// tmp_policy
// Created by lucas on 22-7-26.
// Re-implementation of a typical policy architecture in C++ Template Meta-Programming.

#ifndef TMP_POLICY_ACCPOLICY_H
#define TMP_POLICY_ACCPOLICY_H

// Policy Major Class definition.
struct AccPolicy {
    using MajorClass = AccPolicy;

    struct AccuTypeCate {
        struct Add;
        struct Mul;
    };
    using AccuType = AccuTypeCate::Add;

    struct IsAveValueCate;
    static constexpr bool IsAveValue = false;

    struct ResultTypeCate;
    using ResultType = int;

};

// Auxiliary Macros Definition.
#define TypePolicyObj(TName, TMajor, TMinor, TType) \
struct TName: virtual public TMajor {           \
    using MinorClass = TMinor##TypeCate;                     \
    using TMinor##Type = TMinor##TypeCate::TType;    \
}

#define ValuePolicyObj(TName, TMajor, TMinor, TValueType, TValue) \
struct TName: virtual public TMajor {                         \
    using MinorClass = TMinor##ValueCate;                         \
    static constexpr TValueType TMinor##Value = TValue;           \
}

#define TypePolicyTemplate(TName, TMajor, TMinor) \
template <typename T>                            \
struct TName: virtual public TMajor{          \
    using MinorClass = TMinor##TypeCate;         \
    using TMinor##Type = T;                       \
}

// Policy objects defined with auxiliary macros.
TypePolicyObj(PAdd, AccPolicy, Accu, Add);
TypePolicyObj(PMul, AccPolicy, Accu, Mul);
ValuePolicyObj(PAve, AccPolicy, IsAve, bool, true);
ValuePolicyObj(PNoAve, AccPolicy, IsAve, bool, false);
TypePolicyTemplate(PResultTypeIs, AccPolicy, Result);

#endif //TMP_POLICY_ACCPOLICY_H