// Copyright (C) Parity Technologies (UK) Ltd.
// This file is part of Pezkuwi.

// Pezkuwi 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.

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

//! `ControlledValidatorIndices` implementation.

use pezkuwi_primitives::{IndexedVec, SessionIndex, ValidatorId, ValidatorIndex};
use pezsp_keystore::KeystorePtr;
use schnellru::{ByLength, LruMap};

/// Keeps track of the validator indices controlled by the local validator in a given session. For
/// better performance, the values for each session are cached.
pub struct ControlledValidatorIndices {
	/// The indices of the controlled validators, cached by session.
	controlled_validator_indices: LruMap<SessionIndex, Option<ValidatorIndex>>,
	keystore: KeystorePtr,
}

impl ControlledValidatorIndices {
	/// Create a new instance of `ControlledValidatorIndices`.
	pub fn new(keystore: KeystorePtr, cache_size: u32) -> Self {
		let controlled_validator_indices = LruMap::new(ByLength::new(cache_size));
		Self { controlled_validator_indices, keystore }
	}

	/// Get the controlled validator indices for a given session. If the indices are not known they
	/// will be fetched from `session_validators` and cached.
	pub fn get(
		&mut self,
		session: SessionIndex,
		session_validators: &IndexedVec<ValidatorIndex, ValidatorId>,
	) -> Option<ValidatorIndex> {
		self.controlled_validator_indices
			.get_or_insert(session, || {
				crate::signing_key_and_index(session_validators.iter(), &self.keystore)
					.map(|(_, index)| index)
			})
			.copied()
			.expect("We just inserted the controlled indices; qed")
	}
}