-- TODO warn when trying to create an user before the tombstone expires

-- e.g. via telnet or other admin interface

local datetime = require "util.datetime";

local errors = require "util.error";

local jid_split = require"util.jid".split;

local st = require "util.stanza";

-- Using a map store as key-value store so that removal of all user data

-- does not also remove the tombstone, which would defeat the point

local graveyard = module:open_store(nil, "map");

local ttl = module:get_option_number("user_tombstone_expiry", nil);

-- Keep tombstones forever by default

--

-- Rationale:

-- There is no way to be completely sure when remote services have

-- forgotten and revoked all memberships.

module:hook_global("user-deleted", function(event)

	if event.host == module.host then

		local ok, err = graveyard:set(nil, event.username, os.time());

		if not ok then module:log("error", "Could store tombstone for %s: %s", event.username, err); end

	end

end);

-- Public API

function has_tombstone(username)

	local tombstone, err = graveyard:get(nil, username);

	if err or not tombstone then return tombstone, err; end

	if ttl and tombstone + ttl < os.time() then

		module:log("debug", "Tombstone for %s created at %s has expired", username, datetime.datetime(tombstone));

		graveyard:set(nil, username, nil);

		return nil;

	end

	return tombstone;

end

module:hook("user-registering", function(event)

	local tombstone, err = has_tombstone(event.username);

	if err then

		event.allowed, event.error = errors.coerce(false, err);

		return true;

	elseif not tombstone then

		-- Feel free

		return;

	end

	module:log("debug", "Tombstone for %s created at %s", event.username, datetime.datetime(tombstone));

	event.allowed = false;

	return true;

end);

module:hook("presence/bare", function(event)

	local origin, presence = event.origin, event.stanza;

	-- We want to undo any left-over presence subscriptions and notify the former

	-- contact that they're gone.

	--

	-- FIXME This leaks that the user once existed. Hard to avoid without keeping

	-- the contact list in some form, which we don't want to do for privacy

	-- reasons.  Bloom filter perhaps?

	if has_tombstone(jid_split(presence.attr.to)) then

		if presence.attr.type == "probe" then

			origin.send(st.error_reply(presence, "cancel", "gone", "User deleted"));

			origin.send(st.presence({ type = "unsubscribed"; to = presence.attr.from; from = presence.attr.to }));

		elseif presence.attr.type == nil or presence.attr.type == "unavailable" then

			origin.send(st.error_reply(presence, "cancel", "gone", "User deleted"));

			origin.send(st.presence({ type = "unsubscribe"; to = presence.attr.from; from = presence.attr.to }));

		end

		return true;

	end

end, 1);