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package hedgehog.core

sealed trait Result {

  import Result._

  def success: Boolean =
    this match {
      case Success =>
        true
      case Failure(_) =>
        false
    }

  def logs: List[Log] =
    this match {
      case Success =>
        Nil
      case Failure(l) =>
        l
    }

  def and(other: => Result): Result =
    this match {
      case Success =>
        other
      case Failure(logs) =>
        other match {
          case Success =>
            Failure(logs)
          case Failure(logs2) =>
            Failure(logs ++ logs2)
        }
    }

  def or(other: => Result): Result =
    this match {
      case Success =>
        Success
      case Failure(logs) =>
        other match {
          case Success =>
            Success
          case Failure(logs2) =>
            Failure(logs ++ logs2)
        }
    }

  def log(info: => Log): Result =
    this match {
      case Success =>
        Success
      case Failure(l) =>
        Failure(l ++ List(info))
    }
}

object Result {

  case object Success extends Result
  case class Failure(log: List[Log]) extends Result

  def success: Result =
    Success

  def failure: Result =
    Failure(Nil)

  def error(e: Exception): Result =
    failure.log(Error(e))

  def assert(b: Boolean): Result =
    if (b) success else failure

  def all(l: List[Result]): Result =
    l.foldLeft(Result.success)(_.and(_))

  def any(l: List[Result]): Result =
    l.foldLeft(Result.failure)(_.or(_))

  /**
    * Compare two arguments with the comparison function and return Result.success
    * if the function return true. Otherwise, it returns Result.failure with
    * the Log containing the argument values.
    *
    * @example
    * {{{
    *   val a1 = "abc"
    *   val a2 = "abc"
    *   Result.diff(a1, a2)(_ == _)
    *   // Result.success
    *
    *   Result.diff(123, 456)(_ != _).log("It must be different.")
    *   // Result.success
    *
    *   val x = 'q'
    *   val y = 80
    *   Result.diff(x, y)((x, y) => y < 87 && x <= 'r')
    *   // Result.success
    * }}}
    * @example
    * {{{
    *   val a1 = "abc"
    *   val a2 = "xyz"
    *   Result.diff(a1, a2)(_ == _)
    *   // Result.failure
    *   > === Failed ===
    *   > --- lhs ---
    *   > abc
    *   > --- rhs ---
    *   > xyz
    *
    *   Result.diff(123, 123)(_ != _).log("It must be different.")
    *   // Result.failure
    *   > === Failed ===
    *   > --- lhs ---
    *   > 123
    *   > --- rhs ---
    *   > 123
    *   > It must be different.
    *
    *   val x = 'z'
    *   val y = 100
    *   Result.diff(x, y)((x, y) => y < 87 && x <= 'r')
    *   // Result.failure
    *   > === Failed ===
    *   > --- lhs ---
    *   > z
    *   > --- rhs ---
    *   > 100
    * }}}
    *
    * @see https://github.com/hedgehogqa/haskell-hedgehog/blob/921e4af72a181f01d90816fd7055b823bf885b3b/hedgehog/src/Hedgehog/Internal/Property.hs#L707
    */
  def diff[A, B](a: A, b: B)(f: (A, B) => Boolean): Result =
    diffNamed("=== Failed ===", a, b)(f)

  def diffNamed[A, B](logName: String, a: A, b: B)(f: (A, B) => Boolean): Result =
    assert(f(a, b))
      .log(logName)
      .log("--- lhs ---")
      .log(String.valueOf(a))
      .log("--- rhs ---")
      .log(String.valueOf(b))

}