// Copyright 2021 Protocol Labs.
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//! # File sharing example
//!
//! Basic file sharing application with peers either providing or locating and
//! getting files by name.
//!
//! While obviously showcasing how to build a basic file sharing application,
//! the actual goal of this example is **to show how to integrate rust-libp2p
//! into a larger application**.
//!
//! ## Sample plot
//!
//! Assuming there are 3 nodes, A, B and C. A and B each provide a file while C
//! retrieves a file.
//!
//! Provider nodes A and B each provide a file, file FA and FB respectively.
//! They do so by advertising themselves as a provider for their file on a DHT
//! via [`libp2p-kad`]. The two, among other nodes of the network, are
//! interconnected via the DHT.
//!
//! Node C can locate the providers for file FA or FB on the DHT via
//! [`libp2p-kad`] without being connected to the specific node providing the
//! file, but any node of the DHT. Node C then connects to the corresponding
//! node and requests the file content of the file via
//! [`libp2p-request-response`].
//!
//! ## Architectural properties
//!
//! - Clean clonable async/await interface ([`Client`](network::Client)) to interact with the
//!   network layer.
//!
//! - Single task driving the network layer, no locks required.
//!
//! ## Usage
//!
//! A two node setup with one node providing the file and one node requesting the file.
//!
//! 1. Run command below in one terminal.
//!
//!    ```sh
//!    cargo run -- --listen-address /ip4/127.0.0.1/tcp/40837 \
//!              --secret-key-seed 1 \
//!              provide \
//!              --path <path-to-your-file> \
//!              --name <name-for-others-to-find-your-file>
//!    ```
//!
//! 2. Run command below in another terminal.
//!
//!    ```sh
//!    cargo run -- --peer /ip4/127.0.0.1/tcp/40837/p2p/12D3KooWPjceQrSwdWXPyLLeABRXmuqt69Rg3sBYbU1Nft9HyQ6X \
//!              get \
//!              --name <name-for-others-to-find-your-file>
//!    ```
//!
//! Note: The client does not need to be directly connected to the providing
//! peer, as long as both are connected to some node on the same DHT.
mod network;

use async_std::task::spawn;
use clap::Parser;

use futures::prelude::*;
use futures::StreamExt;
use libp2p::{core::Multiaddr, multiaddr::Protocol, PeerId};
use std::error::Error;
use std::io::Write;
use std::path::PathBuf;

#[async_std::main]
async fn main() -> Result<(), Box<dyn Error>> {
    env_logger::init();

    let opt = Opt::parse();

    let (mut network_client, mut network_events, network_event_loop) =
        network::new(opt.secret_key_seed).await?;

    // Spawn the network task for it to run in the background.
    spawn(network_event_loop.run());

    // In case a listen address was provided use it, otherwise listen on any
    // address.
    match opt.listen_address {
        Some(addr) => network_client
            .start_listening(addr)
            .await
            .expect("Listening not to fail."),
        None => network_client
            .start_listening("/ip4/0.0.0.0/tcp/0".parse()?)
            .await
            .expect("Listening not to fail."),
    };

    // In case the user provided an address of a peer on the CLI, dial it.
    if let Some(addr) = opt.peer {
        let peer_id = match addr.iter().last() {
            Some(Protocol::P2p(hash)) => PeerId::from_multihash(hash).expect("Valid hash."),
            _ => return Err("Expect peer multiaddr to contain peer ID.".into()),
        };
        network_client
            .dial(peer_id, addr)
            .await
            .expect("Dial to succeed");
    }

    match opt.argument {
        // Providing a file.
        CliArgument::Provide { path, name } => {
            // Advertise oneself as a provider of the file on the DHT.
            network_client.start_providing(name.clone()).await;

            loop {
                match network_events.next().await {
                    // Reply with the content of the file on incoming requests.
                    Some(network::Event::InboundRequest { request, channel }) => {
                        if request == name {
                            network_client
                                .respond_file(std::fs::read(&path)?, channel)
                                .await;
                        }
                    }
                    e => todo!("{:?}", e),
                }
            }
        }
        // Locating and getting a file.
        CliArgument::Get { name } => {
            // Locate all nodes providing the file.
            let providers = network_client.get_providers(name.clone()).await;
            if providers.is_empty() {
                return Err(format!("Could not find provider for file {name}.").into());
            }

            // Request the content of the file from each node.
            let requests = providers.into_iter().map(|p| {
                let mut network_client = network_client.clone();
                let name = name.clone();
                async move { network_client.request_file(p, name).await }.boxed()
            });

            // Await the requests, ignore the remaining once a single one succeeds.
            let file_content = futures::future::select_ok(requests)
                .await
                .map_err(|_| "None of the providers returned file.")?
                .0;

            std::io::stdout().write_all(&file_content)?;
        }
    }

    Ok(())
}

#[derive(Parser, Debug)]
#[clap(name = "libp2p file sharing example")]
struct Opt {
    /// Fixed value to generate deterministic peer ID.
    #[clap(long)]
    secret_key_seed: Option<u8>,

    #[clap(long)]
    peer: Option<Multiaddr>,

    #[clap(long)]
    listen_address: Option<Multiaddr>,

    #[clap(subcommand)]
    argument: CliArgument,
}

#[derive(Debug, Parser)]
enum CliArgument {
    Provide {
        #[clap(long)]
        path: PathBuf,
        #[clap(long)]
        name: String,
    },
    Get {
        #[clap(long)]
        name: String,
    },
}