/* CookieJar ADT, Mutable Object-Oriented Version
   Using Scala Lists of Pairs (CookieJarTupleList)
   CSci 556: Multiparadigm Programming, Spring 2012
   CSci 555: Functional Programming, Spring 2016
   H. Conrad Cunningham, Professor
   Computer and Information Science
   University of Mississippi

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2010-Spring: Developed from mutable Ruby version
2012-Spring: Minor updates
2016-03-09:  Some cleanup of Scala code and comments
2022-04-18:  Scala 3 compatibility check, added Unit to procedures

*/

/* Class CookieJarTupleList implements the CookieJar ADT using a Scala
   List of pairs to represent the jar (mathematical bag) of cookies.
   The first component of a pair is the CookieType and the second is
   the nonzero count of cookies with that type in the jar.  Each
   CookieType appears at most once in the list of tuples.

   IMPLEMENTATION INVARIANT: 
     (ForAll c : c IN CookieType ::
                 jar.filter(_ == (c,_)).length <= 1) &&
     (ForAll c, i : c IN CookieType && i IN Int ::
                    jar.filter(_ == (c,i)).length == 1 <=> i>0 &&
		    OCCURENCES(c,Bag) = i)

*/

class CookieJarTupleList[CookieType] extends CookieJar[CookieType] {

  // CookieJar's bag model implemented by tuple List (Cookietype,Int)
  private var jar = List[(CookieType,Int)]()
    .
  def putIn(cookie: CookieType): Unit = { 
    jar.span(_._1 != cookie) match {
      case (l,(_,i)::r) => jar = l ++ ((cookie,i+1)::r)
      case _            => jar = (cookie,1) :: jar
    }
  }
? 
  def eat(cookie: CookieType): Unit = {
    jar.span(_._1 != cookie) match {
      case (l,(_,i)::r) =>
        jar = l ++ (if (i>1) (cookie,i-1)::r else r)
      case _            => sys.error("Attempt to eat cookie \""


        + cookie + "\", which is not in the jar.")
    }
   }
      
  def isEmpty: Boolean                 = jar.isEmpty

  def has(cookie: CookieType): Boolean =
    !jar.filter(_._1 == cookie).isEmpty

  /* Redefine toString to return form "CookieJar(e1,e2,e3,...,en)"
     with all elements of bag in arbitrary order.
  */

  override def toString = "CookieJar(" + jarList.mkString(",") + ")"


  /* Private method jarList converts the map jar to a list with with
     appropriate duplicates.
  */

  private def jarList: List[CookieType] = 
    for ((c,i) <- jar ; j <- 1 to i) yield c

}