountIdFrom, AccountIdTo, GasCost>
+where
+    AccountIdFrom: From<H160>,
+    AccountIdTo: From<[u8; 32]>,
+    CurrencySwapT: primitives_currency_swap::CurrencySwap<AccountIdFrom, AccountIdTo>,
+    FromBalanceFor<CurrencySwapT, AccountIdFrom, AccountIdTo>: TryFrom<U256>,
+    GasCost: Get<u64>,
+{
+    /// Swap EVM tokens to native tokens.
+    fn swap(handle: &mut impl PrecompileHandle) -> EvmResult<PrecompileOutput> {
+        let mut input = handle.read_input()?;
+
+        let fp_evm::Context {
+            address,
+            apparent_value: value,
+            ..
+        } = handle.context();
+
+        // Here we must withdraw from self (i.e. from the precompile address, not from the caller
+        // address), since the funds have already been transferred to us (precompile) as this point.
+        let from: AccountIdFrom = (*address).into();
+
+        let value: FromBalanceFor<CurrencySwapT, AccountIdFrom, AccountIdTo> =
+            (*value).try_into().map_err(|_| PrecompileFailure::Error {
+                exit_status: ExitError::Other("value is out of bounds".into()),
+            })?;
+
+        input
+            .expect_arguments(1)
+            .map_err(|_| PrecompileFailure::Error {
+                exit_status: ExitError::Other("exactly one argument is expected".into()),
+            })?;
+
+        let to: H256 = input.read()?;
+        let to: [u8; 32] = to.into();
+        let to: AccountIdTo = to.into();
+
+        let junk_data = input.read_till_end()?;
+        if !junk_data.is_empty() {
+            return Err(PrecompileFailure::Error {
+                exit_status: ExitError::Other("junk at the end of input".into()),
+            });
+        }
+
+        let imbalance = CurrencySwapT::From::withdraw(
+            &from,
+            value,
+            frame_support::traits::WithdrawReasons::TRANSFER,
+            frame_support::traits::ExistenceRequirement::AllowDeath,
+        )
+        .map_err(|error| match error {
+            sp_runtime::DispatchError::Token(sp_runtime::TokenError::NoFunds) => {
+                PrecompileFailure::Error {
+                    exit_status: ExitError::OutOfFund,
+                }
+            }
+            _ => PrecompileFailure::Error {
+                exit_status: ExitError::Other("unable to withdraw funds".into()),
+            },
+        })?;
+
+        let imbalance = CurrencySwapT::swap(imbalance).map_err(|_| PrecompileFailure::Revert {
+            exit_status: ExitRevert::Reverted,
+            output: "unable to swap the currency".into(),
+        })?;
+
+        CurrencySwapT::To::resolve_creating(&to, imbalance);
+
+        Ok(succeed(EvmDataWriter::new().write(true).build()))
+    }
+}