import jastadd.*;
import java.util.LinkedList;

aspect CheckExtendsCycles {

	public void ASTNode.checkExtendsCycles(){}
	public void ModuleCompilationUnit.checkExtendsCycles() {
		checkExtendsCycles(new LinkedList<ModuleCompilationUnit>());
	}
	public void ModuleCompilationUnit.checkExtendsCycles(LinkedList<ModuleCompilationUnit> visited) {
		if (visited.contains(this)) {
			String cycleStr = "";
			boolean first = true;
			for (ModuleCompilationUnit cycleMember : visited) {
				if (!first) { cycleStr += ", "; }
				cycleStr += cycleMember.getModuleName();
				first = false;
			}
			String msg = "Module " + getModuleName() + 
				" involved in an extends cycle with the following modules: " + cycleStr;
			getModuleDecl().getExtends().error(msg);
			throw new UnrecoverableSemanticError(msg);
		}
		if (hasSuperModule()) {
			ModuleCompilationUnit superMCU = 
				getHostProgram().lookupModuleCUNoTransform(getModuleDecl().getExtends());
			LinkedList<ModuleCompilationUnit> newList =
				new LinkedList<ModuleCompilationUnit>(visited);
			newList.add(this); 
			superMCU.checkExtendsCycles(newList);
		}
	} 
}