-- Fleet-wide writers filter candidates through this VOLATILE predicate in
-- the mutating statement so fenced tenants are skipped before row triggers run.
CREATE FUNCTION community_write_allowed(target UUID) RETURNS BOOLEAN
LANGUAGE plpgsql VOLATILE AS $$
DECLARE
    lifecycle TEXT;
BEGIN
    IF current_setting('transaction_isolation') <> 'read committed' THEN
        RAISE EXCEPTION 'community writes require READ COMMITTED isolation'
            USING ERRCODE = 'invalid_transaction_state';
    END IF;

    IF target IS NULL THEN
        RETURN true;
    END IF;

    PERFORM pg_advisory_xact_lock_shared(community_deletion_lock_key(target));
    SELECT deletion_state
      INTO lifecycle
      FROM communities
     WHERE id = target;
    RETURN FOUND AND lifecycle = 'active';
END
$$;