// SPDX-License-Identifier: CC0-1.0

//! Error code for the `hashes` crate.

use core::fmt;

/// Attempted to create a hash from an invalid length slice.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct FromSliceError(pub(crate) FromSliceErrorInner);

impl_from_infallible!(FromSliceError);

impl FromSliceError {
    /// Returns the expected slice length.
    pub fn expected_length(&self) -> usize { self.0.expected }

    /// Returns the invalid slice length.
    pub fn invalid_length(&self) -> usize { self.0.got }
}

/// Attempted to create a hash from an invalid length slice.
#[derive(Debug, Clone, PartialEq, Eq)]
pub(crate) struct FromSliceErrorInner {
    pub(crate) expected: usize,
    pub(crate) got: usize,
}

impl_from_infallible!(FromSliceErrorInner);

impl fmt::Display for FromSliceError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "invalid slice length {} (expected {})", self.0.got, self.0.expected)
    }
}

#[cfg(feature = "std")]
impl std::error::Error for FromSliceError {}

/// Derives `From<core::convert::Infallible>` for the given type.
// This is a duplicate of `internals::impl_from_infallible`, see there for complete docs.
#[doc(hidden)]
macro_rules! impl_from_infallible {
    ( $name:ident $(< $( $lt:tt $( : $clt:tt $(+ $dlt:tt )* )? ),+ >)? ) => {
        impl $(< $( $lt $( : $clt $(+ $dlt )* )? ),+ >)?
            From<core::convert::Infallible>
        for $name
            $(< $( $lt ),+ >)?
        {
            fn from(never: core::convert::Infallible) -> Self { match never {} }
        }
    }
}
pub(crate) use impl_from_infallible;