use std::future::Future;
use std::pin::Pin;
use std::task::{self, Poll};

use futures::io::{AsyncRead, AsyncWrite};
use imap_codec::types::core::Tag;
use tower::Service;

use super::pipeline::Connection;
use super::Imap;
use crate::proto::{Request, Response};

#[pin_project::pin_project]
pub struct Connecting<C, F, S> {
    pub conn: Connection<C>,
    #[pin]
    pub state: ConnectingState<F, S>,
    pub protocol: Imap,
}

#[pin_project::pin_project(project = ConnectingStateProj)]
pub enum ConnectingState<F, S> {
    Waiting {
        #[pin]
        service_fut: F,
    },
    Ready {
        service: S,
    },
}

impl<C, F, ME, S> Future for Connecting<C, F, S>
where
    C: AsyncRead + AsyncWrite + Unpin,
    F: Future<Output = std::result::Result<S, ME>>,
    ME: std::fmt::Display,
    S: Service<Request, Response = Response>,
    S::Future: Send + 'static,
    S::Error: std::fmt::Display,
{
    type Output = ();

    fn poll(self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<Self::Output> {
        use tokio_tower::pipeline::Server as PipelineServer;

        let mut this = self.project();

        loop {
            let next = match this.state.as_mut().project() {
                ConnectingStateProj::Waiting { service_fut } => {
                    let service = match futures::ready!(service_fut.poll(cx)) {
                        Ok(service) => service,
                        Err(err) => {
                            tracing::error!("Connection error: {}", err);
                            return Poll::Ready(());
                        }
                    };

                    // TODO: Properly handle server greeting
                    {
                        use futures::SinkExt;

                        let greeting = Response::ok("Hello").unwrap(); // "Hello" is a valid
                                                                       // greeting
                        this.conn.start_send_unpin((None, greeting)).unwrap();
                    }

                    ConnectingState::Ready { service }
                }
                ConnectingStateProj::Ready { service } => {
                    let server = PipelineServer::new(this.conn, PipelineService { inner: service });
                    futures::pin_mut!(server);

                    return server.poll(cx).map(|res| {
                        if let Err(err) = res {
                            tracing::debug!("Connection error: {}", err);
                        }
                    });
                }
            };

            this.state.set(next);
        }
    }
}

struct PipelineService<S> {
    inner: S,
}

impl<S> Service<Request> for PipelineService<S>
where
    S: Service<Request>,
    S::Future: Send + 'static,
{
    type Response = (Option<Tag>, S::Response);
    type Error = S::Error;
    type Future = futures::future::BoxFuture<'static, Result<Self::Response, Self::Error>>;

    fn poll_ready(&mut self, cx: &mut task::Context<'_>) -> Poll<Result<(), Self::Error>> {
        self.inner.poll_ready(cx)
    }

    fn call(&mut self, req: Request) -> Self::Future {
        use futures::{FutureExt, TryFutureExt};

        let tag = req.tag.clone();

        self.inner.call(req).map_ok(|res| (Some(tag), res)).boxed()
    }
}