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//! This is a [`Cow`][cow] like type used in this crate.

//!

//! It is read-only unlike the std implementation.

//!

//! Its also specialized for just `str`

//!

//! [cow]: https://doc.rust-lang.org/std/borrow/enum.Cow.html

use std::{fmt::Debug, ops::Deref};

mod into_owned;
pub use into_owned::IntoOwned;

mod maybe_owned_index;
pub use maybe_owned_index::MaybeOwnedIndex;

/// A `str` type that can either be in a borrowed state, or an owned state.

///

/// This is conceptually the same as a `Cow` but specialized for `str` and for this crate.

///

/// This crate uses indices into this type to reduce the number of allocations of each type

///

/// This only exposed for people to extend messages themselves.

#[cfg_attr(feature = "serde", derive(::serde::Serialize), serde(untagged))]
pub enum MaybeOwned<'a> {
    /// Owned variant, a `Box<str>`. This usually means it has a `'static` lifetime

    Owned(Box<str>),
    /// Borrowed variant, a `&'a str`. This means it has a `'a` lifetime

    Borrowed(&'a str),
}

impl<'a> MaybeOwned<'a> {
    /// Checks whether this type is in the `Owned` state

    pub fn is_owned(&self) -> bool {
        !self.is_borrowed()
    }

    /// Checks whether this type is in the `Borrowed` state

    pub fn is_borrowed(&self) -> bool {
        matches!(self, Self::Borrowed{..})
    }
}

impl<'a> Clone for MaybeOwned<'a> {
    fn clone(&self) -> MaybeOwned<'a> {
        match self {
            Self::Owned(s) => Self::Owned(s.to_string().into_boxed_str()),
            Self::Borrowed(s) => Self::Borrowed(s),
        }
    }
}

impl<'a> Debug for MaybeOwned<'a> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        self.as_ref().fmt(f)
    }
}

impl<'a> PartialEq for MaybeOwned<'a> {
    fn eq(&self, other: &Self) -> bool {
        self.as_ref() == other.as_ref()
    }
}

impl<'a> PartialEq<str> for MaybeOwned<'a> {
    fn eq(&self, other: &str) -> bool {
        self.as_ref() == other
    }
}

impl<'a> PartialEq<&str> for MaybeOwned<'a> {
    fn eq(&self, other: &&str) -> bool {
        self.as_ref() == *other
    }
}

impl<'a> AsRef<str> for MaybeOwned<'a> {
    fn as_ref(&self) -> &str {
        match self {
            MaybeOwned::Owned(s) => &*s,
            MaybeOwned::Borrowed(s) => s,
        }
    }
}

impl<'a> Deref for MaybeOwned<'a> {
    type Target = str;
    fn deref(&self) -> &Self::Target {
        self.as_ref()
    }
}

impl From<String> for MaybeOwned<'static> {
    fn from(data: String) -> Self {
        MaybeOwned::Owned(data.into_boxed_str())
    }
}

impl<'a> From<&'a str> for MaybeOwned<'a> {
    fn from(data: &'a str) -> Self {
        MaybeOwned::Borrowed(data)
    }
}

impl From<Box<str>> for MaybeOwned<'static> {
    fn from(data: Box<str>) -> Self {
        MaybeOwned::Owned(data)
    }
}