// Coming from https://github.com/hyperium/h3, the goal is to
// do a PR with the changes afterwards

use std::task::{self, Poll};
use bytes::Buf;
use anyhow::Error;

type ErrorCode = u64;
type StreamId = u64;

/// Trait representing a QUIC connection.
pub trait Connection {
    /// The type produced by `poll_accept_bidi()`
    type BidiStream: SendStream + RecvStream;
    /// The type of the sending part of `BidiStream`
    type SendStream: SendStream;
    /// The type produced by `poll_accept_recv()`
    type RecvStream: RecvStream;
    /// A producer of outgoing Unidirectional and Bidirectional streams.
    type OpenStreams: OpenStreams<
        SendStream = Self::SendStream,
        RecvStream = Self::RecvStream,
        BidiStream = Self::BidiStream,
    >;

    /// Accept an incoming unidirectional stream
    ///
    /// Returning `None` implies the connection is closing or closed.
    fn poll_accept_recv(
        &mut self,
        cx: &mut task::Context<'_>,
    ) -> Poll<Result<Option<Self::RecvStream>, Error>>;

    /// Accept an incoming bidirectional stream
    ///
    /// Returning `None` implies the connection is closing or closed.
    fn poll_accept_bidi(
        &mut self,
        cx: &mut task::Context<'_>,
    ) -> Poll<Result<Option<Self::BidiStream>, Error>>;

    /// Poll the connection to create a new bidirectional stream.
    fn poll_open_bidi(
        &mut self,
        cx: &mut task::Context<'_>,
    ) -> Poll<Result<Self::BidiStream, Error>>;

    /// Poll the connection to create a new unidirectional stream.
    fn poll_open_send(
        &mut self,
        cx: &mut task::Context<'_>,
    ) -> Poll<Result<Self::SendStream, Error>>;

    /// Get an object to open outgoing streams.
    fn opener(&self) -> Self::OpenStreams;

    /// Close the connection immediately
    fn close(&mut self, code: ErrorCode, reason: &[u8]);
}

/// Trait for opening outgoing streams
pub trait OpenStreams {
    /// The type produced by `poll_open_bidi()`
    type BidiStream: SendStream + RecvStream;
    /// The type produced by `poll_open_send()`
    type SendStream: SendStream;
    /// The type of the receiving part of `BidiStream`
    type RecvStream: RecvStream;

    /// Poll the connection to create a new bidirectional stream.
    fn poll_open_bidi(
        &mut self,
        cx: &mut task::Context<'_>,
    ) -> Poll<Result<Self::BidiStream, Error>>;

    /// Poll the connection to create a new unidirectional stream.
    fn poll_open_send(
        &mut self,
        cx: &mut task::Context<'_>,
    ) -> Poll<Result<Self::SendStream, Error>>;

    /// Close the connection immediately
    fn close(&mut self, code: ErrorCode, reason: &[u8]);
}

/// A trait describing the "send" actions of a QUIC stream.
pub trait SendStream {

    /// Polls if the stream can send more data.
    fn poll_ready(&mut self, cx: &mut task::Context<'_>) -> Poll<Result<(), Error>>;

    /// Poll to finish the sending side of the stream.
    fn poll_finish(&mut self, cx: &mut task::Context<'_>) -> Poll<Result<(), Error>>;

    /// Send a QUIC reset code.
    fn reset(&mut self, reset_code: u64);

    /// Get QUIC send stream id
    fn send_id(&self) -> StreamId;
}

/// Allows sending unframed pure bytes to a stream. Similar to [`AsyncWrite`](https://docs.rs/tokio/latest/tokio/io/trait.AsyncWrite.html)
pub trait SendStreamUnframed<B: Buf>: SendStream {
    /// Attempts write data into the stream.
    ///
    /// Returns the number of bytes written.
    ///
    /// `buf` is advanced by the number of bytes written.
    fn poll_send<D: Buf>(
        &mut self,
        cx: &mut task::Context<'_>,
        buf: &mut D,
    ) -> Poll<Result<usize, Error>>;
}

/// A trait describing the "receive" actions of a QUIC stream.
pub trait RecvStream {
    /// The type of `Buf` for data received on this stream.
    type Buf: Buf;
    /// The error type that can occur when receiving data.
    type Error: Into<Box<Error>>;

    /// Poll the stream for more data.
    ///
    /// When the receive side will no longer receive more data (such as because
    /// the peer closed their sending side), this should return `None`.
    fn poll_data(
        &mut self,
        cx: &mut task::Context<'_>,
    ) -> Poll<Result<Option<Self::Buf>, Error>>;

    /// Send a `STOP_SENDING` QUIC code.
    fn stop_sending(&mut self, error_code: u64);

    /// Get QUIC send stream id
    fn recv_id(&self) -> StreamId;
}

/// Optional trait to allow "splitting" a bidirectional stream into two sides.
pub trait BidiStream<B: Buf>: SendStream + RecvStream {
    /// The type for the send half.
    type SendStream: SendStream;
    /// The type for the receive half.
    type RecvStream: RecvStream;

    /// Split this stream into two halves.
    fn split(self) -> (Self::SendStream, Self::RecvStream);
}