InterviewQuest.scala

object TestApp extends App {


  trait Region {
    val start: Int
    val end: Int

    def processRegion(input: String): String
  }

  case class Strong(start: Int,end: Int) extends Region {
    override def processRegion(input: String): String = s"<strong>${input.substring(start, end)}</strong>"
  }

  case class Href(start: Int, end: Int) extends Region {
    override def processRegion(input: String): String = s"""<a href="${input.substring(start, end)}">${input.substring(start, end).replaceFirst("http://", "")}</a>"""
  }

  case class Twitter(start: Int, end: Int) extends Region {
    override def processRegion(input: String): String = s"""${input(start)}<a href="http://twitter.com/${input.substring(start + 1, end)}">${input.substring(start + 1, end)}</a>"""
  }

  trait Processor {
    def process(input: String, list: List[Region]): String
  }

  class ProcessorImpl extends Processor {

    override def process(input: String, list: List[Region]): String = {
      val sorted = list.sortBy(-_.end)
      processSorted(input, sorted)
    }


    private def processSorted(input: String, list: List[Region]): String =
      if (list.nonEmpty) {
        processSorted(processPart(input, list.head), list.tail)
      } else {
        input
      }

    private def processPart(input: String, region: Region): String = {
      input.substring(0, region.start) + region.processRegion(input) + input.substring(region.end)
    }
  }

  val proc = new ProcessorImpl

  val region0 = Strong(14, 22)
  val region1 = Strong(0, 5)
  val region2 = Twitter(55, 67)
  val region3 = Href(37, 54)

  val input = """Obama visited Facebook headquarters: http://bit.ly/xyz @elversatile"""

  println(input.zipWithIndex.toString())

  val result = proc.process(input, List(region0, region1, region2, region3))

  println(result)


}