json-validator/include/jvalidate/adapters/jsoncpp.h

#pragma once
#include <type_traits>

#include <json/reader.h>
#include <json/value.h>

#include <jvalidate/adapter.h>
#include <jvalidate/compat/expected.h>
#include <jvalidate/detail/expect.h>
#include <jvalidate/detail/number.h>
#include <jvalidate/detail/simple_adapter.h>
#include <jvalidate/enum.h>

namespace jvalidate::adapter {
template <>
inline auto load_stream(std::istream & in, Json::Value & out) noexcept
    -> detail::expected<void, std::string> {
  Json::CharReaderBuilder builder;
  if (std::string error; not Json::parseFromStream(builder, in, &out, &error)) {
    return detail::unexpected(error);
  }
  return {};
}

template <typename JSON> class JsonCppAdapter;

template <> struct AdapterTraits<Json::Value> {
  template <typename JSON> using Adapter = adapter::JsonCppAdapter<JSON>;
  using ConstAdapter = adapter::JsonCppAdapter<Json::Value const>;

  static Json::Value const & const_empty() {
    static Json::Value const g_value;
    return g_value;
  }
};

template <typename JSON> class JsonCppObjectAdapter : public detail::SimpleObjectAdapter<JSON> {
public:
  using JsonCppObjectAdapter::SimpleObjectAdapter::SimpleObjectAdapter;

  bool contains(std::string const & key) const { return this->const_value().isMember(key); }

  JsonCppAdapter<JSON> operator[](std::string const & key) const {
    return this->value() ? &(*this->value())[key] : nullptr;
  }

  void assign(std::string const & key, Const const & frozen) const
    requires(not std::is_const_v<JSON>)
  {
    (*this)[key].assign(frozen);
  }
};

template <typename JSON> class JsonCppAdapter final : public detail::SimpleAdapter<JSON> {
public:
  using JsonCppAdapter::SimpleAdapter::SimpleAdapter;

  Type type() const {
    using jvalidate::detail::fits_in_integer;
    switch (const_value().type()) {
    case Json::nullValue:
      return Type::Null;
    case Json::booleanValue:
      return Type::Boolean;
    case Json::realValue:
      // Not strictly necessary - Validation code will safely handle this too
      return fits_in_integer(const_value().asDouble()) ? Type::Integer : Type::Number;
    case Json::stringValue:
      return Type::String;
    case Json::arrayValue:
      return Type::Array;
    case Json::objectValue:
      return Type::Object;
    case Json::intValue:
      return Type::Integer;
    case Json::uintValue:
      return fits_in_integer(const_value().asUInt64()) ? Type::Integer : Type::Number;
    }
  }

  bool as_boolean() const { return const_value().asBool(); }
  int64_t as_integer() const { return const_value().asInt64(); }
  double as_number() const { return const_value().asDouble(); }
  std::string as_string() const { return const_value().asString(); }

  JsonCppObjectAdapter<JSON> as_object() const { return value(); }

  static std::string key(auto it) { return it.key().asString(); }

  using detail::SimpleAdapter<JSON>::assign;
  void assign(Adapter const & adapter) const
    requires(not std::is_const_v<JSON>)
  {
    switch (adapter.type()) {
    case Type::Null:
      *value() = Json::nullValue;
      return;
    case Type::Boolean:
      *value() = adapter.as_boolean();
      return;
    case Type::Integer:
      *value() = adapter.as_integer();
      return;
    case Type::Number:
      *value() = adapter.as_number();
      return;
    case Type::String:
      *value() = adapter.as_string();
      return;
    case Type::Array:
      adapter.apply_array([this, index = 0](Adapter const & elem) mutable {
        JsonCppAdapter((*value())[index]).assign(elem);
        ++index;
        return Status::Accept;
      });
      return;
    case Type::Object:
      adapter.apply_object([this](std::string const & key, Adapter const & elem) {
        JsonCppAdapter((*value())[key]).assign(elem);
        return Status::Accept;
      });
      return;
    }
  }

public:
  using JsonCppAdapter::SimpleAdapter::const_value;
  using JsonCppAdapter::SimpleAdapter::value;
};

template <typename JSON> JsonCppAdapter(JSON const &) -> JsonCppAdapter<JSON const>;
template <typename JSON> JsonCppAdapter(JSON &) -> JsonCppAdapter<JSON>;
}