local id = require "util.id";
local jid = require "util.jid";
local set = require "util.set";
local st = require "util.stanza";

module:depends "track_muc_joins";
module:add_feature("https://modules.prosody.im/mod_" .. module.name);

local local_sessions = prosody.hosts[module.host].sessions;

module:hook_global("s2s-destroyed", function(event)
	local s2s_session = event.session;
	if s2s_session.direction == "outgoing" and s2s_session.from_host ~= module.host then
		return
	elseif s2s_session.direction == "incoming" and s2s_session.to_host ~= module.host then
		return
	end

	local related_hosts = set.new({ s2s_session.direction == "outgoing" and s2s_session.to_host or s2s_session.from_host });

	if s2s_session.hosts then
		-- While rarely used, multiplexing is still supported
		for host, state in pairs(s2s_session.hosts) do if state.authed then related_hosts:add(host); end end
	end

	for _, user_session in pairs(local_sessions) do
		for _, session in pairs(user_session.sessions) do
			if session.rooms_joined then
				for room, info in pairs(session.rooms_joined) do
					local nick = info.nick or info;
					local room_nick = room .. "/" .. nick;
					if related_hosts:contains(jid.host(room)) then
						-- User is in a MUC room for which the s2s connection was lost. Now what?

						-- Self-ping
						-- =========
						--
						-- Response of <iq type=result> means the user is still in the room
						-- (and self-ping is supported), so we do nothing.
						--
						-- An error reply either means the user has fallen out of the room,
						-- or that self-ping is unsupported. In the later case, whether the
						-- user is still joined is indeterminate and we might as well
						-- pretend they fell out.
						module:send_iq(st.iq({ type = "get"; id = id.medium(); from = session.full_jid; to = room_nick })
								:tag("ping", { xmlns = "urn:xmpp:ping"; }))
						:catch(function(err)
							module:send(
								st.presence({ type = "unavailable"; id = id.medium(); to = session.full_jid; from = room_nick })
									:tag("x", { xmlns = "http://jabber.org/protocol/muc#user" })
										:tag("item", { affiliation = "none"; role = "none" })
											:text_tag("reason", err.text or "Connection to remote server lost")
										:up()
										:tag("status", { code = "110" }):up()
										:tag("status", { code = "333" }):up()
									:reset());
						end);
						-- TODO do this with some delay?
					end
				end

			end
		end
	end
end);