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package com.rockymadden.stringmetric.phonetic
import com.rockymadden.stringmetric.Algorithm.StringAlgorithm
case object SoundexAlgorithm extends StringAlgorithm {
import com.rockymadden.stringmetric.Alphabet.Alpha
override def compute(a: Array[Char]): Option[Array[Char]] =
if (a.length == 0 || !(Alpha isSuperset a.head)) None
else {
val fc = a.head.toLower
Some(transcode(a.tail, fc, Array(fc)).padTo(4, '0'))
}
override def compute(string: String): Option[String] = compute(string.toCharArray).map(_.mkString)
@annotation.tailrec
private val transcode: ((Array[Char], Char, Array[Char]) => Array[Char]) = (i, pc, o) =>
if (i.length == 0) o
else {
val c = i.head.toLower
val m2 = (mc: Char) => (mc: @annotation.switch) match {
case 'b' | 'f' | 'p' | 'v' => '1'
case 'c' | 'g' | 'j' | 'k' | 'q' | 's' | 'x' | 'z' => '2'
case 'd' | 't' => '3'
case 'l' => '4'
case 'm' | 'n' => '5'
case 'r' => '6'
case _ => '\0'
}
val m1 = (mc: Char, pc: Char) => (mc: @annotation.switch) match {
case 'b' | 'f' | 'p' | 'v' if pc != '1' => '1'
case 'c' | 'g' | 'j' | 'k' | 'q' | 's' | 'x' | 'z' if pc != '2' => '2'
case 'd' | 't' if pc != '3' => '3'
case 'l' if pc != '4' => '4'
case 'm' | 'n' if pc != '5' => '5'
case 'r' if pc != '6' => '6'
case _ => '\0'
}
val a = pc match {
// Code twice.
case 'a' | 'e' | 'i' | 'o' | 'u' | 'y' => m2(c)
// Code once.
case _ => m1(
c,
(o.last: @annotation.switch) match {
case '1' | '2' | '3' | '4' | '5' | '6' => o.last
case _ => m2(o.last)
}
)
}
if (o.length == 3 && a != '\0') o :+ a
else transcode(i.tail, c, if (a != '\0') o :+ a else o)
}
}
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