json/test/src/unit-udt.cpp

/*
    __ _____ _____ _____
 __|  |   __|     |   | |  JSON for Modern C++ (test suite)
|  |  |__   |  |  | | | |  version 2.0.7
|_____|_____|_____|_|___|  https://github.com/nlohmann/json

Licensed under the MIT License <http://opensource.org/licenses/MIT>.
Copyright (c) 2013-2016 Niels Lohmann <http://nlohmann.me>.

Permission is hereby  granted, free of charge, to any  person obtaining a copy
of this software and associated  documentation files (the "Software"), to deal
in the Software  without restriction, including without  limitation the rights
to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
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LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

#include <array>
#include <map>
#include <string>
#include <memory>
#include "catch.hpp"

#include "json.hpp"

using nlohmann::json;

namespace udt
{
enum class country
{
    china,
    france,
    russia
};

struct age
{
    int m_val;
};

struct name
{
    std::string m_val;
};

struct address
{
    std::string m_val;
};

struct person
{
    age m_age;
    name m_name;
    country m_country;
};

struct contact
{
    person m_person;
    address m_address;
};

struct contact_book
{
    name m_book_name;
    std::vector<contact> m_contacts;
};
}

// to_json methods
namespace udt
{
// templates because of the custom_json tests (see below)
template <typename Json>
void to_json(Json& j, age a)
{
    j = a.m_val;
}

template <typename Json>
void to_json(Json& j, const name& n)
{
    j = n.m_val;
}

template <typename Json>
void to_json(Json& j, country c)
{
    switch (c)
    {
        case country::china:
            j = u8"中华人民共和国";
            return;
        case country::france:
            j = "France";
            return;
        case country::russia:
            j = u8"Российская Федерация";
            return;
    }
}

template <typename Json>
void to_json(Json& j, const person& p)
{
    j = Json{{"age", p.m_age}, {"name", p.m_name}, {"country", p.m_country}};
}

void to_json(nlohmann::json& j, const address& a)
{
    j = a.m_val;
}

void to_json(nlohmann::json& j, const contact& c)
{
    j = json{{"person", c.m_person}, {"address", c.m_address}};
}

void to_json(nlohmann::json& j, const contact_book& cb)
{
    j = json{{"name", cb.m_book_name}, {"contacts", cb.m_contacts}};
}

// operators
bool operator==(age lhs, age rhs)
{
    return lhs.m_val == rhs.m_val;
}

bool operator==(const address& lhs, const address& rhs)
{
    return lhs.m_val == rhs.m_val;
}

bool operator==(const name& lhs, const name& rhs)
{
    return lhs.m_val == rhs.m_val;
}

bool operator==(const person& lhs, const person& rhs)
{
    return std::tie(lhs.m_name, lhs.m_age) == std::tie(rhs.m_name, rhs.m_age);
}

bool operator==(const contact& lhs, const contact& rhs)
{
    return std::tie(lhs.m_person, lhs.m_address) ==
           std::tie(rhs.m_person, rhs.m_address);
}

bool operator==(const contact_book& lhs, const contact_book& rhs)
{
    return std::tie(lhs.m_book_name, lhs.m_contacts) ==
           std::tie(rhs.m_book_name, rhs.m_contacts);
}
}

// from_json methods
namespace udt
{
template <typename Json>
void from_json(const Json& j, age& a)
{
    a.m_val = j.template get<int>();
}

template <typename Json>
void from_json(const Json& j, name& n)
{
    n.m_val = j.template get<std::string>();
}

template <typename Json>
void from_json(const Json& j, country& c)
{
    const auto str = j.template get<std::string>();
    static const std::map<std::string, country> m =
    {
        {u8"中华人民共和国", country::china},
        {"France", country::france},
        {"Российская Федерация", country::russia}
    };

    const auto it = m.find(str);
    // TODO test exceptions
    c = it->second;
}

template <typename Json>
void from_json(const Json& j, person& p)
{
    p.m_age = j["age"].template get<age>();
    p.m_name = j["name"].template get<name>();
    p.m_country = j["country"].template get<country>();
}

void from_json(const nlohmann::json& j, address& a)
{
    a.m_val = j.get<std::string>();
}

void from_json(const nlohmann::json& j, contact& c)
{
    c.m_person = j["person"].get<person>();
    c.m_address = j["address"].get<address>();
}

void from_json(const nlohmann::json& j, contact_book& cb)
{
    cb.m_book_name = j["name"].get<name>();
    cb.m_contacts = j["contacts"].get<std::vector<contact>>();
}
}

TEST_CASE("basic usage", "[udt]")
{

    // a bit narcissic maybe :) ?
    const udt::age a
    {
        23
    };
    const udt::name n{"theo"};
    const udt::country c{udt::country::france};
    const udt::person sfinae_addict{a, n, c};
    const udt::person senior_programmer{{42}, {u8"王芳"}, udt::country::china};
    const udt::address addr{"Paris"};
    const udt::contact cpp_programmer{sfinae_addict, addr};
    const udt::contact_book book{{"C++"}, {cpp_programmer, {senior_programmer, addr}}};

    SECTION("conversion to json via free-functions")
    {
        CHECK(json(a) == json(23));
        CHECK(json(n) == json("theo"));
        CHECK(json(c) == json("France"));
        CHECK(json(sfinae_addict) == R"({"name":"theo", "age":23, "country":"France"})"_json);
        CHECK(json("Paris") == json(addr));
        CHECK(json(cpp_programmer) ==
              R"({"person" : {"age":23, "name":"theo", "country":"France"}, "address":"Paris"})"_json);

        CHECK(
            json(book) ==
            u8R"({"name":"C++", "contacts" : [{"person" : {"age":23, "name":"theo", "country":"France"}, "address":"Paris"}, {"person" : {"age":42, "country":"中华人民共和国", "name":"王芳"}, "address":"Paris"}]})"_json);

    }

    SECTION("conversion from json via free-functions")
    {
        const auto big_json =
            u8R"({"name":"C++", "contacts" : [{"person" : {"age":23, "name":"theo", "country":"France"}, "address":"Paris"}, {"person" : {"age":42, "country":"中华人民共和国", "name":"王芳"}, "address":"Paris"}]})"_json;
        const auto parsed_book = big_json.get<udt::contact_book>();
        const auto book_name = big_json["name"].get<udt::name>();
        const auto contacts = big_json["contacts"].get<std::vector<udt::contact>>();
        const auto contact_json = big_json["contacts"].at(0);
        const auto contact = contact_json.get<udt::contact>();
        const auto person = contact_json["person"].get<udt::person>();
        const auto address = contact_json["address"].get<udt::address>();
        const auto age = contact_json["person"]["age"].get<udt::age>();
        const auto country = contact_json["person"]["country"].get<udt::country>();
        const auto name = contact_json["person"]["name"].get<udt::name>();

        CHECK(age == a);
        CHECK(name == n);
        CHECK(country == c);
        CHECK(address == addr);
        CHECK(person == sfinae_addict);
        CHECK(contact == cpp_programmer);
        CHECK(contacts == book.m_contacts);
        CHECK(book_name == udt::name{"C++"});
        CHECK(book == parsed_book);
    }
}

namespace udt
{
struct legacy_type
{
    std::string number;
};
}

namespace nlohmann
{
template <typename T>
struct adl_serializer<std::shared_ptr<T>>
{
    static void to_json(json& j, const std::shared_ptr<T>& opt)
    {
        if (opt)
        {
            j = *opt;
        }
        else
        {
            j = nullptr;
        }
    }

    static void from_json(const json& j, std::shared_ptr<T>& opt)
    {
        if (j.is_null())
        {
            opt = nullptr;
        }
        else
        {
            opt.reset(new T(j.get<T>()));
        }
    }
};

template <>
struct adl_serializer<udt::legacy_type>
{
    static void to_json(json& j, const udt::legacy_type& l)
    {
        j = std::stoi(l.number);
    }

    static void from_json(const json& j, udt::legacy_type& l)
    {
        l.number = std::to_string(j.get<int>());
    }
};
}

TEST_CASE("adl_serializer specialization", "[udt]")
{
    SECTION("partial specialization")
    {
        SECTION("to_json")
        {
            std::shared_ptr<udt::person> optPerson;

            json j = optPerson;
            CHECK(j.is_null());

            optPerson.reset(new udt::person{{42}, {"John Doe"}});
            j = optPerson;
            CHECK_FALSE(j.is_null());

            CHECK(j.get<udt::person>() == *optPerson);
        }

        SECTION("from_json")
        {
            auto person = udt::person{{42}, {"John Doe"}};
            json j = person;

            auto optPerson = j.get<std::shared_ptr<udt::person>>();
            REQUIRE(optPerson);
            CHECK(*optPerson == person);

            j = nullptr;
            optPerson = j.get<std::shared_ptr<udt::person>>();
            CHECK(!optPerson);
        }
    }

    SECTION("total specialization")
    {
        SECTION("to_json")
        {
            udt::legacy_type lt{"4242"};

            json j = lt;
            CHECK(j.get<int>() == 4242);
        }

        SECTION("from_json")
        {
            json j = 4242;
            auto lt = j.get<udt::legacy_type>();
            CHECK(lt.number == "4242");
        }
    }
}

namespace nlohmann
{
template <>
struct adl_serializer<std::vector<float>>
{
    using type = std::vector<float>;
    static void to_json(json& j, const type&)
    {
        j = "hijacked!";
    }

    static void from_json(const json&, type& opt)
    {
        opt = {42.0, 42.0, 42.0};
    }

    // preferred version
    static type from_json(const json&)
    {
        return {4.0, 5.0, 6.0};
    }
};
}

TEST_CASE("even supported types can be specialized", "[udt]")
{
    json j = std::vector<float> {1.0, 2.0, 3.0};
    CHECK(j.dump() == R"("hijacked!")");
    auto f = j.get<std::vector<float>>();
    // the single argument from_json method is preferred
    CHECK((f == std::vector<float> {4.0, 5.0, 6.0}));
}

namespace nlohmann
{
template <typename T>
struct adl_serializer<std::unique_ptr<T>>
{
    static void to_json(json& j, const std::unique_ptr<T>& opt)
    {
        if (opt)
        {
            j = *opt;
        }
        else
        {
            j = nullptr;
        }
    }

    // this is the overload needed for non-copyable types,
    static std::unique_ptr<T> from_json(const json& j)
    {
        if (j.is_null())
        {
            return nullptr;
        }
        else
        {
            return std::unique_ptr<T>(new T(j.get<T>()));
        }
    }
};
}

TEST_CASE("Non-copyable types", "[udt]")
{
    SECTION("to_json")
    {
        std::unique_ptr<udt::person> optPerson;

        json j = optPerson;
        CHECK(j.is_null());

        optPerson.reset(new udt::person{{42}, {"John Doe"}, udt::country::russia});
        j = optPerson;
        CHECK_FALSE(j.is_null());

        CHECK(j.get<udt::person>() == *optPerson);
    }

    SECTION("from_json")
    {
        auto person = udt::person{{42}, {"John Doe"}, udt::country::russia};
        json j = person;

        auto optPerson = j.get<std::unique_ptr<udt::person>>();
        REQUIRE(optPerson);
        CHECK(*optPerson == person);

        j = nullptr;
        optPerson = j.get<std::unique_ptr<udt::person>>();
        CHECK(!optPerson);
    }
}

// custom serializer - advanced usage
// pack structs that are pod-types (but not scalar types)
// relies on adl for any other type
template <typename T, typename = void>
struct pod_serializer
{
    // use adl for non-pods, or scalar types
    template <
        typename Json, typename U = T,
        typename std::enable_if <
            not(std::is_pod<U>::value and std::is_class<U>::value), int >::type = 0 >
    static void from_json(const Json& j, U& t)
    {
        using nlohmann::from_json;
        from_json(j, t);
    }

    // special behaviour for pods
    template <typename Json, typename U = T,
              typename std::enable_if<
                  std::is_pod<U>::value and std::is_class<U>::value, int>::type = 0>
    static void from_json(const  Json& j, U& t)
    {
        std::uint64_t value;
        // TODO The following block is no longer relevant in this serializer, make another one that shows the issue
        // the problem arises only when one from_json method is defined without any constraint
        //
        // Why cannot we simply use: j.get<std::uint64_t>() ?
        // Well, with the current experiment, the get method looks for a from_json
        // function, which we are currently defining!
        // This would end up in a stack overflow. Calling nlohmann::from_json is a
        // workaround (is it?).
        // I shall find a good way to avoid this once all constructors are converted
        // to free methods
        //
        // In short, constructing a json by constructor calls to_json
        // calling get calls from_json, for now, we cannot do this in custom
        // serializers
        nlohmann::from_json(j, value);
        auto bytes = static_cast<char*>(static_cast<void*>(&value));
        std::memcpy(&t, bytes, sizeof(value));
    }

    template <
        typename Json, typename U = T,
        typename std::enable_if <
            not(std::is_pod<U>::value and std::is_class<U>::value), int >::type = 0 >
    static void to_json(Json& j, const  T& t)
    {
        using nlohmann::to_json;
        to_json(j, t);
    }

    template <typename Json, typename U = T,
              typename std::enable_if<
                  std::is_pod<U>::value and std::is_class<U>::value, int>::type = 0>
    static void to_json(Json& j, const  T& t) noexcept
    {
        auto bytes = static_cast< const unsigned char*>(static_cast<const void*>(&t));
        std::uint64_t value = bytes[0];
        for (auto i = 1; i < 8; ++i)
            value |= std::uint64_t{bytes[i]} << 8 * i;
        nlohmann::to_json(j, value);
    }
};

namespace udt
{
struct small_pod
{
    int begin;
    char middle;
    short end;
};

struct non_pod
{
    std::string s;
};

template <typename Json>
void to_json(Json& j, const non_pod& np)
{
    j = np.s;
}

template <typename Json>
void from_json(const Json& j, non_pod& np)
{
    np.s = j.template get<std::string>();
}

bool operator==(small_pod lhs, small_pod rhs) noexcept
{
    return std::tie(lhs.begin, lhs.middle, lhs.end) ==
           std::tie(rhs.begin, rhs.middle, rhs.end);
}

bool operator==(const  non_pod& lhs, const  non_pod& rhs) noexcept
{
    return lhs.s == rhs.s;
}

std::ostream& operator<<(std::ostream& os, small_pod l)
{
    return os << "begin: " << l.begin << ", middle: " << l.middle << ", end: " << l.end;
}
}

TEST_CASE("custom serializer for pods", "[udt]")
{
    using custom_json =
        nlohmann::basic_json<std::map, std::vector, std::string, bool,
        std::int64_t, std::uint64_t, double, std::allocator,
        pod_serializer>;

    auto p = udt::small_pod{42, '/', 42};
    custom_json j = p;

    auto p2 = j.get<udt::small_pod>();

    CHECK(p == p2);

    auto np = udt::non_pod{{"non-pod"}};
    custom_json j2 = np;
    auto np2 = j2.get<udt::non_pod>();
    CHECK(np == np2);
}

template <typename T, typename>
struct another_adl_serializer;

using custom_json = nlohmann::basic_json<std::map, std::vector, std::string, bool, std::int64_t, std::uint64_t, double, std::allocator, another_adl_serializer>;

template <typename T, typename>
struct another_adl_serializer
{
    static void from_json(const custom_json& j, T& t)
    {
        using nlohmann::from_json;
        from_json(j, t);
    }

    static void to_json(custom_json& j, const T& t)
    {
        using nlohmann::to_json;
        to_json(j, t);
    }
};

TEST_CASE("custom serializer that does adl by default", "[udt]")
{
    using json = nlohmann::json;

    auto me = udt::person{23, "theo", udt::country::france};

    json j = me;
    custom_json cj = me;

    CHECK(j.dump() == cj.dump());

    CHECK(me == j.get<udt::person>());
    CHECK(me == cj.get<udt::person>());
}