/*
 * Copyright (C) 2012-2014 Typesafe Inc. <http://www.typesafe.com>
 */
package scala.async.internal

import scala.reflect.macros.Context
import reflect.ClassTag
import scala.reflect.macros.runtime.AbortMacroException

/**
 * Utilities used in both `ExprBuilder` and `AnfTransform`.
 */
private[async] trait TransformUtils {
  self: AsyncMacro =>

  import global._

  object name {
    val resume        = newTermName("resume")
    val apply         = newTermName("apply")
    val matchRes      = "matchres"
    val ifRes         = "ifres"
    val await         = "await"
    val bindSuffix    = "$bind"

    val state         = newTermName("state")
    val result        = newTermName("result")
    val execContext   = newTermName("execContext")
    val stateMachine  = newTermName(fresh("stateMachine"))
    val stateMachineT = stateMachine.toTypeName
    val tr            = newTermName("tr")
    val t             = newTermName("throwable")

    def fresh(name: TermName): TermName = newTermName(fresh(name.toString))

    def fresh(name: String): String = currentUnit.freshTermName("" + name + "$").toString
  }

  def isAwait(fun: Tree) =
    fun.symbol == defn.Async_await

  private lazy val Boolean_ShortCircuits: Set[Symbol] = {
    import definitions.BooleanClass
    def BooleanTermMember(name: String) = BooleanClass.typeSignature.member(newTermName(name).encodedName)
    val Boolean_&& = BooleanTermMember("&&")
    val Boolean_|| = BooleanTermMember("||")
    Set(Boolean_&&, Boolean_||)
  }

  private def isByName(fun: Tree): ((Int, Int) => Boolean) = {
    if (Boolean_ShortCircuits contains fun.symbol) (i, j) => true
    else {
      val paramss = fun.tpe.paramss
      val byNamess = paramss.map(_.map(_.isByNameParam))
      (i, j) => util.Try(byNamess(i)(j)).getOrElse(false)
    }
  }
  private def argName(fun: Tree): ((Int, Int) => String) = {
    val paramss = fun.tpe.paramss
    val namess = paramss.map(_.map(_.name.toString))
    (i, j) => util.Try(namess(i)(j)).getOrElse(s"arg_${i}_${j}")
  }

  def Expr[A: WeakTypeTag](t: Tree) = global.Expr[A](rootMirror, new FixedMirrorTreeCreator(rootMirror, t))

  object defn {
    def mkList_apply[A](args: List[Expr[A]]): Expr[List[A]] = {
      Expr(Apply(Ident(definitions.List_apply), args.map(_.tree)))
    }

    def mkList_contains[A](self: Expr[List[A]])(elem: Expr[Any]) = reify {
      self.splice.contains(elem.splice)
    }

    def mkFunction_apply[A, B](self: Expr[Function1[A, B]])(arg: Expr[A]) = reify {
      self.splice.apply(arg.splice)
    }

    def mkAny_==(self: Expr[Any])(other: Expr[Any]) = reify {
      self.splice == other.splice
    }

    def mkTry_get[A](self: Expr[util.Try[A]]) = reify {
      self.splice.get
    }

    val TryClass      = rootMirror.staticClass("scala.util.Try")
    val Try_get       = TryClass.typeSignature.member(newTermName("get")).ensuring(_ != NoSymbol)
    val Try_isFailure = TryClass.typeSignature.member(newTermName("isFailure")).ensuring(_ != NoSymbol)
    val TryAnyType    = appliedType(TryClass.toType, List(definitions.AnyTpe))
    val NonFatalClass = rootMirror.staticModule("scala.util.control.NonFatal")
    val Async_await   = asyncBase.awaitMethod(global)(macroApplication.symbol).ensuring(_ != NoSymbol)
  }

  def isSafeToInline(tree: Tree) = {
    treeInfo.isExprSafeToInline(tree)
  }

  // `while(await(x))` ... or `do { await(x); ... } while(...)` contain an `If` that loops;
  // we must break that `If` into states so that it convert the label jump into a state machine
  // transition
  final def containsForiegnLabelJump(t: Tree): Boolean = {
    val labelDefs = t.collect {
      case ld: LabelDef => ld.symbol
    }.toSet
    t.exists {
      case rt: RefTree => !(labelDefs contains rt.symbol)
      case _ => false
    }
  }

  /** Map a list of arguments to:
    * - A list of argument Trees
    * - A list of auxillary results.
    *
    * The function unwraps and rewraps the `arg :_*` construct.
    *
    * @param args The original argument trees
    * @param f  A function from argument (with '_*' unwrapped) and argument index to argument.
    * @tparam A The type of the auxillary result
    */
  private def mapArguments[A](args: List[Tree])(f: (Tree, Int) => (A, Tree)): (List[A], List[Tree]) = {
    args match {
      case args :+ Typed(tree, Ident(tpnme.WILDCARD_STAR)) =>
        val (a, argExprs :+ lastArgExpr) = (args :+ tree).zipWithIndex.map(f.tupled).unzip
        val exprs = argExprs :+ atPos(lastArgExpr.pos.makeTransparent)(Typed(lastArgExpr, Ident(tpnme.WILDCARD_STAR)))
        (a, exprs)
      case args                                            =>
        args.zipWithIndex.map(f.tupled).unzip
    }
  }

  case class Arg(expr: Tree, isByName: Boolean, argName: String)

  /**
   * Transform a list of argument lists, producing the transformed lists, and lists of auxillary
   * results.
   *
   * The function `f` need not concern itself with varargs arguments e.g (`xs : _*`). It will
   * receive `xs`, and it's result will be re-wrapped as `f(xs) : _*`.
   *
   * @param fun   The function being applied
   * @param argss The argument lists
   * @return      (auxillary results, mapped argument trees)
   */
  def mapArgumentss[A](fun: Tree, argss: List[List[Tree]])(f: Arg => (A, Tree)): (List[List[A]], List[List[Tree]]) = {
    val isByNamess: (Int, Int) => Boolean = isByName(fun)
    val argNamess: (Int, Int) => String = argName(fun)
    argss.zipWithIndex.map { case (args, i) =>
      mapArguments[A](args) {
        (tree, j) => f(Arg(tree, isByNamess(i, j), argNamess(i, j)))
      }
    }.unzip
  }


  def statsAndExpr(tree: Tree): (List[Tree], Tree) = tree match {
    case Block(stats, expr) => (stats, expr)
    case _                  => (List(tree), Literal(Constant(())))
  }

  def emptyConstructor: DefDef = {
    val emptySuperCall = Apply(Select(Super(This(tpnme.EMPTY), tpnme.EMPTY), nme.CONSTRUCTOR), Nil)
    DefDef(NoMods, nme.CONSTRUCTOR, List(), List(List()), TypeTree(), Block(List(emptySuperCall), Literal(Constant(()))))
  }

  def applied(className: String, types: List[Type]): AppliedTypeTree =
    AppliedTypeTree(Ident(rootMirror.staticClass(className)), types.map(TypeTree(_)))

  /** Descends into the regions of the tree that are subject to the
    * translation to a state machine by `async`. When a nested template,
    * function, or by-name argument is encountered, the descent stops,
    * and `nestedClass` etc are invoked.
    */
  trait AsyncTraverser extends Traverser {
    def nestedClass(classDef: ClassDef) {
    }

    def nestedModule(module: ModuleDef) {
    }

    def nestedMethod(defdef: DefDef) {
    }

    def byNameArgument(arg: Tree) {
    }

    def function(function: Function) {
    }

    def patMatFunction(tree: Match) {
    }

    override def traverse(tree: Tree) {
      tree match {
        case cd: ClassDef          => nestedClass(cd)
        case md: ModuleDef         => nestedModule(md)
        case dd: DefDef            => nestedMethod(dd)
        case fun: Function         => function(fun)
        case m@Match(EmptyTree, _) => patMatFunction(m) // Pattern matching anonymous function under -Xoldpatmat of after `restorePatternMatchingFunctions`
        case treeInfo.Applied(fun, targs, argss) if argss.nonEmpty =>
          val isInByName = isByName(fun)
          for ((args, i) <- argss.zipWithIndex) {
            for ((arg, j) <- args.zipWithIndex) {
              if (!isInByName(i, j)) traverse(arg)
              else byNameArgument(arg)
            }
          }
          traverse(fun)
        case _                     => super.traverse(tree)
      }
    }
  }

  def abort(pos: Position, msg: String) = throw new AbortMacroException(pos, msg)

  abstract class MacroTypingTransformer extends TypingTransformer(callSiteTyper.context.unit) {
    currentOwner = callSiteTyper.context.owner
    curTree = EmptyTree

    def currOwner: Symbol = currentOwner

    localTyper = global.analyzer.newTyper(callSiteTyper.context.make(unit = callSiteTyper.context.unit))
  }

  def transformAt(tree: Tree)(f: PartialFunction[Tree, (analyzer.Context => Tree)]) = {
    object trans extends MacroTypingTransformer {
      override def transform(tree: Tree): Tree = {
        if (f.isDefinedAt(tree)) {
          f(tree)(localTyper.context)
        } else super.transform(tree)
      }
    }
    trans.transform(tree)
  }

  def changeOwner(tree: Tree, oldOwner: Symbol, newOwner: Symbol): tree.type = {
    new ChangeOwnerAndModuleClassTraverser(oldOwner, newOwner).traverse(tree)
    tree
  }

  class ChangeOwnerAndModuleClassTraverser(oldowner: Symbol, newowner: Symbol)
    extends ChangeOwnerTraverser(oldowner, newowner) {

    override def traverse(tree: Tree) {
      tree match {
        case _: DefTree => change(tree.symbol.moduleClass)
        case _          =>
      }
      super.traverse(tree)
    }
  }

  def toMultiMap[A, B](as: Iterable[(A, B)]): Map[A, List[B]] =
    as.toList.groupBy(_._1).mapValues(_.map(_._2).toList).toMap

  // Attributed version of `TreeGen#mkCastPreservingAnnotations`
  def mkAttributedCastPreservingAnnotations(tree: Tree, tp: Type): Tree = {
    atPos(tree.pos) {
      val casted = gen.mkAttributedCast(tree, uncheckedBounds(tp.withoutAnnotations).dealias)
      Typed(casted, TypeTree(tp)).setType(tp)
    }
  }

  // =====================================
  // Copy/Pasted from Scala 2.10.3. See SI-7694.
  private lazy val UncheckedBoundsClass = {
    global.rootMirror.getClassIfDefined("scala.reflect.internal.annotations.uncheckedBounds")
  }
  final def uncheckedBounds(tp: Type): Type = {
    if (tp.typeArgs.isEmpty || UncheckedBoundsClass == NoSymbol) tp
    else tp.withAnnotation(AnnotationInfo marker UncheckedBoundsClass.tpe)
  }
  // =====================================
}