ipld-nostd 0.2.1

use {
	crate::varint,
	core2::{error::Error as StdError, io},
	varint::decode,
};

/// Opaque error struct for operations involving a
/// [`Multihash`](crate::Multihash).
#[derive(Debug)]
pub struct Error {
	kind: Kind,
}

impl Error {
	pub(crate) const fn invalid_size(size: u64) -> Self {
		Self {
			kind: Kind::InvalidSize(size),
		}
	}

	pub(crate) const fn insufficient_varint_bytes() -> Self {
		Self {
			kind: Kind::Varint(decode::Error::Insufficient),
		}
	}

	pub(crate) const fn varint_overflow() -> Self {
		Self {
			kind: Kind::Varint(decode::Error::Overflow),
		}
	}
}

impl core::fmt::Display for Error {
	fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
		self.kind.fmt(f)
	}
}

#[derive(Debug)]
enum Kind {
	/// Io error.
	Io(io::Error),
	/// Invalid multihash size.
	InvalidSize(u64),
	/// Invalid varint.
	Varint(decode::Error),
}

pub(crate) fn varint_decode_to_multihash_error(
	err: varint::decode::Error,
) -> Error {
	Error {
		kind: Kind::Varint(err),
	}
}

pub(crate) fn io_to_multihash_error(err: io::Error) -> Error {
	Error {
		kind: Kind::Io(err),
	}
}

impl core::fmt::Display for Kind {
	fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
		match self {
			Self::Io(err) => write!(f, "{err}"),
			Self::InvalidSize(size) => write!(f, "Invalid multihash size {size}."),
			Self::Varint(err) => write!(f, "{err}"),
		}
	}
}

impl StdError for Error {
	fn source(&self) -> Option<&(dyn StdError + 'static)> {
		match &self.kind {
			Kind::Io(inner) => Some(inner),
			Kind::InvalidSize(_) => None,
			Kind::Varint(_) => None, // FIXME: Does not implement `core2::Error`.
		}
	}
}