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flat_modular.scala
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flat_modular.scala
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package ncreep.modularity
import io.circe.*
import ncreep.common.combineDecoders
import ncreep.error_generation.*
import ncreep.model.*
import scala.Tuple.*
import scala.compiletime.*
import scala.deriving.Mirror
@main def test(): Unit =
val codec = makeCodec[User]
// val codec2 = makeCodec[User2] // does not compile
val json = codec(user)
println(json)
println(codec.decodeJson(json))
end test
inline def makeCodec[A <: Product](
using mirror: Mirror.ProductOf[A]): Codec[A] =
checkDuplicateFields[A]
val encoders = summonAll[Map[mirror.MirroredElemTypes, Encoder.AsObject]]
val encoder = encodeTuple(encoders).contramap[A](Tuple.fromProductTyped)
val decoders = summonAll[Map[mirror.MirroredElemTypes, Decoder]]
val decoder = decodeTuple(decoders).map(mirror.fromTuple)
Codec.from(decoder, encoder)
// a helper for pattern matching
case class IsDecoderMap[T <: Tuple](value: Map[T, Decoder])
inline def decodeTuple[T <: Tuple](decoders: Map[T, Decoder]): Decoder[T] =
inline IsDecoderMap(decoders) match
case _: IsDecoderMap[EmptyTuple] => Decoder.const(EmptyTuple)
case ds: IsDecoderMap[h *: t] =>
combineDecoders(ds.value.head, decodeTuple(ds.value.tail))
// a helper for pattern matching
case class IsEncoderMap[T <: Tuple](value: Map[T, Encoder.AsObject])
inline def encodeTuple[T <: Tuple](encoders: Map[T, Encoder.AsObject]): Encoder.AsObject[T] =
inline IsEncoderMap(encoders) match
case _: IsEncoderMap[EmptyTuple] => emptyEncoder
case es: IsEncoderMap[h *: t] =>
combineObjectEncoders(es.value.head, encodeTuple(es.value.tail))
def emptyEncoder: Encoder.AsObject[EmptyTuple] = Encoder.AsObject.instance(_ => JsonObject.empty)
def combineObjectEncoders[H, T <: Tuple](eh: Encoder.AsObject[H], et: Encoder.AsObject[T]): Encoder.AsObject[H *: T] =
Encoder.AsObject.instance[H *: T]: ht =>
val headObject = eh.encodeObject(ht.head)
val tailObject = et.encodeObject(ht.tail)
JsonObject.fromIterable(headObject.toIterable ++ tailObject.toIterable)