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// Copyright 2022 Parity Technologies (UK) Ltd.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

//! Mixnet cover packet generation.

use super::{
	packet_queues::AddressedPacket,
	sphinx::build_cover_packet,
	topology::{NetworkStatus, RouteGenerator, RouteKind, Topology, TopologyErr},
	util::default_boxed_array,
};
use arrayvec::ArrayVec;
use rand::{CryptoRng, Rng};

#[derive(PartialEq, Eq)]
pub enum CoverKind {
	Drop,
	Loop,
}

pub fn gen_cover_packet<X>(
	rng: &mut (impl Rng + CryptoRng),
	topology: &Topology<X>,
	ns: &dyn NetworkStatus,
	kind: CoverKind,
	num_hops: usize,
) -> Result<AddressedPacket, TopologyErr> {
	// Generate route
	let route_generator = RouteGenerator::new(topology, ns);
	let route_kind = match kind {
		CoverKind::Drop => RouteKind::ToMixnode(route_generator.choose_destination_index(rng)?),
		CoverKind::Loop => RouteKind::Loop,
	};
	let mut targets = ArrayVec::new();
	let mut their_kx_publics = ArrayVec::new();
	let first_mixnode_index = route_generator.gen_route(
		&mut targets,
		&mut their_kx_publics,
		rng,
		route_kind,
		num_hops,
	)?;
	let peer_id = topology.mixnode_index_to_peer_id(first_mixnode_index)?;

	// Build packet
	let mut packet = default_boxed_array();
	build_cover_packet(&mut packet, rng, &targets, &their_kx_publics, None);

	Ok(AddressedPacket { peer_id, packet })
}