#ifndef LIBWCCL_OPS_ISSUBSETOF_H
#define LIBWCCL_OPS_ISSUBSETOF_H

#include <libwccl/ops/setpredicate.h>

namespace Wccl {

/**
 * Class that realises a predicate checking if one set is in another.
 * Almost like being a subset of, but empty set is considered not to be "in".
 */
template <class T>
class IsSubsetOf : public SetPredicate<T>
{
public:
	typedef typename SetPredicate<T>::SetFunctionPtr SetFunctionPtr;

	IsSubsetOf(const SetFunctionPtr& subset_expr, const SetFunctionPtr& set_expr)
		: SetPredicate<T>(subset_expr, set_expr)
	{
	}

	/**
	 * @returns Name of the function: "in"
	 */
	std::string raw_name() const {
		return "in";
	}

protected:
	typedef FunctionBase::BaseRetValPtr BaseRetValPtr;
	/**
	 * Take value of possible subset in question. If it is an empty set, return False.
	 * Otherwise, take value of the set that is being compared to.
	 * @returns True if the possible subset is inside set compared to.
	 * @note Take note this is not true "subset" function, because empty
	 * set is considered not to be "in" any other set so False is returned.
	 */
	BaseRetValPtr apply_internal(const FunExecContext& context) const {
		const boost::shared_ptr<const T>& possible_subset = this->set1_expr_->apply(context);
		if(!possible_subset->empty())
		{
			const boost::shared_ptr<const T>& set_compared_to = this->set2_expr_->apply(context);
			return Predicate::evaluate(possible_subset->is_subset_of(*set_compared_to), context);
		}
		return Predicate::False(context);
	}

};

} /* end ns Wccl */


#endif // LIBWCCL_OPS_ISSUBSETOF_H