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package com.rockymadden.stringmetric.similarity
import com.rockymadden.stringmetric.{CompareTuple, MatchTuple, StringFilter, StringMetric}
import scala.collection.mutable.{ArrayBuffer, HashSet}
/**
* An implementation of the Jaro metric. One differing detail in this implementation is that if a character is matched
* in string2, it cannot be matched upon again. This results in a more penalized distance in these scenarios.
*/
class JaroMetric extends StringMetric[DummyImplicit, Double] { this: StringFilter =>
final override def compare(charArray1: Array[Char], charArray2: Array[Char])
(implicit di: DummyImplicit): Option[Double] = {
val fca1 = filter(charArray1)
lazy val fca2 = filter(charArray2)
if (fca1.length == 0 || fca2.length == 0) None
else if (fca1.sameElements(fca2)) Some(1d)
else {
val mt = `match`(fca1, fca2)
val ms = scoreMatches(mt._1, mt._2)
if (ms == 0) Some(0d)
else {
val ts = scoreTranspositions(mt._1, mt._2)
Some(((ms.toDouble / fca1.length) + (ms.toDouble / fca2.length) + ((ms.toDouble - ts) / ms)) / 3)
}
}
}
final override def compare(string1: String, string2: String)(implicit di: DummyImplicit): Option[Double] =
compare(string1.toCharArray, string2.toCharArray)
private[this] def `match`(ct: CompareTuple[Char]): MatchTuple[Char] = {
lazy val window = math.abs((math.max(ct._1.length, ct._2.length) / 2d).floor.toInt - 1)
val one = ArrayBuffer.empty[Int]
val two = HashSet.empty[Int]
var i = 0
var bi = false
while (i < ct._1.length && !bi) {
val start = if (i - window <= 0) 0 else i - window
val end = if (i + window >= ct._2.length - 1) ct._2.length - 1 else i + window
if (start > ct._2.length - 1) bi = !bi
else {
var ii = start
var bii = false
while (ii <= end && !bii) {
if (!two.contains(ii) && ct._1(i) == ct._2(ii)) {
one += i
two += ii
bii = !bii
} else ii += 1
}
i += 1
}
}
(one.toArray.map(ct._1(_)), two.toArray.sortWith(_ < _).map(ct._2(_)))
}
private[this] def scoreMatches(mt: MatchTuple[Char]) = {
require(mt._1.length == mt._2.length)
mt._1.length
}
private[this] def scoreTranspositions(mt: MatchTuple[Char]) = {
require(mt._1.length == mt._2.length)
(mt._1.zip(mt._2).count(t => t._1 != t._2) / 2d).floor.toInt
}
}
object JaroMetric {
private lazy val self = apply()
def apply(): JaroMetric = new JaroMetric with StringFilter
def compare(charArray1: Array[Char], charArray2: Array[Char]) = self.compare(charArray1, charArray2)
def compare(string1: String, string2: String) = self.compare(string1, string2)
}
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