com.github.vickumar1981.stringdistance.interfaces.sound.SoundexAlgo.scala Maven / Gradle / Ivy

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A fuzzy matching string distance library for Scala and Java.

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package com.github.vickumar1981.stringdistance.interfaces.sound

import CommonSoundAlgo._

private[stringdistance] case object SoundexAlgo {
  // scalastyle:off
  def compute(a: Array[Char]): Option[Array[Char]] =
    if (a.length == 0 || !isAlpha(a.head)) None
    else {
      val fc = a.head.toLower
      Some(transcode(a.tail, fc, Array(fc)).padTo(4, '0'))
    }
  // scalastyle:on

  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 _ => '\u0000'
        }
      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 _ => '\u0000'
        }
      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 != '\u0000') o :+ a
      else transcode(i.tail, c, if (a != '\u0000') o :+ a else o)
    }
}