Virgil ideas

nextlevel.scala

package io.kaizensolutions.virgil.nextlevel

import io.kaizensolutions.virgil.nextlevel.nextlevel.peopleTable

object nextlevel {

  sealed trait Table {
    type TableTag
  }
  object Table {
    type WithTag[Tag] = Table { type TableTag = Tag }

    sealed trait Source[ColTaggerFunction[_]] extends Table {
      val tableName: String
      val columns: ColTaggerFunction[TableTag]
    }

    def make[ColType, Rest <: ColumnSet](name: String)(
      columnSet: ColumnSet.Cons[ColType, Rest]
    ): Table.Source[columnSet.ColumnsRepr] =
      columnSet.makeTable(name)
  }
  // Need to store Writer + Reader proof
  final case class Column[ColumnType](name: String)
  object Column {
    def int(name: String): Column[Int]             = Column(name)
    def string(name: String): Column[String]       = Column(name)
    def double(name: String): Column[Double]       = Column(name)
    def long(name: String): Column[Long]           = Column(name)
    def uuid(name: String): Column[java.util.UUID] = Column(name)
  }
  final case class ColumnFromTable[ColumnType, TableTag](name: String)

  sealed trait ColumnSet {
    // Type level function used to tag columns to a table
    type ColumnsRepr[TableTag]

    // Append
    def :*:[A](head: Column[A]): ColumnSet

    protected def mkColumns[Tag]: ColumnsRepr[Tag]
  }
  object ColumnSet {
    type Finish = Finish.type
    case object Finish extends ColumnSet {
      override type ColumnsRepr[TableTag] = Unit

      override def :*:[ColType](head: Column[ColType]): Cons[ColType, Finish] = Cons(head, Finish)

      override protected def mkColumns[Tag]: ColumnsRepr[Tag] = ()
    }

    final case class Cons[ColType, Rest <: ColumnSet](head: Column[ColType], rest: Rest) extends ColumnSet { self =>
      override type ColumnsRepr[TableTag] = (ColumnFromTable[ColType, TableTag], rest.ColumnsRepr[TableTag])

      override def :*:[AnotherColType](head: Column[AnotherColType]): Cons[AnotherColType, Cons[ColType, Rest]] =
        Cons(head, self)

      override protected def mkColumns[Tag]: ColumnsRepr[Tag] =
        (ColumnFromTable[ColType, Tag](head.name), rest.mkColumns[Tag])

      def makeTable(name: String): Table.Source[ColumnsRepr] =
        new Table.Source[ColumnsRepr] {
          override type TableTag
          override val tableName: String              = name
          override val columns: ColumnsRepr[TableTag] = self.mkColumns[TableTag]
        }
    }

    object :*: {
      def unapply[A, B](tuple: (A, B)): Some[(A, B)] = Some(tuple)
    }
  }

  import ColumnSet._
  val peopleTable =
    Table.make("people") {
      Column.int("id") :*:
        Column.string("first_name") :*:
        Column.string("last_name") :*:
        Finish
    }

  val (id: ColumnFromTable[Int, peopleTable.TableTag]) :*:
    (firstName: ColumnFromTable[String, peopleTable.TableTag]) :*:
    (lastName: ColumnFromTable[String, peopleTable.TableTag]) :*: _ =
    peopleTable.columns

  /**
   * API
   *
   * val table = Table( column[String]("first_name) ~ column[Int]("age") ~
   * column[String]("email) )
   *
   * val firstName ~ age ~ email ~ _ = table.columns
   *
   * Insert.into(table) .value(firstName, "John") .value(age, 42) .value(email,
   * "[email protected]")
   */

}