Scala example source code file (ConsoleReaderHelper.scala)

This example Scala source code file (ConsoleReaderHelper.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

boolean, compiler, consolereader, int, jcollection, list, none, nsc, seq, string, tabulator, unit

The ConsoleReaderHelper.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author Paul Phillips
 */

package scala.tools.nsc
package interpreter

import jline.console.{ ConsoleReader, CursorBuffer }

trait ConsoleReaderHelper { _: ConsoleReader with Tabulator =>
  def isAcross: Boolean

  def terminal    = getTerminal()
  def width       = terminal.getWidth()
  def height      = terminal.getHeight()

  def readOneKey(prompt: String): Int
  def eraseLine(): Unit

  val marginSize = 3

  private def morePrompt = "--More--"
  private def emulateMore(): Int = {
    val key = readOneKey(morePrompt)
    try key match {
      case '\r' | '\n'  => 1
      case 'q'          => -1
      case _            => height - 1
    }
    finally {
      eraseLine()
      // TODO: still not quite managing to erase --More-- and get
      // back to a scala prompt without another keypress.
      if (key == 'q') {
        putString(getPrompt())
        redrawLine()
        flush()
      }
    }
  }

  override def printColumns(items: JCollection[_ <: CharSequence]): Unit =
    printColumns_(items: List[String])

  private def printColumns_(items: List[String]): Unit = if (items exists (_ != "")) {
    val grouped = tabulate(items)
    var linesLeft  = if (isPaginationEnabled()) height - 1 else Int.MaxValue
    grouped foreach { xs =>
      println(xs.mkString)
      linesLeft -= 1
      if (linesLeft <= 0) {
        linesLeft = emulateMore()
        if (linesLeft < 0)
          return
      }
    }
  }
}

trait Tabulator {
  def isAcross: Boolean
  def width: Int
  def marginSize: Int

  protected def fits(items: Seq[String], width: Int): Boolean = (
    (items map (_.length)).sum + (items.length - 1) * marginSize < width
  )
  def tabulate(items: Seq[String]): Seq[Seq[String]] = (
    if (fits(items, width)) Seq(Seq(items mkString " " * marginSize))
    else printMultiLineColumns(items)
  )
  protected def columnize(ss: Seq[String]): Seq[Seq[String]] = ss map (s => Seq(s))
  protected def printMultiLineColumns(items: Seq[String]): Seq[Seq[String]] = {
    import SimpleMath._
    val longest     = (items map (_.length)).max
    val columnWidth = longest + marginSize
    val maxcols = (
      if (columnWidth >= width) 1
      else 1 max (width / columnWidth)   // make sure it doesn't divide to 0
    )
    val nrows       = items.size /% maxcols
    val ncols       = items.size /% nrows
    val groupSize   = ncols
    val padded      = items map (s"%-${columnWidth}s" format _)
    val xwise       = isAcross || ncols >= items.length
    val grouped: Seq[Seq[String]]    =
      if (groupSize == 1) columnize(items)
      else if (xwise) (padded grouped groupSize).toSeq
      else {
        val h       = 1 max padded.size /% groupSize
        val cols    = (padded grouped h).toList
        for (i <- 0 until h) yield
          for (j <- 0 until groupSize) yield
            if (i < cols(j).size) cols(j)(i) else ""
      }
    grouped
  }
}

/** Adjust the column width and number of columns to minimize the row count. */
trait VariColumnTabulator extends Tabulator {
  override protected def printMultiLineColumns(items: Seq[String]): Seq[Seq[String]] = {
    import SimpleMath._
    val longest  = (items map (_.length)).max
    val shortest = (items map (_.length)).min
    val fattest  = longest + marginSize
    val skinny   = shortest + marginSize

    // given ncols, calculate nrows and a list of column widths, or none if not possible
    // if ncols > items.size, then columnWidths.size == items.size
    def layout(ncols: Int): Option[(Int, Seq[Int], Seq[Seq[String]])] = {
      val nrows = items.size /% ncols
      val xwise = isAcross || ncols >= items.length
      def maxima(sss: Seq[Seq[String]]) =
        (0 until (ncols min items.size)) map (i => (sss map (ss => ss(i).length)).max)
      def resulting(rows: Seq[Seq[String]]) = {
        val columnWidths = maxima(rows) map (_ + marginSize)
        val linelen      = columnWidths.sum
        if (linelen <= width) Some((nrows, columnWidths, rows))
        else None
      }
      if (ncols == 1) resulting(columnize(items))
      else if (xwise) resulting((items grouped ncols).toSeq)
      else {
        val cols = (items grouped nrows).toList
        val rows = for (i <- 0 until nrows) yield
          for (j <- 0 until ncols) yield
            if (j < cols.size && i < cols(j).size) cols(j)(i) else ""
        resulting(rows)
      }
    }

    if (fattest >= width) {
      columnize(items)
    } else {
      // if every col is widest, we have at least this many cols
      val mincols = 1 max (width / fattest)
      // if every other col is skinniest, we have at most this many cols
      val maxcols = 1 + ((width - fattest) / skinny)
      val possibles = (mincols to maxcols).map(n => layout(n)).flatten
      val minrows = (possibles map (_._1)).min

      // select the min ncols that results in minrows
      val (_, columnWidths, sss) = (possibles find (_._1 == minrows)).get

      // format to column width
      sss map (ss => ss.zipWithIndex map {
        case (s, i) => s"%-${columnWidths(i)}s" format s
      })
    }
  }
}

private[interpreter] object SimpleMath {
  implicit class DivRem(private val i: Int) extends AnyVal {
    /** i/n + if (i % n != 0) 1 else 0 */
    def /%(n: Int): Int = (i + n - 1) / n
  }
}