// Copyright 2018 Parity Technologies (UK) Ltd.
//
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//! A basic chat application with logs demonstrating libp2p and the gossipsub protocol.
//!
//! Using two terminal windows, start two instances. Type a message in either terminal and hit return: the
//! message is sent and printed in the other terminal. Close with Ctrl-c.
//!
//! You can of course open more terminal windows and add more participants.
//! Dialing any of the other peers will propagate the new participant to all
//! chat members and everyone will receive all messages.
//!
//! In order to get the nodes to connect, take note of the listening address of the first
//! instance and start the second with this address as the first argument. In the first terminal
//! window, run:
//!
//! ```sh
//! cargo run --example gossipsub-chat
//! ```
//!
//! It will print the [`PeerId`] and the listening address, e.g. `Listening on
//! "/ip4/0.0.0.0/tcp/24915"`
//!
//! In the second terminal window, start a new instance of the example with:
//!
//! ```sh
//! cargo run --example gossipsub-chat -- /ip4/127.0.0.1/tcp/24915
//! ```
//!
//! The two nodes should then connect.

use async_std::{io, task};
use env_logger::{Builder, Env};
use futures::prelude::*;
use tet_libp2p::gossipsub::MessageId;
use tet_libp2p::gossipsub::{
    GossipsubEvent, GossipsubMessage, IdentTopic as Topic, MessageAuthenticity, ValidationMode,
};
use tet_libp2p::{gossipsub, identity, PeerId};
use std::collections::hash_map::DefaultHasher;
use std::hash::{Hash, Hasher};
use std::time::Duration;
use std::{
    error::Error,
    task::{Context, Poll},
};

fn main() -> Result<(), Box<dyn Error>> {
    Builder::from_env(Env::default().default_filter_or("info")).init();

    // Create a random PeerId
    let local_key = identity::Keypair::generate_ed25519();
    let local_peer_id = PeerId::from(local_key.public());
    println!("Local peer id: {:?}", local_peer_id);

    // Set up an encrypted TCP Transport over the Mplex and Remux protocols
    let transport = tet_libp2p::build_development_transport(local_key.clone())?;

    // Create a Gossipsub topic
    let topic = Topic::new("test-net");

    // Create a Swarm to manage peers and events
    let mut swarm = {
        // To content-address message, we can take the hash of message and use it as an ID.
        let message_id_fn = |message: &GossipsubMessage| {
            let mut s = DefaultHasher::new();
            message.data.hash(&mut s);
            MessageId::from(s.finish().to_string())
        };

        // Set a custom gossipsub
        let gossipsub_config = gossipsub::GossipsubConfigBuilder::default()
            .heartbeat_interval(Duration::from_secs(10)) // This is set to aid debugging by not cluttering the log space
            .validation_mode(ValidationMode::Strict) // This sets the kind of message validation. The default is Strict (enforce message signing)
            .message_id_fn(message_id_fn) // content-address messages. No two messages of the
            // same content will be propagated.
            .build()
            .expect("Valid config");
        // build a gossipsub network behaviour
        let mut gossipsub: gossipsub::Gossipsub =
            gossipsub::Gossipsub::new(MessageAuthenticity::Signed(local_key), gossipsub_config)
                .expect("Correct configuration");

        // subscribes to our topic
        gossipsub.subscribe(&topic).unwrap();

        // add an explicit peer if one was provided
        if let Some(explicit) = std::env::args().nth(2) {
            let explicit = explicit.clone();
            match explicit.parse() {
                Ok(id) => gossipsub.add_explicit_peer(&id),
                Err(err) => println!("Failed to parse explicit peer id: {:?}", err),
            }
        }

        // build the swarm
        tet_libp2p::Swarm::new(transport, gossipsub, local_peer_id)
    };

    // Listen on all interfaces and whatever port the OS assigns
    tet_libp2p::Swarm::listen_on(&mut swarm, "/ip4/0.0.0.0/tcp/0".parse().unwrap()).unwrap();

    // Reach out to another node if specified
    if let Some(to_dial) = std::env::args().nth(1) {
        let dialing = to_dial.clone();
        match to_dial.parse() {
            Ok(to_dial) => match tet_libp2p::Swarm::dial_addr(&mut swarm, to_dial) {
                Ok(_) => println!("Dialed {:?}", dialing),
                Err(e) => println!("Dial {:?} failed: {:?}", dialing, e),
            },
            Err(err) => println!("Failed to parse address to dial: {:?}", err),
        }
    }

    // Read full lines from stdin
    let mut stdin = io::BufReader::new(io::stdin()).lines();

    // Kick it off
    let mut listening = false;
    task::block_on(future::poll_fn(move |cx: &mut Context<'_>| {
        loop {
            if let Err(e) = match stdin.try_poll_next_unpin(cx)? {
                Poll::Ready(Some(line)) => swarm.publish(topic.clone(), line.as_bytes()),
                Poll::Ready(None) => panic!("Stdin closed"),
                Poll::Pending => break,
            } {
                println!("Publish error: {:?}", e);
            }
        }

        loop {
            match swarm.poll_next_unpin(cx) {
                Poll::Ready(Some(gossip_event)) => match gossip_event {
                    GossipsubEvent::Message {
                        propagation_source: peer_id,
                        message_id: id,
                        message,
                    } => println!(
                        "Got message: {} with id: {} from peer: {:?}",
                        String::from_utf8_lossy(&message.data),
                        id,
                        peer_id
                    ),
                    _ => {}
                },
                Poll::Ready(None) | Poll::Pending => break,
            }
        }

        if !listening {
            for addr in tet_libp2p::Swarm::listeners(&swarm) {
                println!("Listening on {:?}", addr);
                listening = true;
            }
        }

        Poll::Pending
    }))
}