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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/>.

//! Transaction Pool state client.
//!
//! `Client` encapsulates all external data required for the verifaction and readiness.
//! It includes any Ethereum state parts required for checking the transaction and
//! any consensus-required structure of the transaction.

use std::fmt;

use ethereum_types::{H160 as Address, H256, U256};
use types::transaction;

/// Account Details
#[derive(Debug, Clone)]
pub struct AccountDetails {
    /// Current account nonce
    pub nonce: U256,
    /// Current account balance
    pub balance: U256,
    /// Code hash associated with an account if any
    pub code_hash: Option<H256>,
    /// Is this account a local account?
    pub is_local: bool,
}

/// Transaction type
#[derive(Debug, PartialEq)]
pub enum TransactionType {
    /// Regular transaction
    Regular,
    /// Service transaction (allowed by a contract to have gas_price=0)
    Service,
}

/// Verification client.
pub trait Client: fmt::Debug + Sync {
    /// Is transaction with given hash already in the blockchain?
    fn transaction_already_included(&self, hash: &H256) -> bool;

    /// Perform basic/cheap transaction verification.
    ///
    /// This should include all cheap checks that can be done before
    /// actually checking the signature, like chain-replay protection.
    ///
    /// This method is currently used only for verifying local transactions.
    fn verify_transaction_basic(
        &self,
        t: &transaction::UnverifiedTransaction,
    ) -> Result<(), transaction::Error>;

    /// Structurarily verify given transaction.
    fn verify_transaction(
        &self,
        tx: transaction::UnverifiedTransaction,
    ) -> Result<transaction::SignedTransaction, transaction::Error>;

    /// Estimate minimal gas requirurement for given transaction.
    fn required_gas(&self, tx: &transaction::Transaction) -> U256;

    /// Fetch account details for given sender.
    fn account_details(&self, address: &Address) -> AccountDetails;

    /// Classify transaction (check if transaction is filtered by some contracts).
    fn transaction_type(&self, tx: &transaction::SignedTransaction) -> TransactionType;

    /// Performs pre-validation of RLP decoded transaction
    fn decode_transaction(
        &self,
        transaction: &[u8],
    ) -> Result<transaction::UnverifiedTransaction, transaction::Error>;
}

/// State nonce client
pub trait NonceClient: fmt::Debug + Sync {
    /// Fetch only account nonce for given sender.
    fn account_nonce(&self, address: &Address) -> U256;
}

/// State balance client
pub trait BalanceClient: fmt::Debug + Sync {
    /// Fetch only account balance for given sender.
    fn account_balance(&self, address: &Address) -> U256;
}