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// Copyright 2015-2020 Parity Technologies (UK) Ltd.
// This file is part of OpenEthereum.

// OpenEthereum 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.

// OpenEthereum 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 OpenEthereum.  If not, see <http://www.gnu.org/licenses/>.

//! Generalization of a state machine for a consensus engine.
//! This will define traits for the header, block, and state of a blockchain.

use block::ExecutedBlock;
use ethereum_types::{Address, U256};

/// Generalization of types surrounding blockchain-suitable state machines.
pub trait Machine: Send + Sync {
    /// A handle to a blockchain client for this machine.
    type EngineClient: ?Sized;

    /// Errors which can occur when querying or interacting with the machine.
    type Error;

    /// Get the balance, in base units, associated with an account.
    /// Extracts data from the live block.
    fn balance(&self, live: &ExecutedBlock, address: &Address) -> Result<U256, Self::Error>;

    /// Increment the balance of an account in the state of the live block.
    fn add_balance(
        &self,
        live: &mut ExecutedBlock,
        address: &Address,
        amount: &U256,
    ) -> Result<(), Self::Error>;
}