use core::fmt;

#[cfg(feature = "std")]
use std::io;

#[cfg(not(feature = "std"))]
use multihash::no_std_io as io;

/// Type alias to use this library's [`Error`] type in a `Result`.
pub type Result<T> = core::result::Result<T, Error>;

/// Error types
#[derive(Debug)]
pub enum Error {
    /// Unknown CID codec.
    UnknownCodec,
    /// Input data is too short.
    InputTooShort,
    /// Multibase or multihash codec failure
    ParsingError,
    /// Invalid CID version.
    InvalidCidVersion,
    /// Invalid CIDv0 codec.
    InvalidCidV0Codec,
    /// Invalid CIDv0 multihash.
    InvalidCidV0Multihash,
    /// Invalid CIDv0 base encoding.
    InvalidCidV0Base,
    /// Varint decode failure.
    VarIntDecodeError,
    /// Io error.
    Io(io::Error),
    /// Invalid explicit CIDv0.
    InvalidExplicitCidV0,
}

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

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        use self::Error::*;
        let error = match self {
            UnknownCodec => "Unknown codec",
            InputTooShort => "Input too short",
            ParsingError => "Failed to parse multihash",
            InvalidCidVersion => "Unrecognized CID version",
            InvalidCidV0Codec => "CIDv0 requires a DagPB codec",
            InvalidCidV0Multihash => "CIDv0 requires a Sha-256 multihash",
            InvalidCidV0Base => "CIDv0 requires a Base58 base",
            VarIntDecodeError => "Failed to decode unsigned varint format",
            Io(err) => return write!(f, "{}", err),
            InvalidExplicitCidV0 => "CIDv0 cannot be specified in CIDv1 format",
        };

        f.write_str(error)
    }
}

#[cfg(feature = "alloc")]
impl From<multibase::Error> for Error {
    fn from(_: multibase::Error) -> Error {
        Error::ParsingError
    }
}

impl From<multihash::Error> for Error {
    fn from(_: multihash::Error) -> Error {
        Error::ParsingError
    }
}

impl From<unsigned_varint::decode::Error> for Error {
    fn from(_: unsigned_varint::decode::Error) -> Self {
        Error::VarIntDecodeError
    }
}

#[cfg(feature = "std")]
impl From<unsigned_varint::io::ReadError> for Error {
    fn from(err: unsigned_varint::io::ReadError) -> Self {
        use unsigned_varint::io::ReadError::*;
        match err {
            Io(err) => Self::Io(err),
            _ => Self::VarIntDecodeError,
        }
    }
}

impl From<io::Error> for Error {
    fn from(err: io::Error) -> Self {
        Self::Io(err)
    }
}
