tethys.compat.CollectionBuilder.scala Maven / Gradle / Ivy

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package tethys.compat

import scala.collection.{IterableFactory, MapFactory, mutable}
import scala.quoted.*

trait CollectionBuilder[A, C] {
  def newBuilder: mutable.Builder[A, C]
}

object CollectionBuilder {
  final class IterableFactoryCollectionBuilder[A, C[_]](
      factory: IterableFactory[C]
  ) extends CollectionBuilder[A, C[A]] {
    def newBuilder: mutable.Builder[A, C[A]] = factory.newBuilder[A]
  }

  final class MapFactoryCollectionBuilder[K, V, M[_, _]](factory: MapFactory[M])
      extends CollectionBuilder[(K, V), M[K, V]] {
    def newBuilder: mutable.Builder[(K, V), M[K, V]] = factory.newBuilder[K, V]
  }

  inline given iterableFactoryCollectionBuilder[A, C[X] <: Iterable[X]]
      : CollectionBuilder[A, C[A]] =
    ${ CollectionBuilderMacroImpl.fromIterableFactory[A, C] }

  inline given mapFactoryCollectionBuilder[K, V, M[
      X,
      Y
  ] <: scala.collection.Map[X, Y]]: CollectionBuilder[(K, V), M[K, V]] =
    ${ CollectionBuilderMacroImpl.fromMapFactory[K, V, M] }

  object CollectionBuilderMacroImpl {
    def fromIterableFactory[A: Type, C[X] <: Iterable[X]: Type](using
        Quotes
    ): Expr[IterableFactoryCollectionBuilder[A, C]] = {
      import quotes.reflect.*

      val factory = Ref(TypeRepr.of[C].typeSymbol.companionModule)
        .asExprOf[IterableFactory[C]]
      '{
        new tethys.compat.CollectionBuilder.IterableFactoryCollectionBuilder[
          A,
          C
        ]($factory)
      }
    }

    def fromMapFactory[
        K: Type,
        V: Type,
        M[X, Y] <: scala.collection.Map[X, Y]: Type
    ](using Quotes): Expr[MapFactoryCollectionBuilder[K, V, M]] = {
      import quotes.reflect.*

      val factory =
        Ref(TypeRepr.of[M].typeSymbol.companionModule).asExprOf[MapFactory[M]]
      '{
        new tethys.compat.CollectionBuilder.MapFactoryCollectionBuilder[
          K,
          V,
          M
        ]($factory)
      }
    }
  }
}