// SPDX-FileCopyrightText: 2022 Thomas Kramer <code@tkramer.ch>
//
// SPDX-License-Identifier: GPL-3.0-or-later

//! Types which help to use the type system to distinguish between
//! data in canonical and non-canonical form.
//!
//! Tree data structures for example might be efficiently comparable if they are
//! in a canonical form, but not if they are in a non-canonical form.
//!
//! Note: This is an experiment for now.

use std::ops::Deref;

/// Mark datatype to have canonical form.
#[derive(Copy, Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Hash)]
pub struct Canonical;
/// Mark datatype to have potentially non-canonical form.
#[derive(Copy, Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Hash)]
pub struct NonCanonical;

pub trait CanonicalMarker: Clone {
    fn is_canonical() -> bool;
}

impl CanonicalMarker for Canonical {
    fn is_canonical() -> bool {
        true
    }
}
impl CanonicalMarker for NonCanonical {
    fn is_canonical() -> bool {
        false
    }
}

/// Wrapper which 'guarantees' that the content has canonical form
pub struct Ca<T> {
    data: T,
}

impl<T> Deref for Ca<T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        &self.data
    }
}

pub trait WithCanonicalForm {
    type NonCanonical: WithCanonicalForm;
    fn is_canonical(&self) -> bool;
    fn into_canonical_form(self) -> Ca<Self::NonCanonical>;
}