use bytes::{Buf, BufMut, BytesMut, IntoBuf};
use futures::sink;
use futures::stream;
use futures::sync::mpsc;
use futures::{try_ready, Async, AsyncSink, Future, Poll, Sink, Stream};
use postgres_protocol::message::backend::Message;
use postgres_protocol::message::frontend::{self, CopyData};
use state_machine_future::{transition, RentToOwn, StateMachineFuture};
use std::error::Error as StdError;

use crate::proto::client::{Client, PendingRequest};
use crate::proto::codec::FrontendMessage;
use crate::proto::responses::Responses;
use crate::proto::statement::Statement;
use crate::Error;

pub enum CopyMessage {
    Message(FrontendMessage),
    Done,
}

pub struct CopyInReceiver {
    receiver: mpsc::Receiver<CopyMessage>,
    done: bool,
}

impl CopyInReceiver {
    pub fn new(receiver: mpsc::Receiver<CopyMessage>) -> CopyInReceiver {
        CopyInReceiver {
            receiver,
            done: false,
        }
    }
}

impl Stream for CopyInReceiver {
    type Item = FrontendMessage;
    type Error = ();

    fn poll(&mut self) -> Poll<Option<FrontendMessage>, ()> {
        if self.done {
            return Ok(Async::Ready(None));
        }

        match self.receiver.poll()? {
            Async::Ready(Some(CopyMessage::Message(message))) => Ok(Async::Ready(Some(message))),
            Async::Ready(Some(CopyMessage::Done)) => {
                self.done = true;
                let mut buf = vec![];
                frontend::copy_done(&mut buf);
                frontend::sync(&mut buf);
                Ok(Async::Ready(Some(FrontendMessage::Raw(buf))))
            }
            Async::Ready(None) => {
                self.done = true;
                let mut buf = vec![];
                frontend::copy_fail("", &mut buf).unwrap();
                frontend::sync(&mut buf);
                Ok(Async::Ready(Some(FrontendMessage::Raw(buf))))
            }
            Async::NotReady => Ok(Async::NotReady),
        }
    }
}

#[derive(StateMachineFuture)]
pub enum CopyIn<S>
where
    S: Stream,
    S::Item: IntoBuf,
    <S::Item as IntoBuf>::Buf: 'static + Send,
    S::Error: Into<Box<dyn StdError + Sync + Send>>,
{
    #[state_machine_future(start, transitions(ReadCopyInResponse))]
    Start {
        client: Client,
        request: PendingRequest,
        statement: Statement,
        stream: S,
        sender: mpsc::Sender<CopyMessage>,
    },
    #[state_machine_future(transitions(WriteCopyData))]
    ReadCopyInResponse {
        stream: S,
        sender: mpsc::Sender<CopyMessage>,
        receiver: Responses,
    },
    #[state_machine_future(transitions(WriteCopyDone))]
    WriteCopyData {
        stream: stream::Fuse<S>,
        buf: BytesMut,
        pending_message: Option<CopyMessage>,
        sender: mpsc::Sender<CopyMessage>,
        receiver: Responses,
    },
    #[state_machine_future(transitions(ReadCommandComplete))]
    WriteCopyDone {
        future: sink::Send<mpsc::Sender<CopyMessage>>,
        receiver: Responses,
    },
    #[state_machine_future(transitions(Finished))]
    ReadCommandComplete { receiver: Responses },
    #[state_machine_future(ready)]
    Finished(u64),
    #[state_machine_future(error)]
    Failed(Error),
}

impl<S> PollCopyIn<S> for CopyIn<S>
where
    S: Stream,
    S::Item: IntoBuf,
    <S::Item as IntoBuf>::Buf: 'static + Send,
    S::Error: Into<Box<dyn StdError + Sync + Send>>,
{
    fn poll_start<'a>(state: &'a mut RentToOwn<'a, Start<S>>) -> Poll<AfterStart<S>, Error> {
        let state = state.take();
        let receiver = state.client.send(state.request)?;

        // the statement can drop after this point, since its close will queue up after the copy
        transition!(ReadCopyInResponse {
            stream: state.stream,
            sender: state.sender,
            receiver
        })
    }

    fn poll_read_copy_in_response<'a>(
        state: &'a mut RentToOwn<'a, ReadCopyInResponse<S>>,
    ) -> Poll<AfterReadCopyInResponse<S>, Error> {
        loop {
            let message = try_ready!(state.receiver.poll());

            match message {
                Some(Message::BindComplete) => {}
                Some(Message::CopyInResponse(_)) => {
                    let state = state.take();
                    transition!(WriteCopyData {
                        stream: state.stream.fuse(),
                        buf: BytesMut::new(),
                        pending_message: None,
                        sender: state.sender,
                        receiver: state.receiver
                    })
                }
                Some(Message::ErrorResponse(body)) => return Err(Error::db(body)),
                Some(_) => return Err(Error::unexpected_message()),
                None => return Err(Error::closed()),
            }
        }
    }

    fn poll_write_copy_data<'a>(
        state: &'a mut RentToOwn<'a, WriteCopyData<S>>,
    ) -> Poll<AfterWriteCopyData, Error> {
        if let Some(message) = state.pending_message.take() {
            match state
                .sender
                .start_send(message)
                .map_err(|_| Error::closed())?
            {
                AsyncSink::Ready => {}
                AsyncSink::NotReady(message) => {
                    state.pending_message = Some(message);
                    return Ok(Async::NotReady);
                }
            }
        }

        loop {
            let buf: Box<dyn Buf + Send> = loop {
                match try_ready!(state.stream.poll().map_err(Error::copy_in_stream)) {
                    Some(buf) => {
                        let buf = buf.into_buf();
                        if buf.remaining() > 4096 {
                            if state.buf.is_empty() {
                                break Box::new(buf);
                            } else {
                                let cur_buf = state.buf.take().freeze().into_buf();
                                break Box::new(cur_buf.chain(buf));
                            }
                        }

                        state.buf.reserve(buf.remaining());
                        state.buf.put(buf);
                        if state.buf.len() > 4096 {
                            break Box::new(state.buf.take().freeze().into_buf());
                        }
                    }
                    None => break Box::new(state.buf.take().freeze().into_buf()),
                }
            };

            if buf.has_remaining() {
                let data = CopyData::new(buf).map_err(Error::encode)?;
                let message = CopyMessage::Message(FrontendMessage::CopyData(data));

                match state
                    .sender
                    .start_send(message)
                    .map_err(|_| Error::closed())?
                {
                    AsyncSink::Ready => {}
                    AsyncSink::NotReady(message) => {
                        state.pending_message = Some(message);
                        return Ok(Async::NotReady);
                    }
                }
            } else {
                let state = state.take();
                transition!(WriteCopyDone {
                    future: state.sender.send(CopyMessage::Done),
                    receiver: state.receiver,
                });
            }
        }
    }

    fn poll_write_copy_done<'a>(
        state: &'a mut RentToOwn<'a, WriteCopyDone>,
    ) -> Poll<AfterWriteCopyDone, Error> {
        try_ready!(state.future.poll().map_err(|_| Error::closed()));
        let state = state.take();

        transition!(ReadCommandComplete {
            receiver: state.receiver
        })
    }

    fn poll_read_command_complete<'a>(
        state: &'a mut RentToOwn<'a, ReadCommandComplete>,
    ) -> Poll<AfterReadCommandComplete, Error> {
        let message = try_ready!(state.receiver.poll());

        match message {
            Some(Message::CommandComplete(body)) => {
                let rows = body
                    .tag()
                    .map_err(Error::parse)?
                    .rsplit(' ')
                    .next()
                    .unwrap()
                    .parse()
                    .unwrap_or(0);
                transition!(Finished(rows))
            }
            Some(Message::ErrorResponse(body)) => Err(Error::db(body)),
            Some(_) => Err(Error::unexpected_message()),
            None => Err(Error::closed()),
        }
    }
}

impl<S> CopyInFuture<S>
where
    S: Stream,
    S::Item: IntoBuf,
    <S::Item as IntoBuf>::Buf: Send,
    S::Error: Into<Box<dyn StdError + Sync + Send>>,
{
    pub fn new(
        client: Client,
        request: PendingRequest,
        statement: Statement,
        stream: S,
        sender: mpsc::Sender<CopyMessage>,
    ) -> CopyInFuture<S> {
        CopyIn::start(client, request, statement, stream, sender)
    }
}