/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala
package collection
package immutable

import generic._
import immutable.{RedBlackTree => RB}
import mutable.Builder

/** $factoryInfo
 *  @define Coll immutable.TreeMap
 *  @define coll immutable tree map
 */
object TreeMap extends ImmutableSortedMapFactory[TreeMap] {
  def empty[A, B](implicit ord: Ordering[A]) = new TreeMap[A, B]()(ord)
  /** $sortedMapCanBuildFromInfo */
  implicit def canBuildFrom[A, B](implicit ord: Ordering[A]): CanBuildFrom[Coll, (A, B), TreeMap[A, B]] = new SortedMapCanBuildFrom[A, B]
}

/** This class implements immutable maps using a tree.
 *
 *  @tparam A         the type of the keys contained in this tree map.
 *  @tparam B         the type of the values associated with the keys.
 *  @param ordering   the implicit ordering used to compare objects of type `A`.
 *
 *  @author  Erik Stenman
 *  @author  Matthias Zenger
 *  @since   1
 *  @see [[http://docs.scala-lang.org/overviews/collections/concrete-immutable-collection-classes.html#red-black-trees "Scala's Collection Library overview"]]
 *  section on `Red-Black Trees` for more information.
 *
 *  @define Coll immutable.TreeMap
 *  @define coll immutable tree map
 *  @define orderDependent
 *  @define orderDependentFold
 *  @define mayNotTerminateInf
 *  @define willNotTerminateInf
 */
final class TreeMap[A, +B] private (tree: RB.Tree[A, B])(implicit val ordering: Ordering[A])
  extends SortedMap[A, B]
     with SortedMapLike[A, B, TreeMap[A, B]]
     with MapLike[A, B, TreeMap[A, B]]
     with Serializable {

  override protected[this] def newBuilder : Builder[(A, B), TreeMap[A, B]] =
    TreeMap.newBuilder[A, B]

  override def size = RB.count(tree)

  def this()(implicit ordering: Ordering[A]) = this(null)(ordering)

  override def rangeImpl(from: Option[A], until: Option[A]): TreeMap[A, B] = new TreeMap[A, B](RB.rangeImpl(tree, from, until))
  override def range(from: A, until: A): TreeMap[A, B] = new TreeMap[A, B](RB.range(tree, from, until))
  override def from(from: A): TreeMap[A, B] = new TreeMap[A, B](RB.from(tree, from))
  override def to(to: A): TreeMap[A, B] = new TreeMap[A, B](RB.to(tree, to))
  override def until(until: A): TreeMap[A, B] = new TreeMap[A, B](RB.until(tree, until))

  override def firstKey = RB.smallest(tree).key
  override def lastKey = RB.greatest(tree).key
  override def compare(k0: A, k1: A): Int = ordering.compare(k0, k1)

  override def head = {
    val smallest = RB.smallest(tree)
    (smallest.key, smallest.value)
  }
  override def headOption = if (RB.isEmpty(tree)) None else Some(head)
  override def last = {
    val greatest = RB.greatest(tree)
    (greatest.key, greatest.value)
  }
  override def lastOption = if (RB.isEmpty(tree)) None else Some(last)

  override def tail = new TreeMap(RB.delete(tree, firstKey))
  override def init = new TreeMap(RB.delete(tree, lastKey))

  override def drop(n: Int) = {
    if (n <= 0) this
    else if (n >= size) empty
    else new TreeMap(RB.drop(tree, n))
  }

  override def take(n: Int) = {
    if (n <= 0) empty
    else if (n >= size) this
    else new TreeMap(RB.take(tree, n))
  }

  override def slice(from: Int, until: Int) = {
    if (until <= from) empty
    else if (from <= 0) take(until)
    else if (until >= size) drop(from)
    else new TreeMap(RB.slice(tree, from, until))
  }

  override def dropRight(n: Int) = take(size - math.max(n, 0))
  override def takeRight(n: Int) = drop(size - math.max(n, 0))
  override def splitAt(n: Int) = (take(n), drop(n))

  private[this] def countWhile(p: ((A, B)) => Boolean): Int = {
    var result = 0
    val it = iterator
    while (it.hasNext && p(it.next())) result += 1
    result
  }
  override def dropWhile(p: ((A, B)) => Boolean) = drop(countWhile(p))
  override def takeWhile(p: ((A, B)) => Boolean) = take(countWhile(p))
  override def span(p: ((A, B)) => Boolean) = splitAt(countWhile(p))

  /** A factory to create empty maps of the same type of keys.
   */
  override def empty: TreeMap[A, B] = TreeMap.empty[A, B](ordering)

  /** A new TreeMap with the entry added is returned,
   *  if key is <em>not</em> in the TreeMap, otherwise
   *  the key is updated with the new entry.
   *
   *  @tparam B1     type of the value of the new binding which is a supertype of `B`
   *  @param key     the key that should be updated
   *  @param value   the value to be associated with `key`
   *  @return        a new $coll with the updated binding
   */
  override def updated [B1 >: B](key: A, value: B1): TreeMap[A, B1] = new TreeMap(RB.update(tree, key, value, overwrite = true))

  /** Add a key/value pair to this map.
   *  @tparam   B1   type of the value of the new binding, a supertype of `B`
   *  @param    kv   the key/value pair
   *  @return        A new $coll with the new binding added to this map
   */
  override def + [B1 >: B] (kv: (A, B1)): TreeMap[A, B1] = updated(kv._1, kv._2)

  /** Adds two or more elements to this collection and returns
   *  either the collection itself (if it is mutable), or a new collection
   *  with the added elements.
   *
   *  @tparam B1   type of the values of the new bindings, a supertype of `B`
   *  @param elem1 the first element to add.
   *  @param elem2 the second element to add.
   *  @param elems the remaining elements to add.
   *  @return      a new $coll with the updated bindings
   */
  override def + [B1 >: B] (elem1: (A, B1), elem2: (A, B1), elems: (A, B1) *): TreeMap[A, B1] =
    this + elem1 + elem2 ++ elems

  /** Adds a number of elements provided by a traversable object
   *  and returns a new collection with the added elements.
   *
   *  @param xs     the traversable object.
   */
  override def ++[B1 >: B] (xs: GenTraversableOnce[(A, B1)]): TreeMap[A, B1] =
    ((repr: TreeMap[A, B1]) /: xs.seq) (_ + _)

  /** A new TreeMap with the entry added is returned,
   *  assuming that key is <em>not</em> in the TreeMap.
   *
   *  @tparam B1    type of the values of the new bindings, a supertype of `B`
   *  @param key    the key to be inserted
   *  @param value  the value to be associated with `key`
   *  @return       a new $coll with the inserted binding, if it wasn't present in the map
   */
  def insert [B1 >: B](key: A, value: B1): TreeMap[A, B1] = {
    assert(!RB.contains(tree, key))
    new TreeMap(RB.update(tree, key, value, overwrite = true))
  }

  def - (key:A): TreeMap[A, B] =
    if (!RB.contains(tree, key)) this
    else new TreeMap(RB.delete(tree, key))

  /** Check if this map maps `key` to a value and return the
   *  value if it exists.
   *
   *  @param  key     the key of the mapping of interest
   *  @return         the value of the mapping, if it exists
   */
  override def get(key: A): Option[B] = RB.get(tree, key)

  /** Creates a new iterator over all elements contained in this
   *  object.
   *
   *  @return the new iterator
   */
  override def iterator: Iterator[(A, B)] = RB.iterator(tree)
  override def iteratorFrom(start: A): Iterator[(A, B)] = RB.iterator(tree, Some(start))

  override def keysIterator: Iterator[A] = RB.keysIterator(tree)
  override def keysIteratorFrom(start: A): Iterator[A] = RB.keysIterator(tree, Some(start))

  override def valuesIterator: Iterator[B] = RB.valuesIterator(tree)
  override def valuesIteratorFrom(start: A): Iterator[B] = RB.valuesIterator(tree, Some(start))

  override def contains(key: A): Boolean = RB.contains(tree, key)
  override def isDefinedAt(key: A): Boolean = RB.contains(tree, key)

  override def foreach[U](f : ((A,B)) => U) = RB.foreach(tree, f)
}
