#![cfg(feature = "server")]
use std::{
    fs::File,
    net::SocketAddr,
    sync::{atomic::AtomicUsize, Arc},
    time::Duration,
};

use libpt::log::{debug, error, info, warn};
use rustls::pki_types::{CertificateDer, PrivateKeyDer};
use rustls_pemfile::{certs, private_key};
use tokio::{
    io::{split, AsyncReadExt, AsyncWriteExt},
    net::{TcpListener, TcpStream},
    time::{self},
};
use tokio_rustls::{rustls, TlsAcceptor};

use crate::common::conf::Config;

pub mod errors;
use errors::*;

const BUF_SIZE: usize = 64;

pub struct Server {
    cfg: Config,
    pub timeout: Option<Duration>,
    server: TcpListener,
    num_peers: AtomicUsize,
    acceptor: TlsAcceptor,
}

impl Server {
    pub async fn build(cfg: Config) -> anyhow::Result<Self> {
        let certs = Self::load_certs(cfg.clone())?;
        let key = Self::load_key(cfg.clone())?.expect("bad key?");
        let tls_config = rustls::ServerConfig::builder()
            .with_no_client_auth()
            .with_single_cert(certs, key)?;
        let acceptor = TlsAcceptor::from(Arc::new(tls_config));
        let server = TcpListener::bind(cfg.addr).await?;
        let timeout = Some(Duration::from_secs(5));

        Ok(Server {
            cfg,
            timeout,
            server,
            num_peers: AtomicUsize::new(0),
            acceptor,
        })
    }
    pub async fn run(self) -> anyhow::Result<()> {
        let rc_self = Arc::new(self);
        let ref_self = rc_self.clone();
        tokio::spawn(async move {
            let mut interval = time::interval(Duration::from_millis(5000));
            loop {
                interval.tick().await;
                info!(
                    "status: {} peers",
                    ref_self
                        .num_peers
                        .load(std::sync::atomic::Ordering::Relaxed)
                );
            }
        });
        loop {
            let (stream, addr) = match rc_self.server.accept().await {
                Ok(s) => s,
                Err(err) => {
                    warn!("could not accept stream: {err:?}");
                    continue;
                }
            };
            let ref_self = rc_self.clone();
            // NOTE: we can only start the task now. If we start it before accepting connections
            // (so that the task theoretically accepts the connection), we would create endless
            // tasks in a loop.
            tokio::spawn(async move {
                let stream: tokio_rustls::server::TlsStream<_> =
                    match ref_self.acceptor.accept(stream).await {
                        Ok(s) => s,
                        Err(err) => {
                            error!("could not accept tcp stream: {err}");
                            return;
                        }
                    };
                ref_self.peer_add(1);
                match ref_self.handle_stream(stream, addr).await {
                    Ok(_) => (),
                    Err(err) => match err {
                        ServerError::Timeout(_) => {
                            debug!("stream {:?} timed out", addr)
                        }
                        _ => {
                            warn!("error while handling stream: {:?}", err)
                        }
                    },
                };
                ref_self.peer_sub(1);
            });
        }
    }

    fn load_key(cfg: Config) -> std::io::Result<Option<PrivateKeyDer<'static>>> {
        private_key(&mut std::io::BufReader::new(File::open(cfg.key)?))
    }

    fn load_certs(cfg: Config) -> std::io::Result<Vec<CertificateDer<'static>>> {
        certs(&mut std::io::BufReader::new(File::open(cfg.key)?)).collect()
    }

    #[inline]
    fn peer_add(&self, v: usize) {
        self.num_peers.store(
            self.num_peers.load(std::sync::atomic::Ordering::Relaxed) + v,
            std::sync::atomic::Ordering::Relaxed,
        )
    }

    #[inline]
    fn peer_sub(&self, v: usize) {
        self.num_peers.store(
            self.num_peers.load(std::sync::atomic::Ordering::Relaxed) - v,
            std::sync::atomic::Ordering::Relaxed,
        )
    }

    async fn handle_stream(
        &self,
        stream: tokio_rustls::server::TlsStream<TcpStream>,
        addr: SocketAddr,
    ) -> Result<()> {
        debug!("new peer: {:?}", addr);
        let mut buf = [0; BUF_SIZE];
        let (mut reader, mut writer) = split(stream);
        loop {
            match reader.read(&mut buf).await {
                Ok(len) if len == 0 => {
                    break;
                }
                Ok(_) => (),
                Err(err) => {
                    eprintln!("reader.read err: {err}")
                }
            }
            debug!("< {addr:?} : \"{}\"", self.decode(&buf)?);

            writer.write(b"pong\0").await?;

            // we should wait, so that we don't spam the client
            std::thread::sleep(self.cfg.delay);
        }
        debug!("disconnected peer: {:?}", addr);
        Ok(())
    }

    #[inline]
    fn decode(&self, buf: &[u8]) -> Result<String> {
        match std::str::from_utf8(buf) {
            Ok(s) => Ok(s.to_string()),
            Err(err) => Err(err.into()),
        }
    }
}