// Copyright 2015, 2016 Ethcore (UK) Ltd.
// This file is part of Parity.

// Parity 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.

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

//! Disk-backed HashDB implementation.

use common::*;
use hashdb::*;

/// A HashDB which can manage a short-term journal potentially containing many forks of mutually
/// exclusive actions.
pub trait JournalDB : HashDB + Send + Sync {
	/// Return a copy of ourself, in a box.
	fn spawn(&self) -> Box<JournalDB>;

	/// Returns heap memory size used
	fn mem_used(&self) -> usize;

	/// Check if this database has any commits
	fn is_empty(&self) -> bool;

	/// Commit all recent insert operations and canonical historical commits' removals from the
	/// old era to the backing database, reverting any non-canonical historical commit's inserts.
	fn commit(&mut self, now: u64, id: &H256, end: Option<(u64, H256)>) -> Result<u32, UtilError>;

	/// State data query
	fn state(&self, _id: &H256) -> Option<Bytes> {
		None
	}
}