scanamo

dynamoformat.scala

import shapeless._
import shapeless.labelled._
import shapeless.ops.function._
import shapeless.ops.hlist._
import shapeless.ops.record._
import shapeless.record._
import shapeless.syntax.singleton._
import shapeless.syntax.std._
import shapeless.syntax.std.function._
import shapeless.syntax.std.traversable._
import shapeless.record.recordOps

/**
  * {{{
  * >>> case class User(name: String, age: Int)
  * >>> val df: DynamoFormat[User] = DynamoFormat
  * ...   .genericRenamed('name, 'n)
  * >>> df.write(User("Hello", 5))
  * Right(User(Hello,5))
  * }}}
  */
def genericRenamed[T, R <: HList, InnerR <: HList](oldKey: Witness, newKey: Witness)(implicit 
  gen: LabelledGeneric.Aux[T, R],
  renamerWrite: Renamer.Aux[R, oldKey.T, newKey.T, InnerR],
  renamerRead: Renamer.Aux[InnerR, newKey.T, oldKey.T, R],
  formatR: Lazy[ConstructedDynamoFormat[InnerR]]
): DynamoFormat[T] =
  new DynamoFormat[T] {
    def read(av: AttributeValue): Xor[DynamoReadError, T] =
      formatR.value.read(av).map(l => gen.from(l.renameField(newKey, oldKey))).toXor

    def write(t: T): AttributeValue =
      formatR.value.write(gen.to(t).renameField(oldKey, newKey))
  }