//! Misc helper functions and types for use in parsing network documents

use derive_deftly::define_derive_deftly;

pub(crate) mod str;

pub mod batching_split_before;

use std::iter::Peekable;

define_derive_deftly! {

    /// Implement `AsMut<Self>`

    ///

    /// For Reasons, Rust does not have a blanket:

    ///

    /// ```rust,ignore

    /// impl<T> AsMut<T> for T { .. }

    /// ```

    ///

    /// This derive macro expands to the obvious and trivial implementation,

    /// for the type that it's applied to.

    //

    // TODO move this somewhere lower in the stack, eg tor-basic-utils

    export AsMutSelf expect items:

    impl<$tgens> ::std::convert::AsMut<Self> for $ttype where $twheres {

            self

        }

    }

}

/// An iterator with a `.peek()` method

///

/// We make this a trait to avoid entangling all the types with `Peekable`.

/// Ideally we would do this with `Itertools::PeekingNext`

/// but that was not implemented for `&mut PeekingNext`

/// when we wrote this code,

/// and we need that because we use a lot of `&mut NetdocReader`.

/// <https://github.com/rust-itertools/itertools/issues/678>

///

/// TODO: As of itertools 0.11.0, `PeekingNext` _is_ implemented for

/// `&'a mut I where I: PeekingNext`, so we can remove this type some time.

///

/// # **UNSTABLE**

///

/// This type is UNSTABLE and not part of the semver guarantees.

/// You'll only see it if you ran rustdoc with `--document-private-items`.

// This is needed because this is a trait bound for batching_split_before.

#[doc(hidden)]

pub trait PeekableIterator: Iterator {

    /// Inspect the next item, if there is one

    fn peek(&mut self) -> Option<&Self::Item>;

}

impl<I: Iterator> PeekableIterator for Peekable<I> {

}

impl<I: PeekableIterator> PeekableIterator for &mut I {

}

/// A Private module for declaring a "sealed" trait.

pub(crate) mod private {

    /// A non-exported trait, used to prevent others from implementing a trait.

    ///

    /// For more information on this pattern, see [the Rust API

    /// guidelines](https://rust-lang.github.io/api-guidelines/future-proofing.html#c-sealed).

    #[expect(dead_code, unreachable_pub)] // TODO keep this Sealed trait in case we want it again?

    pub trait Sealed {}

}

#[cfg(test)]

#[allow(unused)]

    use derive_deftly::Deftly;

    #[derive(Deftly)]

    #[derive_deftly(AsMutSelf)]

    struct S<T: Clone>

    where

        Option<T>: Clone,

    {

        t: T,

    }