#![cfg_attr(docsrs, feature(doc_cfg))]

#![doc = include_str!("../README.md")]

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

#![allow(renamed_and_removed_lints)] // @@REMOVE_WHEN(ci_arti_stable)

#![allow(unknown_lints)] // @@REMOVE_WHEN(ci_arti_nightly)

#![warn(missing_docs)]

#![warn(noop_method_call)]

#![warn(unreachable_pub)]

#![warn(clippy::all)]

#![deny(clippy::await_holding_lock)]

#![deny(clippy::cargo_common_metadata)]

#![deny(clippy::cast_lossless)]

#![deny(clippy::checked_conversions)]

#![warn(clippy::cognitive_complexity)]

#![deny(clippy::debug_assert_with_mut_call)]

#![deny(clippy::exhaustive_enums)]

#![deny(clippy::exhaustive_structs)]

#![deny(clippy::expl_impl_clone_on_copy)]

#![deny(clippy::fallible_impl_from)]

#![deny(clippy::implicit_clone)]

#![deny(clippy::large_stack_arrays)]

#![warn(clippy::manual_ok_or)]

#![deny(clippy::missing_docs_in_private_items)]

#![warn(clippy::needless_borrow)]

#![warn(clippy::needless_pass_by_value)]

#![warn(clippy::option_option)]

#![deny(clippy::print_stderr)]

#![deny(clippy::print_stdout)]

#![warn(clippy::rc_buffer)]

#![deny(clippy::ref_option_ref)]

#![warn(clippy::semicolon_if_nothing_returned)]

#![warn(clippy::trait_duplication_in_bounds)]

#![deny(clippy::unchecked_time_subtraction)]

#![deny(clippy::unnecessary_wraps)]

#![warn(clippy::unseparated_literal_suffix)]

#![deny(clippy::unwrap_used)]

#![deny(clippy::mod_module_files)]

#![allow(clippy::let_unit_value)] // This can reasonably be done for explicitness

#![allow(clippy::uninlined_format_args)]

#![allow(clippy::significant_drop_in_scrutinee)] // arti/-/merge_requests/588/#note_2812945

#![allow(clippy::result_large_err)] // temporary workaround for arti#587

#![allow(clippy::needless_raw_string_hashes)] // complained-about code is fine, often best

#![allow(clippy::needless_lifetimes)] // See arti#1765

#![allow(mismatched_lifetime_syntaxes)] // temporary workaround for arti#2060

#![allow(clippy::collapsible_if)] // See arti#2342

#![deny(clippy::unused_async)]

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

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

#![allow(non_upper_case_globals)]

#![allow(clippy::upper_case_acronyms)]

use std::sync::Arc;

use caret::caret_int;

use thiserror::Error;

use tor_basic_utils::intern::InternCache;

pub mod named;

caret_int! {

    /// A recognized subprotocol.

    ///

    /// These names are kept in sync with the names used in consensus

    /// documents; the values are kept in sync with the values in the

    /// cbor document format in the walking onions proposal.

    ///

    /// For the full semantics of each subprotocol, see tor-spec.txt.

    #[derive(Hash,Ord,PartialOrd)]

    pub struct ProtoKind(u8) {

        /// Initiating and receiving channels, and getting cells on them.

        Link = 0,

        /// Different kinds of authenticate cells

        LinkAuth = 1,

        /// CREATE cells, CREATED cells, and the encryption that they

        /// create.

        Relay = 2,

        /// Serving and fetching network directory documents.

        DirCache = 3,

        /// Serving onion service descriptors

        HSDir = 4,

        /// Providing an onion service introduction point

        HSIntro = 5,

        /// Providing an onion service rendezvous point

        HSRend = 6,

        /// Describing a relay's functionality using router descriptors.

        Desc = 7,

        /// Describing a relay's functionality using microdescriptors.

        Microdesc = 8,

        /// Describing the network as a consensus directory document.

        Cons = 9,

        /// Sending and accepting circuit-level padding

        Padding = 10,

        /// Improved means of flow control on circuits.

        FlowCtrl = 11,

        /// Multi-path circuit support.

        Conflux = 12,

    }

}

/// How many recognized protocols are there?

const N_RECOGNIZED: usize = 13;

/// Maximum allowable value for a protocol's version field.

const MAX_VER: usize = 63;

/// A specific, named subversion of a protocol.

#[derive(Eq, PartialEq, Copy, Clone, Debug)]

pub struct NamedSubver {

    /// The protocol in question

    ///

    /// Must be in-range for ProtoKind (0..N_RECOGNIZED).

    kind: ProtoKind,

    /// The version of the protocol

    ///

    /// Must be in 1..=MAX_VER

    version: u8,

}

impl NamedSubver {

    /// Create a new NamedSubver.

    ///

    /// # Panics

    ///

    /// Panics if `kind` is unrecognized or `version` is invalid.

}

/// A subprotocol capability as represented by a (kind, version) tuple.

///

/// Does not necessarily represent a real subprotocol capability;

/// this type is meant for use in other pieces of the protocol.

///

/// # Ordering

///

/// Instances of `NumberedSubver` are sorted in lexicographic order by

/// their (kind, version) tuples.

//

// TODO: As with most other types in the crate, we should decide how to rename them as as part

// of #1934.

#[derive(Clone, Copy, Debug, Ord, PartialOrd, Eq, PartialEq)]

pub struct NumberedSubver {

    /// The protocol in question

    kind: ProtoKind,

    /// The version of the protocol

    version: u8,

}

impl NumberedSubver {

    /// Construct a new [`NumberedSubver`]

    /// Return the ProtoKind and version for this [`NumberedSubver`].

}

impl From<NamedSubver> for NumberedSubver {

}

#[cfg(feature = "tor-bytes")]

impl tor_bytes::Readable for NumberedSubver {

}

#[cfg(feature = "tor-bytes")]

impl tor_bytes::Writeable for NumberedSubver {

}

/// Representation for a known or unknown protocol.

#[derive(Eq, PartialEq, Clone, Debug, Hash, Ord, PartialOrd)]

enum Protocol {

    /// A known protocol; represented by one of ProtoKind.

    ///

    /// ProtoKind must always be in the range 0..N_RECOGNIZED.

    Proto(ProtoKind),

    /// An unknown protocol; represented by its name.

    Unrecognized(String),

}

impl Protocol {

    /// Return true iff `s` is the name of a protocol we do not recognize.

        }

    /// Return a string representation of this protocol.

        }

}

/// Representation of a set of versions supported by a protocol.

///

/// For now, we only use this type for unrecognized protocols.

#[derive(Debug, Clone, PartialEq, Eq, Hash, Ord, PartialOrd)]

struct SubprotocolEntry {

    /// Which protocol's versions does this describe?

    proto: Protocol,

    /// A bit-vector defining which versions are supported.  If bit

    /// `(1<<i)` is set, then protocol version `i` is supported.

    supported: u64,

}

/// A set of supported or required subprotocol versions.

///

/// This type supports both recognized subprotocols (listed in ProtoKind),

/// and unrecognized subprotocols (stored by name).

///

/// To construct an instance, use the FromStr trait:

/// ```

/// use tor_protover::Protocols;

/// let p: Result<Protocols,_> = "Link=1-3 LinkAuth=2-3 Relay=1-2".parse();

/// ```

///

/// # Implementation notes

///

/// Because the number of distinct `Protocols` sets at any given time

/// is much smaller than the number of relays, this type is interned in order to

/// save memory and copying time.

///

/// This type is an Arc internally; it is cheap to clone.

#[derive(Debug, Clone, Default, Eq, PartialEq, Hash)]

#[cfg_attr(

    feature = "serde",

    derive(serde_with::DeserializeFromStr, serde_with::SerializeDisplay)

)]

pub struct Protocols(Arc<ProtocolsInner>);

/// Inner representation of Protocols.

///

/// We make this a separate type so that we can intern it inside an Arc.

#[derive(Default, Clone, Debug, Eq, PartialEq, Hash)]

struct ProtocolsInner {

    /// A mapping from protocols' integer encodings to bit-vectors.

    recognized: [u64; N_RECOGNIZED],

    /// A vector of unrecognized protocol versions,

    /// in sorted order.

    ///

    /// Every entry in this list has supported != 0.

    unrecognized: Vec<SubprotocolEntry>,

}

/// An InternCache of ProtocolsInner.

///

/// We intern ProtocolsInner objects because:

///  - There are very few _distinct_ values in any given set of relays.

///  - Every relay has one.

///  - We often want to copy them when we're remembering information about circuits.

static PROTOCOLS: InternCache<ProtocolsInner> = InternCache::new();

impl From<ProtocolsInner> for Protocols {

        // TODO: Use Intern more natively.

}

impl Protocols {

    /// Return a new empty set of protocol versions.

    ///

    /// # Warning

    ///

    /// To the extend possible, avoid using empty lists to represent the capabilities

    /// of an unknown target.  Instead, if there is a consensus present, use the

    /// `required-relay-protocols` field of the consensus.

    /// Helper: return true iff this protocol set contains the

    /// version `ver` of the protocol represented by the integer `proto`.

    /// Helper: return true iff this protocol set contains version

    /// `ver` of the unrecognized protocol represented by the string

    /// `proto`.

    ///

    /// Requires that `proto` is not the name of a recognized protocol.

        }

    /// Return true if this list of protocols is empty.

    // TODO: Combine these next two functions into one by using a trait.

    /// Check whether a known protocol version is supported.

    ///

    /// ```

    /// use tor_protover::*;

    /// let protos: Protocols = "Link=1-3 HSDir=2,4-5".parse().unwrap();

    ///

    /// assert!(protos.supports_known_subver(ProtoKind::Link, 2));

    /// assert!(protos.supports_known_subver(ProtoKind::HSDir, 4));

    /// assert!(! protos.supports_known_subver(ProtoKind::HSDir, 3));

    /// assert!(! protos.supports_known_subver(ProtoKind::LinkAuth, 3));

    /// ```

    /// Check whether a protocol version identified by a string is supported.

    ///

    /// ```

    /// use tor_protover::*;

    /// let protos: Protocols = "Link=1-3 Foobar=7".parse().unwrap();

    ///

    /// assert!(protos.supports_subver("Link", 2));

    /// assert!(protos.supports_subver("Foobar", 7));

    /// assert!(! protos.supports_subver("Link", 5));

    /// assert!(! protos.supports_subver("Foobar", 6));

    /// assert!(! protos.supports_subver("Wombat", 3));

    /// ```

        }

    /// Check whether a protocol version is supported.

    ///

    /// ```

    /// use tor_protover::*;

    /// let protos: Protocols = "Link=1-5 Desc=2-4".parse().unwrap();

    /// assert!(protos.supports_named_subver(named::DESC_FAMILY_IDS)); // Desc=4

    /// assert!(! protos.supports_named_subver(named::CONFLUX_BASE)); // Conflux=1

    /// ```

    /// Check whether a numbered subprotocol capability is supported.

    ///

    /// ```

    /// use tor_protover::*;

    /// let protos: Protocols = "Link=1-5 Desc=2-4".parse().unwrap();

    /// assert!(protos.supports_numbered_subver(NumberedSubver::new(ProtoKind::Desc, 4)));

    /// assert!(! protos.supports_numbered_subver(NumberedSubver::new(ProtoKind::Conflux, 1)));

    /// ```

    /// Return a Protocols holding every protocol flag that is present in `self`

    /// but not `other`.

    ///

    /// ```

    /// use tor_protover::*;

    /// let protos: Protocols = "Desc=2-4 Microdesc=1-5".parse().unwrap();

    /// let protos2: Protocols = "Desc=3 Microdesc=3".parse().unwrap();

    /// assert_eq!(protos.difference(&protos2),

    ///            "Desc=2,4 Microdesc=1-2,4-5".parse().unwrap());

    /// ```

        // This is not super efficient, but we don't have to do it often.

        }

    /// Return a Protocols holding every protocol flag that is present in `self`

    /// or `other` or both.

    ///

    /// ```

    /// use tor_protover::*;

    /// let protos: Protocols = "Desc=2-4 Microdesc=1-5".parse().unwrap();

    /// let protos2: Protocols = "Desc=3 Microdesc=10".parse().unwrap();

    /// assert_eq!(protos.union(&protos2),

    ///            "Desc=2-4 Microdesc=1-5,10".parse().unwrap());

    /// ```

        }

    /// Return a Protocols holding every protocol flag that is present in both `self`

    /// and `other`.

    ///

    /// ```

    /// use tor_protover::*;

    /// let protos: Protocols = "Desc=2-4 Microdesc=1-5".parse().unwrap();

    /// let protos2: Protocols = "Desc=3 Microdesc=10".parse().unwrap();

    /// assert_eq!(protos.intersection(&protos2),

    ///            "Desc=3".parse().unwrap());

    /// ```

        }

}

impl ProtocolsInner {

    /// Parsing helper: Try to add a new entry `ent` to this set of protocols.

    ///

    /// Uses `foundmask`, a bit mask saying which recognized protocols

    /// we've already found entries for.  Returns an error if `ent` is

    /// for a protocol we've already added.

    ///

    /// Does not preserve sorting order; the caller must call `self.unrecognized.sort()` before returning.

            }

                {

            }

        }

}

/// An error representing a failure to parse a set of protocol versions.

#[derive(Error, Debug, PartialEq, Eq, Clone)]

#[non_exhaustive]

pub enum ParseError {

    /// A protocol version was not in the range 1..=63.

    #[error("Protocol version out of range")]

    OutOfRange,

    /// Some subprotocol or protocol version appeared more than once.

    #[error("Duplicate protocol entry")]

    Duplicate,

    /// The list of protocol versions was malformed in some other way.

    #[error("Malformed protocol entry")]

    Malformed,

}

/// Helper: return a new u64 in which bits `lo` through `hi` inclusive

/// are set to 1, and all the other bits are set to 0.

///

/// In other words, `bitrange(a,b)` is how we represent the range of

/// versions `a-b` in a protocol version bitmask.

///

/// ```ignore

/// # use tor_protover::bitrange;

/// assert_eq!(bitrange(0, 5), 0b111111);

/// assert_eq!(bitrange(2, 5), 0b111100);

/// assert_eq!(bitrange(2, 7), 0b11111100);

/// ```

/// Helper: return true if the provided string is a valid "integer"

/// in the form accepted by the protover spec.  This is stricter than

/// rust's integer parsing format.

/// A single SubprotocolEntry is parsed from a string of the format

/// Name=Versions, where Versions is a comma-separated list of

/// integers or ranges of integers.

impl std::str::FromStr for SubprotocolEntry {

    type Err = ParseError;

        // split the string on the =.

        // Look up the protocol by name.

        };

            // We need to handle this case specially, since otherwise

            // it would be treated below as a single empty value, which

            // would be rejected.

        // Construct a bitmask based on the comma-separated versions.

            // Find and parse lo and hi for a single range of versions.

            // (If this is not a range, but rather a single version v,

            // treat it as if it were a range v-v.)

            // Make sure that lo and hi are in-bounds and consistent.

            // Make sure that no version is included twice.

            // Add the appropriate bits to the mask.

        }

}

/// A Protocols set can be parsed from a string according to the

/// format used in Tor consensus documents.

///

/// A protocols set is represented by a space-separated list of

/// entries.  Each entry is of the form `Name=Versions`, where `Name`

/// is the name of a protocol, and `Versions` is a comma-separated

/// list of version numbers and version ranges.  Each version range is

/// a pair of integers separated by `-`.

///

/// No protocol name may be listed twice.  No version may be listed

/// twice for a single protocol.  All versions must be in range 0

/// through 63 inclusive.

impl std::str::FromStr for Protocols {

    type Err = ParseError;

        }

}

/// Given a bitmask, return a list of the bits set in the mask, as a

/// String in the format expected by Tor consensus documents.

///

/// This implementation constructs ranges greedily.  For example, the

/// bitmask `0b0111011` will be represented as `0-1,3-5`, and not

/// `0,1,3,4,5` or `0,1,3-5`.

///

/// ```ignore

/// # use tor_protover::dumpmask;

/// assert_eq!(dumpmask(0b111111), "0-5");

/// assert_eq!(dumpmask(0b111100), "2-5");

/// assert_eq!(dumpmask(0b11111100), "2-7");

/// ```

    /// Helper: push a range (which may be a singleton) onto `v`.

    // We'll be building up our result here, then joining it with

    // commas.

    // This implementation is a little tricky, but it should be more

    // efficient than a raw search.  Basically, we're using the

    // function u64::trailing_zeros to count how large each range of

    // 1s or 0s is, and then shifting by that amount.

    // How many bits have we already shifted `mask`?

            // We have to do this check to avoid overflow when formatting

            // the range `0-63`.

    }

/// The Display trait formats a protocol set in the format expected by Tor

/// consensus documents.

///

/// ```

/// use tor_protover::*;

/// let protos: Protocols = "Link=1,2,3 Foobar=7 Relay=2".parse().unwrap();

/// assert_eq!(format!("{}", protos),

///            "Foobar=7 Link=1-3 Relay=2");

/// ```

impl std::fmt::Display for Protocols {

        }

        }

        // This sort is required.

}

impl FromIterator<NamedSubver> for Protocols {

            // These are guaranteed by invariants on NamedSubver.

        }

}

/// Documentation: when is a protocol "supported"?

///

/// Arti should consider itself to "support" a protocol if, _as built_,

/// it implements the protocol completely.

///

/// Just having the protocol listed among the [`named`]

/// protocols is not enough, and neither is an incomplete

/// or uncompliant implementation.

///

/// Similarly, if the protocol is not compiled in,

/// it is not technically _supported_.

///

/// When in doubt, ask yourself:

/// - If another Tor implementation believed that we implemented this protocol,

///   and began to speak it to us, would we be able to do so?

/// - If the protocol were required,

///   would this software as built actually meet that requirement?

///

/// If either answer is no, the protocol is not supported.

pub mod doc_supported {}

/// Documentation about changing lists of supported versions.

///

/// # Warning

///

/// You need to be extremely careful when removing

/// _any_ entry from a list of supported protocols.

///

/// If you remove an entry while it still appears as "recommended" in the consensus,

/// you'll cause all the instances without it to warn.

///

/// If you remove an entry while it still appears as "required" in the

///  consensus, you'll cause all the instances without it to refuse to connect

/// to the network, and shut down.

///

/// If you need to remove a version from a list of supported protocols,

/// you need to make sure that it is not listed in the _current consensuses_:

/// just removing it from the list that the authorities vote for is NOT ENOUGH.

/// You need to remove it from the required list,

/// and THEN let the authorities upgrade and vote on new

/// consensuses without it. Only once those consensuses are out is it safe to

/// remove from the list of required protocols.

///

/// ## Example

///

/// One concrete example of a very dangerous race that could occur:

///

/// Suppose that the client supports protocols "HsDir=1-2" and the consensus

/// requires protocols "HsDir=1-2".  If the client supported protocol list is

/// then changed to "HSDir=2", while the consensus stills lists "HSDir=1-2",

/// then these clients, even very recent ones, will shut down because they

/// don't support "HSDir=1".

///

/// And so, changes need to be done in strict sequence as described above.

pub mod doc_changing {}

#[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 @@ -->

    use std::str::FromStr;

    use super::*;

    #[test]

    fn test_bitrange() {

        assert_eq!(0b1, bitrange(0, 0));

        assert_eq!(0b10, bitrange(1, 1));

        assert_eq!(0b11, bitrange(0, 1));

        assert_eq!(0b1111110000000, bitrange(7, 12));

        assert_eq!(!0, bitrange(0, 63));

    }

    #[test]

    fn test_dumpmask() {

        assert_eq!("", dumpmask(0));

        assert_eq!("0-5", dumpmask(0b111111));

        assert_eq!("4-5", dumpmask(0b110000));

        assert_eq!("1,4-5", dumpmask(0b110010));

        assert_eq!("0-63", dumpmask(!0));

    }

    #[test]

    fn test_canonical() -> Result<(), ParseError> {

        fn t(orig: &str, canonical: &str) -> Result<(), ParseError> {

            let protos: Protocols = orig.parse()?;

            let enc = format!("{}", protos);

            assert_eq!(enc, canonical);

            Ok(())

        }

        t("", "")?;

        t(" ", "")?;

        t("Link=5,6,7,9 Relay=4-7,2", "Link=5-7,9 Relay=2,4-7")?;

        t("FlowCtrl= Padding=8,7 Desc=1-5,6-8", "Desc=1-8 Padding=7-8")?;

        t("Zelda=7 Gannon=3,6 Link=4", "Gannon=3,6 Link=4 Zelda=7")?;

        Ok(())

    }

    #[test]

    fn test_invalid() {

        fn t(s: &str) -> ParseError {

            let protos: Result<Protocols, ParseError> = s.parse();

            assert!(protos.is_err());

            protos.err().unwrap()

        }

        assert_eq!(t("Link=1-100"), ParseError::OutOfRange);

        assert_eq!(t("Zelda=100"), ParseError::OutOfRange);

        assert_eq!(t("Link=100-200"), ParseError::OutOfRange);

        assert_eq!(t("Link=1,1"), ParseError::Duplicate);

        assert_eq!(t("Link=1 Link=1"), ParseError::Duplicate);

        assert_eq!(t("Link=1 Link=3"), ParseError::Duplicate);

        assert_eq!(t("Zelda=1 Zelda=3"), ParseError::Duplicate);

        assert_eq!(t("Link=Zelda"), ParseError::Malformed);

        assert_eq!(t("Link=6-2"), ParseError::Malformed);

        assert_eq!(t("Link=6-"), ParseError::Malformed);

        assert_eq!(t("Link=6-,2"), ParseError::Malformed);

        assert_eq!(t("Link=1,,2"), ParseError::Malformed);

        assert_eq!(t("Link=6-frog"), ParseError::Malformed);

        assert_eq!(t("Link=gannon-9"), ParseError::Malformed);

        assert_eq!(t("Link Zelda"), ParseError::Malformed);

        assert_eq!(t("Link=01"), ParseError::Malformed);

        assert_eq!(t("Link=waffle"), ParseError::Malformed);

        assert_eq!(t("Link=1_1"), ParseError::Malformed);

    }

    #[test]

    fn test_supports() -> Result<(), ParseError> {

        let p: Protocols = "Link=4,5-7 Padding=2 Lonk=1-3,5".parse()?;

        assert!(p.supports_known_subver(ProtoKind::Padding, 2));

        assert!(!p.supports_known_subver(ProtoKind::Padding, 1));

        assert!(p.supports_known_subver(ProtoKind::Link, 6));

        assert!(!p.supports_known_subver(ProtoKind::Link, 255));

        assert!(!p.supports_known_subver(ProtoKind::Cons, 1));

        assert!(!p.supports_known_subver(ProtoKind::Cons, 0));

        assert!(p.supports_subver("Link", 6));

        assert!(!p.supports_subver("link", 6));

        assert!(!p.supports_subver("Cons", 0));

        assert!(p.supports_subver("Lonk", 3));

        assert!(!p.supports_subver("Lonk", 4));

        assert!(!p.supports_subver("lonk", 3));

        assert!(!p.supports_subver("Lonk", 64));

        Ok(())

    }

    #[test]

    fn test_difference() -> Result<(), ParseError> {

        let p1: Protocols = "Link=1-10 Desc=5-10 Relay=1,3,5,7,9 Other=7-60 Mine=1-20".parse()?;

        let p2: Protocols = "Link=3-4 Desc=1-6 Relay=2-6 Other=8 Theirs=20".parse()?;

        assert_eq!(

            p1.difference(&p2),

            Protocols::from_str("Link=1-2,5-10 Desc=7-10 Relay=1,7,9 Other=7,9-60 Mine=1-20")?

        );

        assert_eq!(

            p2.difference(&p1),

            Protocols::from_str("Desc=1-4 Relay=2,4,6 Theirs=20")?,

        );

        let nil = Protocols::default();

        assert_eq!(p1.difference(&nil), p1);

        assert_eq!(p2.difference(&nil), p2);

        assert_eq!(nil.difference(&p1), nil);

        assert_eq!(nil.difference(&p2), nil);

        Ok(())

    }

    #[test]

    fn test_union() -> Result<(), ParseError> {

        let p1: Protocols = "Link=1-10 Desc=5-10 Relay=1,3,5,7,9 Other=7-60 Mine=1-20".parse()?;

        let p2: Protocols = "Link=3-4 Desc=1-6 Relay=2-6 Other=2,8 Theirs=20".parse()?;

        assert_eq!(

            p1.union(&p2),

            Protocols::from_str(

                "Link=1-10 Desc=1-10 Relay=1-7,9 Other=2,7-60 Theirs=20 Mine=1-20"

            )?

        );

        assert_eq!(

            p2.union(&p1),

            Protocols::from_str(

                "Link=1-10 Desc=1-10 Relay=1-7,9 Other=2,7-60 Theirs=20 Mine=1-20"

            )?

        );

        let nil = Protocols::default();

        assert_eq!(p1.union(&nil), p1);

        assert_eq!(p2.union(&nil), p2);

        assert_eq!(nil.union(&p1), p1);

        assert_eq!(nil.union(&p2), p2);

        Ok(())

    }

    #[test]

    fn test_intersection() -> Result<(), ParseError> {

        let p1: Protocols = "Link=1-10 Desc=5-10 Relay=1,3,5,7,9 Other=7-60 Mine=1-20".parse()?;

        let p2: Protocols = "Link=3-4 Desc=1-6 Relay=2-6 Other=2,8 Theirs=20".parse()?;

        assert_eq!(

            p1.intersection(&p2),

            Protocols::from_str("Link=3-4 Desc=5-6 Relay=3,5 Other=8")?

        );

        assert_eq!(

            p2.intersection(&p1),

            Protocols::from_str("Link=3-4 Desc=5-6 Relay=3,5 Other=8")?

        );

        let nil = Protocols::default();

        assert_eq!(p1.intersection(&nil), nil);

        assert_eq!(p2.intersection(&nil), nil);

        assert_eq!(nil.intersection(&p1), nil);

        assert_eq!(nil.intersection(&p2), nil);

        Ok(())

    }

    #[test]

    fn from_iter() {

        use named as n;

        let empty: [NamedSubver; 0] = [];

        let prs: Protocols = empty.iter().copied().collect();

        assert_eq!(prs, Protocols::default());

        let prs: Protocols = empty.into_iter().collect();

        assert_eq!(prs, Protocols::default());

        let prs = [

            n::LINK_V3,

            n::HSDIR_V3,

            n::LINK_V4,

            n::LINK_V5,

            n::CONFLUX_BASE,

        ]

        .into_iter()

        .collect::<Protocols>();

        assert_eq!(prs, "Link=3-5 HSDir=2 Conflux=1".parse().unwrap());

    }

    #[test]

    fn order_numbered_subvers() {

        // We rely on this sort order elsewhere in our protocol.

        assert!(NumberedSubver::new(5, 7) < NumberedSubver::new(7, 5));

        assert!(NumberedSubver::new(7, 5) < NumberedSubver::new(7, 6));

        assert!(NumberedSubver::new(7, 6) < NumberedSubver::new(8, 6));

    }

}