juce_JSONSerialisation.h

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 /*
  ==============================================================================
 
   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited
 
   JUCE is an open source library subject to commercial or open-source
   licensing.
 
   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
   To use, copy, modify, and/or distribute this software for any purpose with or
   without fee is hereby granted provided that the above copyright notice and
   this permission notice appear in all copies.
 
   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.
 
  ==============================================================================
*/
 
namespace juce
{
 
class ToVarOptions
{
public:
    [[nodiscard]] ToVarOptions withExplicitVersion (std::optional<int> x) const { return withMember (*this, &ToVarOptions::explicitVersion, x); }
 
    [[nodiscard]] ToVarOptions withVersionIncluded (bool x)               const { return withMember (*this, &ToVarOptions::versionIncluded, x); }
 
    [[nodiscard]] auto getExplicitVersion() const { return explicitVersion; }
 
    [[nodiscard]] auto getVersionIncluded() const { return versionIncluded; }
 
private:
    std::optional<std::optional<int>> explicitVersion;
    bool versionIncluded = true;
};
 
class ToVar
{
public:
    using Options = ToVarOptions;
 
    template <typename T>
    static std::optional<var> convert (const T& t, const Options& options = {})
    {
        return Visitor::convert (t, options);
    }
 
private:
    class Visitor
    {
    public:
        template <typename T>
        static std::optional<var> convert (const T& t, const Options& options)
        {
            constexpr auto fallbackVersion = detail::ForwardingSerialisationTraits<T>::marshallingVersion;
            const auto versionToUse = options.getExplicitVersion()
                                             .value_or (fallbackVersion);
 
            if (versionToUse > fallbackVersion)
            {
                // The requested explicit version is higher than the declared version of the type.
                return std::nullopt;
            }
 
            Visitor visitor { versionToUse, options.getVersionIncluded() };
            detail::doSave (visitor, t);
            return visitor.value;
        }
 
        std::optional<int> getVersion() const { return version; }
 
        template <typename... Ts>
        void operator() (Ts&&... ts)
        {
            (visit (std::forward<Ts> (ts)), ...);
        }
 
    private:
        Visitor (const std::optional<int>& explicitVersion, bool includeVersion)
            : version (explicitVersion),
              value ([&]() -> var
              {
                  if (! (version.has_value() && includeVersion))
                      return var();
 
                  auto obj = std::make_unique<DynamicObject>();
                  obj->setProperty ("__version__", *version);
                  return obj.release();
              }()),
              versionIncluded (includeVersion) {}
 
        template <typename T>
        void visit (const T& t)
        {
            if constexpr (std::is_integral_v<T>)
            {
                push ((int64) t);
            }
            else if constexpr (std::is_floating_point_v<T>)
            {
                push ((double) t);
            }
            else if (auto converted = convert (t))
            {
                push (*converted);
            }
            else
            {
                value.reset();
            }
        }
 
        template <typename T>
        void visit (const Named<T>& named)
        {
            if (! value.has_value())
                return;
 
            if (value == var())
                value = new DynamicObject;
 
            auto* obj = value->getDynamicObject();
 
            if (obj == nullptr)
            {
                // Serialisation failure! This may be caused by archiving a primitive or
                // SerialisationSize, and then attempting to archive a named pair to the same
                // archive instance.
                // When using named pairs, *all* items serialised with a particular archiver must be
                // named pairs.
                jassertfalse;
 
                value.reset();
                return;
            }
 
            if (! trySetProperty (*obj, named))
                value.reset();
        }
 
        template <typename T>
        void visit (const SerialisationSize<T>&)
        {
            push (Array<var>{});
        }
 
        void visit (const bool& t)
        {
            push (t);
        }
 
        void visit (const String& t)
        {
            push (t);
        }
 
        void visit (const var& t)
        {
            push (t);
        }
 
        template <typename T>
        std::optional<var> convert (const T& t)
        {
            return convert (t, Options{}.withVersionIncluded (versionIncluded));
        }
 
        void push (var v)
        {
            if (! value.has_value())
                return;
 
            if (*value == var())
                *value = v;
            else if (auto* array = value->getArray())
                array->add (v);
            else
                value.reset();
        }
 
        template <typename T>
        bool trySetProperty (DynamicObject& obj, const Named<T>& n)
        {
            if (const auto converted = convert (n.value))
            {
                obj.setProperty (Identifier (std::string (n.name)), *converted);
                return true;
            }
 
            return false;
        }
 
        std::optional<int> version;
        std::optional<var> value;
        bool versionIncluded = true;
    };
};
 
//==============================================================================
class FromVar
{
public:
    template <typename T>
    static std::optional<T> convert (const var& v)
    {
        return Visitor::convert<T> (v);
    }
 
private:
    class Visitor
    {
    public:
        template <typename T>
        static std::optional<T> convert (const var& v)
        {
            const auto version = [&]() -> std::optional<int>
            {
                if (auto* obj = v.getDynamicObject())
                    if (obj->hasProperty ("__version__"))
                        return (int) obj->getProperty ("__version__");
 
                return std::nullopt;
            }();
 
            Visitor visitor { version, v };
            T t{};
            detail::doLoad (visitor, t);
            return ! visitor.failed ? std::optional<T> (std::move (t))
                                    : std::nullopt;
        }
 
        std::optional<int> getVersion() const { return version; }
 
        template <typename... Ts>
        void operator() (Ts&&... ts)
        {
            (visit (std::forward<Ts> (ts)), ...);
        }
 
    private:
        Visitor (std::optional<int> vn, const var& i)
            : version (vn), input (i) {}
 
        template <typename T>
        void visit (T& t)
        {
            if constexpr (std::is_integral_v<T>)
            {
                readPrimitive (std::in_place_type<int64>, t);
            }
            else if constexpr (std::is_floating_point_v<T>)
            {
                readPrimitive (std::in_place_type<double>, t);
            }
            else
            {
                auto node = getNodeToRead();
 
                if (! node.has_value())
                    return;
 
                auto converted = convert<T> (*node);
 
                if (converted.has_value())
                    t = *converted;
                else
                    failed = true;
            }
        }
 
        template <typename T>
        void visit (const Named<T>& named)
        {
            auto node = getNodeToRead();
 
            if (! node.has_value())
                return;
 
            auto* obj = node->getDynamicObject();
 
            failed = obj == nullptr || ! tryGetProperty (*obj, named);
        }
 
        template <typename T>
        void visit (const SerialisationSize<T>& t)
        {
            if (failed)
                return;
 
            if (auto* array = input.getArray())
            {
                t.size = static_cast<T> (array->size());
                currentArrayIndex = 0;
            }
            else
            {
                failed = true;
            }
        }
 
        void visit (bool& t)
        {
            readPrimitive (std::in_place_type<bool>, t);
        }
 
        void visit (String& t)
        {
            readPrimitive (std::in_place_type<String>, t);
        }
 
        void visit (var& t)
        {
            t = input;
        }
 
        static std::optional<double> pullTyped (std::in_place_type_t<double>, const var& source)
        {
            return source.isDouble() ? std::optional<double> ((double) source) : std::nullopt;
        }
 
        static std::optional<int64> pullTyped (std::in_place_type_t<int64>, const var& source)
        {
            return source.isInt() || source.isInt64() ? std::optional<int64> ((int64) source) : std::nullopt;
        }
 
        static std::optional<bool> pullTyped (std::in_place_type_t<bool>, const var& source)
        {
            return std::optional<bool> ((bool) source);
        }
 
        static std::optional<String> pullTyped (std::in_place_type_t<String>, const var& source)
        {
            return source.isString() ? std::optional<String> (source.toString()) : std::nullopt;
        }
 
        std::optional<var> getNodeToRead()
        {
            if (failed)
                return std::nullopt;
 
            if (currentArrayIndex == std::numeric_limits<size_t>::max())
                return input;
 
            const auto* array = input.getArray();
 
            if (array == nullptr)
                return input;
 
            if ((int) currentArrayIndex < array->size())
                return array->getReference ((int) currentArrayIndex++);
 
            failed = true;
            return std::nullopt;
        }
 
        template <typename TypeToRead, typename T>
        void readPrimitive (std::in_place_type_t<TypeToRead> tag, T& t)
        {
            auto node = getNodeToRead();
 
            if (! node.has_value())
                return;
 
            auto typed = pullTyped (tag, *node);
 
            if (typed.has_value())
                t = static_cast<T> (*typed);
            else
                failed = true;
        }
 
        template <typename T>
        static bool tryGetProperty (const DynamicObject& obj, const Named<T>& n)
        {
            const Identifier identifier (String (n.name.data(), n.name.size()));
 
            if (! obj.hasProperty (identifier))
                return false;
 
            const auto converted = convert<T> (obj.getProperty (identifier));
 
            if (! converted.has_value())
                return false;
 
            n.value = *converted;
            return true;
        }
 
        std::optional<int> version;
        var input;
        size_t currentArrayIndex = std::numeric_limits<size_t>::max();
        bool failed = false;
    };
};
 
//==============================================================================
template <typename Type>
struct VariantConverter
{
    static Type fromVar (const var& v)
    {
        return static_cast<Type> (v);
    }
 
    static var toVar (const Type& t)
    {
        return t;
    }
};
 
#ifndef DOXYGEN
 
template <>
struct VariantConverter<String>
{
    static String fromVar (const var& v)           { return v.toString(); }
    static var toVar (const String& s)             { return s; }
};
 
#endif
 
template <typename Type>
struct StrictVariantConverter
{
    static_assert (detail::serialisationKind<Type> != detail::SerialisationKind::none);
 
    static Type fromVar (const var& v)
    {
        auto converted = FromVar::convert<Type> (v);
        jassert (converted.has_value());
        return std::move (converted).value_or (Type{});
    }
 
    static var toVar (const Type& t)
    {
        auto converted = ToVar::convert<> (t);
        jassert (converted.has_value());
        return std::move (converted).value_or (var{});
    }
};
 
} // namespace juce