// This file is part of Substrate.

// Copyright (C) 2018-2021 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/>.

use futures::prelude::*;
use libp2p::PeerId;
use rand::{
	distributions::{Distribution, Uniform, WeightedIndex},
	seq::IteratorRandom,
};
use sc_peerset::{
	DropReason, IncomingIndex, Message, Peerset, PeersetConfig, ReputationChange, SetConfig, SetId,
};
use std::{
	collections::{HashMap, HashSet},
	pin::Pin,
	task::Poll,
};

#[test]
fn run() {
	for _ in 0..50 {
		test_once();
	}
}

fn test_once() {
	// PRNG to use.
	let mut rng = rand::thread_rng();

	// Nodes that the peerset knows about.
	let mut known_nodes = HashSet::<PeerId>::new();
	// Nodes that we have reserved. Always a subset of `known_nodes`.
	let mut reserved_nodes = HashSet::<PeerId>::new();

	let (mut peerset, peerset_handle) = Peerset::from_config(PeersetConfig {
		sets: vec![SetConfig {
			bootnodes: (0..Uniform::new_inclusive(0, 4).sample(&mut rng))
				.map(|_| {
					let id = PeerId::random();
					known_nodes.insert(id.clone());
					id
				})
				.collect(),
			reserved_nodes: {
				(0..Uniform::new_inclusive(0, 2).sample(&mut rng))
					.map(|_| {
						let id = PeerId::random();
						known_nodes.insert(id.clone());
						reserved_nodes.insert(id.clone());
						id
					})
					.collect()
			},
			in_peers: Uniform::new_inclusive(0, 25).sample(&mut rng),
			out_peers: Uniform::new_inclusive(0, 25).sample(&mut rng),
			reserved_only: Uniform::new_inclusive(0, 10).sample(&mut rng) == 0,
		}],
	});

	futures::executor::block_on(futures::future::poll_fn(move |cx| {
		// List of nodes the user of `peerset` assumes it's connected to. Always a subset of
		// `known_nodes`.
		let mut connected_nodes = HashSet::<PeerId>::new();
		// List of nodes the user of `peerset` called `incoming` with and that haven't been
		// accepted or rejected yet.
		let mut incoming_nodes = HashMap::<IncomingIndex, PeerId>::new();
		// Next id for incoming connections.
		let mut next_incoming_id = IncomingIndex(0);

		// Perform a certain number of actions while checking that the state is consistent. If we
		// reach the end of the loop, the run has succeeded.
		for _ in 0..2500 {
			// Each of these weights corresponds to an action that we may perform.
			let action_weights = [150, 90, 90, 30, 30, 1, 1, 4, 4];
			match WeightedIndex::new(&action_weights).unwrap().sample(&mut rng) {
				// If we generate 0, poll the peerset.
				0 => match Stream::poll_next(Pin::new(&mut peerset), cx) {
					Poll::Ready(Some(Message::Connect { peer_id, .. })) => {
						if let Some(id) =
							incoming_nodes.iter().find(|(_, v)| **v == peer_id).map(|(&id, _)| id)
						{
							incoming_nodes.remove(&id);
						}
						assert!(connected_nodes.insert(peer_id));
					},
					Poll::Ready(Some(Message::Drop { peer_id, .. })) => {
						connected_nodes.remove(&peer_id);
					},
					Poll::Ready(Some(Message::Accept(n))) => {
						assert!(connected_nodes.insert(incoming_nodes.remove(&n).unwrap()))
					},
					Poll::Ready(Some(Message::Reject(n))) => {
						assert!(!connected_nodes.contains(&incoming_nodes.remove(&n).unwrap()))
					},
					Poll::Ready(None) => panic!(),
					Poll::Pending => {},
				},

				// If we generate 1, discover a new node.
				1 => {
					let new_id = PeerId::random();
					known_nodes.insert(new_id.clone());
					peerset.add_to_peers_set(SetId::from(0), new_id);
				},

				// If we generate 2, adjust a random reputation.
				2 =>
					if let Some(id) = known_nodes.iter().choose(&mut rng) {
						let val = Uniform::new_inclusive(i32::MIN, i32::MAX).sample(&mut rng);
						peerset_handle.report_peer(id.clone(), ReputationChange::new(val, ""));
					},

				// If we generate 3, disconnect from a random node.
				3 =>
					if let Some(id) = connected_nodes.iter().choose(&mut rng).cloned() {
						connected_nodes.remove(&id);
						peerset.dropped(SetId::from(0), id, DropReason::Unknown);
					},

				// If we generate 4, connect to a random node.
				4 => {
					if let Some(id) = known_nodes
						.iter()
						.filter(|n| {
							incoming_nodes.values().all(|m| m != *n) &&
								!connected_nodes.contains(*n)
						})
						.choose(&mut rng)
					{
						peerset.incoming(SetId::from(0), id.clone(), next_incoming_id.clone());
						incoming_nodes.insert(next_incoming_id.clone(), id.clone());
						next_incoming_id.0 += 1;
					}
				},

				// 5 and 6 are the reserved-only mode.
				5 => peerset_handle.set_reserved_only(SetId::from(0), true),
				6 => peerset_handle.set_reserved_only(SetId::from(0), false),

				// 7 and 8 are about switching a random node in or out of reserved mode.
				7 => {
					if let Some(id) =
						known_nodes.iter().filter(|n| !reserved_nodes.contains(*n)).choose(&mut rng)
					{
						peerset_handle.add_reserved_peer(SetId::from(0), id.clone());
						reserved_nodes.insert(id.clone());
					}
				},
				8 =>
					if let Some(id) = reserved_nodes.iter().choose(&mut rng).cloned() {
						reserved_nodes.remove(&id);
						peerset_handle.remove_reserved_peer(SetId::from(0), id);
					},

				_ => unreachable!(),
			}
		}

		Poll::Ready(())
	}));
}
