// Copyright 2015-2018 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/>.

//! Engine timeout transitioning calls `Engine.step()` on timeout.

use std::sync::Weak;
use std::time::Duration;
use io::{IoContext, IoHandler, TimerToken};
use engines::Engine;
use parity_machine::Machine;

/// Timeouts lookup
pub trait Timeouts<S: Sync + Send + Clone>: Send + Sync {
	/// Return the first timeout.
	fn initial(&self) -> Duration;

	/// Get a timeout based on step.
	fn timeout(&self, step: &S) -> Duration;
}

/// Timeout transition handling.
pub struct TransitionHandler<S: Sync + Send + Clone, M: Machine>  {
	engine: Weak<Engine<M>>,
	timeouts: Box<Timeouts<S>>,
}

impl<S, M: Machine> TransitionHandler<S, M> where S: Sync + Send + Clone {
	/// New step caller by timeouts.
	pub fn new(engine: Weak<Engine<M>>, timeouts: Box<Timeouts<S>>) -> Self {
		TransitionHandler {
			engine: engine,
			timeouts: timeouts,
		}
	}
}

/// Timer token representing the consensus step timeouts.
pub const ENGINE_TIMEOUT_TOKEN: TimerToken = 23;

fn set_timeout<S: Sync + Send + Clone>(io: &IoContext<S>, timeout: Duration) {
	io.register_timer_once(ENGINE_TIMEOUT_TOKEN, timeout)
		.unwrap_or_else(|e| warn!(target: "engine", "Failed to set consensus step timeout: {}.", e))
}

impl<S, M> IoHandler<S> for TransitionHandler<S, M>
	where S: Sync + Send + Clone + 'static, M: Machine
{
	fn initialize(&self, io: &IoContext<S>) {
		let initial = self.timeouts.initial();
		trace!(target: "engine", "Setting the initial timeout to {:?}.", initial);
		set_timeout(io, initial);
	}

	/// Call step after timeout.
	fn timeout(&self, _io: &IoContext<S>, timer: TimerToken) {
		if timer == ENGINE_TIMEOUT_TOKEN {
			if let Some(engine) = self.engine.upgrade() {
				engine.step();
			}
		}
	}

	/// Set a new timer on message.
	fn message(&self, io: &IoContext<S>, next: &S) {
		if let Err(io_err) = io.clear_timer(ENGINE_TIMEOUT_TOKEN) {
			warn!(target: "engine", "Could not remove consensus timer {}.", io_err)
		}
		set_timeout(io, self.timeouts.timeout(next));
	}
}
