/* NSC -- new scala compiler
 * Copyright 2005 LAMP/EPFL
 * @author  Martin Odersky
 */
// $Id$
package scala.tools.nsc.typechecker;

import symtab.Flags._;
import scala.tools.util.Position;

[_trait_] abstract class Contexts: Analyzer {
  import global._;

  val NoContext = new Context {
    override def implicitss: List[List[ImplicitInfo]] = List();
  }
  NoContext.enclClass = NoContext;

  val startContext = {
    import definitions._;
    var sc = NoContext.make(
      Template(List(), List()) setSymbol NoSymbol setType NoType,
      definitions.RootClass,
      definitions.RootClass.info.decls);
    def addImport(pkg: Symbol): unit = {
      val qual = gen.mkStableRef(pkg);
      sc = sc.makeNewImport(
	Import(qual, List(Pair(nme.WILDCARD, null)))
           setSymbol NoSymbol.newImport(Position.NOPOS).setInfo(ImportType(qual))
           setType NoType);
      sc.depth = sc.depth + 1
    }
    if (!settings.noimports.value) {
      addImport(JavaLangPackage);
      addImport(ScalaPackage);
      if (!settings.nopredefs.value)
	addImport(PredefModule);
    }
    sc
  }

  def resetContexts: unit = {
    var sc = startContext;
    while (sc != NoContext) {
      sc.tree match {
	case Import(qual, _) => qual.tpe = singleType(qual.symbol.owner.thisType, qual.symbol);
	case _ =>
      }
      sc = sc.outer
    }
  }

  class Context {
    var unit: CompilationUnit = _;
    var tree: Tree = _;                     // Tree associated with this context
    var owner: Symbol = NoSymbol;                  // The current owner
    var scope: Scope = _;                   // The current scope
    var outer: Context = _;                 // The next outer context
    var enclClass: Context = _;             // The next outer context whose tree is a
                                            // template or package definition
    var variance: int = _;                  // Variance relative to enclosing class.
    private var _undetparams: List[Symbol] = List(); // Undetermined type parameters
    var depth: int = 0;
    var imports: List[ImportInfo] = List();
    var typeSubstFrom: List[Symbol] = List();  // The set of type parameters in scope.
    var typeSubstTo: List[Type] = List();  // Types to which parameters are mapped.

    var reportAmbiguousErrors = false;
    var reportGeneralErrors = false;
    var checking = false;

    def undetparams = _undetparams;
    def undetparams_=(ps: List[Symbol]) = {
      //System.out.println("undetparams = " + ps);//debug
      _undetparams = ps
    }

    def make(unit: CompilationUnit, tree: Tree, owner: Symbol, scope: Scope, imports: List[ImportInfo]): Context = {
      val c = new Context;
      c.unit = unit;
      c.tree = tree;
      c.owner = owner;
      c.scope = scope;
      c.enclClass = tree match {
        case Template(_, _) | PackageDef(_, _) => c
        case _ => this.enclClass
      }
      c.variance = this.variance;
      c.depth = if (scope == this.scope) this.depth else this.depth + 1;
      c.imports = imports;
      c.typeSubstFrom = this.typeSubstFrom;
      c.typeSubstTo = this.typeSubstTo;
      c.reportAmbiguousErrors = this.reportAmbiguousErrors;
      c.reportGeneralErrors = this.reportGeneralErrors;
      c.checking = this.checking;
      c.outer = this;
      c
    }

    def make(unit: CompilationUnit): Context = {
      val c = make(unit, EmptyTree, owner, scope, imports);
      c.reportAmbiguousErrors = true;
      c.reportGeneralErrors = true;
      c
    }

    def makeNewImport(imp: Import): Context =
      make(unit, imp, owner, scope, new ImportInfo(imp, depth) :: imports);

    def make(tree: Tree, owner: Symbol, scope: Scope): Context =
      make(unit, tree, owner, scope, imports);

    def makeNewScope(tree: Tree, owner: Symbol): Context =
      make(tree, owner, new Scope(scope));

    def make(tree: Tree, owner: Symbol): Context =
      make(tree, owner, scope);

    def make(tree: Tree): Context =
      make(tree, owner);

    def makeImplicit(reportAmbiguousErrors: boolean) = {
      val c = make(tree);
      c.reportAmbiguousErrors = reportAmbiguousErrors;
      c.reportGeneralErrors = false;
      c
    }

    def error(pos: int, msg: String): unit =
      if (reportGeneralErrors)
        unit.error(pos, if (checking) "**** ERROR DURING INTERNAL CHECKING ****\n" + msg else msg)
      else
        throw new TypeError(msg);

    def ambiguousError(pos: int, pre: Type, sym1: Symbol, sym2: Symbol, rest: String): unit = {
      val msg =
	"ambiguous reference to overloaded definition,\n" +
	"both " + sym1 + sym1.locationString + " of type " + pre.memberType(sym1) +
	"\nand  " + sym2 + sym2.locationString + " of type " + pre.memberType(sym2) +
        "\nmatch " + rest;
      if (reportAmbiguousErrors) unit.error(pos, msg)
      else throw new TypeError(msg);
    }

    def outerContext(clazz: Symbol): Context = {
      var c = this;
      while (c != NoContext && c.owner != clazz) c = c.outer.enclClass;
      c
    }

    def isLocal(): boolean = tree match {
      case Block(_,_) => true
      case PackageDef(_, _) => false
      case EmptyTree => false
      case _ => outer.isLocal()
    }

    override def toString(): String = {
      if (this == NoContext) "NoContext";
      else owner.toString() + " @ " + tree.getClass() + " " + tree.toString() + ", scope = " + scope.hashCode() + " " + scope.toList + "\n:: " + outer.toString()
    }

    /** Is `sym' accessible as a member of tree `site' with type `pre' in current context?
     */
    def isAccessible(sym: Symbol, pre: Type, superAccess: boolean): boolean = {

      /** Are we inside definition of `owner'? */
      def accessWithin(owner: Symbol): boolean = {
	var c = this;
	while (c != NoContext && c.owner != owner) {
	  if (c.outer == null) assert(false, "accessWithin(" + owner + ") " + c);//debug
	  if (c.outer.enclClass == null) assert(false, "accessWithin(" + owner + ") " + c);//debug
	  c = c.outer.enclClass;
	}
	c != NoContext
      }

      /** Is `clazz' a subclass of an enclosing class? */
      def isSubClassOfEnclosing(clazz: Symbol): boolean = {
	var c = this;
	while (c != NoContext && !clazz.isSubClass(c.owner)) c = c.outer.enclClass;
	c != NoContext;
      }

      pre == NoPrefix
      ||
      (!sym.hasFlag(PRIVATE | PROTECTED))
      ||
      accessWithin(sym.owner) && (!sym.hasFlag(LOCAL) || pre =:= sym.owner.thisType)
      ||
      (!sym.hasFlag(PRIVATE) &&
       (superAccess ||
	(pre.widen.symbol.isSubClass(sym.owner) && isSubClassOfEnclosing(pre.widen.symbol))))
    }

    private var implicitsCache: List[List[ImplicitInfo]] = null;
    private var implicitsRun: CompilerRun = NoRun;

    private def collectImplicits(syms: List[Symbol], pre: Type): List[ImplicitInfo] =
      for (val sym <- syms; sym.hasFlag(IMPLICIT) && isAccessible(sym, pre, false))
      yield ImplicitInfo(sym.name, pre.memberType(sym), sym);

    private def collectImplicitImports(imp: ImportInfo): List[ImplicitInfo] = {
      val pre = imp.qual.tpe;
      def collect(sels: List[Pair[Name, Name]]): List[ImplicitInfo] = sels match {
	case List() => List()
	case List(Pair(nme.WILDCARD, _)) => collectImplicits(pre.implicitMembers, pre)
	case Pair(from, to) :: sels1 =>
	  var impls = collect(sels1) filter (info => info.name != from);
	  if (to != nme.WILDCARD) {
	    val sym = imp.importedSymbol(to);
	    if (sym.hasFlag(IMPLICIT)) impls = ImplicitInfo(to, pre.memberType(sym), sym) :: impls;
	  }
	  impls
      }
      if (settings.debug.value) log("collect implicit imports " + imp + "=" + collect(imp.tree.selectors));//debug
      collect(imp.tree.selectors)
    }

    def implicitss: List[List[ImplicitInfo]] = {
      if (implicitsRun != currentRun) {
	implicitsRun = currentRun;
	val newImplicits: List[ImplicitInfo] =
	  if (owner != outer.owner && owner.isClass && !owner.isPackageClass) {
            if (!owner.isInitialized) return outer.implicitss;
	    if (settings.debug.value) log("collect member implicits " + owner + ", implicit members = " + owner.thisType.implicitMembers);//debug
	    collectImplicits(owner.thisType.implicitMembers, owner.thisType)
	  } else if (scope != outer.scope && !owner.isPackageClass) {
	    if (settings.debug.value) log("collect local implicits " + scope.toList);//debug
	    collectImplicits(scope.toList, NoPrefix)
	  } else if (imports != outer.imports) {
	    assert(imports.tail == outer.imports);
	    collectImplicitImports(imports.head)
	  } else List();
	implicitsCache = if (newImplicits.isEmpty) outer.implicitss
			 else newImplicits :: outer.implicitss;
      }
      implicitsCache
    }
  }

  class ImportInfo(val tree: Import, val depth: int) {

    /** The prefix expression */
    def qual: Tree = tree.symbol.info match {
      case ImportType(expr) => expr
      case _ => throw new FatalError("symbol " + tree.symbol + " has bad type: " + tree.symbol.info);//debug
    }

    /** Is name imported explicitly, not via wildcard? */
    def isExplicitImport(name: Name): boolean =
      tree.selectors exists (._2.==(name.toTermName));

    /** The symbol with name `name' imported from import clause `tree'.
     */
    def importedSymbol(name: Name): Symbol = {
      var result: Symbol = NoSymbol;
      var renamed = false;
      var selectors = tree.selectors;
      while (selectors != Nil && result == NoSymbol) {
        if (selectors.head._2 == name.toTermName)
	  result = qual.tpe.member(
            if (name.isTypeName) selectors.head._1.toTypeName else selectors.head._1);
        else if (selectors.head._1 == name.toTermName)
          renamed = true
        else if (selectors.head._1 == nme.WILDCARD && !renamed)
          result = qual.tpe.member(name);
        selectors = selectors.tail
      }
      result
    }

    override def toString() = tree.toString();
  }

  case class ImplicitInfo(val name: Name, val tpe: Type, val sym: Symbol);

  case class ImportType(expr: Tree) extends Type;
}