xref: /base/update/updater/utils/json/json_visitor.h (revision fb299fa2) 
1/*
2 * Copyright (c) 2022 Huawei Device Co., Ltd.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
14 */
15
16#ifndef JSON_VISITOR_H
17#define JSON_VISITOR_H
18
19#include <type_traits>
20
21#include "json_node.h"
22#include "log/log.h"
23
24namespace Updater {
25template<typename T> struct Traits;
26enum Action { SETVAL, PRINTVAL };
27namespace Detail {
28template<typename Traits>
29constexpr bool CheckTrait()
30{
31    bool res = true;
32    for (int i = 0; i < Traits::COUNT; ++i) {
33        res = res && Traits::MEMBER_KEY[i] != nullptr && std::string_view("") != Traits::MEMBER_KEY[i];
34    }
35    return res;
36};
37
38template<Action action>
39struct MemberVisitor;
40
41template<typename T, std::size_t idx>
42using memberType = std::remove_reference_t<decltype(Traits<T>::template Get<idx>(std::declval<T&>()))>;
43
44template<Action action>
45struct StructVisitor {
46    template<typename T, std::size_t F, std::size_t... R>
47    static bool VisitStruct(const JsonNode &node, const JsonNode &defaultNode, T &t, std::index_sequence<F, R...>)
48    {
49        static_assert(CheckTrait<Traits<T>>(), "Trait member key invalid, please check");
50        constexpr auto key = Traits<T>::MEMBER_KEY[F];
51        auto &FthMember = Traits<T>::template Get<F>(t);
52        if (!MemberVisitor<action>::template VisitMember<memberType<T, F>>(
53            node[key], defaultNode[key], FthMember, key)) {
54            return false;
55        }
56
57        if constexpr (sizeof...(R) == 0) {
58            return true;
59        } else { // don't remove else, otherwise can't compile
60            return VisitStruct(node, defaultNode, t, std::index_sequence<R...> {});
61        }
62    }
63};
64
65template<>
66struct MemberVisitor<SETVAL> {
67    // visit string, int, bool
68    template<typename T, std::enable_if_t<Detail::G_IS_BASE_TYPE<T>, bool> = true>
69    static bool VisitMember(const JsonNode &node, const JsonNode &defaultNode, T &obj, const char *key)
70    {
71        auto r = node.As<T>();
72        auto defaultR = defaultNode.As<T>();
73        if (!r.has_value() && !defaultR.has_value()) {
74            LOG(ERROR) << key << " has not both default and non-default value!!!";
75            return false;
76        }
77        if (r) {
78            obj = *r;
79            return true;
80        }
81        if (defaultR) {
82            obj = *defaultR;
83            return true;
84        }
85        return false;
86    }
87    // visit vector, T is std::vector<T::value_type>
88    template<typename T, std::enable_if_t<Detail::G_IS_VECTOR<T>, bool> = true>
89    static auto VisitMember(const JsonNode &node, const JsonNode &defaultNode, T &obj, const char *key)
90    {
91        if ((node.Type() != NodeType::UNKNOWN && node.Type() != NodeType::NUL && node.Type() != NodeType::ARRAY) ||
92            (defaultNode.Type() != NodeType::UNKNOWN && defaultNode.Type() != NodeType::NUL &&
93            defaultNode.Type() != NodeType::ARRAY)) {
94                LOG(ERROR) << "Node type not matched with " << key;
95                return false;
96        }
97        typename T::value_type ele {};
98        for (auto &subNode : node) {
99            ele = {};
100            if (!VisitMember(subNode, {}, ele, "")) {
101                return false;
102            }
103            obj.push_back(std::move(ele));
104        }
105        for (auto &subNode : defaultNode) {
106            ele = {};
107            // using subNode to contruct an element of i-th type of T
108            if (!VisitMember(subNode, {}, ele, "")) {
109                return false;
110            }
111            obj.push_back(std::move(ele));
112        }
113        return true;
114    }
115    // visit struct
116    template<typename T, std::enable_if_t<std::is_integral_v<decltype(Traits<T>::COUNT)>, bool> = true>
117    static bool VisitMember(const JsonNode &node, const JsonNode &defaultNode, T &obj, const char *key)
118    {
119        return StructVisitor<SETVAL>::VisitStruct(node, defaultNode, obj,
120            std::make_index_sequence<Traits<T>::COUNT> {});
121    }
122};
123}  // namespace Detail
124
125template<Action act, typename T, std::enable_if_t<Detail::G_IS_VECTOR<T>, bool> = true>
126bool Visit(const JsonNode &node, T &obj)
127{
128    static_assert(act == SETVAL, "only for setting stl vector without default node");
129    return Detail::MemberVisitor<act>::VisitMember(node, {}, obj, "");
130}
131
132template<Action act, typename T, std::enable_if_t<Detail::G_IS_NUM<decltype(Traits<T>::COUNT)>, bool> = true>
133bool Visit(const JsonNode &node, const JsonNode &defaultNode, T &obj)
134{
135    static_assert(act == SETVAL,
136        "Only for setting member of struct with default node!");
137    return Detail::StructVisitor<act>::VisitStruct(node, defaultNode, obj,
138                                                   std::make_index_sequence<Traits<T>::COUNT> {});
139}
140
141template<Action act, typename T, std::enable_if_t<Detail::G_IS_NUM<decltype(Traits<T>::COUNT)>, bool> = true>
142bool Visit(const JsonNode &node, T &obj)
143{
144    static_assert(act == SETVAL,
145        "Only for setting member of struct without default node!");
146    return Detail::StructVisitor<act>::VisitStruct(node, {}, obj,
147                                                   std::make_index_sequence<Traits<T>::COUNT> {});
148}
149}  // namespace Updater
150
151#endif
152