import java.util.Collection;
import java.util.ArrayList;

aspect ErrorCheck {
  public Collection Program.errors() {
    Collection c = new ArrayList();
    collectErrors(c);
    return c;
  }

  // generic traversal that collects errors in AST
  public void ASTNode.collectErrors(Collection c) {
    for(int i = 0; i < getNumChild(); i++)
      getChild(i).collectErrors(c);
  }

  // add an error msg associated with a certain context
  protected void ASTNode.error(Collection c, String s) {
    //c.add(getLine(getStart()) + ": " + s);
    c.add(s);
  }

  // add error for incompatible assignment
  public void AssignStmt.collectErrors(Collection c) {
    super.collectErrors(c);
    if(!getValue().type().isSubtypeOf(getVariable().type()))
      error(c, "Can not assign a variable of type " + getVariable().type().getName() +
        " to a value of type " + getValue().type().getName());
  }
  
  // add error for cyclic class hierarchy
  public void ClassDecl.collectErrors(Collection c) {
    super.collectErrors(c);
    if(hasCycleOnSuperclassChain())
      error(c, "Cyclic inheritance chain for class " + getName());
  }

  // add error for non-boolean condition in while
  public void WhileStmt.collectErrors(Collection c) {
    super.collectErrors(c);
    if(!getCondition().type().isSubtypeOf(booleanType()))
      error(c, "Condition must be a boolean expression");
    if(!getCondition().isValue())
      error(c, "Condition must be a value");
  }

  // add error for the first unbound name in a, possibly qualified, name 
  public void IdUse.collectErrors(Collection c) {
    super.collectErrors(c);
    if(decl().isUnknown() && (!isQualified() || !qualifier().type().isUnknown()))
      error(c, "Unknown identifier " + getName());
  }

  // TODO: maybe move these attributes to another module?
  eq Program.getBlock().isQualified() = false;
  eq Program.getPredefinedType(int i).isQualified() = false;
  eq Dot.getIdUse().isQualified() = true;
  inh boolean IdUse.isQualified();
  inh boolean TypeDecl.isQualified();

  eq Program.getBlock().qualifier() {
    throw new Error("Can not compute qualifier for non qualified names");
  }
  eq Program.getPredefinedType(int i).qualifier() {
    throw new Error("Can not compute qualifier for non qualified names");
  }
  eq Dot.getIdUse().qualifier() = getObjectReference();
  inh Access IdUse.qualifier();
  inh Access TypeDecl.qualifier();

}