TypeCoercion.scala

/*
 * Copyright 2014–2019 SlamData Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package quasar.api.destination

import cats.{Eq, Show}
import cats.data.NonEmptyList
import cats.implicits._

import quasar.api.table.ColumnType

import shims._

import scala.{List, Nothing, Option, Product, Serializable, StringContext}
import scala.util.Either

sealed trait TypeCoercion[+C, +T] extends Product with Serializable

object TypeCoercion {

  implicit def equal[C: Eq, T: Eq]: Eq[TypeCoercion[C, T]] =
    Eq instance {
      case (Unsatisfied(a1, t1), Unsatisfied(a2, t2)) =>
        a1 === a2 && t1 === t2

      case (Satisfied(p1), Satisfied(p2)) =>
        p1 === p2

      case _ =>
        false
    }

  implicit def show[C: Show, T: Show]: Show[TypeCoercion[C, T]] =
    Show show {
      case Unsatisfied(alt, top) =>
        s"Unsatisfied(${alt.show}, ${top.show})"

      case Satisfied(priority) =>
        s"Unsatisfied(${priority.show})"
    }

  final case class Unsatisfied[T](alternatives: List[ColumnType], top: Option[T]) extends TypeCoercion[Nothing, T]
  final case class Satisfied[C, T](priority: NonEmptyList[Either[C, T]]) extends TypeCoercion[C, T]
}