package scala
package tools.nsc

import scala.tools.nsc.reporters.{ ConsoleReporter, Reporter }
import Properties.{ versionMsg, residentPromptString }
import scala.reflect.internal.util.FakePos

abstract class Driver {

  val prompt = residentPromptString

  var reporter: Reporter = _
  protected var command: CompilerCommand = _
  protected var settings: Settings = _

  /** Forward errors to the (current) reporter. */
  protected def scalacError(msg: String): Unit = {
    reporter.error(FakePos("scalac"), msg + "\n  scalac -help  gives more information")
  }

  /** True to continue compilation. */
  protected def processSettingsHook(): Boolean = {
    if (settings.version) { reporter echo versionMsg ; false }
    else !reporter.hasErrors
  }

  protected def newCompiler(): Global

  protected def doCompile(compiler: Global): Unit = {
    if (command.files.isEmpty) {
      reporter.echo(command.usageMsg)
      reporter.echo(compiler.pluginOptionsHelp)
    } else {
      val run = new compiler.Run()
      run compile command.files
      reporter.finish()
    }
  }

  def process(args: Array[String]): Boolean = {
    val ss   = new Settings(scalacError)
    reporter = new ConsoleReporter(ss)    // for reporting early config errors, before compiler is constructed
    command  = new CompilerCommand(args.toList, ss)
    settings = command.settings

    if (processSettingsHook()) {
      val compiler = newCompiler()
      reporter     = compiler.reporter    // adopt the configured reporter
      try {
        if (reporter.hasErrors)
          reporter.flush()
        else if (command.shouldStopWithInfo)
          reporter.echo(command.getInfoMessage(compiler))
        else
          doCompile(compiler)
      } catch {
        case ex: Throwable =>
          compiler.reportThrowable(ex)
          ex match {
            case FatalError(msg)  => // signals that we should fail compilation.
            case _                => throw ex // unexpected error, tell the outside world.
          }
      }
    } else if (reporter.hasErrors) reporter.flush()
    !reporter.hasErrors
  }

  def main(args: Array[String]): Unit = sys.exit(if (process(args)) 0 else 1)
}