forstio/source/forstio/message_container.h

#pragma once

#include "schema.h"

#include <variant>
#include <vector>

namespace saw {
template <class T> class message_container;

template <class T, class Container = message_container<T>> class message;

template <size_t N, class... T> struct MessageParameterPackType;

template <class TN, class... T> struct MessageParameterPackType<0, TN, T...> {
	using Type = TN;
};

template <size_t N, class TN, class... T>
struct MessageParameterPackType<N, TN, T...> {
	static_assert(sizeof...(T) > 0, "Exhausted parameters");
	using Type = typename MessageParameterPackType<N - 1, T...>::Type;
};

template <class T, class... TL> struct MessageParameterPackIndex;

template <class T, class... TL> struct MessageParameterPackIndex<T, T, TL...> {
	static constexpr size_t Value = 0u;
};

template <class T, class TL0, class... TL>
struct MessageParameterPackIndex<T, TL0, TL...> {
	static constexpr size_t Value =
		1u + MessageParameterPackIndex<T, TL...>::Value;
};

/*
 * Nightmare inducing compiler problems found here. Somehow non-type
 * StringLiterals cannot be resolved as non-type primitive template values can.
 * This is the workaround
 */
template <string_literal V, string_literal Key0, string_literal... Keys>
struct MessageParameterKeyPackIndexHelper {
	static constexpr size_t Value =
		(V == Key0)
			? (0u)
			: (1u + MessageParameterKeyPackIndexHelper<V, Keys...>::Value);
};

template <string_literal V, string_literal Key0>
struct MessageParameterKeyPackIndexHelper<V, Key0> {
	static constexpr size_t Value = (V == Key0) ? (0u) : (1u);
};

template <string_literal V, string_literal... Keys>
struct MessageParameterKeyPackIndex {
	static constexpr size_t Value =
		MessageParameterKeyPackIndexHelper<V, Keys...>::Value;
	static_assert(Value < sizeof...(Keys),
				  "Provided StringLiteral doesn't exist in searched list");
};

template <class T> struct SchemaIsArray {
	constexpr static bool Value = false;
};

template <class T> struct SchemaIsArray<schema::Array<T>> {
	constexpr static bool Value = true;
};

template <class... V, string_literal... Keys>
class message_container<schema::Struct<schema::NamedMember<V, Keys>...>> {
private:
	using ValueType = std::tuple<message<V, message_container<V>>...>;
	ValueType values_;

public:
	using SchemaType = schema::Struct<schema::NamedMember<V, Keys>...>;

	template <size_t i>
	using ElementType = typename MessageParameterPackType<
		i, message<V, message_container<V>>...>::Type;

	template <size_t i> ElementType<i> &get() { return std::get<i>(values_); }
};

/*
 * Union storage
 */
template <class... V, string_literal... Keys>
class message_container<schema::Union<schema::NamedMember<V, Keys>...>> {
private:
	using ValueType = std::variant<message<V, message_container<V>>...>;
	ValueType value_;

public:
	using SchemaType = schema::Union<schema::NamedMember<V, Keys>...>;

	template <size_t i>
	using ElementType = typename MessageParameterPackType<
		i, message<V, message_container<V>>...>::Type;

	template <size_t i> ElementType<i> &get() {
		if (i != value_.index()) {
			using MessageIV = typename MessageParameterPackType<i, V...>::Type;
			value_ = message<MessageIV, message_container<MessageIV>>{};
		}
		return std::get<i>(value_);
	}

	size_t index() const noexcept { return value_.index(); }
};

/*
 * Array storage
 */

template <class T> class message_container<schema::Array<T>> {
private:
	using ValueType = std::vector<message<T, message_container<T>>>;
	ValueType values_;

public:
	using SchemaType = schema::Array<T>;

	using ElementType = message<T, message_container<T>>;

	message<T, message_container<T>> &get(size_t index) {
		return values_.at(index);
	}

	void resize(size_t size) { values_.resize(size); }

	size_t size() const { return values_.size(); }
};

/*
 * Tuple storage
 */
template <class... T> class message_container<schema::Tuple<T...>> {
private:
	using ValueType = std::tuple<message<T, message_container<T>>...>;
	ValueType values_;

public:
	using SchemaType = schema::Tuple<T...>;

	template <size_t i>
	using ElementType = typename MessageParameterPackType<
		i, message<T, message_container<T>>...>::Type;

	template <size_t i> ElementType<i> &get() { return std::get<i>(values_); }
};

/*
 * Helper for the basic message container, so the class doesn't have to be
 * specialized 10 times.
 */
template <class T> struct PrimitiveTypeHelper;

template <>
struct PrimitiveTypeHelper<schema::Primitive<schema::SignedInteger, 1>> {
	using Type = int8_t;
};

template <>
struct PrimitiveTypeHelper<schema::Primitive<schema::SignedInteger, 2>> {
	using Type = int16_t;
};

template <>
struct PrimitiveTypeHelper<schema::Primitive<schema::SignedInteger, 4>> {
	using Type = int32_t;
};

template <>
struct PrimitiveTypeHelper<schema::Primitive<schema::SignedInteger, 8>> {
	using Type = int64_t;
};

template <>
struct PrimitiveTypeHelper<schema::Primitive<schema::UnsignedInteger, 1>> {
	using Type = uint8_t;
};

template <>
struct PrimitiveTypeHelper<schema::Primitive<schema::UnsignedInteger, 2>> {
	using Type = uint16_t;
};

template <>
struct PrimitiveTypeHelper<schema::Primitive<schema::UnsignedInteger, 4>> {
	using Type = uint32_t;
};

template <>
struct PrimitiveTypeHelper<schema::Primitive<schema::UnsignedInteger, 8>> {
	using Type = uint64_t;
};

template <>
struct PrimitiveTypeHelper<schema::Primitive<schema::FloatingPoint, 4>> {
	using Type = float;
};

template <>
struct PrimitiveTypeHelper<schema::Primitive<schema::FloatingPoint, 8>> {
	using Type = double;
};

template <class T, size_t N> class message_container<schema::Primitive<T, N>> {
public:
	using SchemaType = schema::Primitive<T, N>;
	using ValueType =
		typename PrimitiveTypeHelper<schema::Primitive<T, N>>::Type;

private:
	ValueType value_;

public:
	message_container() : value_{0} {}

	void set(const ValueType &v) { value_ = v; }

	const ValueType &get() const { return value_; }
};

template <> class message_container<schema::String> {
public:
	using SchemaType = schema::String;
	using ValueType = std::string;
	using ValueViewType = std::string_view;

private:
	ValueType value_;

public:
	void set(ValueType &&v) { value_ = std::move(v); }
	void set(const ValueType &v) { value_ = v; }
	void set(const ValueViewType v) { value_ = std::string{v}; }

	const ValueType &get() const { return value_; }
};
} // namespace saw