hadilq

fun doWork(): Result<Unit> {
  return input() into
    ::parse elseIf
    {
      return Failure("Cannot parse email")
    } into
    ::validate elseIf
    {
      InvalidEmailAddress { message -> return Failure(message) }
      EmptySubject(::fixEmptySubject)

hadilq

fun doWork(): Result<Unit> {
  return input() into
    ::parse elseIf
    {
      return Failure("Cannot parse email")
    } into
    ::validate elseIf
    {
      InvalidEmailAddress { message -> return Failure(message) }
      EmptySubject { message -> return Failure(message) }

hadilq

send() elseIf {
  IOFailure { error: IOException -> /* handle failure */ }
  Timeout { error: TimeoutException -> /* handle failure */ }
  UnAuthorized { error: UnAuthorizedException -> 
    /* handle failure */ 
  }
}

hadilq

public inline infix fun ValidationResult.elseIf(build: ValidationResultElseIfBuilder.() -> Unit):
    Success {
  if (this is Success) {
    return this
  } else {
    val builder = ValidationResultElseIfBuilder(this)
    builder.build()
    return builder.result
  }
}

hadilq

public class ValidationResultElseIfBuilder(
  public val parent: ValidationResult
) {
  public lateinit var result: Success

  public inline fun InvalidEmailAddress(block: (errorMessage: String) -> Success): Unit {
    if(parent is InvalidEmailAddress) {
      result = block(parent.errorMessage)
    }
  }

hadilq

doWork() : Result<Email> {
  ...
  validate() elseIf {
    InvalidEmailAddress { errorMessage: String -> 
      return Failure(errorMessage)
    }
    EmptySubject { errorMessage: String -> /* handle failure */ }
    EmptyBody { errorMessage: String -> /* handle failure */ }
  }
  ...

hadilq

validate() elseIf {
  InvalidEmailAddress { errorMessage: String -> 
    /* handle failure */ 
  }
  EmptySubject { errorMessage: String -> /* handle failure */ }
  EmptyBody { errorMessage: String -> /* handle failure */ }
}

hadilq

sealed class SendResult
data class SendSuccess(val email: Email): SendResult()
data class IOFailure(val error: IOException): SendResult()
data class Timeout(val error: TimeoutException): SendResult()
data class UnAuthorized(val error: UnAuthorizedException): SendResult()

hadilq

sealed class Result<T>
data class Success<T>(val value: T): Result<T>()
data class Failure<T>(val errorMessage: String): Result<T>()

hadilq

sealed class ValidationResult
data class ValidationSuccess(val email: Email): ValidationResult()
data class InvalidEmailAddress(val errorMessage: String): ValidationResult()
data class EmptySubject(val errorMessage: String): ValidationResult()
data class EmptyBody(val errorMessage: String): ValidationResult()