Add a `bytes` helper method to `Index`

[valencik]

Currently we get the ByteVector of an Index with something like:

val indexBytes = MultiIndex.codec
  .encode(index)
  .map(_.bytes)
  .toEither
  .leftMap(err => new Throwable(err.message))

This feels like a lot of ceremony, let's add a bytes method to the Index trait that does this for us.

[abinashlingank]

Hi! I'd like to work on this issue.

Solution:
I'll add a bytes method to the Index trait to simplify encoding and error handling. The new method will return the byte array as Either[Throwable, Array[Byte]], reducing the boilerplate code.

trait Index {
  def bytes: Either[Throwable, Array[Byte]] = {
    MultiIndex.codec.encode(this)
      .map(_.bytes)
      .toEither
      .leftMap(err => new Throwable(err.message))
  }
}

Now, we can call index.bytes to get the byte array directly.

Let me know if I can proceed!

[valencik]

Hi @abinashlingank! 👋

That's close, but I think if you were to write that code you'd find that it won't compile.
The return type of your code isn't an Array[Byte], it is a ByteVector, which is actually what we want.

Additionally, because FrequencyIndex and PositionalIndex have different Codecs, this would have to be abstract on the Index trait.
Unless we made an abstract def codec: Codec[Index] on the Index and then the bytes helper method could be concrete and leverage that.
That would work.

I'm happy to have you proceed, it just might not be as straightforward as you've initially sketched out.