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|
-- | A Module that allows easy rendering of RSS feeds. If you use this module,
-- you must make sure you set the `absoluteUrl` field in the main Hakyll
-- configuration.
--
-- Apart from that, the main rendering functions (@renderRss@, @renderAtom@)
-- all assume that you pass the list of items so that the most recent entry
-- in the feed is the first item in the list.
--
-- Also note that the @Context@s should have (at least) the following
-- fields to produce a correct feed:
--
-- - @$title@: Title of the item.
--
-- - @$description@: Description to appear in the feed.
--
-- - @$url@: URL to the item - this is usually set automatically.
--
-- Furthermore, the feed will be generated, but will be incorrect (it won't
-- validate) if an empty list is passed.
--
module Text.Hakyll.Feed
( FeedConfiguration (..)
, renderRss
, renderAtom
) where
import Control.Arrow ((>>>), second)
import Control.Monad.Reader (liftIO)
import Data.Maybe (fromMaybe)
import qualified Data.Map as M
import Text.Hakyll.Context (Context (..))
import Text.Hakyll.CreateContext (createListing)
import Text.Hakyll.ContextManipulations (renderDate)
import Text.Hakyll.HakyllMonad (Hakyll)
import Text.Hakyll.Render (render, renderChain)
import Text.Hakyll.HakyllAction
import Paths_hakyll
-- | This is a data structure to keep the configuration of a feed.
data FeedConfiguration = FeedConfiguration
{ -- | Url of the feed (relative to site root). For example, @rss.xml@.
feedUrl :: String
, -- | Title of the feed.
feedTitle :: String
, -- | Description of the feed.
feedDescription :: String
, -- | Name of the feed author.
feedAuthorName :: String
}
-- | This is an auxiliary function to create a listing that is, in fact, a feed.
-- The items should be sorted on date.
createFeed :: FeedConfiguration -- ^ Feed configuration.
-> [HakyllAction () Context] -- ^ Items to include.
-> FilePath -- ^ Feed template.
-> FilePath -- ^ Item template.
-> HakyllAction () Context
createFeed configuration renderables template itemTemplate =
listing >>> render template
where
listing = createListing (feedUrl configuration)
[itemTemplate] renderables additional
additional = map (second $ Left . ($ configuration))
[ ("title", feedTitle)
, ("description", feedDescription)
, ("authorName", feedAuthorName)
] ++ updated
-- Take the first timestamp, which should be the most recent.
updated = let action = createHakyllAction $ return . fromMaybe "foo"
. M.lookup "timestamp" . unContext
toTuple r = ("timestamp", Right $ r >>> action)
in map toTuple $ take 1 renderables
-- | Abstract function to render any feed.
renderFeed :: FeedConfiguration -- ^ Feed configuration.
-> [HakyllAction () Context] -- ^ Items to include in the feed.
-> FilePath -- ^ Feed template.
-> FilePath -- ^ Item template.
-> Hakyll ()
renderFeed configuration renderables template itemTemplate = do
template' <- liftIO $ getDataFileName template
itemTemplate' <- liftIO $ getDataFileName itemTemplate
let renderFeed' = createFeed configuration renderables
template' itemTemplate'
renderChain [] renderFeed'
-- | Render an RSS feed with a number of items.
renderRss :: FeedConfiguration -- ^ Feed configuration.
-> [HakyllAction () Context] -- ^ Items to include in the feed.
-> Hakyll ()
renderRss configuration renderables =
renderFeed configuration (map (>>> renderRssDate) renderables)
"templates/rss.xml" "templates/rss-item.xml"
where
renderRssDate = renderDate "timestamp" "%a, %d %b %Y %H:%M:%S UT"
"No date found."
-- | Render an Atom feed with a number of items.
renderAtom :: FeedConfiguration -- ^ Feed configuration.
-> [HakyllAction () Context] -- ^ Items to include in the feed.
-> Hakyll ()
renderAtom configuration renderables =
renderFeed configuration (map (>>> renderAtomDate) renderables)
"templates/atom.xml" "templates/atom-item.xml"
where
renderAtomDate = renderDate "timestamp" "%Y-%m-%dT%H:%M:%SZ"
"No date found."
|
