orcus.bigtable.codec.DerivedFamilyDecoder.scala Maven / Gradle / Ivy
package orcus.bigtable.codec
import com.google.cloud.bigtable.data.v2.models.RowCell
import shapeless3.deriving.*
import scala.annotation.tailrec
trait DerivedFamilyDecoder[A] extends FamilyDecoder[A]
object DerivedFamilyDecoder extends DerivedFamilyDecoder1
private[codec] trait DerivedFamilyDecoder1:
private val pure = [A] => (a: A) => Right(a)
private val map = [A, B] => (fa: Either[Throwable, A], f: A => B) => fa.map(f)
private val tailRecM = [A, B] =>
(a: A, f: A => Either[Throwable, Either[A, B]]) =>
@tailrec def loop(a: A): Either[Throwable, B] = f(a) match
case Left(err) => Left(err)
case Right(Left(a)) => loop(a)
case Right(Right(b)) => Right(b)
loop(a)
given familyDecoderGen[A](using
inst: K0.ProductInstances[ValueDecoder, A],
labelling: Labelling[A]
): DerivedFamilyDecoder[A] with
def apply(family: List[RowCell]): Either[Throwable, A] =
val labels = labelling.elemLabels.iterator
val decode = [t] =>
(f: ValueDecoder[t]) =>
val label = labels.next()
val cells = family.collect { case r if r.getQualifier.toStringUtf8 == label => r }
f(cells)
inst.constructM(decode)(pure, map, tailRecM)
inline def derived[A](using K0.ProductGeneric[A]): DerivedFamilyDecoder[A] = familyDecoderGen