use futures::FutureExt;
use libp2p_core::muxing::{StreamMuxer, StreamMuxerEvent};
use libp2p_core::{OutboundUpgrade, UpgradeInfo};
use libp2p_identity::{Keypair, PeerId};
use multihash::Multihash;
use send_wrapper::SendWrapper;
use std::collections::HashSet;
use std::future::poll_fn;
use std::pin::Pin;
use std::task::{ready, Context, Poll};
use wasm_bindgen_futures::JsFuture;
use web_sys::ReadableStreamDefaultReader;

use crate::bindings::{WebTransport, WebTransportBidirectionalStream};
use crate::endpoint::Endpoint;
use crate::fused_js_promise::FusedJsPromise;
use crate::utils::{detach_promise, parse_reader_response, to_js_type};
use crate::{Error, Stream};

/// An opened WebTransport connection.
#[derive(Debug)]
pub struct Connection {
    // Swarm needs all types to be Send. WASM is single-threaded
    // and it is safe to use SendWrapper.
    inner: SendWrapper<ConnectionInner>,
}

#[derive(Debug)]
struct ConnectionInner {
    session: WebTransport,
    create_stream_promise: FusedJsPromise,
    incoming_stream_promise: FusedJsPromise,
    incoming_streams_reader: ReadableStreamDefaultReader,
    closed: bool,
}

impl Connection {
    pub(crate) fn new(endpoint: &Endpoint) -> Result<Self, Error> {
        let url = endpoint.url();

        let session = if endpoint.certhashes.is_empty() {
            // Endpoint has CA-signed TLS certificate.
            WebTransport::new(&url).map_err(Error::from_js_value)?
        } else {
            // Endpoint has self-signed TLS certificates.
            let opts = endpoint.webtransport_opts();
            WebTransport::new_with_options(&url, &opts).map_err(Error::from_js_value)?
        };

        let incoming_streams = session.incoming_bidirectional_streams();
        let incoming_streams_reader =
            to_js_type::<ReadableStreamDefaultReader>(incoming_streams.get_reader())?;

        Ok(Connection {
            inner: SendWrapper::new(ConnectionInner {
                session,
                create_stream_promise: FusedJsPromise::new(),
                incoming_stream_promise: FusedJsPromise::new(),
                incoming_streams_reader,
                closed: false,
            }),
        })
    }

    pub(crate) async fn authenticate(
        &mut self,
        keypair: &Keypair,
        remote_peer: Option<PeerId>,
        certhashes: HashSet<Multihash<64>>,
    ) -> Result<PeerId, Error> {
        let fut = SendWrapper::new(self.inner.authenticate(keypair, remote_peer, certhashes));
        fut.await
    }
}

impl ConnectionInner {
    /// Authenticates with the server
    ///
    /// This methods runs the security handshake as descripted
    /// in the [spec][1]. It validates the certhashes and peer ID
    /// of the server.
    ///
    /// [1]: https://github.com/libp2p/specs/tree/master/webtransport#security-handshake
    async fn authenticate(
        &mut self,
        keypair: &Keypair,
        remote_peer: Option<PeerId>,
        certhashes: HashSet<Multihash<64>>,
    ) -> Result<PeerId, Error> {
        JsFuture::from(self.session.ready())
            .await
            .map_err(Error::from_js_value)?;

        let stream = poll_fn(|cx| self.poll_create_bidirectional_stream(cx)).await?;
        let mut noise = libp2p_noise::Config::new(keypair)?;

        if !certhashes.is_empty() {
            noise = noise.with_webtransport_certhashes(certhashes);
        }

        // We do not use `upgrade::apply_outbound` function because it uses
        // `multistream_select` protocol, which is not used by WebTransport spec.
        let info = noise.protocol_info().next().unwrap_or_default();
        let (peer_id, _io) = noise.upgrade_outbound(stream, info).await?;

        // TODO: This should be part libp2p-noise
        if let Some(expected_peer_id) = remote_peer {
            if peer_id != expected_peer_id {
                return Err(Error::UnknownRemotePeerId);
            }
        }

        Ok(peer_id)
    }

    /// Initiates and polls a promise from `create_bidirectional_stream`.
    fn poll_create_bidirectional_stream(
        &mut self,
        cx: &mut Context,
    ) -> Poll<Result<Stream, Error>> {
        // Create bidirectional stream
        let val = ready!(self
            .create_stream_promise
            .maybe_init(|| self.session.create_bidirectional_stream())
            .poll_unpin(cx))
        .map_err(Error::from_js_value)?;

        let bidi_stream = to_js_type::<WebTransportBidirectionalStream>(val)?;
        let stream = Stream::new(bidi_stream)?;

        Poll::Ready(Ok(stream))
    }

    /// Polls for incoming stream from `incoming_bidirectional_streams` reader.
    fn poll_incoming_bidirectional_streams(
        &mut self,
        cx: &mut Context,
    ) -> Poll<Result<Stream, Error>> {
        // Read the next incoming stream from the JS channel
        let val = ready!(self
            .incoming_stream_promise
            .maybe_init(|| self.incoming_streams_reader.read())
            .poll_unpin(cx))
        .map_err(Error::from_js_value)?;

        let val = parse_reader_response(&val)
            .map_err(Error::from_js_value)?
            .ok_or_else(|| Error::JsError("incoming_bidirectional_streams closed".to_string()))?;

        let bidi_stream = to_js_type::<WebTransportBidirectionalStream>(val)?;
        let stream = Stream::new(bidi_stream)?;

        Poll::Ready(Ok(stream))
    }

    /// Closes the session.
    ///
    /// This closes the streams also and they will return an error
    /// when they will be used.
    fn close_session(&mut self) {
        if !self.closed {
            detach_promise(self.incoming_streams_reader.cancel());
            self.session.close();
            self.closed = true;
        }
    }
}

impl Drop for ConnectionInner {
    fn drop(&mut self) {
        self.close_session();
    }
}

/// WebTransport native multiplexing
impl StreamMuxer for Connection {
    type Substream = Stream;
    type Error = Error;

    fn poll_inbound(
        mut self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<Self::Substream, Self::Error>> {
        self.inner.poll_incoming_bidirectional_streams(cx)
    }

    fn poll_outbound(
        mut self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<Self::Substream, Self::Error>> {
        self.inner.poll_create_bidirectional_stream(cx)
    }

    fn poll_close(
        mut self: Pin<&mut Self>,
        _cx: &mut Context<'_>,
    ) -> Poll<Result<(), Self::Error>> {
        self.inner.close_session();
        Poll::Ready(Ok(()))
    }

    fn poll(
        self: Pin<&mut Self>,
        _cx: &mut Context<'_>,
    ) -> Poll<Result<StreamMuxerEvent, Self::Error>> {
        Poll::Pending
    }
}