gistfile1.hs

-- This changes bookAuthorCredit from AuthorCreditReference to AuthorCredit
loadAuthorCredit :: Book -> Model Book

-- This changes all PersonReference's in an AuthorCredit to just Person
loadForAuthorCredits :: AuthorCredit -> Model AuthorCredit

-- This gets the AuthorCredit for a Book
bookAuthorCredit :: Book -> AuthorCredit

-- This 'sets' the AuthorCredit for a Book (returning a new Book)
setAuthorCredit :: Book -> AuthorCredit -> Book

---

do
  book <- loadAuthorCredit book
  book <- setAuthorCredit book <$> (loadForAuthorCredits $ bookAuthorCredit book)

--


bookResource :: Controller ()
bookResource = do
  maybeGid <- (fromString . unpack . fromJust) <$> getParam "gid"
  case maybeGid of
    Nothing -> genericError 400 "Invalid BBID"
    Just gid -> do
      maybeBook <- model $ getBook gid
      case maybeBook of
        Nothing -> generic404 "The request book could not be found"
        Just book -> do
          book <- model $ loadAuthorCredit book
          book <- model $ set lBookAuthorCredit book <$> (loadForAuthorCredits $ bookAuthorCredit book)
          editions <- model $ findBookEditions book
          output $ showBook book editions
          where set field on = \val -> setL field val on