use core::task::{Context, Poll};
use futures::ready;
use hyper::server::accept::Accept;
use hyper::server::conn::{AddrIncoming, AddrStream};
use rustls::{Certificate, PrivateKey};
use std::future::Future;
use std::net::SocketAddr;
use std::pin::Pin;
use std::sync::Arc;
use std::{fs, io};
use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
use tokio_rustls::rustls::ServerConfig;

enum State {
    Handshaking(tokio_rustls::Accept<AddrStream>),
    Streaming(tokio_rustls::server::TlsStream<AddrStream>),
}

// tokio_rustls::server::TlsStream doesn't expose constructor methods,
// so we have to TlsAcceptor::accept and handshake to have access to it
// TlsStream implements AsyncRead/AsyncWrite handshaking tokio_rustls::Accept first
pub struct TlsStream {
    state: State,
    remote_addr: SocketAddr,
}

impl TlsStream {
    fn new(stream: AddrStream, config: Arc<ServerConfig>) -> TlsStream {
        let remote_addr = stream.remote_addr();
        let accept = tokio_rustls::TlsAcceptor::from(config).accept(stream);
        TlsStream {
            state: State::Handshaking(accept),
            remote_addr,
        }
    }
    pub fn remote_addr(&self) -> SocketAddr {
        self.remote_addr
    }
}

impl AsyncRead for TlsStream {
    fn poll_read(
        self: Pin<&mut Self>,
        cx: &mut Context,
        buf: &mut ReadBuf,
    ) -> Poll<io::Result<()>> {
        let pin = self.get_mut();
        match pin.state {
            State::Handshaking(ref mut accept) => match ready!(Pin::new(accept).poll(cx)) {
                Ok(mut stream) => {
                    let result = Pin::new(&mut stream).poll_read(cx, buf);
                    pin.state = State::Streaming(stream);
                    result
                }
                Err(err) => Poll::Ready(Err(err)),
            },
            State::Streaming(ref mut stream) => Pin::new(stream).poll_read(cx, buf),
        }
    }
}

impl AsyncWrite for TlsStream {
    fn poll_write(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &[u8],
    ) -> Poll<io::Result<usize>> {
        let pin = self.get_mut();
        match pin.state {
            State::Handshaking(ref mut accept) => match ready!(Pin::new(accept).poll(cx)) {
                Ok(mut stream) => {
                    let result = Pin::new(&mut stream).poll_write(cx, buf);
                    pin.state = State::Streaming(stream);
                    result
                }
                Err(err) => Poll::Ready(Err(err)),
            },
            State::Streaming(ref mut stream) => Pin::new(stream).poll_write(cx, buf),
        }
    }

    fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
        match self.state {
            State::Handshaking(_) => Poll::Ready(Ok(())),
            State::Streaming(ref mut stream) => Pin::new(stream).poll_flush(cx),
        }
    }

    fn poll_shutdown(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
        match self.state {
            State::Handshaking(_) => Poll::Ready(Ok(())),
            State::Streaming(ref mut stream) => Pin::new(stream).poll_shutdown(cx),
        }
    }
}

pub struct TlsAcceptor {
    config: Arc<ServerConfig>,
    incoming: AddrIncoming,
}

impl TlsAcceptor {
    pub fn new(config: Arc<ServerConfig>, incoming: AddrIncoming) -> TlsAcceptor {
        TlsAcceptor { config, incoming }
    }
}

impl Accept for TlsAcceptor {
    type Conn = TlsStream;
    type Error = io::Error;

    fn poll_accept(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Option<Result<Self::Conn, Self::Error>>> {
        let pin = self.get_mut();
        match ready!(Pin::new(&mut pin.incoming).poll_accept(cx)) {
            Some(Ok(sock)) => Poll::Ready(Some(Ok(TlsStream::new(sock, pin.config.clone())))),
            Some(Err(e)) => Poll::Ready(Some(Err(e))),
            None => Poll::Ready(None),
        }
    }
}

// Load public certificate from file.
pub fn load_certs(filename: &str) -> Result<Vec<Certificate>, Box<dyn std::error::Error>> {
    // Open certificate file.
    let certfile = fs::File::open(&filename)
        .map_err(|e| format!("Failed to access `{}`, {}", &filename, e))?;
    let mut reader = io::BufReader::new(certfile);

    // Load and return certificate.
    let certs = rustls_pemfile::certs(&mut reader).map_err(|_| "Failed to load certificate")?;
    if certs.is_empty() {
        return Err("No supported certificate in file".into());
    }
    Ok(certs.into_iter().map(Certificate).collect())
}

// Load private key from file.
pub fn load_private_key(filename: &str) -> Result<PrivateKey, Box<dyn std::error::Error>> {
    // Open keyfile.
    let keyfile = fs::File::open(&filename)
        .map_err(|e| format!("Failed to access `{}`, {}", &filename, e))?;
    let mut reader = io::BufReader::new(keyfile);

    // Load and return a single private key.
    let keys = rustls_pemfile::read_all(&mut reader)
        .map_err(|e| format!("There was a problem with reading private key: {:?}", e))?
        .into_iter()
        .find_map(|item| match item {
            rustls_pemfile::Item::RSAKey(key) | rustls_pemfile::Item::PKCS8Key(key) => Some(key),
            _ => None,
        })
        .ok_or("No supported private key in file")?;

    Ok(PrivateKey(keys))
}