[i] I hope that you have a lot of fun at the flower festival.
[ii] I don't think I'll go again, but it was a lot of fun! (daum.net)
At first, I took it granted that a lot of fun’s both in [i] an [ii] have the same structure. But when this idea struck me that a lot of fun in [ii] seems to be adjective, I flipped over grammar books, looking for which says a lot of is a modifier for adjectives. But I have not found.
So I started to think [ii] has this structure and meaning:
‘it was a lot [= very] of fun [= fun]’ Can I get exact meaning of [ii]?