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package com.github.mdr.ascii.util

import scala.annotation.tailrec

object Utils {

  def transformValues[K, V, V2](map: Map[K, V])(f: V ⇒ V2): Map[K, V2] = map.map { case (k, v) ⇒ (k, f(v)) }

  def withPrevious[T](iterable: Iterable[T]): List[(Option[T], T)] =
    withPreviousAndNext(iterable).map { case (a, b, c) ⇒ (a, b) }

  def withPreviousAndNext[T](iterable: Iterable[T]): List[(Option[T], T, Option[T])] = {
    if (iterable.isEmpty)
      Nil
    else {
      val previous = None :: (iterable.init map Some[T]).toList
      val next = (iterable.tail map Some[T]).toList ::: List(None)
      previous zip iterable zip next map { case ((a, b), c) ⇒ (a, b, c) }
    }
  }

  def adjacentPairs[T](xs: List[T]): List[(T, T)] = xs zip xs.drop(1)

  def adjacentTriples[T](xs: List[T]): List[(T, T, T)] = xs zip xs.drop(1) zip xs.drop(2) map { case ((x, y), z) ⇒ (x, y, z) }

  @tailrec
  def iterate[T](t: T, f: T ⇒ Option[T]): T = f(t) match {
    case Some(t2) ⇒ iterate(t2, f)
    case None     ⇒ t
  }

  def multisetCompare[T](set1: List[T], set2: List[T]): Boolean =
    mkMultiset(set1) == mkMultiset(set2)

  def mkMultiset[T](set1: List[T]): Map[T, Int] = set1.groupBy(identity).mapValues(_.size).toMap

  def removeFirst[T](xs: List[T], x: T): List[T] = xs match {
    case Nil    ⇒ Nil
    case h :: t ⇒ if (h == x) t else h :: removeFirst(t, x)
  }

  def makeMap[T, U](s: Iterable[T], f: T ⇒ U): Map[T, U] =
    s.map(t ⇒ t -> f(t))(collection.breakOut)

  def signum(x: Int) = x match {
    case _ if x < 0 ⇒ -1
    case 0          ⇒ 0
    case _ if x > 0 ⇒ +1
  }

}