// Copyright 2015-2017 Parity Technologies (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/>.

// Chain verifiers.

use error::Error;
use header::Header;

/// Sequential chain verifier.
///
/// See docs on `Engine` relating to proving functions for more details.
/// Headers here will have already passed "basic" verification.
pub trait ChainVerifier {
	/// Lightly verify the next block header.
	/// This may not be a header that requires a proof.
	fn verify_light(&self, header: &Header) -> Result<(), Error>;

	/// Perform potentially heavier checks on the next block header.
	fn verify_heavy(&self, header: &Header) -> Result<(), Error> {
		self.verify_light(header)
	}
}

/// No-op chain verifier.
pub struct NoOp;

impl ChainVerifier for NoOp {
	fn verify_light(&self, _header: &Header) -> Result<(), Error> { Ok(()) }
}