#ifndef PFOR_PFOR_EXPRESSION_TRAITS_H
#define PFOR_PFOR_EXPRESSION_TRAITS_H

#include <utility>

#include "tag.h"

namespace pfor {
namespace expr {

/**
 * @brief tests a type and return true if it is an expression
 *
 * @return true if the type is an expression
 */
template<typename, typename = void>
struct IsExpression: std::false_type {};

template<typename T>
struct IsExpression<T, std::enable_if_t<std::is_same<typename std::decay_t<T>::IsExpression, tag::Expression>{}>>: std::true_type {};

template<typename E>
constexpr bool isExpression = IsExpression<E>::value;

/**
 * @brief tests a pack of types and returns true is all are expressions
 */
template<typename...> struct AllExpression: std::false_type {};

template<typename T, typename... Ts>
struct AllExpression<T, Ts...> {
	static constexpr bool value = IsExpression<T>::value && AllExpression<Ts...>::value;
};

template<typename T> struct AllExpression<T>: IsExpression<T> {};

template<typename... Ts>
constexpr bool allExpression = AllExpression<Ts...>::value;

/**
 * @brief tests a pack of types and returns true if any of them is an expression
 */
template<typename...> struct AnyExpression: std::false_type {};

template<typename T, typename... Ts>
struct AnyExpression<T, Ts...> {
	static constexpr bool value = IsExpression<T>::value || AnyExpression<Ts...>::value;
};

template<typename T> struct AnyExpression<T>: IsExpression<T> {};

template<typename... Ts>
constexpr bool anyExpression = AnyExpression<Ts...>::value;

}
}

#endif