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/*
 * Copyright 2018-2024 OVO Energy Limited
 *
 * SPDX-License-Identifier: Apache-2.0
 */

package fs2.kafka

import cats.effect.Sync
import cats.syntax.functor.*
import cats.Applicative

/**
  * [[Jitter]] represents the ability to apply jitter to an existing value `n`, effectively
  * multiplying `n` with a pseudorandom value between `0` and `1` (both inclusive, although
  * implementation dependent).


  *
  * The default [[Jitter#default]] uses `java.util.Random` for pseudorandom values and always
  * applies jitter with a value between `0` (inclusive) and `1` (exclusive). If no jitter is
  * desired, use [[Jitter#none]].
  */
sealed abstract class Jitter[F[_]] {
  def withJitter(n: Double): F[Double]
}

object Jitter {

  def apply[F[_]](implicit F: Jitter[F]): Jitter[F] = F

  /**
    * Creates a default [[Jitter]] instance, which uses `java.util.Random` for generating
    * pseudorandom values, always applying jitter with a value between `0` (inclusive) and `1`
    * (exclusive).
    */
  def default[F[_]](implicit F: Sync[F]): F[Jitter[F]] =
    F.delay(new java.util.Random())
      .map { random =>
        new Jitter[F] {

          override def withJitter(n: Double): F[Double] =
            F.delay(random.nextDouble()).map(_ * n)

        }
      }

  /**
    * Creates a [[Jitter]] instance which does not apply jitter, meaning all input values will be
    * returned unmodified.
    */
  def none[F[_]](implicit F: Applicative[F]): Jitter[F] =
    new Jitter[F] {

      override def withJitter(n: Double): F[Double] =
        F.pure(n)

    }

}