Sheet.scala

package com.jiwire.pca.tasks.output.views

import mist.api.data.{JsData, JsList, JsMap, JsString}
import mist.api.encoding.JsEncoder
import shadedshapeless._
import shadedshapeless.labelled.FieldType
import shadedshapeless.ops.hlist.{Mapper, ToTraversable}
import shadedshapeless.ops.record._

case class Sheet(
  name: String,
  columns: Seq[String],
  rows: Seq[Seq[JsData]]
)


trait ToRow[A] {
  type Out
  def apply(a: A): Out
}
object ToRow {
  type Aux[A, Out0] = ToRow[A] {
    type Out = Out0
  }

  implicit val hnilToTab: Aux[HNil, HNil] = new ToRow[HNil] {
    type Out = HNil
    override def apply(a: HNil): HNil = HNil
  }

  implicit def hlistToTab[H, T <: HList, O <: HList](
    implicit headEnc: JsEncoder[H],
    toRow: ToRow.Aux[T, O]
  ): Aux[H :: T, JsData :: O] =
    new ToRow[H :: T] {
      type Out = JsData :: O
      def apply(a:  H :: T): JsData :: O = {
        headEnc.apply(a.head) :: toRow.apply(a.tail)
      }
    }

}

trait ToColumns[A] {
  def apply(): Seq[String]
}

object ToColumns {

  implicit def keysToCols[A, Repr <: HList, KeysRepr <: HList, O <: HList](implicit
    labGen: LabelledGeneric.Aux[A, Repr],
    keys: Keys.Aux[Repr, KeysRepr],
    traversable: ToTraversable.Aux[KeysRepr, List, Symbol]
  ): ToColumns[A] = new ToColumns[A] {
    override def apply(): Seq[String] = {
      traversable(keys.apply()).map(_.name)
    }
  }
}

trait ToSheet[A] {
  def apply(name: String, as: Seq[A]): Sheet
}

object ToSheet {

  implicit def labGenToSheet[A, H <: HList, F <: HList, O <: HList, Repr <: HList, KeysRepr <: HList, O2<: HList](implicit
    gen: Generic.Aux[A, H],
    toRow: ToRow.Aux[H, O],
    toCols: ToColumns[A],
    toList: ToTraversable.Aux[O, List, JsData]
  ): ToSheet[A] = new ToSheet[A] {
    override def apply(name: String, as: Seq[A]): Sheet = {
      val rows = as.map(a => toList.apply(toRow.apply(gen.to(a))))
      Sheet(name, toCols.apply(), rows)
    }
  }

  def apply[A](implicit toSheet: ToSheet[A]): ToSheet[A] = toSheet
}