Final encoded email filter

functional-dsl-blog-8.scala

object final_encoded_email_filter {
  final case class Address(emailAddress: String)
  final case class Email(sender: Address, to: List[Address], subject: String, body: String)

  case class EmailFilter(run: Email => Boolean) { self =>
    def &&(that: EmailFilter): EmailFilter = EmailFilter(email => self.run(email) && that.run(email))

    def ||(that: EmailFilter): EmailFilter =  EmailFilter(email => self.run(email) || that.run(email))

    def negate : EmailFilter = EmailFilter(email => !self.run(email))
  }

  object EmailFilter {

    val always: EmailFilter = EmailFilter(_ => true)

    val never: EmailFilter = always.negate

    def senderIs(sender: Address): EmailFilter = EmailFilter(email => email.sender == sender)

    def senderIsNot(sender: Address): EmailFilter = senderIs(sender).negate

    def recipientIs(recipient: Address): EmailFilter = EmailFilter(email => email.to.contains(recipient))

    def recipientIsNot(recipient: Address): EmailFilter = recipientIs(recipient).negate

    def senderIn(senders: Set[Address]): EmailFilter = senders.foldLeft(never)(_ || senderIs(_))

    def recipientIn(recipients: Set[Address]): EmailFilter = recipients.foldLeft(never)(_ || recipientIs(_))

    def bodyContains(phrase: String): EmailFilter = EmailFilter(email => email.body.contains(phrase))

    def bodyDoesNotContain(phrase: String): EmailFilter = bodyContains(phrase).negate
  }

  val filter: EmailFilter = EmailFilter.senderIsNot(Address("[email protected]")) && EmailFilter.bodyContains("Unsubscribe")
  val emails: List[Email] = List(Email(Address("[email protected]"), List(Address("[email protected]")), "Promotion", "10% off. Unsubscribe"))
  val newsletters: List[Email] = emails.filter(filter.run)
}