A Kotlin port of `AlphanumComparator` by Dave Koelle from http://www.davekoelle.com/alphanum.html

AlphanumComparator.kt

class AlphanumComparator : Comparator<String> {
  override fun compare(s1: String, s2: String): Int {
    var thisMarker = 0
    var thatMarker = 0
    val s1Length = s1.length
    val s2Length = s2.length

    while (thisMarker < s1Length && thatMarker < s2Length) {
      val thisChunk = getChunk(s1, s1Length, thisMarker)
      thisMarker += thisChunk.length

      val thatChunk = getChunk(s2, s2Length, thatMarker)
      thatMarker += thatChunk.length

      // If both chunks contain numeric characters, sort them numerically.
      var result: Int
      if (isDigit(thisChunk[0]) && isDigit(thatChunk[0])) {
        // Simple chunk comparison by length.
        val thisChunkLength = thisChunk.length
        result = thisChunkLength - thatChunk.length
        // If equal, the first different number counts.
        if (result == 0) {
          for (i in 0..thisChunkLength - 1) {
            result = thisChunk[i] - thatChunk[i]
            if (result != 0) {
              return result
            }
          }
        }
      } else {
        result = thisChunk.compareTo(thatChunk)
      }

      if (result != 0) {
        return result
      }
    }

    return s1Length - s2Length
  }

  private fun getChunk(string: String, length: Int, marker: Int): String {
    var current = marker
    val chunk = StringBuilder()
    var c = string[current]
    chunk.append(c)
    current++
    if (isDigit(c)) {
      while (current < length) {
        c = string[current]
        if (!isDigit(c)) {
          break
        }
        chunk.append(c)
        current++
      }
    } else {
      while (current < length) {
        c = string[current]
        if (isDigit(c)) {
          break
        }
        chunk.append(c)
        current++
      }
    }
    return chunk.toString()
  }

  private fun isDigit(ch: Char): Boolean {
    return '0' <= ch && ch <= '9'
  }
}