Generators.scala

import zio.random.Random
import zio.test.Gen.alphaNumericChar
import zio.test.{ Gen, Sized }

object Generators {

  val anyIntX: Gen[Random, Int] =
    Gen.oneOf(
      Gen.oneOf(
        Gen.const(0),
        Gen.const(1),
        Gen.const(-1),
        Gen.const(Int.MaxValue),
        Gen.const(Int.MaxValue - 1),
        Gen.const(Int.MinValue),
        Gen.const(Int.MinValue + 1)
      ),
      Gen.anyInt
    )

  val anyLongX: Gen[Random, Long] =
    Gen.oneOf(
      Gen.oneOf(
        Gen.const(0L),
        Gen.const(1L),
        Gen.const(-1L),
        Gen.const(Long.MaxValue),
        Gen.const(Long.MaxValue - 1L),
        Gen.const(Long.MinValue),
        Gen.const(Long.MinValue + 1L)
      ),
      Gen.anyLong
    )

  def intX(min: Int, max: Int): Gen[Random, Int] =
    Gen.oneOf(
      Gen.oneOf(
        Gen.const(min),
        Gen.const(Math.min(min + 1, max)),
        Gen.const(max),
        Gen.const(Math.max(min, max - 1))
      ),
      Gen.int(min, max)
    )

  def longX(min: Long, max: Long): Gen[Random, Long] =
    Gen.oneOf(
      Gen.oneOf(
        Gen.const(min),
        Gen.const(Math.min(min + 1L, max)),
        Gen.const(max),
        Gen.const(Math.max(min, max - 1L))
      ),
      Gen.long(min, max)
    )

  ////

  def stringN(min: Int, max: Int): Gen[Random with Sized, String] =
    for {
      n <- intX(min, max)
      s <- Gen.stringN(n)(alphaNumericChar)
    } yield s

  def stringTuple2(min: Int, max: Int): Gen[Random with Sized, (String, String)] =
    for {
      s1 <- stringN(min, max)
      s2 <- stringN(min, max)
    } yield (s1, s2)

  def listN[A](min: Int, max: Int)(gen: Gen[Random with Sized, A]): Gen[Random with Sized, List[A]] =
    for {
      n <- intX(min, max)
      l <- Gen.listOfN(n)(gen)
    } yield l

}