fuga.scala

import scala.collection.immutable.TreeMap
import scala.io.Source

object Main extends App {

  val file  = Source.fromFile("./hoge.txt", "utf-8")
  val lines = file.getLines

  val dateTimeSep = """- (\d\d\d\d)年(\d\d)月(\d\d)日 .曜日 (\d\d:\d\d)""".r

  val articles = lines.foldLeft("" -> TreeMap.empty[String, String]) { (acc, line) =>
    val (marker, treeMap) = acc
    line match {
      case dateTimeSep(year, month, day, time) =>
        val nowDate = s"$year-$month-$day $time"
        nowDate -> treeMap.+(nowDate -> "")
      case _ =>
        val data = treeMap.getOrElse(marker, "") + line + "\n"
        marker -> treeMap.+(marker -> data)
    }
  }

  println(articles)
}