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/*
 * SPDX-License-Identifier: Apache-2.0
 * Copyright 2016-2024 Daniel Urban and contributors listed in NOTICE.txt
 *
 * 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 dev.tauri.choam
package data

import cats.kernel.{ Hash, Order }

sealed trait Set[A] {

  def contains: A =#> Boolean

  /** @return `true` iff it did not already contain the element */
  def add: A =#> Boolean

  /** @return `true` iff it did contain the element */
  def remove: A =#> Boolean
}

object Set {

  final def hashSet[A](implicit A: Hash[A]): Axn[Set[A]] =
    Map.hashMap[A, Unit].map(new SetFromMap(_))

  final def orderedSet[A](implicit A: Order[A]): Axn[Set[A]] =
    Map.orderedMap[A, Unit].map(new SetFromMap(_))

  private[this] final class SetFromMap[A](m: Map[A, Unit]) extends Set[A] {
    final override val contains: A =#> Boolean =
      m.get.map(_.isDefined)
    final override val add: A =#> Boolean =
      m.putIfAbsent.contramap[A](a => (a, ())).map(_.isEmpty)
    final override val remove: A =#> Boolean =
      m.del
  }
}