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package com.rockymadden.stringmetric.phonetic
import com.rockymadden.stringmetric.{StringAlgorithm, StringFilter}
import com.rockymadden.stringmetric.Alphabet.{Alpha, LowercaseVowel}
import scala.annotation.{switch, tailrec}
/** An implementation of the Metaphone algorithm. */
class MetaphoneAlgorithm extends StringAlgorithm[DummyImplicit, String] { this: StringFilter =>
final override def compute(charArray: Array[Char])(implicit di: DummyImplicit): Option[Array[Char]] = {
val fca = filter(charArray)
if (fca.length == 0 || !(Alpha isSuperset fca.head)) None
else {
val th = deduplicate(transcodeHead(fca.map(_.toLower)))
val t = transcode(Array.empty[Char], th.head, th.tail, Array.empty[Char])
if (t.length == 0) None else Some(t) // Single Y or W would have 0 length.
}
}
final override def compute(string: String)(implicit di: DummyImplicit): Option[String] =
compute(string.toCharArray).map(_.mkString)
private[this] def deduplicate(ca: Array[Char]) =
if (ca.length <= 1) ca
else ca.sliding(2).withFilter(a => a(0) == 'c' || a(0) != a(1)).map(a => a(0)).toArray[Char] :+ ca.last
@tailrec
private[this] def transcode(l: Array[Char], c: Char, r: Array[Char], o: Array[Char]): Array[Char] = {
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: @switch) match {
case 'a' | 'e' | 'i' | 'o' | 'u' => if (l.length == 0) shift(1, o:+ c) else shift(1, o)
case 'f' | 'j' | 'l' | 'm' | 'n' | 'r' => shift(1, o :+ c)
case 'b' => if (l.length >= 1 && l.last == 'm' && r.length == 0) shift(1, o) else shift(1, o :+ 'b')
case 'c' =>
if (r.length >= 1 && r.head == 'h' && l.length >= 1 && l.last == 's') shift(1, o :+ 'k')
else if (r.length >= 2 && r.head == 'i' && r(1) == 'a') shift(3, o :+ 'x')
else if ((r.length >= 1 && r.head == 'h')
|| (l.length >= 1 && r.length >= 1 && l.last == 's' && r.head == 'h')) shift(2, o :+ 'x')
else if (l.length >= 1 && r.length >= 1 && l.last == 's'
&& (r.head == 'i' || r.head == 'e' || r.head == 'y')) shift(1, o)
else if (r.length >= 1 && (r.head == 'i' || r.head == 'e' || r.head == 'y')) shift(1, o :+ 's')
else shift(1, o :+ 'k')
case 'd' =>
if (r.length >= 2 && r.head == 'g'
&& (r(1) == 'e' || r(1) == 'y' || r(1) == 'i')) shift(1, o :+ 'j')
else shift(1, o :+ 't')
case 'g' =>
if ((r.length > 1 && r.head == 'h')
|| (r.length == 1 && r.head == 'n')
|| (r.length == 3 && r.head == 'n' && r(1) == 'e' && r(2) == 'd')) shift(1, o)
else if (r.length >= 1 && (r.head == 'i' || r.head == 'e' || r.head == 'y')) shift(2, o :+ 'j')
else shift(1, o :+ 'k')
case 'h' =>
if ((l.length >= 1 && (LowercaseVowel isSuperset l.last) && (r.length == 0 || !(LowercaseVowel isSuperset r.head)))
|| (l.length >= 2 && l.last == 'h'
&& (l(l.length - 2) == 'c' || l(l.length - 2) == 's' || l(l.length - 2) == 'p'
|| l(l.length - 2) == 't' || l(l.length - 2) == 'g'))) shift(1, o)
else shift(1, o :+ 'h')
case 'k' => if (l.length >= 1 && l.last == 'c') shift(1, o) else shift(1, o :+ 'k')
case 'p' => if (r.length >= 1 && r.head == 'h') shift(2, o :+ 'f') else shift(1, o :+ 'p')
case 'q' => shift(1, o :+ 'k')
case 's' =>
if (r.length >= 2 && r.head == 'i' && (r(1) == 'o' || r(1) == 'a')) shift(3, o :+ 'x')
else if (r.length >= 1 && r.head == 'h') shift(2, o :+ 'x')
else shift(1, o :+ 's')
case 't' =>
if (r.length >= 2 && r.head == 'i' && (r(1) == 'a' || r(1) == 'o')) shift(3, o :+ 'x')
else if (r.length >= 1 && r.head == 'h') shift(2, o :+ '0')
else if (r.length >= 2 && r.head == 'c' && r(1) == 'h') shift(1, o)
else shift(1, o :+ 't')
case 'v' => shift(1, o :+ 'f')
case 'w' | 'y' => if (r.length == 0 || !(LowercaseVowel isSuperset r.head)) shift(1, o) else shift(1, o :+ c)
case 'x' => shift(1, (o :+ 'k') :+ 's')
case 'z' => shift(1, o :+ 's')
case _ => shift(1, o)
}
}
transcode(t._1, t._2, t._3, t._4)
}
}
private[this] def transcodeHead(ca: Array[Char]) = {
(ca.length: @switch) match {
case 0 => ca
case 1 => if (ca.head == 'x') Array('s') else ca
case _ =>
(ca.head: @switch) match {
case 'a' if (ca(1) == 'e') => ca.tail
case 'g' | 'k' | 'p' if (ca(1) == 'n') => ca.tail
case 'w' if (ca(1) == 'r') => ca.tail
case 'w' if (ca(1) == 'h') => 'w' +: ca.drop(2)
case 'x' => 's' +: ca.tail
case _ => ca
}
}
}
}
object MetaphoneAlgorithm {
private lazy val self = apply()
def apply(): MetaphoneAlgorithm = new MetaphoneAlgorithm with StringFilter
def compute(charArray: Array[Char]) = self.compute(charArray)
def compute(string: String) = self.compute(string)
}
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