Detect and use custom summary and featured image for articles

src/Dom.hs

@@ -10,12 +10,12 @@ import ArticlesList (ArticlesList(..), otherUrl, pageTitle)
 import Blog (Blog(..), Path(..), Skin(..), Wording(..))
 import qualified Blog (get)
 import Control.Monad.Reader (ReaderT)
-import qualified Data.Map as Map (keys)
+import qualified Data.Map as Map (keys, lookup)
 import Data.Monoid ((<>))
 import Data.Text (Text, pack, empty)
 import Lucid
 import Lucid.Base (makeAttribute)
-import Prelude hiding (head)
+import Prelude hiding (head, lookup)
 import Pretty ((.$))
 import System.FilePath.Posix ((</>), (<.>))
 
@@ -26,15 +26,21 @@ class Page a where
   content :: a -> HtmlGenerator ()
 
 instance Page Article where
-  card (Article {title}) =
-    makeCard title =<< (Blog.get $name.$("A new article on " <>).$pack)
+  card (Article {title, metadata}) = do
+    description <- getDescription (Map.lookup "summary" metadata)
+    makeCard title (pack description) (Map.lookup "featuredImage" metadata)
+    where
+      getDescription = maybe (Blog.get $name.$("A new article on " <>)) return
 
   content = article True
 
 instance Page ArticlesList where
   card al = do
-    blogName <- Blog.get name
-    makeCard (maybe blogName ((blogName ++ " - ") ++) $ tagged al) =<< pageTitle al
+    cardTitle <- getTitle <$> Blog.get name
+    description <- pageTitle al
+    makeCard cardTitle description Nothing
+    where
+      getTitle name = maybe name ((name ++ " - ") ++) $ tagged al
 
   content al@(ArticlesList {featured, full}) = do
     preview <- Article.preview <$> (Blog.get $skin.$previewLinesCount)
@@ -58,11 +64,11 @@ article raw (Article {key, body, title}) = do
   where
     (aElem, extension) = if raw then (a_, "md") else (navigationA, "html")
 
-makeCard :: String -> Text -> HtmlGenerator ()
-makeCard title description = do
+makeCard :: String -> Text -> Maybe String -> HtmlGenerator ()
+makeCard title description image = do
   og "title" $ pack title
   og "description" description
-  og "image" =<< (Blog.get $skin.$cardImage.$pack)
+  og "image" =<< pack <$> maybe (Blog.get $skin.$cardImage) return image
   og "site_name" =<< (Blog.get $name.$pack)
   where
     og attribute value = meta_ [makeAttribute "property" $ "og:" <> attribute , content_ value]