package dotty.tools
package dotc
package core

import Periods._
import Transformers._
import Names._
import Scopes._
import Flags._
import java.lang.AssertionError
import Decorators._
import Symbols._
import Contexts._
import SymDenotations._
import printing.Texts._
import printing.Printer
import Types._
import Annotations._
import util.Positions._
import StdNames._
import NameOps._
import ast.tpd.{TreeMapper, SharedTree}
import Denotations.{ Denotation, SingleDenotation, MultiDenotation }
import collection.mutable
import io.AbstractFile
import language.implicitConversions
import util.DotClass

/** Creation methods for symbols */
trait Symbols { this: Context =>

// ---- Factory methods for symbol creation ----------------------
//
// All symbol creations should be done via the next two methods.

  /** Create a symbol without a denotation.
   *  Note this uses a cast instead of a direct type refinement because
   *  it's debug-friendlier not to create an anonymous class here.
   */
  def newNakedSymbol[N <: Name](coord: Coord = NoCoord): Symbol { type ThisName = N } =
    new Symbol(coord).asInstanceOf[Symbol { type ThisName = N }]

  /** Create a class symbol without a denotation. */
  def newNakedClassSymbol(coord: Coord = NoCoord, assocFile: AbstractFile = null) =
    new ClassSymbol(coord, assocFile)

// ---- Symbol creation methods ----------------------------------

  /** Create a symbol from a function producing its denotation */
  def newSymbolDenoting[N <: Name](denotFn: Symbol => SymDenotation, coord: Coord = NoCoord): Symbol { type ThisName = N } = {
    val sym = newNakedSymbol[N](coord)
    sym.denot = denotFn(sym)
    sym
  }

  /** Create a symbol from its fields (info may be lazy) */
  def newSymbol[N <: Name](
      owner: Symbol,
      name: N,
      flags: FlagSet,
      info: Type,
      privateWithin: Symbol = NoSymbol,
      coord: Coord = NoCoord): Symbol { type ThisName = N } = {
    val sym = newNakedSymbol[N](coord)
    val denot = SymDenotation(sym, owner, name, flags, info, privateWithin)
    sym.denot = denot
    sym
  }

  /** Create a class symbol from a function producing its denotation */
  def newClassSymbolDenoting(denotFn: ClassSymbol => SymDenotation, coord: Coord = NoCoord, assocFile: AbstractFile = null): ClassSymbol = {
    val cls = newNakedClassSymbol(coord, assocFile)
    cls.denot = denotFn(cls)
    cls
  }

  /** Create a class symbol from its non-info fields and a function
   *  producing its info (the produced info may be lazy).
   */
  def newClassSymbol(
      owner: Symbol,
      name: TypeName,
      flags: FlagSet,
      infoFn: ClassSymbol => Type,
      privateWithin: Symbol = NoSymbol,
      coord: Coord = NoCoord,
      assocFile: AbstractFile = null): ClassSymbol
  = {
    val cls = newNakedClassSymbol(coord, assocFile)
    val denot = SymDenotation(cls, owner, name, flags, infoFn(cls), privateWithin)
    cls.denot = denot
    cls
  }

  /** Create a class symbol from its non-info fields and the fields of its info. */
  def newCompleteClassSymbol(
      owner: Symbol,
      name: TypeName,
      flags: FlagSet,
      parents: List[TypeRef],
      decls: Scope = newScope,
      selfInfo: Type = NoType,
      privateWithin: Symbol = NoSymbol,
      coord: Coord = NoCoord,
      assocFile: AbstractFile = null): ClassSymbol =
    newClassSymbol(
        owner, name, flags,
        ClassInfo(owner.thisType, _, parents, decls, selfInfo),
        privateWithin, coord, assocFile)

  /** Create a module symbol with associated module class
   *  from its non-info fields and a function producing the info
   *  of the module class (this info may be lazy).
   */
  def newModuleSymbol(
      owner: Symbol,
      name: TermName,
      modFlags: FlagSet,
      clsFlags: FlagSet,
      infoFn: (TermSymbol, ClassSymbol) => Type, // typically a ModuleClassCompleterWithDecls
      privateWithin: Symbol = NoSymbol,
      coord: Coord = NoCoord,
      assocFile: AbstractFile = null): TermSymbol
  = {
    val base = owner.thisType
    val module = newNakedSymbol[TermName](coord)
    val modcls = newNakedClassSymbol(coord, assocFile)
    val modclsFlags = clsFlags | ModuleClassCreationFlags
    val modclsName = name.toTypeName.adjustIfModuleClass(modclsFlags)
    val cdenot = SymDenotation(
        modcls, owner, modclsName, modclsFlags,
        infoFn(module, modcls), privateWithin)
    val mdenot = SymDenotation(
        module, owner, name, modFlags | ModuleCreationFlags,
        if (cdenot.isCompleted) TypeRef(owner.thisType, modclsName) withSym modcls
        else new ModuleCompleter(modcls))
    module.denot = mdenot
    modcls.denot = cdenot
    module
  }

  /** Create a module symbol with associated module class
   *  from its non-info fields and the fields of the module class info.
   *  @param flags  The combined flags of the module and the module class
   *                These are masked with RetainedModuleValFlags/RetainedModuleClassFlags.
   */
  def newCompleteModuleSymbol(
      owner: Symbol,
      name: TermName,
      modFlags: FlagSet,
      clsFlags: FlagSet,
      parents: List[TypeRef],
      decls: Scope,
      privateWithin: Symbol = NoSymbol,
      coord: Coord = NoCoord,
      assocFile: AbstractFile = null): TermSymbol =
    newModuleSymbol(
        owner, name, modFlags, clsFlags,
        (module, modcls) => ClassInfo(
          owner.thisType, modcls, parents, decls, TermRef(owner.thisType, name) withSym module),
        privateWithin, coord, assocFile)

  /** Create a package symbol with associated package class
   *  from its non-info fields and a lazy type for loading the package's members.
   */
  def newPackageSymbol(
      owner: Symbol,
      name: TermName,
      infoFn: (TermSymbol, ClassSymbol) => LazyType): TermSymbol =
    newModuleSymbol(owner, name, PackageCreationFlags, PackageCreationFlags, infoFn)

  /** Create a package symbol with associated package class
   *  from its non-info fields its member scope.
   */
  def newCompletePackageSymbol(
      owner: Symbol,
      name: TermName,
      modFlags: FlagSet = EmptyFlags,
      clsFlags: FlagSet = EmptyFlags,
      decls: Scope = newScope): TermSymbol =
    newCompleteModuleSymbol(
      owner, name,
      modFlags | PackageCreationFlags, clsFlags | PackageCreationFlags,
      Nil, decls)


  /** Create a stub symbol that will issue a missing reference error
   *  when attempted to be completed.
   */
  def newStubSymbol(owner: Symbol, name: Name, file: AbstractFile = null): Symbol = {
    def stubCompleter = new StubInfo()
    val normalizedOwner = if (owner is ModuleVal) owner.moduleClass else owner
    println(s"creating stub for ${name.show}, owner = ${normalizedOwner.denot.debugString}, file = $file")
    println(s"decls = ${normalizedOwner.decls.toList.map(_.debugString).mkString("\n  ")}") // !!! DEBUG
    //if (base.settings.debug.value) throw new Error()
    val stub = name match {
      case name: TermName =>
        newModuleSymbol(normalizedOwner, name, EmptyFlags, EmptyFlags, stubCompleter, assocFile = file)
      case name: TypeName =>
        newClassSymbol(normalizedOwner, name, EmptyFlags, stubCompleter, assocFile = file)
    }
    stubs = stub :: stubs
    stub
  }

  /** Create the local template dummy of given class `cls`.
   *  In a template
   *
   *     trait T { val fld: Int; { val x: int = 2 }; val fld2 = { val y = 2; y }}
   *
   *  the owner of `x` is the local dummy of the template. The owner of the local
   *  dummy is then the class of the template itself. By contrast, the owner of `y`
   *  would be `fld2`. There is a single local dummy per template.
   */
  def newLocalDummy(cls: Symbol, coord: Coord = NoCoord) =
    newSymbol(cls, nme.localDummyName(cls), EmptyFlags, NoType)

  /** Create an import symbol pointing back to given qualifier `expr`. */
  def newImportSymbol(expr: SharedTree, coord: Coord = NoCoord) =
    newSymbol(NoSymbol, nme.IMPORT, EmptyFlags, ImportType(expr), coord = coord)

  /** Create a class constructor symbol for given class `cls`. */
  def newConstructor(cls: ClassSymbol, flags: FlagSet, paramNames: List[TermName], paramTypes: List[Type], privateWithin: Symbol = NoSymbol, coord: Coord = NoCoord) =
    newSymbol(cls, nme.CONSTRUCTOR, flags | Method, MethodType(paramNames, paramTypes)(_ => cls.typeRef), privateWithin, coord)

  /** Create an empty default constructor symbol for given class `cls`. */
  def newDefaultConstructor(cls: ClassSymbol) =
    newConstructor(cls, EmptyFlags, Nil, Nil)

  /** Create a symbol representing a selftype declaration for class `cls`. */
  def newSelfSym(cls: ClassSymbol, name: TermName = nme.WILDCARD, selfInfo: Type = NoType): TermSymbol =
    ctx.newSymbol(cls, name, SelfSymFlags, selfInfo orElse cls.classInfo.selfType, coord = cls.coord)

  /** Create new type parameters with given owner, names, and flags.
   *  @param boundsFn  A function that, given type refs to the newly created
   *                   parameters returns a list of their bounds.
   */
  def newTypeParams(
    owner: Symbol,
    names: List[TypeName],
    flags: FlagSet,
    boundsFn: List[TypeRef] => List[Type]): List[TypeSymbol] = {

    val tparamBuf = new mutable.ListBuffer[TypeSymbol]
    val trefBuf = new mutable.ListBuffer[TypeRef]
    for (name <- names) {
      val tparam = newNakedSymbol[TypeName](NoCoord)
      tparamBuf += tparam
      trefBuf += TypeRef(owner.thisType, name) withSym tparam
    }
    val tparams = tparamBuf.toList
    val bounds = boundsFn(trefBuf.toList)
    for ((name, tparam, bound) <- (names, tparams, bounds).zipped)
      tparam.denot = SymDenotation(tparam, owner, name, flags | TypeParamCreationFlags, bound)
    tparams
  }

  def newSkolem(tp: Type) = newSymbol(defn.RootClass, nme.SKOLEM, SyntheticArtifact | Permanent, tp)

  def newErrorSymbol(owner: Symbol, name: Name) =
    newSymbol(owner, name, SyntheticArtifact,
      if (name.isTypeName) TypeAlias(ErrorType) else ErrorType)

  type OwnerMap = Symbol => Symbol

  /** Map given symbols, subjecting all types to given type map and owner map.
   *  Cross symbol references are brought over from originals to copies.
   *  Do not copy any symbols if all attributes of all symbols stay the same.
   */
  def mapSymbols(
      originals: List[Symbol],
      typeMap: TypeMap = IdentityTypeMap,
      ownerMap: OwnerMap = identity)
  =
    if (originals forall (sym =>
        (typeMap(sym.info) eq sym.info) && (ownerMap(sym.owner) eq sym.owner)))
      originals
    else {
      val copies: List[Symbol] = for (original <- originals) yield
        newNakedSymbol[original.ThisName](original.coord)
      val treeMap = new TreeMapper(typeMap, ownerMap)
        .withSubstitution(originals, copies)
      (originals, copies).zipped foreach {(original, copy) =>
        val odenot = original.denot
        copy.denot = odenot.copySymDenotation(
          symbol = copy,
          owner = treeMap.ownerMap(odenot.owner),
          info = treeMap.typeMap(odenot.info),
          privateWithin = ownerMap(odenot.privateWithin), // since this refers to outer symbols, need not include copies (from->to) in ownermap here.
          annotations = odenot.annotations.mapConserve(treeMap.apply))
      }
      copies
    }

// ----- Locating predefined symbols ----------------------------------------

  def requiredPackage(path: PreName): TermSymbol =
    base.staticRef(path.toTermName).requiredSymbol(_ is Package).asTerm

  def requiredClass(path: PreName): ClassSymbol =
    base.staticRef(path.toTypeName).requiredSymbol(_.isClass).asClass

  def requiredModule(path: PreName): TermSymbol =
    base.staticRef(path.toTermName).requiredSymbol(_ is Module).asTerm

  def requiredMethod(cls: ClassSymbol, name: PreName): TermSymbol =
    cls.info.member(name.toTermName).requiredSymbol(_ is Method).asTerm
}

object Symbols {

  var _nextId = 0 // !!! DEBUG, use global counter instead
  def nextId = { _nextId += 1; _nextId }


  /** A Symbol represents a Scala definition/declaration or a package.
   */
  class Symbol private[Symbols] (val coord: Coord) extends DotClass with printing.Showable {

    type ThisName <: Name

    private[this] var _id: Int = nextId
    //assert(_id != 5859)

    /** The unique id of this symbol */
    def id = _id

    /** The last denotation of this symbol */
    private[this] var lastDenot: SymDenotation = _

    /** Set the denotation of this symbol */
    private[core] def denot_=(d: SymDenotation) =
      lastDenot = d

    /** The current denotation of this symbol */
    final def denot(implicit ctx: Context): SymDenotation = {
      var denot = lastDenot
      if (!(denot.validFor contains ctx.period)) {
        denot = denot.current.asInstanceOf[SymDenotation]
        lastDenot = denot
      }
      denot
    }

    private[core] def defRunId: RunId =
      if (lastDenot == null) NoRunId else lastDenot.validFor.runId

    /** Does this symbol come from a currently compiled source file? */
    final def isDefinedInCurrentRun(implicit ctx: Context): Boolean = {
      pos.exists && defRunId == ctx.runId
    }

    /** Subclass tests and casts */
    final def isTerm(implicit ctx: Context): Boolean = denot.isTerm
    final def isType(implicit ctx: Context): Boolean = denot.isType
    final def isClass: Boolean = isInstanceOf[ClassSymbol]

    final def asTerm(implicit ctx: Context): TermSymbol = { assert(isTerm); asInstanceOf[TermSymbol] }
    final def asType(implicit ctx: Context): TypeSymbol = { assert(isType); asInstanceOf[TypeSymbol] }
    final def asClass: ClassSymbol = asInstanceOf[ClassSymbol]

    /** A unique, densely packed integer tag for each class symbol, -1
     *  for all other symbols. To save memory, this method
     *  should be called only if class is a super class of some other class.
     */
    def superId(implicit ctx: Context): Int = -1

    /** This symbol entered into owner's scope (owner must be a class). */
    final def entered(implicit ctx: Context): this.type = {
      assert(this.owner.isClass) // !!! DEBUG
      this.owner.asClass.enter(this)
      if (this is Module) this.owner.asClass.enter(this.moduleClass)
      this
    }

    /** This symbol, if it exists, otherwise the result of evaluating `that` */
    def orElse(that: => Symbol)(implicit ctx: Context) =
      if (this.exists) this else that

    /** If this symbol satisfies predicate `p` this symbol, otherwise `NoSymbol` */
    def filter(p: Symbol => Boolean): Symbol = if (p(this)) this else NoSymbol

    /** Is symbol a primitive value class? */
    def isPrimitiveValueClass(implicit ctx: Context) = defn.ScalaValueClasses contains this

    /** Is symbol a phantom class for which no runtime representation exists? */
    def isPhantomClass(implicit ctx: Context) = defn.PhantomClasses contains this

    /** The current name of this symbol */
    final def name(implicit ctx: Context): ThisName = denot.name.asInstanceOf[ThisName]

    /** The source or class file from which this class or
     *  the class containing this symbol was generated, null if not applicable.
     *  Overridden in ClassSymbol
     */
    def associatedFile(implicit ctx: Context): AbstractFile =
      denot.topLevelClass.symbol.associatedFile

    /** The class file from which this class was generated, null if not applicable. */
    final def binaryFile(implicit ctx: Context): AbstractFile =
      pickFile(associatedFile, classFile = true)

    /** The source file from which this class was generated, null if not applicable. */
    final def sourceFile(implicit ctx: Context): AbstractFile =
      pickFile(associatedFile, classFile = false)

   /** Desire to re-use the field in ClassSymbol which stores the source
     *  file to also store the classfile, but without changing the behavior
     *  of sourceFile (which is expected at least in the IDE only to
     *  return actual source code.) So sourceFile has classfiles filtered out.
     */
    private def pickFile(file: AbstractFile, classFile: Boolean): AbstractFile =
      if ((file eq null) || classFile != (file.path endsWith ".class")) null else file

    /** The position of this symbol, or NoPosition is symbol was not loaded
     *  from source.
     */
    def pos: Position = if (coord.isPosition) coord.toPosition else NoPosition

// -------- GADT handling -----------------------------------------------

    /** Perform given operation `op` where this symbol allows tightening of
     *  its type bounds.
     */
    private[dotc] def withGADTFlexType[T](op: () => T)(implicit ctx: Context): () => T = { () =>
      assert((denot is TypeParam) && denot.owner.isTerm)
      val saved = denot
      denot = denot.copySymDenotation(initFlags = denot.flags | GADTFlexType)
      try op()
      finally denot = saved
    }

    /** Disallow tightening of type bounds for this symbol from now on */
    private[dotc] def resetGADTFlexType()(implicit ctx: Context): Unit = {
      assert(denot is GADTFlexType)
      denot = denot.copySymDenotation(initFlags = denot.flags &~ GADTFlexType)
    }

    /** Change info of this symbol to new, tightened type bounds */
    private[core] def changeGADTInfo(bounds: TypeBounds)(implicit ctx: Context): Unit = {
      assert(denot is GADTFlexType)
      denot = denot.copySymDenotation(info = bounds)
    }

// -------- Printing --------------------------------------------------------

    /** The prefix string to be used when displaying this symbol without denotation */
    protected def prefixString = "Symbol"

    override def toString: String =
      if (lastDenot == null) s"Naked$prefixString#$id"
      else lastDenot.toString// +"#"+id // !!! DEBUG

    def toText(printer: Printer): Text = printer.toText(this)

    def showLocated(implicit ctx: Context): String = ctx.locatedText(this).show
    def showDcl(implicit ctx: Context): String = ctx.dclText(this).show
    def showKind(implicit ctx: Context): String = ctx.kindString(this)
    def showName(implicit ctx: Context): String = ctx.nameString(this)
    def showFullName(implicit ctx: Context): String = ctx.fullNameString(this)
  }

  type TermSymbol = Symbol { type ThisName = TermName }
  type TypeSymbol = Symbol { type ThisName = TypeName }

  class ClassSymbol private[Symbols] (coord: Coord, assocFile: AbstractFile)
    extends Symbol(coord) {

    type ThisName = TypeName

    /** The source or class file from which this class was generated, null if not applicable. */
    override def associatedFile(implicit ctx: Context): AbstractFile =
      if (assocFile != null || (this.owner is PackageClass)) assocFile
      else super.associatedFile

    final def classDenot(implicit ctx: Context): ClassDenotation =
      denot.asInstanceOf[ClassDenotation]

    private var superIdHint: Int = -1

    override def superId(implicit ctx: Context): Int = {
      val hint = superIdHint
      if (hint >= 0 && hint <= ctx.lastSuperId && (ctx.classOfId(hint) eq this))
        hint
      else {
        val id = ctx.superIdOfClass get this match {
          case Some(id) =>
            id
          case None =>
            val id = ctx.nextSuperId
            ctx.superIdOfClass(this) = id
            ctx.classOfId(id) = this
            id
        }
        superIdHint = id
        id
      }
    }

    override protected def prefixString = "ClassSymbol"
  }

  class ErrorSymbol(val underlying: Symbol, msg: => String)(implicit ctx: Context) extends Symbol(NoCoord) {
    type ThisName = underlying.ThisName
    denot = underlying.denot
  }

  object NoSymbol extends Symbol(NoCoord) {
    denot = NoDenotation
  }

  implicit class Copier[N <: Name](sym: Symbol { type ThisName = N })(implicit ctx: Context) {
    /** Copy a symbol, overriding selective fields */
    def copy(
        owner: Symbol = sym.owner,
        name: N = sym.name,
        flags: FlagSet = sym.flags,
        info: Type = sym.info,
        privateWithin: Symbol = sym.privateWithin,
        coord: Coord = sym.coord,
        associatedFile: AbstractFile = sym.associatedFile): Symbol =
      if (sym.isClass)
        ctx.newClassSymbol(owner, name.asTypeName, flags, _ => info, privateWithin, coord, associatedFile)
      else
        ctx.newSymbol(owner, name, flags, info, privateWithin, coord)
  }

  implicit def defn(implicit ctx: Context): Definitions = ctx.definitions

  /** Makes all denotation operations available on symbols */
  implicit def toDenot(sym: Symbol)(implicit ctx: Context): SymDenotation = sym.denot

  /** Makes all class denotations available on class symbols */
  implicit def toClassDenot(cls: ClassSymbol)(implicit ctx: Context): ClassDenotation = cls.classDenot

  var stubs: List[Symbol] = Nil // diagnostic
}