com.rockymadden.stringmetric.phonetic.NysiisAlgorithm.scala Maven / Gradle / Ivy

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String metrics and phonetic algorithms for Scala.
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package com.rockymadden.stringmetric.phonetic

import com.rockymadden.stringmetric.Algorithm.StringAlgorithm

case object NysiisAlgorithm extends StringAlgorithm {
	import com.rockymadden.stringmetric.Alphabet.{Alpha, LowercaseVowel}

	override def compute(a: Array[Char]): Option[Array[Char]] =
		if (a.length == 0 || !(Alpha isSuperset a.head)) None
		else {
			val tr = transcodeRight(a.map(_.toLower))
			val tl = transcodeLeft(tr._1)
			val t =
				if (tl._2.length == 0) tl._1 ++ tr._2
				else tl._1 ++ transcodeCenter(
					Array.empty[Char],
					tl._2.head,
					if (tl._2.length > 1) tl._2.tail else Array.empty[Char],
					Array.empty[Char]
				) ++ tr._2

			if (t.length == 1) Some(t)
			else Some(t.head +: (cleanLast andThen cleanTerminal andThen deduplicate)(t.tail))
		}

	override def compute(a: String): Option[String] = compute(a.toCharArray).map(_.mkString)

	private val cleanLast: (Array[Char] => Array[Char]) = (ca) =>
		if (ca.length == 0) ca
		else if(ca.last == 'a' || ca.last == 's')
			ca.dropRight(ca.reverseIterator.takeWhile(c => c == 'a' || c == 's').length)
		else ca

	private val cleanTerminal: (Array[Char] => Array[Char]) = (ca) =>
		if (ca.length >= 2 && ca.last == 'y' && ca(ca.length - 2) == 'a') ca.dropRight(2) :+ 'y'
		else ca

	private val deduplicate: (Array[Char] => Array[Char]) = (ca) =>
		if (ca.length <= 1) ca
		else ca.sliding(2).withFilter(a => a(0) != a(1)).map(_(0)).toArray[Char] :+ ca.last

	@annotation.tailrec
	private val transcodeCenter: ((Array[Char], Char, Array[Char], Array[Char]) => Array[Char]) = (l, c, r, o) =>
		if (c == '\0' && r.length == 0) o
		else {
			def shift(d: Int, ca: Array[Char]) = {
				val sca = r.splitAt(d - 1)

				(
					if (sca._1.length > 0) (l :+ c) ++ sca._1 else l :+ c,
					if (sca._2.length > 0) sca._2.head else '\0',
					if (sca._2.length > 1) sca._2.tail else Array.empty[Char],
					ca
				)
			}

			val t = {
				(c: @annotation.switch) match {
					case 'a' | 'i' | 'o' | 'u' => shift(1, o :+ 'a')
					case 'b' | 'c' | 'd' | 'f' | 'g' | 'j' | 'l' | 'n' | 'r' | 't' | 'v' | 'x' | 'y' => shift(1, o :+ c)
					case 'e' =>
						if (r.length >= 1 && r.head == 'v') shift(2, o ++ Array('a', 'f'))
						else shift(1, o :+ 'a')
					case 'h' =>
						if (l.length >= 1 && (!(LowercaseVowel isSuperset l.last) || (r.length >= 1 && !(LowercaseVowel isSuperset r.head))))
							shift(1, o)
						else shift(1, o :+ c)
					case 'k' => if (r.length >= 1 && r.head == 'n') shift(2, o :+ 'n') else shift(1, o :+ 'c')
					case 'm' => shift(1, o :+ 'n')
					case 'p' => if (r.length >= 1 && r.head == 'h') shift(2, o :+ 'f') else shift(1, o :+ c)
					case 'q' => shift(1, o :+ 'g')
					case 's' =>
						if (r.length >= 2 && r.head == 'c' && r(1) == 'h') shift(3, o :+ c)
						else shift(1, o :+ c)
					case 'w' =>
						if (l.length >= 1 && (LowercaseVowel isSuperset l.last)) shift(1, o)
						else shift(1, o :+ c)
					case 'z' => shift(1, o :+ 's')
					case _ => shift(1, o)
				}
			}

			transcodeCenter(t._1, t._2, t._3, t._4)
		}

	private val transcodeLeft: (Array[Char] => (Array[Char], Array[Char])) = (ca) =>
		if (ca.length == 0) (Array.empty[Char], ca)
		else {
			lazy val tr2 = ca.takeRight(ca.length - 2)
			lazy val tr3 = ca.takeRight(ca.length - 3)

			(ca.head: @annotation.switch) match {
				case 'k' if ca.length >= 2 && ca(1) == 'n' => (Array('n', 'n'), tr2)
				case 'k' => (Array('c'), ca.tail)
				case 'm' if ca.length >= 3 && (ca(1) == 'a' && ca(2) == 'c') => (Array('m', 'c'), tr3)
				case 'p' if ca.length >= 2 && (ca(1) == 'h' || ca(1) == 'f') => (Array('f', 'f'), tr2)
				case 's' if ca.length >= 3 && (ca(1) == 'c' && ca(2) == 'h') => (Array('s', 's'), tr3)
				case _ => (Array(ca.head), ca.tail)
			}
		}

	private val transcodeRight: (Array[Char] => (Array[Char], Array[Char])) = (ca) =>
		if (ca.length >= 2) {
			val lc = ca(ca.length - 1)
			val lcm1 = ca(ca.length - 2)
			lazy val t2 = ca.take(ca.length - 2)

			(lc: @annotation.switch) match {
				case 'd' if lcm1 == 'n' || lcm1 == 'r' => (t2, Array('d'))
				case 'e' if lcm1 == 'e' || lcm1 == 'i' => (t2, Array('y'))
				case 't' if lcm1 == 'd' || lcm1 == 'n' || lcm1 == 'r' => (t2, Array('d'))
				case _ => (ca, Array.empty[Char])
			}
		} else (ca, Array.empty[Char])
}