// This file is part of Substrate.

// Copyright (C) 2020 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/>.

//! RPC API for GRANDPA.
#![warn(missing_docs)]

use futures::{FutureExt, TryFutureExt};
use jsonrpc_derive::rpc;

mod error;
mod report;

use report::{ReportAuthoritySet, ReportVoterState, ReportedRoundStates};

/// Returned when Grandpa RPC endpoint is not ready.
pub const NOT_READY_ERROR_CODE: i64 = 1;

type FutureResult<T> =
	Box<dyn jsonrpc_core::futures::Future<Item = T, Error = jsonrpc_core::Error> + Send>;

/// Provides RPC methods for interacting with GRANDPA.
#[rpc]
pub trait GrandpaApi {
	/// Returns the state of the current best round state as well as the
	/// ongoing background rounds.
	#[rpc(name = "grandpa_roundState")]
	fn round_state(&self) -> FutureResult<ReportedRoundStates>;
}

/// Implements the GrandpaApi RPC trait for interacting with GRANDPA.
pub struct GrandpaRpcHandler<AuthoritySet, VoterState> {
	authority_set: AuthoritySet,
	voter_state: VoterState,
}

impl<AuthoritySet, VoterState> GrandpaRpcHandler<AuthoritySet, VoterState> {
	/// Creates a new GrandpaRpcHander instance.
	pub fn new(authority_set: AuthoritySet, voter_state: VoterState) -> Self {
		Self {
			authority_set,
			voter_state,
		}
	}
}

impl<AuthoritySet, VoterState> GrandpaApi for GrandpaRpcHandler<AuthoritySet, VoterState>
where
	VoterState: ReportVoterState + Send + Sync + 'static,
	AuthoritySet: ReportAuthoritySet + Send + Sync + 'static,
{
	fn round_state(&self) -> FutureResult<ReportedRoundStates> {
		let round_states = ReportedRoundStates::from(&self.authority_set, &self.voter_state);
		let future = async move { round_states }.boxed();
		Box::new(future.map_err(jsonrpc_core::Error::from).compat())
	}
}

#[cfg(test)]
mod tests {
	use super::*;
	use jsonrpc_core::IoHandler;
	use sc_finality_grandpa::{report, AuthorityId};
	use sp_core::crypto::Public;
	use std::{collections::HashSet, convert::TryInto};

	struct TestAuthoritySet;
	struct TestVoterState;
	struct EmptyVoterState;

	fn voters() -> HashSet<AuthorityId> {
		let voter_id_1 = AuthorityId::from_slice(&[1; 32]);
		let voter_id_2 = AuthorityId::from_slice(&[2; 32]);

		vec![voter_id_1, voter_id_2].into_iter().collect()
	}

	impl ReportAuthoritySet for TestAuthoritySet {
		fn get(&self) -> (u64, HashSet<AuthorityId>) {
			(1, voters())
		}
	}

	impl ReportVoterState for EmptyVoterState {
		fn get(&self) -> Option<report::VoterState<AuthorityId>> {
			None
		}
	}

	impl ReportVoterState for TestVoterState {
		fn get(&self) -> Option<report::VoterState<AuthorityId>> {
			let voter_id_1 = AuthorityId::from_slice(&[1; 32]);
			let voters_best: HashSet<_> = vec![voter_id_1].into_iter().collect();

			let best_round_state = report::RoundState {
				total_weight: 100_u64.try_into().unwrap(),
				threshold_weight: 67_u64.try_into().unwrap(),
				prevote_current_weight: 50.into(),
				prevote_ids: voters_best,
				precommit_current_weight: 0.into(),
				precommit_ids: HashSet::new(),
			};

			let past_round_state = report::RoundState {
				total_weight: 100_u64.try_into().unwrap(),
				threshold_weight: 67_u64.try_into().unwrap(),
				prevote_current_weight: 100.into(),
				prevote_ids: voters(),
				precommit_current_weight: 100.into(),
				precommit_ids: voters(),
			};

			let background_rounds = vec![(1, past_round_state)].into_iter().collect();

			Some(report::VoterState {
				background_rounds,
				best_round: (2, best_round_state),
			})
		}
	}

	#[test]
	fn uninitialized_rpc_handler() {
		let handler = GrandpaRpcHandler::new(TestAuthoritySet, EmptyVoterState);
		let mut io = IoHandler::new();
		io.extend_with(GrandpaApi::to_delegate(handler));

		let request = r#"{"jsonrpc":"2.0","method":"grandpa_roundState","params":[],"id":1}"#;
		let response = r#"{"jsonrpc":"2.0","error":{"code":1,"message":"GRANDPA RPC endpoint not ready"},"id":1}"#;

		assert_eq!(Some(response.into()), io.handle_request_sync(request));
	}

	#[test]
	fn working_rpc_handler() {
		let handler = GrandpaRpcHandler::new(TestAuthoritySet, TestVoterState);
		let mut io = IoHandler::new();
		io.extend_with(GrandpaApi::to_delegate(handler));

		let request = r#"{"jsonrpc":"2.0","method":"grandpa_roundState","params":[],"id":1}"#;
		let response = "{\"jsonrpc\":\"2.0\",\"result\":{\
			\"background\":[{\
				\"precommits\":{\"currentWeight\":100,\"missing\":[]},\
				\"prevotes\":{\"currentWeight\":100,\"missing\":[]},\
				\"round\":1,\"thresholdWeight\":67,\"totalWeight\":100\
			}],\
			\"best\":{\
				\"precommits\":{\"currentWeight\":0,\"missing\":[\"5C62Ck4UrFPiBtoCmeSrgF7x9yv9mn38446dhCpsi2mLHiFT\",\"5C7LYpP2ZH3tpKbvVvwiVe54AapxErdPBbvkYhe6y9ZBkqWt\"]},\
				\"prevotes\":{\"currentWeight\":50,\"missing\":[\"5C7LYpP2ZH3tpKbvVvwiVe54AapxErdPBbvkYhe6y9ZBkqWt\"]},\
				\"round\":2,\"thresholdWeight\":67,\"totalWeight\":100\
			},\
			\"setId\":1\
		},\"id\":1}";

		assert_eq!(io.handle_request_sync(request), Some(response.into()));
	}
}