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// License: see LICENSE file at root directory of `master` branch

//! # Read-only zeros

use alloc::{
    string::ToString,
    vec::Vec,
};

use core::{
    convert::TryFrom,
    fmt::{self, Display, Formatter},
    ops::Deref,
};

use crate::{Error, Z128, Z224, Z256, Z384, Z512, Zeros};

/// # Read-only zeros
///
/// This struct is simply a read-only wrapper of [`Zeros`][::Zeros].
///
/// ## Examples
///
/// ```
/// use std::convert::TryFrom;
/// use zeros::{ReadOnlyZeros, Zeros};
///
/// const SOME_HASH: ReadOnlyZeros = ReadOnlyZeros::new(Zeros::Z128([
///     0xb2, 0xc2, 0x5d, 0x4b, 0x26, 0xd9, 0xfc, 0xb0,
///     0xb3, 0x6f, 0xc9, 0xdf, 0x33, 0xb2, 0x8b, 0x46,
/// ]));
///
/// // Zeros implements AsRef<[u8]> and TryFrom<&[u8]>
/// let another_hash = Zeros::try_from(SOME_HASH.as_ref())?;
/// assert_eq!(SOME_HASH, another_hash);
/// assert_eq!(SOME_HASH.to_string(), another_hash.to_string());
/// assert_eq!(SOME_HASH, ReadOnlyZeros::from(another_hash));
///
/// # Ok::<_, zeros::Error>(())
/// ```
///
/// [::new()]: #method.new
/// [::Zeros]: enum.Zeros.html
#[derive(Debug, Eq, PartialEq, Hash, Clone)]
pub struct ReadOnlyZeros {

    /// # Zeros
    zeros: Zeros,

}

impl ReadOnlyZeros {

    /// # Makes new instance
    pub const fn new(zeros: Zeros) -> Self {
        Self {
            zeros,
        }
    }

}

impl Deref for ReadOnlyZeros {

    type Target = Zeros;

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

}

impl PartialEq<Zeros> for ReadOnlyZeros {

    fn eq(&self, other: &Zeros) -> bool {
        self.zeros.eq(other)
    }

}

impl PartialEq<ReadOnlyZeros> for Zeros {

    fn eq(&self, other: &ReadOnlyZeros) -> bool {
        self.eq(&other.zeros)
    }

}

impl Display for ReadOnlyZeros {

    fn fmt(&self, f: &mut Formatter) -> Result<(), fmt::Error> {
        f.write_str(&self.zeros.to_string())
    }

}

impl From<Zeros> for ReadOnlyZeros {

    fn from(zeros: Zeros) -> Self {
        Self::new(zeros)
    }

}

impl TryFrom<&[u8]> for ReadOnlyZeros {

    type Error = Error;

    fn try_from(bytes: &[u8]) -> Result<Self, Self::Error> {
        Ok(Self::new(Zeros::try_from(bytes)?))
    }

}

impl TryFrom<Vec<u8>> for ReadOnlyZeros {

    type Error = Error;

    fn try_from(bytes: Vec<u8>) -> Result<Self, Self::Error> {
        Self::try_from(bytes.as_slice())
    }

}

macro_rules! impl_from_slices_for_read_only_zeros { ($($ty: ty, $code: tt,)+) => {
    $(
        impl From<$ty> for ReadOnlyZeros {

            fn from(slice: $ty) -> Self {
                Self::new($code(slice))
            }

        }
    )+
}}

impl_from_slices_for_read_only_zeros! {
    Z128, (Zeros::Z128),
    Z224, (Zeros::Z224),
    Z256, (Zeros::Z256),
    Z384, (Zeros::Z384),
    Z512, (Zeros::Z512),
}