// Copyright 2021 Protocol Labs.
//
// 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.

#![doc = include_str!("../README.md")]

use clap::Parser;
use futures::{executor::block_on, future::FutureExt, stream::StreamExt};
use libp2p::{
    core::multiaddr::{Multiaddr, Protocol},
    dcutr, identify, identity, noise, ping, relay,
    swarm::{NetworkBehaviour, SwarmEvent},
    tcp, yamux, PeerId,
};
use std::str::FromStr;
use std::{error::Error, time::Duration};
use tracing_subscriber::EnvFilter;

#[derive(Debug, Parser)]
#[clap(name = "libp2p DCUtR client")]
struct Opts {
    /// The mode (client-listen, client-dial).
    #[clap(long)]
    mode: Mode,

    /// Fixed value to generate deterministic peer id.
    #[clap(long)]
    secret_key_seed: u8,

    /// The listening address
    #[clap(long)]
    relay_address: Multiaddr,

    /// Peer ID of the remote peer to hole punch to.
    #[clap(long)]
    remote_peer_id: Option<PeerId>,
}

#[derive(Clone, Debug, PartialEq, Parser)]
enum Mode {
    Dial,
    Listen,
}

impl FromStr for Mode {
    type Err = String;
    fn from_str(mode: &str) -> Result<Self, Self::Err> {
        match mode {
            "dial" => Ok(Mode::Dial),
            "listen" => Ok(Mode::Listen),
            _ => Err("Expected either 'dial' or 'listen'".to_string()),
        }
    }
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    let _ = tracing_subscriber::fmt()
        .with_env_filter(EnvFilter::from_default_env())
        .try_init();

    let opts = Opts::parse();

    #[derive(NetworkBehaviour)]
    struct Behaviour {
        relay_client: relay::client::Behaviour,
        ping: ping::Behaviour,
        identify: identify::Behaviour,
        dcutr: dcutr::Behaviour,
    }

    let mut swarm =
        libp2p::SwarmBuilder::with_existing_identity(generate_ed25519(opts.secret_key_seed))
            .with_tokio()
            .with_tcp(
                tcp::Config::default().nodelay(true),
                noise::Config::new,
                yamux::Config::default,
            )?
            .with_quic()
            .with_dns()?
            .with_relay_client(noise::Config::new, yamux::Config::default)?
            .with_behaviour(|keypair, relay_behaviour| Behaviour {
                relay_client: relay_behaviour,
                ping: ping::Behaviour::new(ping::Config::new()),
                identify: identify::Behaviour::new(identify::Config::new(
                    "/TODO/0.0.1".to_string(),
                    keypair.public(),
                )),
                dcutr: dcutr::Behaviour::new(keypair.public().to_peer_id()),
            })?
            .with_swarm_config(|c| c.with_idle_connection_timeout(Duration::from_secs(60)))
            .build();

    swarm
        .listen_on("/ip4/0.0.0.0/udp/0/quic-v1".parse().unwrap())
        .unwrap();
    swarm
        .listen_on("/ip4/0.0.0.0/tcp/0".parse().unwrap())
        .unwrap();

    // Wait to listen on all interfaces.
    block_on(async {
        let mut delay = futures_timer::Delay::new(std::time::Duration::from_secs(1)).fuse();
        loop {
            futures::select! {
                event = swarm.next() => {
                    match event.unwrap() {
                        SwarmEvent::NewListenAddr { address, .. } => {
                            tracing::info!(%address, "Listening on address");
                        }
                        event => panic!("{event:?}"),
                    }
                }
                _ = delay => {
                    // Likely listening on all interfaces now, thus continuing by breaking the loop.
                    break;
                }
            }
        }
    });

    // Connect to the relay server. Not for the reservation or relayed connection, but to (a) learn
    // our local public address and (b) enable a freshly started relay to learn its public address.
    swarm.dial(opts.relay_address.clone()).unwrap();
    block_on(async {
        let mut learned_observed_addr = false;
        let mut told_relay_observed_addr = false;

        loop {
            match swarm.next().await.unwrap() {
                SwarmEvent::NewListenAddr { .. } => {}
                SwarmEvent::Dialing { .. } => {}
                SwarmEvent::ConnectionEstablished { .. } => {}
                SwarmEvent::Behaviour(BehaviourEvent::Ping(_)) => {}
                SwarmEvent::Behaviour(BehaviourEvent::Identify(identify::Event::Sent {
                    ..
                })) => {
                    tracing::info!("Told relay its public address");
                    told_relay_observed_addr = true;
                }
                SwarmEvent::Behaviour(BehaviourEvent::Identify(identify::Event::Received {
                    info: identify::Info { observed_addr, .. },
                    ..
                })) => {
                    tracing::info!(address=%observed_addr, "Relay told us our observed address");
                    learned_observed_addr = true;
                }
                event => panic!("{event:?}"),
            }

            if learned_observed_addr && told_relay_observed_addr {
                break;
            }
        }
    });

    match opts.mode {
        Mode::Dial => {
            swarm
                .dial(
                    opts.relay_address
                        .with(Protocol::P2pCircuit)
                        .with(Protocol::P2p(opts.remote_peer_id.unwrap())),
                )
                .unwrap();
        }
        Mode::Listen => {
            swarm
                .listen_on(opts.relay_address.with(Protocol::P2pCircuit))
                .unwrap();
        }
    }

    block_on(async {
        loop {
            match swarm.next().await.unwrap() {
                SwarmEvent::NewListenAddr { address, .. } => {
                    tracing::info!(%address, "Listening on address");
                }
                SwarmEvent::Behaviour(BehaviourEvent::RelayClient(
                    relay::client::Event::ReservationReqAccepted { .. },
                )) => {
                    assert!(opts.mode == Mode::Listen);
                    tracing::info!("Relay accepted our reservation request");
                }
                SwarmEvent::Behaviour(BehaviourEvent::RelayClient(event)) => {
                    tracing::info!(?event)
                }
                SwarmEvent::Behaviour(BehaviourEvent::Dcutr(event)) => {
                    tracing::info!(?event)
                }
                SwarmEvent::Behaviour(BehaviourEvent::Identify(event)) => {
                    tracing::info!(?event)
                }
                SwarmEvent::Behaviour(BehaviourEvent::Ping(_)) => {}
                SwarmEvent::ConnectionEstablished {
                    peer_id, endpoint, ..
                } => {
                    tracing::info!(peer=%peer_id, ?endpoint, "Established new connection");
                }
                SwarmEvent::OutgoingConnectionError { peer_id, error, .. } => {
                    tracing::info!(peer=?peer_id, "Outgoing connection failed: {error}");
                }
                _ => {}
            }
        }
    })
}

fn generate_ed25519(secret_key_seed: u8) -> identity::Keypair {
    let mut bytes = [0u8; 32];
    bytes[0] = secret_key_seed;

    identity::Keypair::ed25519_from_bytes(bytes).expect("only errors on wrong length")
}