Scala example source code file (JLineReader.scala)

This example Scala source code file (JLineReader.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

argumentcompleter, candidates, completer, int, int, jlineconsolereader, jlineconsolereader, jlinehistory, keybinding, nohistory, string, string, unit, unit

The Scala JLineReader.scala source code

/* NSC -- new Scala compiler
 * Copyright 2005-2011 LAMP/EPFL
 * @author Stepan Koltsov
 */

package scala.tools.nsc
package interpreter

import scala.tools.jline.console.ConsoleReader
import scala.tools.jline.console.completer._
import session._
import scala.collection.JavaConverters._
import Completion._
import io.Streamable.slurp

/**
 *  Reads from the console using JLine.
 */
class JLineReader(_completion: => Completion) extends InteractiveReader {
  val interactive = true
  val consoleReader = new JLineConsoleReader()
  
  lazy val completion = _completion
  lazy val history: JLineHistory = JLineHistory()
  lazy val keyBindings =
    try KeyBinding parse slurp(term.getDefaultBindings)
    catch { case _: Exception => Nil }

  private def term = consoleReader.getTerminal()
  def reset() = term.reset()
  def init()  = term.init()
  
  def scalaToJline(tc: ScalaCompleter): Completer = new Completer {
    def complete(_buf: String, cursor: Int, candidates: JList[CharSequence]): Int = {
      val buf   = if (_buf == null) "" else _buf      
      val Candidates(newCursor, newCandidates) = tc.complete(buf, cursor)
      newCandidates foreach (candidates add _)
      newCursor
    }
  }
    
  class JLineConsoleReader extends ConsoleReader with ConsoleReaderHelper {
    // working around protected/trait/java insufficiencies.
    def goBack(num: Int): Unit = back(num)
    def readOneKey(prompt: String) = {
      this.print(prompt)
      this.flush()
      this.readVirtualKey()
    }
    def eraseLine() = consoleReader.resetPromptLine("", "", 0)
    def redrawLineAndFlush(): Unit = { flush() ; drawLine() ; flush() }
    // override def readLine(prompt: String): String

    // A hook for running code after the repl is done initializing.
    lazy val postInit: Unit = {
      this setBellEnabled false
      if (history ne NoHistory)
        this setHistory history
    
      if (completion ne NoCompletion) {
        val argCompletor: ArgumentCompleter =
          new ArgumentCompleter(new JLineDelimiter, scalaToJline(completion.completer()))
        argCompletor setStrict false
      
        this addCompleter argCompletor
        this setAutoprintThreshold 400 // max completion candidates without warning
      }
    }
  }
 
  def currentLine = consoleReader.getCursorBuffer.buffer.toString
  def redrawLine() = consoleReader.redrawLineAndFlush()
  def eraseLine() = consoleReader.eraseLine()
  // Alternate implementation, not sure if/when I need this.
  // def eraseLine() = while (consoleReader.delete()) { }
  def readOneLine(prompt: String) = consoleReader readLine prompt
  def readOneKey(prompt: String)  = consoleReader readOneKey prompt
}