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

namespace ircd {
namespace json {

/// All tuple templates inherit from this non-template type for tagging.
struct tuple_base
{
	// EBO tag
};

/// A compile-time construct to describe a JSON object's members and types.
///
/// Member access by name is O(1) because of recursive constexpr function
/// inlining when translating a name to the index number which is then used
/// as the template argument to std::get() for the value.
///
/// 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. Thus at runtime, the tuple only carries around its values like a
/// `struct`. Unlike a `struct`, the tuple is abstractly iterable and we have
/// implemented logic operating on all JSON tuples regardless of their makeup
/// without any effort from a developer when creating a new tuple.
///
/// The member structure for the tuple is called `property` because json::member
/// is already used to pair together runtime oriented json::values.
///
/// 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.
///
template<class... T>
struct tuple
:std::tuple<T...>
,tuple_base
{
	using tuple_type = std::tuple<T...>;
	using super_type = tuple<T...>;

	static constexpr size_t size();

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

template<class tuple>
constexpr bool
is_tuple()
{
	return std::is_base_of<tuple_base, tuple>::value;
}

template<class tuple, class R>
using enable_if_tuple = typename std::enable_if<is_tuple<tuple>(), R>::type;

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... T>
constexpr size_t
tuple<T...>::size()
{
	return std::tuple_size<tuple_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 enable_if_tuple<tuple, size_t>
size()
{
	return tuple_size<tuple>::value;
}

template<class tuple,
         size_t i>
constexpr enable_if_tuple<tuple, const char *const &>
key()
{
	return tuple_element<tuple, i>::key;
}

template<size_t i,
         class tuple>
enable_if_tuple<tuple, const char *const &>
key(const tuple &t)
{
	return std::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 tuple>
enable_if_tuple<tuple, tuple_value_type<tuple, i> &>
get(tuple &t)
{
	return std::get<i>(t);
}

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

template<size_t i,
         class tuple>
enable_if_tuple<tuple, const tuple_value_type<tuple, i> &>
val(const tuple &t)
{
	using value_type = tuple_value_type<tuple, i>;
	return static_cast<const value_type &>(get<i>(t));
}

template<size_t i,
         class tuple>
enable_if_tuple<tuple, tuple_value_type<tuple, i> &>
val(tuple &t)
{
	using value_type = tuple_value_type<tuple, i>;
	return static_cast<value_type &>(get<i>(t));
}

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

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

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

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

	using value_type = tuple_value_type<tuple, 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 tuple>
enable_if_tuple<tuple, tuple_value_type<tuple, indexof<tuple>(name)> &>
at(tuple &t)
{
	constexpr size_t idx
	{
		indexof<tuple>(name)
	};

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

	using value_type = tuple_value_type<tuple, 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 json::iov &iov)
{
	//TODO: is tcmalloc zero-initializing all tuple elements, or is something else doing that?
	std::for_each(std::begin(iov), std::end(iov), [this]
	(const auto &member)
	{
		switch(type(member.second))
		{
			case type::OBJECT:
			case type::ARRAY:
				if(unlikely(!member.second.serial))
					throw print_error("iov member '%s' must be JSON to be used by the tuple",
					                  string_view{member.first});
			default:
				break;
		}

		at(*this, member.first, [&member]
		(auto &target)
		{
			using target_type = decltype(target);
			using cast_type = typename std::remove_reference<target_type>::type; try
			{
				target = static_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<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,
         class closure>
constexpr void
_key_transform(it_a it,
               const it_b end,
               closure&& lambda)
{
	for(size_t i(0); i < tuple::size() && it != end; ++i)
	{
		*it = lambda(key<tuple, i>());
		++it;
	}
}

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() && it != end; ++i)
	{
		*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 closure,
         class... T>
void
_member_transform(const tuple<T...> &tuple,
                  it_a it,
                  const it_b end,
                  closure&& lambda)
{
	until(tuple, [&it, &end, &lambda]
	(const auto &key, const auto &val)
	{
		if(it == end)
			return false;

		*it = lambda(key, val);
		++it;
		return true;
	});
}

template<class it_a,
         class it_b,
         class... T>
void
_member_transform(const tuple<T...> &tuple,
                  it_a it,
                  const it_b end)
{
	until(tuple, [&it, &end]
	(const auto &key, const auto &val)
	{
		if(it == end)
			return false;

		*it = member { key, val };
		++it;
		return true;
	});
}

template<class T>
constexpr bool
serialized_lex_cast()
{
	using type = typename std::remove_reference<T>::type;
	return std::is_arithmetic<type>::value;
}

template<class T>
typename std::enable_if<serialized_lex_cast<T>(), size_t>::type
serialized(T&& t)
{
	return lex_cast(t).size();
}

template<class... T>
size_t
serialized(const tuple<T...> &t)
{
	constexpr const size_t member_count
	{
		tuple<T...>::size()
	};

	// Number of commas for this object is one less than the member count, or 0
	const size_t commas
	{
		member_count? member_count - 1 : 0
	};

	// 2 for the {} and the comma count
	const size_t overhead
	{
		2 + commas
	};

	std::array<size_t, member_count> sizes;
	_member_transform(t, begin(sizes), end(sizes), []
	(const string_view &key, auto&& val)
	{
		//     "                "   :
		return 1 + key.size() + 1 + 1 + serialized(val);
	});

	return std::accumulate(begin(sizes), end(sizes), overhead);
}

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

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

} // namespace json
} // namespace ircd