// 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/>.

//! Service for culling the light client's transaction queue.

use std::sync::Arc;
use std::time::Duration;

use ethcore::service::ClientIoMessage;
use ethsync::LightSync;
use io::{IoContext, IoHandler, TimerToken};

use light::client::Client;
use light::on_demand::{request, OnDemand};
use light::TransactionQueue;

use futures::{future, stream, Future, Stream};

use parity_reactor::Remote;

use util::RwLock;

// Attepmt to cull once every 10 minutes.
const TOKEN: TimerToken = 1;
const TIMEOUT_MS: u64 = 1000 * 60 * 10;

// But make each attempt last only 9 minutes
const PURGE_TIMEOUT_MS: u64 = 1000 * 60 * 9;

/// Periodically culls the transaction queue of mined transactions.
pub struct QueueCull {
	/// A handle to the client, for getting the latest block header.
	pub client: Arc<Client>,
	/// A handle to the sync service.
	pub sync: Arc<LightSync>,
	/// The on-demand request service.
	pub on_demand: Arc<OnDemand>,
	/// The transaction queue.
	pub txq: Arc<RwLock<TransactionQueue>>,
	/// Event loop remote.
	pub remote: Remote,
}

impl IoHandler<ClientIoMessage> for QueueCull {
	fn initialize(&self, io: &IoContext<ClientIoMessage>) {
		io.register_timer(TOKEN, TIMEOUT_MS).expect("Error registering timer");
	}

	fn timeout(&self, _io: &IoContext<ClientIoMessage>, timer: TimerToken) {
		if timer != TOKEN { return }

		let senders = self.txq.read().queued_senders();
		if senders.is_empty() { return }

		let (sync, on_demand, txq) = (self.sync.clone(), self.on_demand.clone(), self.txq.clone());
		let best_header = self.client.best_block_header();
		let start_nonce = self.client.engine().account_start_nonce();

		info!(target: "cull", "Attempting to cull queued transactions from {} senders.", senders.len());
		self.remote.spawn_with_timeout(move || {
			let maybe_fetching = sync.with_context(move |ctx| {
				// fetch the nonce of each sender in the queue.
				let nonce_futures = senders.iter()
					.map(|&address| request::Account { header: best_header.clone(), address: address })
					.map(move |request| {
						on_demand.account(ctx, request)
							.map(move |maybe_acc| maybe_acc.map_or(start_nonce, |acc| acc.nonce))
					})
					.zip(senders.iter())
					.map(|(fut, &addr)| fut.map(move |nonce| (addr, nonce)));

				// as they come in, update each sender to the new nonce.
				stream::futures_unordered(nonce_futures)
					.fold(txq, |txq, (address, nonce)| {
						txq.write().cull(address, nonce);
						future::ok(txq)
					})
					.map(|_| ()) // finally, discard the txq handle and log errors.
					.map_err(|_| debug!(target: "cull", "OnDemand prematurely closed channel."))
			});

			match maybe_fetching {
				Some(fut) => fut.boxed(),
				None => future::ok(()).boxed(),
			}
		}, Duration::from_millis(PURGE_TIMEOUT_MS), || {})
	}
}