// Matrix Construct
//
// Copyright (C) Matrix Construct Developers, Authors & Contributors
// Copyright (C) 2016-2018 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. The
// full license for this software is available in the LICENSE file.

ircd::mapi::header
IRCD_MODULE
{
	"Client Sync :Presence"
};

namespace ircd::m::sync
{
	static bool presence_polylog(data &);
	static bool presence_linear(data &);

	extern item presence;
}

decltype(ircd::m::sync::presence)
ircd::m::sync::presence
{
	"presence",
	presence_polylog,
	presence_linear,
};

bool
ircd::m::sync::presence_linear(data &data)
{
	if(!data.event_idx)
		return false;

	assert(data.event);
	const m::event &event{*data.event};
	if(json::get<"type"_>(event) != "ircd.presence")
		return false;

	if(!my_host(json::get<"origin"_>(event)))
		return false;

	json::stack::array array
	{
		*data.out, "events"
	};

	json::stack::object object
	{
		*data.out
	};

	// sender
	json::stack::member
	{
		*data.out, "sender", unquote(at<"content"_>(event).get("user_id"))
	};

	// type
	json::stack::member
	{
		*data.out, "type", json::value{"m.presence"}
	};

	// content
	json::stack::member
	{
		*data.out, "content", at<"content"_>(event)
	};

	return true;
}

bool
ircd::m::sync::presence_polylog(data &data)
{
	json::stack::array array
	{
		*data.out, "events"
	};

	bool ret{false};
	ctx::mutex mutex;
	const auto append_event{[&data, &array, &mutex, &ret]
	(const json::object &event)
	{
		// Lock the json::stack for the append operations. This mutex will only be
		// contended during a json::stack flush to the client; not during database
		// queries leading to this.
		const std::lock_guard l{mutex};
		ret = true;

		json::stack::object object
		{
			array
		};

		// sender
		json::stack::member
		{
			object, "sender", unquote(event.get("user_id"))
		};

		// type
		json::stack::member
		{
			object, "type", json::value{"m.presence"}
		};

		// content
		json::stack::member
		{
			object, "content", event
		};
	}};

	// Setup for parallelization.
	static const size_t fibers(64); //TODO: conf
	using buffer = std::array<char[m::id::MAX_SIZE+1], fibers>;
	const auto buf(std::make_unique<buffer>());
	std::array<string_view, fibers> q;
	ctx::parallel<string_view> parallel
	{
		m::sync::pool, q, [&data, &append_event]
		(const m::user::id user_id)
		{
			const event::idx event_idx
			{
				m::presence::get(std::nothrow, user_id)
			};

			if(apropos(data, event_idx))
				m::get(std::nothrow, event_idx, "content", append_event);
		}
	};

	// Iterate all of the users visible to our user in joined rooms.
	const m::user::mitsein mitsein{data.user};
	mitsein.for_each("join", [&parallel, &q, &buf]
	(const m::user &user)
	{
		// Manual copy of the user_id string to the buffer and assignment
		// of q at the next position. parallel.snd is the position in q
		// which ctx::parallel wants us to store the next data at. The
		// parallel() call doesn't return (blocks this context) until there's
		// a next position available; propagating flow-control for the iter.
		const auto pos(parallel.nextpos());
		q[pos] = strlcpy(buf->at(pos), user.user_id);
		parallel();
	});

	return ret;
}