sbt/util/collection/PMap.scala

/* sbt -- Simple Build Tool
 * Copyright 2010 Mark Harrah
 */
package sbt

	import Types._
	import collection.mutable

trait RMap[K[_], V[_]]
{
	def apply[T](k: K[T]): V[T]
	def get[T](k: K[T]): Option[V[T]]
	def contains[T](k: K[T]): Boolean
	def toSeq: Seq[(K[_], V[_])]
}

trait IMap[K[_], V[_]] extends (K ~> V) with RMap[K,V]
{
	def put[T](k: K[T], v: V[T]): IMap[K,V]
	def remove[T](k: K[T]): IMap[K,V]
	def mapValue[T](k: K[T], init: V[T], f: V[T] => V[T]): IMap[K,V]
	def mapValues[V2[_]](f: V ~> V2): IMap[K,V2]
}
trait PMap[K[_], V[_]] extends (K ~> V) with RMap[K,V]
{
	def update[T](k: K[T], v: V[T]): Unit
	def remove[T](k: K[T]): Option[V[T]]
	def getOrUpdate[T](k: K[T], make: => V[T]): V[T]
	def mapValue[T](k: K[T], init: V[T], f: V[T] => V[T]): V[T]
}
object PMap
{
	implicit def toFunction[K[_], V[_]](map: PMap[K,V]): K[_] => V[_] = k => map(k)
	def empty[K[_], V[_]]: PMap[K,V] = new DelegatingPMap[K,V](new mutable.HashMap)
}
object IMap
{
	/**
	* Only suitable for K that is invariant in its type parameter.
	* Option and List keys are not suitable, for example,
	*  because None <:< Option[String] and None <: Option[Int].
	*/
	def empty[K[_], V[_]]: IMap[K,V] = new IMap0[K,V](Map.empty)

	private[this] class IMap0[K[_], V[_]](backing: Map[K[_], V[_]]) extends AbstractRMap[K,V] with IMap[K,V]
	{
		def get[T](k: K[T]): Option[V[T]] = ( backing get k ).asInstanceOf[Option[V[T]]]
		def put[T](k: K[T], v: V[T]) = new IMap0[K,V]( backing.updated(k, v) )
		def remove[T](k: K[T]) = new IMap0[K,V]( backing - k )

		def mapValue[T](k: K[T], init: V[T], f: V[T] => V[T]) =
			put(k, f(this get k getOrElse init))

		def mapValues[V2[_]](f: V ~> V2) =
			new IMap0[K,V2](backing.mapValues(x => f(x)).toMap)
		def toSeq = backing.toSeq

		override def toString = backing.toString
	}
}

abstract class AbstractRMap[K[_], V[_]] extends RMap[K,V]
{
	def apply[T](k: K[T]): V[T] = get(k).get
	def contains[T](k: K[T]): Boolean = get(k).isDefined
}

/**
* Only suitable for K that is invariant in its type parameter.
* Option and List keys are not suitable, for example,
*  because None <:< Option[String] and None <: Option[Int].
*/
class DelegatingPMap[K[_], V[_]](backing: mutable.Map[K[_], V[_]]) extends AbstractRMap[K,V] with PMap[K,V]
{
	def get[T](k: K[T]): Option[V[T]] = cast[T]( backing.get(k) )
	def update[T](k: K[T], v: V[T]) { backing(k) = v }
	def remove[T](k: K[T]) = cast( backing.remove(k) )
	def getOrUpdate[T](k: K[T], make: => V[T]) = cast[T]( backing.getOrElseUpdate(k, make) )
	def mapValue[T](k: K[T], init: V[T], f: V[T] => V[T]): V[T] =
	{
		val v = f(this get k getOrElse init)
		update(k, v)
		v
	}
	def toSeq = backing.toSeq

	private[this] def cast[T](v: V[_]): V[T] = v.asInstanceOf[V[T]]
	private[this] def cast[T](o: Option[V[_]]): Option[V[T]] = o map cast[T]

	override def toString = backing.toString
}