use super::*;
use std::io::Write;
use rustls::Session;


/// A wrapper around an underlying raw stream which implements the TLS or SSL
/// protocol.
#[derive(Debug)]
pub struct TlsStream<IO> {
    pub(crate) io: IO,
    pub(crate) session: ClientSession,
    pub(crate) state: TlsState,
    pub(crate) early_data: (usize, Vec<u8>)
}

#[derive(Debug)]
pub(crate) enum TlsState {
    EarlyData,
    Stream,
    Eof,
    Shutdown
}

pub(crate) enum MidHandshake<IO> {
    Handshaking(TlsStream<IO>),
    EarlyData(TlsStream<IO>),
    End
}

impl<IO> TlsStream<IO> {
    #[inline]
    pub fn get_ref(&self) -> (&IO, &ClientSession) {
        (&self.io, &self.session)
    }

    #[inline]
    pub fn get_mut(&mut self) -> (&mut IO, &mut ClientSession) {
        (&mut self.io, &mut self.session)
    }

    #[inline]
    pub fn into_inner(self) -> (IO, ClientSession) {
        (self.io, self.session)
    }
}

impl<IO> Future for MidHandshake<IO>
where IO: AsyncRead + AsyncWrite,
{
    type Item = TlsStream<IO>;
    type Error = io::Error;

    #[inline]
    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
        if let MidHandshake::Handshaking(stream) = self {
            let (io, session) = stream.get_mut();
            let mut stream = Stream::new(io, session);

            if stream.session.is_handshaking() {
                try_nb!(stream.complete_io());
            }

            if stream.session.wants_write() {
                try_nb!(stream.complete_io());
            }
        }

        match mem::replace(self, MidHandshake::End) {
            MidHandshake::Handshaking(stream)
            | MidHandshake::EarlyData(stream) => Ok(Async::Ready(stream)),
            MidHandshake::End => panic!()
        }
    }
}

impl<IO> io::Read for TlsStream<IO>
where IO: AsyncRead + AsyncWrite
{
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        let mut stream = Stream::new(&mut self.io, &mut self.session);

        match self.state {
            TlsState::EarlyData => {
                let (pos, data) = &mut self.early_data;

                // complete handshake
                if stream.session.is_handshaking() {
                    stream.complete_io()?;
                }

                // write early data (fallback)
                if !stream.session.is_early_data_accepted() {
                    while *pos < data.len() {
                        let len = stream.write(&data[*pos..])?;
                        *pos += len;
                    }
                }

                // end
                self.state = TlsState::Stream;
                data.clear();
                stream.read(buf)
            },
            TlsState::Stream => match stream.read(buf) {
                Ok(0) => {
                    self.state = TlsState::Eof;
                    Ok(0)
                },
                Ok(n) => Ok(n),
                Err(ref e) if e.kind() == io::ErrorKind::ConnectionAborted => {
                    self.state = TlsState::Shutdown;
                    stream.session.send_close_notify();
                    Ok(0)
                },
                Err(e) => Err(e)
            },
            TlsState::Eof | TlsState::Shutdown => Ok(0),
        }
    }
}

impl<IO> io::Write for TlsStream<IO>
where IO: AsyncRead + AsyncWrite
{
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        let mut stream = Stream::new(&mut self.io, &mut self.session);

        match self.state {
            TlsState::EarlyData => {
                let (pos, data) = &mut self.early_data;

                // write early data
                if let Some(mut early_data) = stream.session.early_data() {
                    let len = early_data.write(buf)?;
                    data.extend_from_slice(&buf[..len]);
                    return Ok(len);
                }

                // complete handshake
                if stream.session.is_handshaking() {
                    stream.complete_io()?;
                }

                // write early data (fallback)
                if !stream.session.is_early_data_accepted() {
                    while *pos < data.len() {
                        let len = stream.write(&data[*pos..])?;
                        *pos += len;
                    }
                }

                // end
                self.state = TlsState::Stream;
                data.clear();
                stream.write(buf)
            },
            _ => stream.write(buf)
        }
    }

    fn flush(&mut self) -> io::Result<()> {
        Stream::new(&mut self.io, &mut self.session).flush()?;
        self.io.flush()
    }
}

impl<IO> AsyncRead for TlsStream<IO>
where IO: AsyncRead + AsyncWrite
{
    unsafe fn prepare_uninitialized_buffer(&self, _: &mut [u8]) -> bool {
        false
    }
}

impl<IO> AsyncWrite for TlsStream<IO>
where IO: AsyncRead + AsyncWrite
{
    fn shutdown(&mut self) -> Poll<(), io::Error> {
        match self.state {
            TlsState::Shutdown => (),
            _ => {
                self.session.send_close_notify();
                self.state = TlsState::Shutdown;
            }
        }

        let mut stream = Stream::new(&mut self.io, &mut self.session);
        try_nb!(stream.complete_io());
        stream.io.shutdown()
    }
}