import java.util.HashSet;

aspect NameResolution {
  
  // ***API***
  
  // Declaration of *decl*
  // *decl* refers to the appropriate declaration of the Access,
  // or to unknownDecl if the declaration is missing
  syn lazy Decl Access.decl();  

  
  // ***Implementation***
  
  //   Definitions of *decl*
  eq IdUse.decl() = lookup(getName());
  eq Dot.decl() = getIdUse().decl();
  
  //   Definitions of *lookup*
  eq Program.getBlock().lookup(String name) = localLookup(name); // lookup predefined types
  eq Program.getPredefinedType(int index).lookup(String name) = unknownDecl();
  
  eq Block.getBlockStmt(int index).lookup(String name) {
    // First, look in the local declarations
    if (!localLookup(name).isUnknown())
      return localLookup(name);
    // Then, look in surrounding context
    return lookup(name);
  }
  
  eq ClassDecl.getBody().lookup(String name) {
    // First, look in superclass chain
    if (superClass() != null && !superClass().remoteLookup(name).isUnknown())
      return superClass().remoteLookup(name);
    // Then, look in surrounding context
    return lookup(name);
  }
  
  eq Dot.getIdUse().lookup(String name) =
    // Do a remote lookup on the object's type.
    getObjectReference().decl().type().remoteLookup(name);
  
  // *remoteLookup*
  // Looks through declarations of this type that are accessible from outside the type
  // By default, there are no such declarations, so return unknownDecl.
  syn Decl TypeDecl.remoteLookup(String name) = unknownDecl();
  
  // *remoteLookup* - looks through the declarations in this class and superclasses
  eq ClassDecl.remoteLookup(String name) {
    // First, look in local declarations
    if (!getBody().localLookup(name).isUnknown())
      return getBody().localLookup(name); 
    // Then, look in the superclass chain
    if (superClass() != null && !superClass().remoteLookup(name).isUnknown())
      return superClass().remoteLookup(name);
    // Otherwise, return null object unknown
    return unknownDecl();
  }
  
  // Expose *lookup* at various places in the AST
  inh Decl IdUse.lookup(String name);
  inh Decl Block.lookup(String name);
  inh Decl TypeDecl.lookup(String name);
  
  // *localLookup* - looks through the local declarations in a block
  
  syn lazy Decl Block.localLookup(String name) {
    for (int k = 0; k < getNumBlockStmt(); k++) {
      Decl d = getBlockStmt(k).declarationOf(name);
      if (d != null) return d;
    }
    return unknownDecl();
  }
  
  syn lazy Decl Program.localLookup(String name) {
    for (int k = 0; k < getNumPredefinedType(); k++) {
      Decl d = getPredefinedType(k).declarationOf(name);
      if (d != null) return d;
    }
    return unknownDecl();
  }
  
  syn Decl BlockStmt.declarationOf(String name) = null;
  eq Decl.declarationOf(String name) {
    if (getName().equals(name)) return this;
    return null;
  }

}