use bstr::BStr;

///
pub mod name {
    use bstr::BString;
    use quick_error::quick_error;

    quick_error! {
        /// The error returned by [`name()`]
        #[derive(Debug)]
        #[allow(missing_docs)]
        pub enum Error {
            InvalidByte(name: BString) {
                display("A ref must not contain invalid bytes or ascii control characters: '{}'", name)
            }
            DoubleDot {
                display("A ref must not contain '..' as it may be mistaken for a range")
            }
            LockFileSuffix {
                display("A ref must not end with '.lock'")
            }
            ReflogPortion {
                display("A ref must not contain '@{{' which is a part of a ref-log")
            }
            Asterisk {
                display("A ref must not contain '*' character")
            }
            StartsWithDot {
                display("A ref must not start with a '.'")
            }
            EndsWithSlash {
                display("A ref must not end with a '/'")
            }
            Empty {
                display("A ref must not be empty")
            }
        }
    }
}

/// Assure the given `bytes` resemble a valid git ref name, which are returned unchanged on success.
pub fn name(bytes: &BStr) -> Result<&BStr, name::Error> {
    if bytes.is_empty() {
        return Err(name::Error::Empty);
    }
    if *bytes.last().expect("non-empty") == b'/' {
        return Err(name::Error::EndsWithSlash);
    }

    let mut previous = 0;
    for byte in bytes.iter() {
        match byte {
            b'\\' | b'^' | b':' | b'[' | b'?' | b' ' | b'~' | b'\0'..=b'\x1F' | b'\x7F' => {
                return Err(name::Error::InvalidByte((&[*byte][..]).into()))
            }
            b'*' => return Err(name::Error::Asterisk),
            b'.' if previous == b'.' => return Err(name::Error::DoubleDot),
            b'{' if previous == b'@' => return Err(name::Error::ReflogPortion),
            _ => {}
        }
        previous = *byte;
    }
    if bytes[0] == b'.' {
        return Err(name::Error::StartsWithDot);
    }
    if bytes.ends_with(b".lock") {
        return Err(name::Error::LockFileSuffix);
    }
    Ok(bytes)
}