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

package scala.tools.nsc
package interpreter

import scala.language.implicitConversions

/** Mix this into an object and use it as a phasing
 *  Swiss Army knife.
 */
trait Phased {
  val global: Global
  import global._

  private var active: PhaseName = NoPhaseName
  private var multi: Seq[PhaseName] = Nil

  def get = active
  def set(phase: PhaseName): Boolean = phase match {
    case NoPhaseName  => false
    case name         => active = name ; true
  }
  def setMulti(phases: Seq[PhaseName]): Boolean = {
    if (phases contains NoPhaseName) false
    else {
      multi = phases
      true
    }
  }

  private def parsePhaseChange(str: String): Option[Int] = {
    if (str == "") Some(0)
    else if (str startsWith ".prev") parsePhaseChange(str drop 5) map (_ - 1)
    else if (str startsWith ".next") parsePhaseChange(str drop 5) map (_ + 1)
    else str.head match {
      case '+' | '-' =>
        val (num, rest) = str.tail.span(_.isDigit)
        val diff = if (str.head == '+') num.toInt else -num.toInt
        parsePhaseChange(rest) map (_ + diff)
      case _ =>
        None
    }
  }

  /** Takes a string like 4, typer+2, typer.next, etc.
   *  and turns it into a PhaseName instance.
   */
  private def parseInternal(str: String): PhaseName = {
    if (str == "") NoPhaseName
    else if (str forall (_.isDigit)) PhaseName(str.toInt)
    else {
      val (name, rest) = str.toLowerCase span (_.isLetter)
      val start        = PhaseName(name)
      val change       = parsePhaseChange(rest)

      if (start.isEmpty || change.isEmpty) NoPhaseName
      else PhaseName(start.id + change.get)
    }
  }
  def parse(str: String): PhaseName =
    try parseInternal(str)
    catch { case _: Exception => NoPhaseName }

  def atCurrent[T](body: => T): T = enteringPhase(get)(body)
  def multi[T](body: => T): Seq[T] = multi map (ph => at(ph)(body))

  def at[T](ph: PhaseName)(body: => T): T = {
    val saved = get
    set(ph)
    try atCurrent(body)
    finally set(saved)
  }
  def atMulti[T](phs: Seq[PhaseName])(body: => T): Seq[T] = {
    val saved = multi
    setMulti(phs)
    try multi(body)
    finally setMulti(saved)
  }

  def atMap[T](phs: Seq[PhaseName])(body: => T): Seq[(PhaseName, T)] =
    phs zip atMulti(phs)(body)

  object PhaseName {
    implicit lazy val phaseNameOrdering: Ordering[PhaseName] = Ordering[Int] on (_.id)

    lazy val all = List(
      Parser, Namer, Packageobjects, Typer, Superaccessors, Pickler, Refchecks,
      Uncurry, Tailcalls, Specialize, Explicitouter, Erasure, Fields, Lambdalift,
      Constructors, Flatten, Mixin, Cleanup, Delambdafy, Jvm, Terminal
    )
    lazy val nameMap = all.map(x => x.name -> x).toMap withDefaultValue NoPhaseName
    multi = all

    def apply(id: Int): PhaseName = all find (_.id == id) getOrElse NoPhaseName
    implicit def apply(s: String): PhaseName = nameMap(s)
  }
  sealed abstract class PhaseName {
    lazy val id   = phase.id
    lazy val name = toString.toLowerCase
    def phase     = currentRun.phaseNamed(name)
    def isEmpty   = this eq NoPhaseName
  }

  case object Parser extends PhaseName
  case object Namer extends PhaseName
  case object Packageobjects extends PhaseName
  case object Typer extends PhaseName
  case object Patmat extends PhaseName
  case object Superaccessors extends PhaseName
  case object Extmethods extends PhaseName
  case object Pickler extends PhaseName
  case object Refchecks extends PhaseName
  case object Uncurry extends PhaseName
  case object Fields extends PhaseName
  case object Tailcalls extends PhaseName
  case object Specialize extends PhaseName
  case object Explicitouter extends PhaseName
  case object Erasure extends PhaseName
  case object PostErasure extends PhaseName
  case object Lambdalift extends PhaseName
  case object Constructors extends PhaseName
  case object Flatten extends PhaseName
  case object Mixin extends PhaseName
  case object Cleanup extends PhaseName
  case object Delambdafy extends PhaseName
  case object Jvm extends PhaseName
  case object Terminal extends PhaseName
  case object NoPhaseName extends PhaseName {
    override lazy val id   = -1
    override lazy val name = phase.name
    override def phase     = NoPhase
  }

  implicit def phaseEnumToPhase(name: PhaseName): Phase = name.phase
}