// 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.

using namespace ircd;

mapi::header
IRCD_MODULE
{
	"Client 6.2.3 :initialSync"
};

const string_view
initialsync_description
{R"(

6.2.3

This returns the full state for this user, with an optional limit on the number
of messages per room to return.

This endpoint was deprecated in r0 of this specification. Clients should instead
call the /sync API with no since parameter.

)"};

//
// sync resource
//

m::resource
initialsync_resource
{
	"/_matrix/client/r0/initialSync",
	{
		initialsync_description
	}
};

m::resource::response
initialsync(client &client,
            const m::resource::request &request);

m::resource::method
get_initialsync
{
	initialsync_resource, "GET", initialsync,
	{
		get_initialsync.REQUIRES_AUTH,
		-1s // No timer for this method.
	}
};

conf::item<size_t>
initialsync_limit_default
{
	{ "name",     "ircd.client.initialsync.limit.default" },
	{ "default",  16L                                     },
};

conf::item<size_t>
initialsync_limit_max
{
	{ "name",     "ircd.client.initialsync.limit.max"     },
	{ "default",  64L                                     },
};

static void
_initialsync(client &client,
             const m::resource::request &request,
             json::stack::object &out);

m::resource::response
initialsync(client &client,
            const m::resource::request &request)
try
{
	const auto &filter_id
	{
		request.query["filter"]
	};

	const auto &set_presence
	{
		request.query.get("set_presence", "online"_sv)
	};

	const auto &limit{[&request]
	{
		auto ret(request.query.get("limit", size_t(initialsync_limit_default)));
		ret = std::min(ret, size_t(initialsync_limit_max));
		return ret;
	}()};

	// Due to the way json::stack works the chunk buffer must be at least
	// the size of an appended input (for ex. a json::tuple). In our case this
	// buffer must hold a 64_KiB worst-case event and then a little extra.
	const unique_buffer<mutable_buffer> buf
	{
		128_KiB
	};

	m::resource::response::chunked response
	{
		client, http::OK, "application/json; charset=utf-8"
	};

	json::stack out
	{
		buf, [&response](const const_buffer &buf)
		{
			response.write(buf);
			return buf;
		}
	};

	json::stack::object object{out};
	_initialsync(client, request, object);
	return {};
}
catch(const std::exception &e)
{
	log::error
	{
		"Initial sync for %s from %s failed because :%s",
		request.user_id,
		string(remote(client)),
		e.what()
	};

	throw;
}

static void
initialsync_rooms(client &client,
                  const m::resource::request &request,
                  json::stack::object &out,
                  const m::user::room &);

static void
initialsync_presence(client &client,
                     const m::resource::request &request,
                     json::stack::object &out,
                     const m::user &user);

static void
initialsync_account_data(client &client,
                         const m::resource::request &request,
                         json::stack::object &out,
                         const m::user::room &);

void
_initialsync(client &client,
             const m::resource::request &request,
             json::stack::object &out)
{
	const m::user user{request.user_id};
	const m::user::room user_room{user};

	const auto next_batch
	{
		int64_t(m::vm::sequence::retired)
	};

	// rooms
	{
		json::stack::member member{out, "rooms"};
		json::stack::object object{member};
		initialsync_rooms(client, request, object, user_room);
	}

	// presence
	{
		json::stack::member member{out, "presence"};
		json::stack::object object{member};
		initialsync_presence(client, request, object, user);
	}

	// account_data
	{
		json::stack::member member{out, "account_data"};
		json::stack::object object{member};
		initialsync_account_data(client, request, object, user_room);
	}

	// next_batch
	{
		json::stack::member member
		{
			out, "next_batch", json::value{next_batch}
		};
	}
}

void
initialsync_presence(client &client,
                     const m::resource::request &request,
                     json::stack::object &out,
                     const m::user &user)
{
	json::stack::member member{out, "events"};
	json::stack::array array{member};

	const m::user::mitsein mitsein{user};
	mitsein.for_each("join", [&array]
	(const m::user &user)
	{
		m::presence::get(std::nothrow, user, [&array]
		(const json::object &event)
		{
			json::stack::object object{array};

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

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

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

		return true;
	});
}

void
initialsync_account_data(client &client,
                         const m::resource::request &request,
                         json::stack::object &out,
                         const m::user::room &user_room)
{
	json::stack::member member{out, "events"};
	json::stack::array array{member};

	const m::room::state state{user_room};
	state.for_each("ircd.account_data", [&array]
	(const m::event &event)
	{
		json::stack::object object{array};

		// type
		{
			json::stack::member member
			{
				object, "type", at<"state_key"_>(event)
			};
		}

		// content
		{
			json::stack::member member
			{
				object, "content", at<"content"_>(event)
			};
		}
	});
}

static void
initialsync_rooms_join(client &client,
                       const m::resource::request &request,
                       json::stack::object &out,
                       const m::user::room &user_room);

static void
initialsync_rooms_leave(client &client,
                        const m::resource::request &request,
                        json::stack::object &out,
                        const m::user::room &user_room);

static void
initialsync_rooms_invite(client &client,
                         const m::resource::request &request,
                         json::stack::object &out,
                         const m::user::room &user_room);

void
initialsync_rooms(client &client,
                  const m::resource::request &request,
                  json::stack::object &out,
                  const m::user::room &user_room)
{
	// join
	{
		json::stack::member member{out, "join"};
		json::stack::object object{member};
		initialsync_rooms_join(client, request, object, user_room);
	}

	// leave
	{
		json::stack::member member{out, "leave"};
		json::stack::object object{member};
		initialsync_rooms_leave(client, request, object, user_room);
	}

	// invite
	{
		json::stack::member member{out, "invite"};
		json::stack::object object{member};
		initialsync_rooms_invite(client, request, object, user_room);
	}
}

void
initialsync_rooms__membership(client &client,
                              const m::resource::request &request,
                              json::stack::object &out,
                              const m::user::room &user_room,
                              const string_view &membership);
void
initialsync_rooms_join(client &client,
                       const m::resource::request &request,
                       json::stack::object &out,
                       const m::user::room &user_room)
{
	initialsync_rooms__membership(client, request, out, user_room, "join");
}

void
initialsync_rooms_leave(client &client,
                        const m::resource::request &request,
                        json::stack::object &out,
                        const m::user::room &user_room)
{
	initialsync_rooms__membership(client, request, out, user_room, "leave");
}

void
initialsync_rooms_invite(client &client,
                         const m::resource::request &request,
                         json::stack::object &out,
                         const m::user::room &user_room)
{
	initialsync_rooms__membership(client, request, out, user_room, "invite");
}

static void
initialsync_room(client &client,
                 const m::resource::request &request,
                 json::stack::object &out,
                 const m::user::room &user_room,
                 const m::room &room,
                 const string_view &membership);

void
initialsync_rooms__membership(client &client,
                              const m::resource::request &request,
                              json::stack::object &out,
                              const m::user::room &user_room,
                              const string_view &membership)
{
	const m::user::rooms rooms
	{
		user_room.user
	};

	rooms.for_each(membership, [&client, &request, &out, &user_room, &membership]
	(const m::room &room, const string_view &)
	{
		const m::room::id &room_id{room.room_id};
		json::stack::member member{out, room_id};
		json::stack::object object{member};
		initialsync_room(client, request, object, user_room, room_id, membership);
	});
}

static void
initialsync_room_state(client &client,
                       const m::resource::request &request,
                       json::stack::object &out,
                       const m::user::room &user_room,
                       const m::room &room);

static void
initialsync_room_timeline(client &client,
                          const m::resource::request &request,
                          json::stack::object &out,
                          const m::user::room &user_room,
                          const m::room &room);

static void
initialsync_room_ephemeral(client &client,
                           const m::resource::request &request,
                           json::stack::object &out,
                           const m::user::room &user_room,
                           const m::room &room);

static void
initialsync_room_account_data(client &client,
                              const m::resource::request &request,
                              json::stack::object &out,
                              const m::user::room &user_room,
                              const m::room &room);

static void
initialsync_room_unread_notifications(client &client,
                                      const m::resource::request &request,
                                      json::stack::object &out,
                                      const m::user::room &user_room,
                                      const m::room &room);

void
initialsync_room(client &client,
                 const m::resource::request &request,
                 json::stack::object &out,
                 const m::user::room &user_room,
                 const m::room &room,
                 const string_view &membership)
{
	// state
	{
		json::stack::member member
		{
			out, membership != "invite"?
				"state":
				"invite_state"
		};

		json::stack::object object{member};
		initialsync_room_state(client, request, object, user_room, room);
	}

	// timeline
	{
		json::stack::member member{out, "timeline"};
		json::stack::object object{member};
		initialsync_room_timeline(client, request, object, user_room, room);
	}

	// ephemeral
	{
		json::stack::member member{out, "ephemeral"};
		json::stack::object object{member};
		initialsync_room_ephemeral(client, request, object, user_room, room);
	}

	// account_data
	{
		json::stack::member member{out, "account_data"};
		json::stack::object object{member};
		initialsync_room_ephemeral(client, request, object, user_room, room);
	}

	// unread_notifications
	{
		json::stack::member member{out, "unread_notifications"};
		json::stack::object object{member};
		initialsync_room_unread_notifications(client, request, object, user_room, room);
	}
}

void
initialsync_room_state(client &client,
                       const m::resource::request &request,
                       json::stack::object &out,
                       const m::user::room &user_room,
                       const m::room &room)
{
	json::stack::array array
	{
		out, "events"
	};

	const m::room::state state
	{
		room
	};

	state.for_each([&array](const m::event &event)
	{
		array.append(event);
	});
}

static m::event::id::buf
initialsync_room_timeline_events(client &client,
                                 const m::resource::request &request,
                                 json::stack::array &out,
                                 const m::user::room &user_room,
                                 const m::room &room);

void
initialsync_room_timeline(client &client,
                          const m::resource::request &request,
                          json::stack::object &out,
                          const m::user::room &user_room,
                          const m::room &room)
{
	// events
	m::event::id::buf prev;
	{
		json::stack::array array
		{
			out, "events"
		};

		prev = initialsync_room_timeline_events(client, request, array, user_room, room);
	}

	// prev_batch
	{
		json::stack::member member
		{
			out, "prev_batch", string_view{prev}
		};
	}

	// limited
	{
		json::stack::member member
		{
			out, "limited", json::value{false}
		};
	}
}

m::event::id::buf
initialsync_room_timeline_events(client &client,
                                 const m::resource::request &request,
                                 json::stack::array &out,
                                 const m::user::room &user_room,
                                 const m::room &room)
{
	// messages seeks to the newest event, but the client wants the oldest
	// event first so we seek down first and then iterate back up. Due to
	// an issue with rocksdb's prefix-iteration this iterator becomes
	// toxic as soon as it becomes invalid. As a result we have to copy the
	// event_id on the way down in case of renewing the iterator for the
	// way back. This is not a big deal but rocksdb should fix their shit.
	ssize_t i(0);
	m::event::idx event_idx{0};
	m::event::id::buf event_id;
	m::room::events it{room};
	m::event::fetch event;
	for(; it && i < 10; --it, ++i)
	{
		event_idx = it.event_idx();
		event_id = m::event_id(event_idx);
	}

	if(i > 0 && !it)
		it.seek(event_idx);

	if(i > 0)
		for(; it && i > -1; ++it, --i)
			if(seek(std::nothrow, event, it.event_idx()))
				out.append(event);

	return event_id;
}

static void
initialsync_room_ephemeral_events(client &client,
                                  const m::resource::request &request,
                                  json::stack::array &out,
                                  const m::room &room);

void
initialsync_room_ephemeral(client &client,
                           const m::resource::request &request,
                           json::stack::object &out,
                           const m::user::room &user_room,
                           const m::room &room)
{
	{
		json::stack::member member{out, "events"};
		json::stack::array array{member};
		initialsync_room_ephemeral_events(client, request, array, room);
	}
}

void
initialsync_room_ephemeral_events(client &client,
                                  const m::resource::request &request,
                                  json::stack::array &events,
                                  const m::room &room)
{
	const m::room::members members{room};
	//TODO: We're skipping receipts from members who left so we enjoy the
	//TODO: joined members optimizations. Need to figure out if anyone
	//TODO: left in the synced timeline and include them manually.
	members.for_each("join", [&events, &room]
	(const m::user &user)
	{
		const m::user::room user_room{user};
		user_room.get(std::nothrow, "ircd.read", room.room_id, [&events, &room, &user]
		(const m::event &event)
		{
			//TODO: skip if receipt is not for event we're actually syncing
			//TODO: in the related messages timeline array.

			json::stack::object object{events};

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

			// content
			{
				const json::object data
				{
					at<"content"_>(event)
				};

				thread_local char buf[1024];
				const json::members reformat
				{
					{ unquote(data.at("event_id")),
					{
						{ "m.read",
						{
							{ at<"sender"_>(event),
							{
								{ "ts", data.at("ts") }
							}}
						}}
					}}
				};

				json::stack::member member
				{
					object, "content", json::stringify(mutable_buffer{buf}, reformat)
				};
			}
		});

		return true;
	});
}

void
initialsync_room_account_data(client &client,
                              const m::resource::request &request,
                              json::stack::object &out,
                              const m::user::room &user_room,
                              const m::room &room)
{

}

void
initialsync_room_unread_notifications(client &client,
                                      const m::resource::request &request,
                                      json::stack::object &out,
                                      const m::user::room &user_room,
                                      const m::room &room)
{
	// highlight_count
	{
		json::stack::member member
		{
			out, "highlight_count", json::value{0L}
		};
	}

	// notification_count
	{
		json::stack::member member
		{
			out, "notification_count", json::value{0L}
		};
	}
}