Playing around with Hakyll and Atom

gistfile1.hs

postCtx :: Context String
postCtx =
    dateFieldWith esArLocale "date" "%x" `mappend`
    dateField "isoPublishDate" "%FT%TZ" `mappend`
    defaultContext

authors :: [Person]
authors = [ Person
            { personName = "Tordek"
            , personURI = Just absoluteRoot
            , personEmail = Nothing
            , personOther = []
            }
          ]

hakyllGenerator = Generator
    { genURI = Just "http://jaspervdj.be/hakyll/tutorials.html"
    , genVersion = Nothing
    , genText = "Hakyll"
    }

atomCompiler :: Context String -> [Item String] -> Item String -> Compiler (Item String)
atomCompiler itemContext items item = do
    body <- atomCompiler' itemContext items item
    return $ itemSetBody body item

atomCompiler' :: Context String -> [Item String] -> Item String -> Compiler String
atomCompiler' itemContext items item = do
      lastUpdateDate <- lastUpdateDateCompiler
      recentPosts <- atomEntryCompiler itemContext items
      return . showTopElement . xmlFeed $ Feed
        { feedId = absoluteRoot
        , feedTitle = TextString "Feed for Tordek"
        , feedUpdated = lastUpdateDate
        , feedAuthors = authors
        , feedCategories = [] -- all blog cats?
        , feedContributors = []
        , feedGenerator = Just hakyllGenerator
        , feedIcon = Just "http://tordek.com.ar/tordek.png"
        , feedLinks = [] -- missing self link
        , feedLogo = Just "http://tordek.com.ar/tordek.png"
        , feedRights = Nothing
        , feedSubtitle = Nothing
        , feedEntries = recentPosts
        , feedAttrs = []
        , feedOther = []
        }

  where
      lastUpdateDateCompiler = case items of
        [] -> return "Unknown"
        (x:_) -> unContext itemContext "isoPublishDate" x >>= getString "isoPublishDate"

atomEntryCompiler :: Context String -> [Item String] -> Compiler [Entry]
atomEntryCompiler itemContext = mapM (atomSingleEntryCompiler itemContext)

atomSingleEntryCompiler :: Context String -> Item String -> Compiler Entry
atomSingleEntryCompiler itemContext item@(Item id body) = do
    url <- getField "url"
    title <- getField "title"
    update <- getField "isoPublishDate"
    return $ (nullEntry (absoluteRoot ++ url)
                        (TextString title)
                        update) { entryContent = Just (HTMLContent body) }

--  return $ Entry
--    { entryId = url
--    , entryTitle = title
--    , 
--    }

   where
     getField s = unContext itemContext s item >>= getString s

getString _ (StringField s) = return s
getString x _ = fail $
   "atomSingleEntryCompiler: expected StringField " ++
   x ++ " but got something different."