Scala List MultiMaps

gistfile1.scala

trait ListMultiMaps {
  type ListMultiMap[A, B] = Map[A, List[B]]

  implicit def listMultiMap2ListMultiMapOperations[A, B](map: ListMultiMap[A, B]) = new ListMultiMapOperations(map)

  object ListMultiMap {
    def apply[A, B](): ListMultiMap[A, B] = Map[A, List[B]]()
    def apply[A, B](kvs: List[(A, B)]): ListMultiMap[A, B] = {
      var rst = apply[A, B]()
      kvs foreach { kv =>
        rst = rst addBinding kv
      }

      rst
    }
  }

  class ListMultiMapOperations[A, B](map: ListMultiMap[A, B]) {
    def addBinding(key: A, value: B): ListMultiMap[A, B] = {
      val current = (map get key) getOrElse Nil
      map + (key -> (current ++ List(value)))
    }

    def addBinding(kv: (A, B)): ListMultiMap[A, B] = addBinding(kv._1, kv._2)

    def addBindings(key: A, values: List[B]): ListMultiMap[A, B] = {
      val current = (map get key) getOrElse Nil
      map + (key -> (current ++ values))
    }
    def addBindings(kv: (A, List[B])): ListMultiMap[A, B] = addBindings(kv._1, kv._2)
    def addBindings(that: ListMultiMap[A, B]): ListMultiMap[A, B] = {
      var rst = map
      that foreach { kvs =>
        rst = rst.addBindings(kvs)
      }

      rst
    }

    def removeBinding(key: A, value: B): ListMultiMap[A, B] = {
      val current = (map get key) getOrElse Nil
      current filterNot { _ == value } match {
        case Nil => map - key
        case updated => map + (key -> updated)
      }
    }

    def removeBinding(kv: (A, B)): ListMultiMap[A, B] = removeBinding(kv._1, kv._2)

    def removeBindings(key: A, values: List[B]): ListMultiMap[A, B] = {
      val current = (map get key) getOrElse Nil
      current filterNot { values contains _ } match {
        case Nil => map - key
        case updated => map + (key -> updated)
      }
    }
    def removeBindings(kv: (A, List[B])): ListMultiMap[A, B] = removeBindings(kv._1, kv._2)
    def removeBindings(that: ListMultiMap[A, B]): ListMultiMap[A, B] = {
      var rst = map
      that foreach { kvs =>
        rst = rst.removeBindings(kvs)
      }

      rst
    }

    def entryExists(key: A, p: B => Boolean): Boolean = (map get key) match {
      case Some(list) => list exists p
      case _ => false
    }
  }
}