//! This module contains a WIP relay tunnel reactor.

//!

//! The initial version will duplicate some of the logic from

//! the client tunnel reactor.

//!

//! TODO(relay): refactor the relay tunnel

//! to share the same base tunnel implementation

//! as the client tunnel (to reduce code duplication).

//!

//! See the design notes at doc/dev/notes/relay-reactor.md

pub(crate) mod channel;

#[allow(unreachable_pub)] // TODO(relay): use in tor-chanmgr(?)

pub mod channel_provider;

pub(crate) mod reactor;

pub use channel::MaybeVerifiableRelayResponderChannel;

pub use channel::create_handler::{

    CircNetParameters, CongestionControlNetParams, CreateRequestHandler,

};

use derive_deftly::Deftly;

use futures::StreamExt as _;

use oneshot_fused_workaround as oneshot;

use tor_cell::chancell::msg::{self as chanmsg};

use tor_cell::relaycell::StreamId;

use tor_cell::relaycell::flow_ctrl::XonKbpsEwma;

use tor_memquota::derive_deftly_template_HasMemoryCost;

use tor_memquota::mq_queue::{ChannelSpec as _, MpscSpec};

use crate::Error;

use crate::circuit::celltypes::derive_deftly_template_RestrictedChanMsgSet;

use crate::circuit::circhop::ReactorStreamComponents;

use crate::circuit::reactor::CircReactorHandle;

use crate::circuit::reactor::{CtrlCmd, forward};

use crate::congestion::sendme::StreamRecvWindow;

use crate::memquota::SpecificAccount;

use crate::relay::reactor::backward::Backward;

use crate::relay::reactor::forward::Forward;

use crate::stream::flow_ctrl::xon_xoff::reader::XonXoffReaderCtrl;

use crate::stream::incoming::{

    IncomingCmdChecker, IncomingStream, IncomingStreamRequestFilter, StreamReqInfo,

};

use crate::stream::raw::StreamReceiver;

use crate::stream::{RECV_WINDOW_INIT, StreamComponents, StreamTarget, Tunnel};

use std::sync::Arc;

/// A subclass of ChanMsg that can correctly arrive on a live relay

/// circuit (one where a CREATE* has been received).

#[derive(Debug, Deftly)]

#[derive_deftly(HasMemoryCost)]

#[derive_deftly(RestrictedChanMsgSet)]

#[deftly(usage = "on an open relay circuit")]

#[cfg(feature = "relay")]

#[cfg_attr(not(test), allow(unused))] // TODO(relay)

pub(crate) enum RelayCircChanMsg {

    /// A relay cell telling us some kind of remote command from some

    /// party on the circuit.

    Relay(chanmsg::Relay),

    /// A relay early cell that is allowed to contain a CREATE message.

    RelayEarly(chanmsg::RelayEarly),

    /// A cell telling us to destroy the circuit.

    Destroy(chanmsg::Destroy),

    /// A cell telling us to enable/disable channel padding.

    PaddingNegotiate(chanmsg::PaddingNegotiate),

}

/// A handle for interacting with a relay circuit.

#[allow(unused)] // TODO(relay)

#[derive(Debug)]

pub struct RelayCirc(pub(crate) CircReactorHandle<Forward, Backward>);

impl RelayCirc {

    /// Shut down this circuit, along with all streams that are using it.

    /// Happens asynchronously (i.e. the tunnel won't necessarily be done shutting down

    /// immediately after this function returns!).

    ///

    /// Note that other references to this tunnel may exist.

    /// If they do, they will stop working after you call this function.

    ///

    /// It's not necessary to call this method if you're just done with a circuit:

    /// the circuit should close on its own once nothing is using it any more.

    /// Return true if this circuit is closed and therefore unusable.

    /// Inform the circuit reactor that there has been a change in the drain rate for this stream.

    ///

    /// Typically the circuit reactor would send this new rate in an XON message to the other end of

    /// the stream.

    /// But it may decide not to, and may discard this update.

    /// For example the stream may have a large amount of buffered data, and the reactor may not

    /// want to send an XON while the buffer is large.

    ///

    /// This sends a message to inform the circuit reactor of the new drain rate,

    /// but it does not block or wait for a response from the reactor.

    /// An error is only returned if we are unable to send the update.

    //

    // TODO(relay): this duplicates the ClientTunnel API and docs. Do we care?

    }

    /// Request to send a SENDME cell for this stream.

    ///

    /// This sends a request to the circuit reactor to send a stream-level SENDME, but it does not

    /// block or wait for a response from the circuit reactor.

    /// An error is only returned if we are unable to send the request.

    /// This means that if the circuit reactor is unable to send the SENDME, we are not notified of

    /// this here and an error will not be returned.

    //

    // TODO(relay): this duplicates the ClientTunnel API and docs. Do we care?

    }

    /// Close the pending stream that owns this StreamTarget, delivering the specified

    /// END message (if any)

    ///

    /// The stream is closed by sending a control message (`ClosePendingStream`)

    /// to the reactor.

    ///

    /// Returns a [`oneshot::Receiver`] that can be used to await the reactor's response.

    ///

    /// The StreamTarget will set the correct stream ID and pick the

    /// right hop, but will not validate that the message is well-formed

    /// or meaningful in context.

    ///

    /// Note that in many cases, the actual contents of an END message can leak unwanted

    /// information. Please consider carefully before sending anything but an

    /// [`End::new_misc()`](tor_cell::relaycell::msg::End::new_misc) message over a `ClientTunnel`.

    /// (For onion services, we send [`DONE`](tor_cell::relaycell::msg::EndReason::DONE) )

    ///

    /// In addition to sending the END message, this function also ensures

    /// the state of the stream map entry of this stream is updated

    /// accordingly.

    ///

    /// Normally, you shouldn't need to call this function, as streams are implicitly closed by the

    /// reactor when their corresponding `StreamTarget` is dropped. The only valid use of this

    /// function is for closing pending incoming streams (a stream is said to be pending if we have

    /// received the message initiating the stream but have not responded to it yet).

    ///

    /// **NOTE**: This function should be called at most once per request.

    /// Calling it twice is an error.

    //

    // TODO(relay): this duplicates the ClientTunnel API and docs. Do we care?

    }

    /// Tell this reactor to begin allowing incoming stream requests,

    /// and to return those pending requests in an asynchronous stream.

    ///

    /// Ordinarily, these requests are rejected.

    ///

    /// Needed for exits. Middle relays should reject every incoming stream,

    /// either through the `filter` provided in `filter`,

    /// or by explicitly calling .reject() on each received stream.

    ///

    // TODO(relay): I think we will prefer using the .reject() approach

    // for this, because the filter is only meant for inexpensive quick

    // checks that are done immediately in the reactor (any blocking

    // in the filter will block the relay reactor main loop!).

    ///

    /// The user of the reactor **must** handle this stream

    /// (either by .accept()ing and opening and proxying the corresponding

    /// streams as appropriate, or by .reject()ing).

    ///

    // TODO: declare a type-alias for the return type when support for

    // impl in type aliases gets stabilized.

    //

    // See issue #63063 <https://github.com/rust-lang/rust/issues/63063>

    //

    /// There can only be one [`Stream`](futures::Stream) of this type created on a given reactor.

    /// If a such a [`Stream`](futures::Stream) already exists, this method will return

    /// an error.

    ///

    /// After this method has been called on a reactor, the reactor is expected

    /// to receive requests of this type indefinitely, until it is finally closed.

    /// If the `Stream` is dropped, the next request on this reactor will cause it to close.

    ///

    // TODO: Someday, we might want to allow a stream request handler to be

    // un-registered.  However, nothing in the Tor protocol requires it.

    //

    // TODO(DEDUP): *very* similar to ServiceOnionServiceDataTunnel::allow_stream_requests

    #[allow(unused)] // TODO(relay): call this from the task that creates the circ

        /// The size of the channel receiving IncomingStreamRequestContexts.

        ///

        // TODO(relay-tuning): buffer size

        const INCOMING_BUFFER: usize = crate::stream::STREAM_READER_BUFFER;

        // Check whether the AwaitStreamRequest was processed successfully.

        // TODO(relay): this is more or less copy-pasta from client code

            let StreamReqInfo {

                stream_components:

                    ReactorStreamComponents {

                    },

            // There is no originating hop if we're a relay

            // can be used to build a reader that supports XON/XOFF flow control

}

#[cfg(test)]

mod test {

    // @@ begin test lint list maintained by maint/add_warning @@

    #![allow(clippy::bool_assert_comparison)]

    #![allow(clippy::clone_on_copy)]

    #![allow(clippy::dbg_macro)]

    #![allow(clippy::mixed_attributes_style)]

    #![allow(clippy::print_stderr)]

    #![allow(clippy::print_stdout)]

    #![allow(clippy::single_char_pattern)]

    #![allow(clippy::unwrap_used)]

    #![allow(clippy::unchecked_time_subtraction)]

    #![allow(clippy::useless_vec)]

    #![allow(clippy::needless_pass_by_value)]

    #![allow(clippy::string_slice)] // See arti#2571

    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->

    #[test]

    fn relay_circ_chan_msg() {

        use tor_cell::chancell::msg::{self, AnyChanMsg};

        fn good(m: AnyChanMsg) {

            use crate::relay::RelayCircChanMsg;

            assert!(RelayCircChanMsg::try_from(m).is_ok());

        }

        fn bad(m: AnyChanMsg) {

            use crate::relay::RelayCircChanMsg;

            assert!(RelayCircChanMsg::try_from(m).is_err());

        }

        good(msg::Destroy::new(2.into()).into());

        bad(msg::CreatedFast::new(&b"The great globular mass"[..]).into());

        bad(msg::Created2::new(&b"of protoplasmic slush"[..]).into());

        good(msg::Relay::new(&b"undulated slightly,"[..]).into());

        good(msg::AnyChanMsg::RelayEarly(

            msg::Relay::new(&b"as if aware of him"[..]).into(),

        ));

        bad(msg::Versions::new([1, 2, 3]).unwrap().into());

        good(msg::PaddingNegotiate::start_default().into());

        good(msg::RelayEarly::from(msg::Relay::new(b"snail-like unipedular organism")).into());

    }

}