137 lines
3.9 KiB
C++
137 lines
3.9 KiB
C++
#include <concepts>
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#include <iostream>
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#include <string>
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#include <string_view>
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#include <type_traits>
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#include <nlohmann/json.hpp>
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using json = nlohmann::json;
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struct FieldOptions {
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double min = 0;
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double max = 0;
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bool hasMin = false;
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bool hasMax = false;
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bool hidden = false;
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bool transient = false;
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bool readOnly = false;
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std::string_view label;
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};
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struct FieldOps {
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void (*save)(const void*, json&);
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void (*load)(void*, const json&);
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std::string (*show)(const void*);
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};
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template<class T>
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struct Codec {
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static void Save(const void* value, json& out) {
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out = *static_cast<const T*>(value);
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}
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static void Load(void* value, const json& in) {
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*static_cast<T*>(value) = in.get<T>();
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}
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static std::string Show(const void* value) {
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if constexpr (std::same_as<T, std::string>) return *static_cast<const T*>(value);
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else if constexpr (std::same_as<T, bool>) return *static_cast<const T*>(value) ? "true" : "false";
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else return std::to_string(*static_cast<const T*>(value));
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}
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static constexpr FieldOps ops{Save, Load, Show};
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};
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class FieldVisitor {
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public:
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template<class T>
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void Field(std::string_view key, T& value, FieldOptions options = {}) {
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Visit(key, &value, options, Codec<T>::ops);
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}
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protected:
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virtual void Visit(std::string_view key, void* value, const FieldOptions& options, const FieldOps& ops) = 0;
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};
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class JsonWriter final : public FieldVisitor {
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public:
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json Result() const { return result; }
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protected:
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void Visit(std::string_view key, void* value, const FieldOptions& options, const FieldOps& ops) override {
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if (!options.transient) ops.save(value, result[std::string(key)]);
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}
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private:
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json result = json::object();
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};
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class JsonReader final : public FieldVisitor {
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public:
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explicit JsonReader(const json& source) : data(source) {}
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protected:
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void Visit(std::string_view key, void* value, const FieldOptions& options, const FieldOps& ops) override {
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if (options.transient || !data.is_object()) return;
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const auto it = data.find(std::string(key));
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if (it != data.end()) ops.load(value, *it);
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}
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private:
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const json& data;
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};
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class ConsoleInspector final : public FieldVisitor {
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protected:
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void Visit(std::string_view key, void* value, const FieldOptions& options, const FieldOps& ops) override {
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if (options.hidden) return;
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const auto label = options.label.empty() ? key : options.label;
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std::cout << label << " = " << ops.show(value);
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if (options.readOnly) std::cout << " [read only]";
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if (options.hasMin || options.hasMax) {
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std::cout << " [";
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if (options.hasMin) std::cout << options.min;
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std::cout << ", ";
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if (options.hasMax) std::cout << options.max;
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std::cout << "]";
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}
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std::cout << '\n';
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}
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};
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struct Player {
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std::string name = "Ada";
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int health = 100;
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float speed = 4.5f;
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bool active = true;
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std::string runtimeNote = "created at runtime";
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void Reflect(FieldVisitor& visitor) {
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visitor.Field("name", name);
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visitor.Field("health", health, {.min = 0, .max = 100, .hasMin = true, .hasMax = true});
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visitor.Field("speed", speed, {.min = 0, .hasMin = true, .label = "Move Speed"});
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visitor.Field("active", active);
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visitor.Field("internalId", runtimeNote, {.hidden = true});
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visitor.Field("runtimeNote", runtimeNote, {.transient = true});
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}
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};
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int main() {
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Player player;
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JsonWriter writer;
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player.Reflect(writer);
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const json saved = writer.Result();
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std::cout << "Saved JSON\n" << saved.dump(2) << "\n\n";
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player.health = 1;
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player.speed = 0;
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JsonReader reader(saved);
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player.Reflect(reader);
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std::cout << "Console inspector\n";
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ConsoleInspector inspector;
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player.Reflect(inspector);
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}
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