//! Code for exporting events from the channel manager.

#![allow(dead_code, unreachable_pub)]

use educe::Educe;

use futures::{Stream, StreamExt};

use postage::watch;

use std::fmt;

use tor_basic_utils::skip_fmt;

use web_time_compat::{Duration, Instant, InstantExt};

/// The status of our connection to the internet.

#[derive(Default, Debug, Clone)]

pub struct ConnStatus {

    /// Have we been able to make TCP connections?

    ///

    /// True if we've been able to make outgoing connections recently.

    /// False if we've definitely been failing.

    /// None if we haven't succeeded yet, but it's too early to say if

    /// that's a problem.

    online: Option<bool>,

    /// Have we ever been able to make TLS handshakes and negotiate

    /// certificates, _not including timeliness checking_?

    ///

    /// True if we've been able to make TLS handshakes and talk to Tor relays we

    /// like recently. False if we've definitely been failing. None if we

    /// haven't succeeded yet, but it's too early to say if that's a problem.

    auth_works: Option<bool>,

    /// Have we been able to successfully negotiate full Tor handshakes?

    ///

    /// True if we've been able to make Tor handshakes recently.

    /// False if we've definitely been failing.

    /// None if we haven't succeeded yet, but it's too early to say if

    /// that's a problem.

    handshake_works: Option<bool>,

}

/// A problem detected while connecting to the Tor network.

#[derive(Debug, Clone, Eq, PartialEq, derive_more::Display)]

#[non_exhaustive]

pub enum ConnBlockage {

    #[display("unable to connect to the internet")]

    /// We haven't been able to make successful TCP connections.

    NoTcp,

    /// We've made TCP connections, but our TLS connections either failed, or

    /// got hit by an attempted man-in-the-middle attack.

    #[display("our internet connection seems to be filtered")]

    NoHandshake,

    /// We've made TCP connections, and our TLS connections mostly succeeded,

    /// but we encountered failures that are well explained by clock skew,

    /// or expired certificates.

    #[display("relays all seem to be using expired certificates")]

    CertsExpired,

}

impl ConnStatus {

    /// Return true if this status is equal to `other`.

    ///

    /// Note:(This would just be a PartialEq implementation, but I'm not sure I

    /// want to expose that PartialEq for this struct.)

    /// Return true if this status indicates that we can successfully open Tor channels.

    /// Return a float representing "how bootstrapped" we are with respect to

    /// connecting to the Tor network, where 0 is "not at all" and 1 is

    /// "successful".

    ///

    /// Callers _should not_ depend on the specific meaning of any particular

    /// fraction; we may change these fractions in the future.

            Self {

                online: Some(true),

                auth_works: Some(true),

                handshake_works: Some(true),

            Self {

                online: Some(true), ..

        }

    /// Return the cause of why we aren't able to connect to the Tor network,

    /// if we think we're stuck.

            Self {

                online: Some(false),

                ..

            Self {

                auth_works: Some(false),

                ..

            Self {

                handshake_works: Some(false),

                ..

        }

}

impl fmt::Display for ConnStatus {

            ConnStatus {

                online: Some(false),

                ..

            ConnStatus {

                handshake_works: None,

                ..

            ConnStatus {

                auth_works: Some(true),

                handshake_works: Some(false),

                ..

            ),

            ConnStatus {

                handshake_works: Some(false),

                ..

            ConnStatus {

                online: Some(true),

                handshake_works: Some(true),

                ..

        }

}

/// A stream of [`ConnStatus`] events describing changes in our connected-ness.

///

/// This stream is lossy; a reader might not see some events on the stream, if

/// they are produced faster than the reader can consume.  In that case, the

/// reader will see more recent updates, and miss older ones.

///

/// Note that the bootstrap status is not monotonic: we might become less

/// bootstrapped than we were before.  (For example, the internet could go

/// down.)

#[derive(Clone, Educe)]

#[educe(Debug)]

pub struct ConnStatusEvents {

    /// The receiver that implements this stream.

    ///

    /// (We wrap it in a new type here so that we can replace the implementation

    /// later on if we need to.)

    #[educe(Debug(method = "skip_fmt"))]

    inner: watch::Receiver<ConnStatus>,

}

impl Stream for ConnStatusEvents {

    type Item = ConnStatus;

}

/// Crate-internal view of "how connected are we to the internet?"

///

/// This is a more complex and costly structure than ConnStatus, so we track

/// this here, and only expose the minimum via ConnStatus over a

/// `postage::watch`.  Later, we might want to expose more of this information.

//

// TODO: Eventually we should add some ability to reset our bootstrap status, if

// our connections start failing.

#[derive(Debug, Clone)]

struct ChanMgrStatus {

    /// When did we first get initialized?

    startup: Instant,

    /// Since we started, how many channels have we tried to build?

    n_attempts: usize,

    /// When (if ever) have we made a TCP connection to (what we hoped was) a

    /// Tor relay?

    ///

    /// If we don't reach this point, we're probably not on the internet.

    ///

    /// If we get no further than this, we're probably having our TCP

    /// connections captured or replaced.

    last_tcp_success: Option<Instant>,

    /// When (if ever) have we successfully finished a TLS handshake to (what we

    /// hoped was) a Tor relay?

    ///

    /// If we get no further than this, we might be facing a TLS MITM attack.

    //

    // TODO: We don't actually use this information yet: our output doesn't

    // distinguish filtering where TLS succeeds but gets MITM'd from filtering

    // where TLS fails.

    last_tls_success: Option<Instant>,

    /// When (if ever) have we ever finished the inner Tor handshake with a relay,

    /// up to the point where we check for certificate timeliness?

    last_chan_auth_success: Option<Instant>,

    /// When (if ever) have we successfully finished the inner Tor handshake

    /// with a relay?

    ///

    /// If we get to this point, we can successfully talk to something that

    /// holds the private key that it's supposed to.

    last_chan_success: Option<Instant>,

}

impl ChanMgrStatus {

    /// Construct a new ChanMgr status.

    ///

    /// It will be built as having been initialized at the time `now`.

    /// Return a [`ConnStatus`] for the current state, at time `now`.

    ///

    /// (The time is necessary because a lack of success doesn't indicate a

    /// problem until enough time has passed.)

        /// How long do we need to be online before we'll acknowledge failure?

        const MIN_DURATION: Duration = Duration::from_secs(60);

        /// How many attempts do we need to launch before we'll acknowledge failure?

        const MIN_ATTEMPTS: usize = 6;

        // If set, it's too early to determine failure.

        };

        };

        };

    /// Note that an attempt to connect has been started.

    /// Note that we've successfully done a TCP handshake with an alleged relay.

    /// Note that we've completed a TLS handshake with an alleged relay.

    ///

    /// (Its identity won't be verified till the next step.)

    /// Note that we've completed a Tor handshake with a relay, _but failed to

    /// verify the certificates in a way that could indicate clock skew_.

    /// Note that we've completed a Tor handshake with a relay.

    ///

    /// (This includes performing the TLS handshake, and verifying that the

    /// relay was indeed the one that we wanted to reach.)

}

/// Object that manages information about a `ChanMgr`'s status, and sends

/// information about connectivity changes over an asynchronous channel

pub(crate) struct ChanMgrEventSender {

    /// The last ConnStatus that we sent over the channel.

    last_conn_status: ConnStatus,

    /// The unsummarized status information from the ChanMgr.

    mgr_status: ChanMgrStatus,

    /// The channel that we use for sending ConnStatus information.

    sender: watch::Sender<ConnStatus>,

}

impl ChanMgrEventSender {

    /// If the status has changed as of `now`, tell any listeners.

    ///

    /// (This takes a time because we need to know how much time has elapsed

    /// without successful attempts.)

    ///

    /// # Limitations

    ///

    /// We are dependent on calls to `record_attempt()` and similar methods to

    /// actually invoke this function; if they were never called, we'd never

    /// notice that we had gone too long without building connections.  That's

    /// okay for now, though, since any Tor client will immediately start

    /// building circuits, which will launch connection attempts until one

    /// succeeds or the client gives up entirely.  

    /// Note that an attempt to connect has been started.

    /// Note that we've successfully done a TCP handshake with an alleged relay.

    /// Note that we've completed a TLS handshake with an alleged relay.

    ///

    /// (Its identity won't be verified till the next step.)

    /// Record that a handshake has succeeded _except for the certificate

    /// timeliness check, which may indicate a skewed clock.

    /// Note that we've completed a Tor handshake with a relay.

    ///

    /// (This includes performing the TLS handshake, and verifying that the

    /// relay was indeed the one that we wanted to reach.)

}

/// Create a new channel for sending connectivity status events to other crates.

#[cfg(test)]

#[allow(clippy::cognitive_complexity)]

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)]

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

    use super::*;

    use float_eq::assert_float_eq;

    /// Tolerance for float comparison.

    const TOL: f32 = 0.00001;

    #[test]

    fn status_basics() {

        let s1 = ConnStatus::default();

        assert_eq!(s1.to_string(), "connecting to the internet");

        assert_float_eq!(s1.frac(), 0.0, abs <= TOL);

        assert!(s1.eq(&s1));

        assert!(s1.blockage().is_none());

        assert!(!s1.usable());

        let s2 = ConnStatus {

            online: Some(false),

            auth_works: None,

            handshake_works: None,

        };

        assert_eq!(s2.to_string(), "unable to connect to the internet");

        assert_float_eq!(s2.frac(), 0.0, abs <= TOL);

        assert!(s2.eq(&s2));

        assert!(!s2.eq(&s1));

        assert_eq!(s2.blockage(), Some(ConnBlockage::NoTcp));

        assert_eq!(

            s2.blockage().unwrap().to_string(),

            "unable to connect to the internet"

        );

        assert!(!s2.usable());

        let s3 = ConnStatus {

            online: Some(true),

            auth_works: None,

            handshake_works: None,

        };

        assert_eq!(s3.to_string(), "handshaking with Tor relays");

        assert_float_eq!(s3.frac(), 0.5, abs <= TOL);

        assert_eq!(s3.blockage(), None);

        assert!(!s3.eq(&s1));

        assert!(!s3.usable());

        let s4 = ConnStatus {

            online: Some(true),

            auth_works: Some(false),

            handshake_works: Some(false),

        };

        assert_eq!(s4.to_string(), "unable to handshake with Tor relays");

        assert_float_eq!(s4.frac(), 0.5, abs <= TOL);

        assert_eq!(s4.blockage(), Some(ConnBlockage::NoHandshake));

        assert_eq!(

            s4.blockage().unwrap().to_string(),

            "our internet connection seems to be filtered"

        );

        assert!(!s4.eq(&s1));

        assert!(!s4.eq(&s2));

        assert!(!s4.eq(&s3));

        assert!(s4.eq(&s4));

        assert!(!s4.usable());

        let s5 = ConnStatus {

            online: Some(true),

            auth_works: Some(true),

            handshake_works: Some(true),

        };

        assert_eq!(s5.to_string(), "connecting successfully");

        assert_float_eq!(s5.frac(), 1.0, abs <= TOL);

        assert!(s5.blockage().is_none());

        assert!(s5.eq(&s5));

        assert!(!s5.eq(&s4));

        assert!(s5.usable());

    }

    #[test]

    fn derive_status() {

        let start = Instant::get();

        let sec = Duration::from_secs(1);

        let hour = Duration::from_secs(3600);

        let mut ms = ChanMgrStatus::new_at(start);

        // when we start, we're unable to reach any conclusions.

        let s0 = ms.conn_status_at(start);

        assert!(s0.online.is_none());

        assert!(s0.handshake_works.is_none());

        // Time won't let us make conclusions either, unless there have been

        // attempts.

        let s = ms.conn_status_at(start + hour);

        assert!(s.eq(&s0));

        // But if there have been attempts, _and_ time has passed, we notice

        // failure.

        for _ in 0..10 {

            ms.record_attempt();

        }

        // (Not immediately...)

        let s = ms.conn_status_at(start);

        assert!(s.eq(&s0));

        // (... but after a while.)

        let s = ms.conn_status_at(start + hour);

        assert_eq!(s.online, Some(false));

        assert_eq!(s.handshake_works, Some(false));

        // If TCP has succeeded, we should notice that.

        ms.record_tcp_success(start + sec);

        let s = ms.conn_status_at(start + sec * 2);

        assert_eq!(s.online, Some(true));

        assert!(s.handshake_works.is_none());

        let s = ms.conn_status_at(start + hour);

        assert_eq!(s.online, Some(true));

        assert_eq!(s.handshake_works, Some(false));

        // If the handshake succeeded, we can notice that too.

        ms.record_handshake_done(start + sec * 2);

        let s = ms.conn_status_at(start + sec * 3);

        assert_eq!(s.online, Some(true));

        assert_eq!(s.handshake_works, Some(true));

    }

    #[test]

    fn sender() {

        let (mut snd, rcv) = channel();

        {

            let s = rcv.inner.borrow().clone();

            assert_float_eq!(s.frac(), 0.0, abs <= TOL);

        }

        snd.record_attempt();

        snd.record_tcp_success();

        snd.record_tls_finished();

        snd.record_handshake_done();

        {

            let s = rcv.inner.borrow().clone();

            assert_float_eq!(s.frac(), 1.0, abs <= TOL);

        }

    }

}