finds facts that happen in given interval and shifts them to
        make room for new fact

def __solve_overlaps(self, start_time, end_time):
        """finds facts that happen in given interval and shifts them to
        make room for new fact
        """
        if end_time is None or start_time is None:
            return

        # possible combinations and the OR clauses that catch them
        # (the side of the number marks if it catches the end or start time)
        #             |----------------- NEW -----------------|
        #      |--- old --- 1|   |2 --- old --- 1|   |2 --- old ---|
        # |3 -----------------------  big old   ------------------------ 3|
        query = """
                   SELECT a.*, b.name, c.name as category
                     FROM facts a
                LEFT JOIN activities b on b.id = a.activity_id
                LEFT JOIN categories c on b.category_id = c.id
                    WHERE (end_time > ? and end_time < ?)
                       OR (start_time > ? and start_time < ?)
                       OR (start_time < ? and end_time > ?)
                 ORDER BY start_time
                """
        conflicts = self.fetchall(query, (start_time, end_time,
                                          start_time, end_time,
                                          start_time, end_time))

        for fact in conflicts:
            # won't eliminate as it is better to have overlapping entries than loosing data
            if start_time < fact["start_time"] and end_time > fact["end_time"]:
                continue

            # split - truncate until beginning of new entry and create new activity for end
            if fact["start_time"] < start_time < fact["end_time"] and \
               fact["start_time"] < end_time < fact["end_time"]:

                logger.info("splitting %s" % fact["name"])
                # truncate until beginning of the new entry
                self.execute("""UPDATE facts
                                   SET end_time = ?
                                 WHERE id = ?""", (start_time, fact["id"]))
                fact_name = fact["name"]

                # create new fact for the end
                new_fact = Fact(fact["name"],
                                category = fact["category"],
                                description = fact["description"])
                new_fact_id = self.__add_fact(new_fact.serialized_name(), end_time, fact["end_time"])

                # copy tags
                tag_update = """INSERT INTO fact_tags(fact_id, tag_id)
                                     SELECT ?, tag_id
                                       FROM fact_tags
                                      WHERE fact_id = ?"""
                self.execute(tag_update, (new_fact_id, fact["id"])) #clone tags

            # overlap start
            elif start_time < fact["start_time"] < end_time:
                logger.info("Overlapping start of %s" % fact["name"])
                self.execute("UPDATE facts SET start_time=? WHERE id=?",
                             (end_time, fact["id"]))

            # overlap end
            elif start_time < fact["end_time"] < end_time:
                logger.info("Overlapping end of %s" % fact["name"])
                self.execute("UPDATE facts SET end_time=? WHERE id=?",
                             (start_time, fact["id"]))