construct/include/ircd/json/tuple.h

/*
 * Copyright (C) 2017 Charybdis Development Team
 * Copyright (C) 2017 Jason Volk <jason@zemos.net>
 *
 * 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 is present in all copies.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once
#define HAVE_IRCD_JSON_TUPLE_H

//
// Here we represent a JSON object with a named tuple, allowing the programmer
// to create a structure specifying all of the potentially valid members of the
// object. Access to a specific member is O(1) just like a native `struct`
// rather than a linear or logn lookup into a map. The size of the tuple is
// extremely minimal: only the size of the values it stores. This is because
// the member keys and type data are all static or dealt with at compile time.
//
// Create and use a tuple to efficiently extract members from a json::object.
// The tuple will populate its own members during a single-pass iteration of
// the JSON input. If the JSON does not contain a member specified in the
// tuple, the value will be default initialized. If the JSON contains a member
// not specified in the tuple, it is ignored. If you need to know all of the
// members specified in the JSON dynamically, use a json::index or iterate
// manually.
//
namespace ircd {
namespace json {

//
// Non-template common base for all ircd::json::tuple templates.
//
struct tuple_base
{
	// class must be empty for EBO

	struct member;
};

//
// Non-template common base for all tuple members
//
struct tuple_base::member
{
};

///////////////////////////////////////////////////////////////////////////////
//
// ircd::json::tuple template. Create your own struct inheriting this
// class template with the members.
//
template<class... T>
struct tuple
:tuple_base
,std::tuple<T...>
{
	using tuple_type = std::tuple<T...>;
	using super_type = tuple<T...>;

	static constexpr size_t size();

	tuple(const json::object &);
	tuple(const std::initializer_list<json::index::member> &);
	tuple() = default;
};

template<class... T>
constexpr size_t
tuple<T...>::size()
{
	return std::tuple_size<tuple_type>();
}

///////////////////////////////////////////////////////////////////////////////
//
// tuple member template. Specify a list of these in the tuple template to
// form the members of the object.
//
template<const char *const &name,
         class T>
struct member
:tuple_base::member
{
	using key_type = const char *const &;
	using value_type = T;

	static constexpr auto &key{name};
	T value;

	operator const T &() const;
	operator T &();

	member(T&& value);
	member() = default;
};

template<const char *const &name,
         class T>
member<name, T>::member(T&& value)
:value{value}
{
}

template<const char *const &name,
         class T>
member<name, T>::operator
T &()
{
	return value;
}

template<const char *const &name,
         class T>
member<name, T>::operator
const T &()
const
{
	return value;
}

///////////////////////////////////////////////////////////////////////////////
//
// Tools
//

template<class tuple>
using tuple_type = typename tuple::tuple_type;

template<class tuple>
using tuple_size = std::tuple_size<tuple_type<tuple>>;

template<class tuple,
         size_t i>
using tuple_element = typename std::tuple_element<i, tuple_type<tuple>>::type;

template<class tuple,
         size_t i>
using tuple_value_type = typename tuple_element<tuple, i>::value_type;

template<class tuple>
auto &
stdcast(const tuple &o)
{
	return static_cast<const typename tuple::tuple_type &>(o);
}

template<class tuple>
auto &
stdcast(tuple &o)
{
	return static_cast<typename tuple::tuple_type &>(o);
}

template<class tuple>
constexpr size_t
size()
{
	return tuple_size<tuple>::value;
}

template<class tuple,
         size_t i>
constexpr auto &
key()
{
	return tuple_element<tuple, i>::key;
}

template<size_t i,
         class... T>
auto &
key(const tuple<T...> &t)
{
	return get<i>(t).key;
}

template<class tuple,
         size_t i>
constexpr typename std::enable_if<i == size<tuple>(), size_t>::type
indexof(const char *const &name)
{
	return size<tuple>();
}

template<class tuple,
         size_t i = 0>
constexpr typename std::enable_if<i < size<tuple>(), size_t>::type
indexof(const char *const &name)
{
	const auto equal
	{
		_constexpr_equal(key<tuple, i>(), name)
	};

	return equal? i : indexof<tuple, i + 1>(name);
}

template<class tuple,
         size_t i>
constexpr typename std::enable_if<i == size<tuple>(), size_t>::type
indexof(const string_view &name)
{
	return size<tuple>();
}

template<class tuple,
         size_t i = 0>
constexpr typename std::enable_if<i < size<tuple>(), size_t>::type
indexof(const string_view &name)
{
	const auto equal
	{
		name == key<tuple, i>()
	};

	return equal? i : indexof<tuple, i + 1>(name);
}

template<size_t i,
         class... T>
auto &
get(const tuple<T...> &t)
{
	return std::get<i>(t);
}

template<size_t i,
         class... T>
auto &
get(tuple<T...> &t)
{
	return std::get<i>(t);
}

template<size_t i,
         class... T>
auto &
val(const tuple<T...> &t)
{
	using value_type = tuple_value_type<tuple<T...>, i>;

	return static_cast<const value_type &>(get<i>(t));
}

template<size_t i,
         class... T>
auto &
val(tuple<T...> &t)
{
	using value_type = tuple_value_type<tuple<T...>, i>;

	return static_cast<value_type &>(get<i>(t));
}

template<const char *const &name,
         class... T>
auto &
val(const tuple<T...> &t)
{
	return val<indexof<tuple<T...>>(name)>(t);
}

template<const char *const &name,
         class... T>
auto &
val(tuple<T...> &t)
{
	return val<indexof<tuple<T...>>(name)>(t);
}

template<const char *const &name,
         class... T>
const tuple_value_type<tuple<T...>, indexof<tuple<T...>>(name)> &
at(const tuple<T...> &t)
{
	constexpr size_t idx
	{
		indexof<tuple<T...>>(name)
	};

	auto &ret
	{
		val<idx>(t)
	};

	using value_type = tuple_value_type<tuple<T...>, idx>;

	//TODO: does tcmalloc zero this or huh?
	if(ret == value_type{})
		throw not_found("%s", name);

	return ret;
}

template<const char *const &name,
         class... T>
tuple_value_type<tuple<T...>, indexof<tuple<T...>>(name)> &
at(tuple<T...> &t)
{
	constexpr size_t idx
	{
		indexof<tuple<T...>>(name)
	};

	auto &ret
	{
		val<idx>(t)
	};

	using value_type = tuple_value_type<tuple<T...>, idx>;

	//TODO: does tcmalloc zero this or huh?
	if(ret == value_type{})
		throw not_found("%s", name);

	return ret;
}

template<const char *const &name,
         class... T>
tuple_value_type<tuple<T...>, indexof<tuple<T...>>(name)>
get(const tuple<T...> &t,
    const tuple_value_type<tuple<T...>, indexof<tuple<T...>>(name)> &def = {})
{
	constexpr size_t idx
	{
		indexof<tuple<T...>>(name)
	};

	const auto &ret
	{
		val<idx>(t)
	};

	using value_type = tuple_value_type<tuple<T...>, idx>;

	//TODO: does tcmalloc zero this or huh?
	return ret != value_type{}? ret : def;
}

template<const char *const &name,
         class... T>
tuple_value_type<tuple<T...>, indexof<tuple<T...>>(name)> &
get(tuple<T...> &t,
    tuple_value_type<tuple<T...>, indexof<tuple<T...>>(name)> &def)
{
	constexpr size_t idx
	{
		indexof<tuple<T...>>(name)
	};

	auto &ret
	{
		val<idx>(t)
	};

	using value_type = tuple_value_type<tuple<T...>, idx>;

	//TODO: does tcmalloc zero this or huh?
	return ret != value_type{}? ret : def;
}

template<size_t i,
         class tuple,
         class function>
typename std::enable_if<i == size<tuple>(), void>::type
for_each(const tuple &t,
         function&& f)
{}

template<size_t i,
         class tuple,
         class function>
typename std::enable_if<i == size<tuple>(), void>::type
for_each(tuple &t,
         function&& f)
{}

template<size_t i = 0,
         class tuple,
         class function>
typename std::enable_if<i < size<tuple>(), void>::type
for_each(const tuple &t,
         function&& f)
{
	f(key<i>(t), val<i>(t));
	for_each<i + 1>(t, std::forward<function>(f));
}

template<size_t i = 0,
         class tuple,
         class function>
typename std::enable_if<i < size<tuple>(), void>::type
for_each(tuple &t,
         function&& f)
{
	f(key<i>(t), val<i>(t));
	for_each<i + 1>(t, std::forward<function>(f));
}

template<class tuple,
         class function,
         ssize_t i>
typename std::enable_if<(i < 0), void>::type
rfor_each(const tuple &t,
          function&& f)
{}

template<class tuple,
         class function,
         ssize_t i>
typename std::enable_if<(i < 0), void>::type
rfor_each(tuple &t,
          function&& f)
{}

template<class tuple,
         class function,
         ssize_t i = size<tuple>() - 1>
typename std::enable_if<i < tuple_size<tuple>(), void>::type
rfor_each(const tuple &t,
          function&& f)
{
	f(key<i>(t), val<i>(t));
	rfor_each<tuple, function, i - 1>(t, std::forward<function>(f));
}

template<class tuple,
         class function,
         ssize_t i = size<tuple>() - 1>
typename std::enable_if<i < tuple_size<tuple>(), void>::type
rfor_each(tuple &t,
          function&& f)
{
	f(key<i>(t), val<i>(t));
	rfor_each<tuple, function, i - 1>(t, std::forward<function>(f));
}

template<size_t i,
         class tuple,
         class function>
typename std::enable_if<i == size<tuple>(), bool>::type
until(const tuple &t,
      function&& f)
{
	return true;
}

template<size_t i,
         class tuple,
         class function>
typename std::enable_if<i == size<tuple>(), bool>::type
until(tuple &t,
      function&& f)
{
	return true;
}

template<size_t i = 0,
         class tuple,
         class function>
typename std::enable_if<i < size<tuple>(), bool>::type
until(const tuple &t,
      function&& f)
{
	return f(key<i>(t), val<i>(t))?
	       until<i + 1>(t, std::forward<function>(f)):
	       false;
}

template<size_t i = 0,
         class tuple,
         class function>
typename std::enable_if<i < size<tuple>(), bool>::type
until(tuple &t,
      function&& f)
{
	return f(key<i>(t), val<i>(t))?
	       until<i + 1>(t, std::forward<function>(f)):
	       false;
}

template<class tuple,
         class function,
         ssize_t i>
typename std::enable_if<(i < 0), bool>::type
runtil(const tuple &t,
       function&& f)
{
	return true;
}

template<class tuple,
         class function,
         ssize_t i>
typename std::enable_if<(i < 0), bool>::type
runtil(tuple &t,
       function&& f)
{
	return true;
}

template<class tuple,
         class function,
         ssize_t i = size<tuple>() - 1>
typename std::enable_if<i < size<tuple>(), bool>::type
runtil(const tuple &t,
       function&& f)
{
	return f(key<i>(t), val<i>(t))?
	       runtil<tuple, function, i - 1>(t, std::forward<function>(f)):
	       false;
}

template<class tuple,
         class function,
         ssize_t i = size<tuple>() - 1>
typename std::enable_if<i < size<tuple>(), bool>::type
runtil(tuple &t,
       function&& f)
{
	return f(key<i>(t), val<i>(t))?
	       runtil<tuple, function, i - 1>(t, std::forward<function>(f)):
	       false;
}

template<class tuple,
         class function,
         size_t i>
typename std::enable_if<i == size<tuple>(), void>::type
at(tuple &t,
   const string_view &name,
   function&& f)
{
}

template<class tuple,
         class function,
         size_t i = 0>
typename std::enable_if<i < size<tuple>(), void>::type
at(tuple &t,
   const string_view &name,
   function&& f)
{
	if(indexof<tuple>(name) == i)
		f(val<i>(t));
	else
		at<tuple, function, i + 1>(t, name, std::forward<function>(f));
}

template<class tuple,
         class function,
         size_t i>
typename std::enable_if<i == size<tuple>(), void>::type
at(const tuple &t,
   const string_view &name,
   function&& f)
{
}

template<class tuple,
         class function,
         size_t i = 0>
typename std::enable_if<i < size<tuple>(), void>::type
at(const tuple &t,
   const string_view &name,
   function&& f)
{
	if(indexof<tuple>(name) == i)
		f(val<i>(t));
	else
		at<tuple, function, i + 1>(t, name, std::forward<function>(f));
}

template<class V,
         class... T>
tuple<T...> &
set(tuple<T...> &t,
    const string_view &key,
    const V &val)
{
	at(t, key, [&key, &val]
	(auto &target)
	{
		using target_type = decltype(target);
		using cast_type = typename std::remove_reference<target_type>::type;
		target = byte_view<cast_type>(val);
	});

	return t;
}

template<class... T>
tuple<T...>::tuple(const json::object &object)
{
	//TODO: is tcmalloc zero-initializing all tuple elements, or is something else doing that?
	std::for_each(std::begin(object), std::end(object), [this]
	(const auto &member)
	{
		at(*this, member.first, [&member]
		(auto &target)
		{
			using target_type = decltype(target);
			using cast_type = typename std::remove_reference<target_type>::type; try
			{
				target = lex_cast<cast_type>(member.second);
			}
			catch(const bad_lex_cast &e)
			{
				throw parse_error("member '%s' must convert to '%s'",
				                  member.first,
				                  typeid(target_type).name());
			}
		});
	});
}

template<class... T>
tuple<T...>::tuple(const std::initializer_list<json::index::member> &members)
{
	std::for_each(std::begin(members), std::end(members), [this]
	(const auto &member)
	{
		switch(type(member.second))
		{
			case type::STRING:
			case type::LITERAL:
				set(*this, member.first, string_view{member.second});
				break;

			case type::NUMBER:
				if(member.second.floats)
					set(*this, member.first, member.second.floating);
				else
					set(*this, member.first, member.second.integer);
				break;

			case type::ARRAY:
			case type::OBJECT:
				if(!member.second.serial)
					throw parse_error("Unserialized value not supported yet");

				set(*this, member.first, string_view{member.second});
				break;
		}
	});
}

template<class tuple,
         class it_a,
         class it_b>
constexpr void
_key_transform(it_a it,
               const it_b end)
{
	for(size_t i(0); i < tuple::size(); ++i)
	{
		if(it == end)
			break;

		*it = key<tuple, i>();
		++it;
	}
}

template<class it_a,
         class it_b,
         class... T>
void
_key_transform(const tuple<T...> &tuple,
               it_a it,
               const it_b end)
{
	for_each(tuple, [&it, &end]
	(const auto &key, const auto &val)
	{
		if(it != end)
		{
			*it = key;
			++it;
		}
	});
}

template<class it_a,
         class it_b,
         class... T>
void
_member_transform(const tuple<T...> &tuple,
                  it_a it,
                  const it_b end)
{
	for_each(tuple, [&it, &end]
	(const auto &key, const auto &val)
	{
		if(it != end)
		{
			*it = { key, val };
			++it;
		}
	});
}

template<class... T>
object
serialize(const tuple<T...> &tuple,
          char *&start,
          char *const &stop)
{
	std::array<index::member, tuple.size()> members;
	_member_transform(tuple, begin(members), end(members));
	return serialize(begin(members), end(members), start, stop);
}

template<class... T>
size_t
print(char *const &buf,
      const size_t &max,
      const tuple<T...> &tuple)
{
	std::array<index::member, tuple.size()> members;
	_member_transform(tuple, begin(members), end(members));
	return print(buf, max, begin(members), end(members));
}

template<class... T>
std::string
string(const tuple<T...> &tuple)
{
	std::array<index::member, tuple.size()> members;
	_member_transform(tuple, begin(members), end(members));
	return string(begin(members), end(members));
}

template<class... T>
std::ostream &
operator<<(std::ostream &s, const tuple<T...> &t)
{
    s << string(t);
    return s;
}

} // namespace json
} // namespace ircd