//! Management for flow control windows.

//!

//! Tor maintains a separate windows on circuits and on streams.

//! These are controlled by SENDME cells, which (confusingly) are

//! applied either at the circuit or the stream level depending on

//! whether they have a stream ID set.

//!

//! Circuit sendmes are _authenticated_: they include a cryptographic

//! tag generated by the cryptography layer.  This tag proves that the

//! other side of the circuit really has read all of the data that it's

//! acknowledging.

use std::collections::VecDeque;

use tor_cell::relaycell::RelayCmd;

use tor_cell::relaycell::UnparsedRelayMsg;

use tor_error::internal;

use crate::{Error, Result};

/// A circuit's send window.

pub(crate) type CircSendWindow = SendWindow<CircParams>;

/// A stream's send window.

pub(crate) type StreamSendWindow = SendWindow<StreamParams>;

/// A circuit's receive window.

pub(crate) type CircRecvWindow = RecvWindow<CircParams>;

/// A stream's receive window.

pub(crate) type StreamRecvWindow = RecvWindow<StreamParams>;

/// Tracks how many cells we can safely send on a circuit or stream.

///

/// Additionally, remembers a list of tags that could be used to

/// acknowledge the cells we have already sent, so we know it's safe

/// to send more.

#[derive(Clone, Debug)]

pub(crate) struct SendWindow<P>

where

    P: WindowParams,

{

    /// Current value for this window

    window: u16,

    /// Marker type to tell the compiler that the P type is used.

    _dummy: std::marker::PhantomData<P>,

}

/// Helper: parametrizes a window to determine its maximum and its increment.

pub(crate) trait WindowParams {

    /// Largest allowable value for this window.

    #[allow(dead_code)] // TODO #1383 failure to ever use this is probably a bug

    fn maximum() -> u16;

    /// Increment for this window.

    fn increment() -> u16;

    /// The default starting value.

    fn start() -> u16;

}

/// Parameters used for SENDME windows on circuits: limit at 1000 cells,

/// and each SENDME adjusts by 100.

#[derive(Clone, Debug)]

pub(crate) struct CircParams;

impl WindowParams for CircParams {

}

/// Parameters used for SENDME windows on streams: limit at 500 cells,

/// and each SENDME adjusts by 50.

#[derive(Clone, Debug)]

pub(crate) struct StreamParams;

impl WindowParams for StreamParams {

}

/// Object used to validate SENDMEs as in managing the authenticated tag and verifying it.

#[derive(Clone, Debug)]

pub(crate) struct SendmeValidator<T>

where

    T: PartialEq + Eq + Clone,

{

    /// Tag values that incoming "SENDME" messages need to match in order

    /// for us to send more data.

    tags: VecDeque<T>,

}

impl<T> SendmeValidator<T>

where

    T: PartialEq + Eq + Clone,

{

    /// Constructor

    /// Record a SENDME tag for future validation once we receive it.

    /// Validate a received tag (if any). A mismatch leads to a protocol violation and the circuit

    /// MUST be closed.

            (Some(_), Some(_)) => {

            }

            (None, _) => {

            }

        }

    #[cfg(test)]

}

impl<P> SendWindow<P>

where

    P: WindowParams,

{

    /// Construct a new SendWindow.

    /// Return true iff the SENDME tag should be recorded.

    /// Remove one item from this window (since we've sent a cell).

    /// If the window was empty, returns an error.

    /// Handle an incoming sendme.

    ///

    /// On failure, return an error: the caller must close the circuit due to a protocol violation.

    #[must_use = "didn't check whether SENDME was expected."]

        // Overflow check.

        // Make sure we never go above our maximum else this wasn't expected.

    /// Return the current send window value.

}

/// Structure to track when we need to send SENDME cells for incoming data.

#[derive(Clone, Debug)]

pub(crate) struct RecvWindow<P: WindowParams> {

    /// Number of cells that we'd be willing to receive on this window

    /// before sending a SENDME.

    window: u16,

    /// Marker type to tell the compiler that the P type is used.

    _dummy: std::marker::PhantomData<P>,

}

impl<P: WindowParams> RecvWindow<P> {

    /// Create a new RecvWindow.

    /// Called when we've just received a cell; return true if we need to send

    /// a sendme, and false otherwise.

    ///

    /// Returns None if we should not have sent the cell, and we just

    /// violated the window.

        } else {

        }

    /// Reduce this window by `n`; give an error if this is not possible.

    /// Called when we've just sent a SENDME.

}

/// Return true if this message type is counted by flow-control windows.

/// Return true if this message is counted by flow-control windows.

#[cfg(test)]

    use tor_cell::relaycell::RelayMsg;

/// Return true if this message is counted by flow-control windows.

#[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_duration_subtraction)]

    #![allow(clippy::useless_vec)]

    #![allow(clippy::needless_pass_by_value)]

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

    use super::*;

    use tor_basic_utils::test_rng::testing_rng;

    use tor_cell::relaycell::{msg, AnyRelayMsgOuter, RelayCellFormat, StreamId};

    #[test]

    fn what_counts() {

        let mut rng = testing_rng();

        let fmt = RelayCellFormat::V0;

        let m = msg::Begin::new("www.torproject.org", 443, 0)

            .unwrap()

            .into();

        assert!(!msg_counts_towards_windows(&m));

        assert!(!cell_counts_towards_windows(

            &UnparsedRelayMsg::from_singleton_body(

                RelayCellFormat::V0,

                AnyRelayMsgOuter::new(StreamId::new(77), m)

                    .encode(fmt, &mut rng)

                    .unwrap()

            )

            .unwrap()

        ));

        let m = msg::Data::new(&b"Education is not a prerequisite to political control-political control is the cause of popular education."[..]).unwrap().into(); // Du Bois

        assert!(msg_counts_towards_windows(&m));

        assert!(cell_counts_towards_windows(

            &UnparsedRelayMsg::from_singleton_body(

                RelayCellFormat::V0,

                AnyRelayMsgOuter::new(StreamId::new(128), m)

                    .encode(fmt, &mut rng)

                    .unwrap()

            )

            .unwrap()

        ));

    }

    #[test]

    fn recvwindow() {

        let mut w: RecvWindow<StreamParams> = RecvWindow::new(500);

        for _ in 0..49 {

            assert!(!w.take().unwrap());

        }

        assert!(w.take().unwrap());

        assert_eq!(w.window, 450);

        assert!(w.decrement_n(123).is_ok());

        assert_eq!(w.window, 327);

        w.put();

        assert_eq!(w.window, 377);

        // failing decrement.

        assert!(w.decrement_n(400).is_err());

        // failing take.

        assert!(w.decrement_n(377).is_ok());

        assert!(w.take().is_err());

    }

    fn new_sendwindow() -> SendWindow<CircParams> {

        SendWindow::new(1000)

    }

    #[test]

    fn sendwindow_basic() -> Result<()> {

        let mut w = new_sendwindow();

        w.take()?;

        assert_eq!(w.window(), 999);

        for _ in 0_usize..98 {

            w.take()?;

        }

        assert_eq!(w.window(), 901);

        w.take()?;

        assert_eq!(w.window(), 900);

        w.take()?;

        assert_eq!(w.window(), 899);

        // Try putting a good tag.

        w.put()?;

        assert_eq!(w.window(), 999);

        for _ in 0_usize..300 {

            w.take()?;

        }

        // Put without a tag.

        w.put()?;

        assert_eq!(w.window(), 799);

        Ok(())

    }

    #[test]

    fn sendwindow_erroring() -> Result<()> {

        let mut w = new_sendwindow();

        for _ in 0_usize..1000 {

            w.take()?;

        }

        assert_eq!(w.window(), 0);

        let ready = w.take();

        assert!(ready.is_err());

        Ok(())

    }

}