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// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
// This file is part of Frontier.
//
// Copyright (c) 2019-2022 Moonsong Labs.
// Copyright (c) 2023 Parity Technologies (UK) Ltd.
//
// This program 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.
//
// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.

//! Provide checks related to function modifiers (view/payable).

use crate::solidity::revert::{MayRevert, RevertReason};
use fp_evm::Context;
use sp_core::U256;

/// Represents modifiers a Solidity function can be annotated with.
#[derive(Copy, Clone, PartialEq, Eq)]
pub enum FunctionModifier {
	/// Function that doesn't modify the state.
	View,
	/// Function that modifies the state but refuse receiving funds.
	/// Correspond to a Solidity function with no modifiers.
	NonPayable,
	/// Function that modifies the state and accept funds.
	Payable,
}

/// Check that a function call is compatible with the context it is
/// called into.
pub fn check_function_modifier(
	context: &Context,
	is_static: bool,
	modifier: FunctionModifier,
) -> MayRevert {
	if is_static && modifier != FunctionModifier::View {
		return Err(
			RevertReason::custom("Can't call non-static function in static context").into(),
		);
	}

	if modifier != FunctionModifier::Payable && context.apparent_value > U256::zero() {
		return Err(RevertReason::custom("Function is not payable").into());
	}

	Ok(())
}