// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0

// This program 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.

// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.

//! Schema for BEEFY state persisted in the aux-db.

use crate::{error::Error, worker::PersistedState, LOG_TARGET};
use codec::{Decode, Encode};
use log::{debug, trace};
use sc_client_api::{backend::AuxStore, Backend};
use sp_runtime::traits::Block as BlockT;

const VERSION_KEY: &[u8] = b"beefy_auxschema_version";
const WORKER_STATE_KEY: &[u8] = b"beefy_voter_state";

const CURRENT_VERSION: u32 = 4;

pub(crate) fn write_current_version<BE: AuxStore>(backend: &BE) -> Result<(), Error> {
	debug!(target: LOG_TARGET, "🥩 write aux schema version {:?}", CURRENT_VERSION);
	AuxStore::insert_aux(backend, &[(VERSION_KEY, CURRENT_VERSION.encode().as_slice())], &[])
		.map_err(|e| Error::Backend(e.to_string()))
}

/// Write voter state.
pub(crate) fn write_voter_state<B: BlockT, BE: AuxStore>(
	backend: &BE,
	state: &PersistedState<B>,
) -> Result<(), Error> {
	trace!(target: LOG_TARGET, "🥩 persisting {:?}", state);
	AuxStore::insert_aux(backend, &[(WORKER_STATE_KEY, state.encode().as_slice())], &[])
		.map_err(|e| Error::Backend(e.to_string()))
}

fn load_decode<BE: AuxStore, T: Decode>(backend: &BE, key: &[u8]) -> Result<Option<T>, Error> {
	match backend.get_aux(key).map_err(|e| Error::Backend(e.to_string()))? {
		None => Ok(None),
		Some(t) => T::decode(&mut &t[..])
			.map_err(|e| Error::Backend(format!("BEEFY DB is corrupted: {}", e)))
			.map(Some),
	}
}

/// Load or initialize persistent data from backend.
pub(crate) fn load_persistent<B, BE>(backend: &BE) -> Result<Option<PersistedState<B>>, Error>
where
	B: BlockT,
	BE: Backend<B>,
{
	let version: Option<u32> = load_decode(backend, VERSION_KEY)?;

	match version {
		None => (),
		Some(1) | Some(2) | Some(3) => (), // versions 1, 2 & 3 are obsolete and should be ignored
		Some(4) => return load_decode::<_, PersistedState<B>>(backend, WORKER_STATE_KEY),
		other => return Err(Error::Backend(format!("Unsupported BEEFY DB version: {:?}", other))),
	}

	// No persistent state found in DB.
	Ok(None)
}

#[cfg(test)]
pub(crate) mod tests {
	use super::*;
	use crate::tests::BeefyTestNet;
	use sc_network_test::TestNetFactory;

	// also used in tests.rs
	pub fn verify_persisted_version<B: BlockT, BE: Backend<B>>(backend: &BE) -> bool {
		let version: u32 = load_decode(backend, VERSION_KEY).unwrap().unwrap();
		version == CURRENT_VERSION
	}

	#[tokio::test]
	async fn should_load_persistent_sanity_checks() {
		let mut net = BeefyTestNet::new(1);
		let backend = net.peer(0).client().as_backend();

		// version not available in db -> None
		assert_eq!(load_persistent(&*backend).unwrap(), None);

		// populate version in db
		write_current_version(&*backend).unwrap();
		// verify correct version is retrieved
		assert_eq!(load_decode(&*backend, VERSION_KEY).unwrap(), Some(CURRENT_VERSION));

		// version is available in db but state isn't -> None
		assert_eq!(load_persistent(&*backend).unwrap(), None);

		// full `PersistedState` load is tested in `tests.rs`.
	}
}
