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

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

use crate::common::{conf::Config, decode};

pub mod errors;
use errors::*;

const BUF_SIZE: usize = 512;

pub struct Server {
    cfg: Config,
    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())?;
        trace!("loaded certs: {:?}", certs);
        let key = Self::load_key(cfg.clone())?.expect("bad key?");
        trace!("loaded key: {:?}", 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?;

        Ok(Server {
            cfg,
            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 tcp 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) => {
                            warn!("could not accept tls 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>>> {
        if cfg.key.is_none() {
            error!("the server needs a key!");
            return Err(std::io::ErrorKind::InvalidInput.into());
        }

        private_key(&mut std::io::BufReader::new(File::open(
            cfg.key.clone().unwrap(),
        )?))
    }

    fn load_certs(cfg: Config) -> std::io::Result<Vec<CertificateDer<'static>>> {
        if cfg.certs.is_none() {
            error!("the server needs at least one certificate!");
            return Err(std::io::ErrorKind::InvalidInput.into());
        }
        match certs(&mut std::io::BufReader::new(File::open(
            cfg.certs.clone().unwrap(),
        )?))
        .collect::<std::io::Result<Vec<CertificateDer<'static>>>>()
        {
            Ok(v) if !v.is_empty() => Ok(v),
            Ok(_) => {
                error!("no certs found in provided file {:?}", cfg.certs);
                Err(std::io::ErrorKind::InvalidInput.into())
            }
            Err(err) => {
                error!("could not load certs: {err:?}");
                Err(err)
            }
        }
    }

    #[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,
        mut stream: tokio_rustls::server::TlsStream<TcpStream>,
        addr: SocketAddr,
    ) -> Result<()> {
        let mut buf = [0; BUF_SIZE];
        let mut pings: usize = 0;
        debug!("new peer: {:?}", addr);
        while stream.read(&mut buf).await? > 0 {
            let request = decode(&buf)?;
            debug!(pings, "< ({})\n\"{}\"", addr, request);
            if request == "ping" {
                pings = pings.saturating_add(1);
                if (pings > self.cfg.win_after && !self.cfg.indefinitely)
                    || (pings > usize::MAX - 1)
                {
                    stream.write_all(b"You win!").await?;
                    debug!(pings, "> ({})\n\"{}\"", addr, "You win!");
                    info!("{} won!", addr);
                    stream.flush().await?;
                    stream.shutdown().await?;
                    break;
                }
                let response = format!("pong ({:x})", pings);
                stream.write_all(response.as_bytes()).await?;
                debug!(pings, "> ({})\n\"{}\"", addr, response);
            } else {
                stream.write_all(b"what is the magic word?").await?;
                debug!(pings, "> ({})\n\"{}\"", addr, "what is the magic word?");
                stream.flush().await?;
            }
            // we should wait, so that we don't spam the client
            std::thread::sleep(self.cfg.delay);
        }
        debug!("disconnected peer: {:?}", addr);
        Ok(())
    }
}