Make cardImage optional and detect it just like favicons

src/Blog/Skin.hs

@@ -14,30 +14,31 @@ import System.FilePath ((</>), (<.>))
 
 data Skin = Skin {
       banner :: Maybe String
-    , cardImage :: FilePath
+    , cardImage :: Maybe FilePath
     , favicon :: Maybe FilePath
     , head :: Maybe String
     , previewArticlesCount :: Int
     , previewLinesCount :: Int
   }
 
-findFavicon :: Arguments -> IO (Maybe FilePath)
-findFavicon arguments =
-  case Arguments.favicon arguments of
-    Just path -> return . Just $ absolute path
-    _ -> fmap absolute . listToMaybe <$> filterM doesFileExist pathsToCheck
+absolute :: FilePath -> FilePath
+absolute ('.':path) = path
+absolute path = "/" </> path
+
+findImage :: String -> Maybe FilePath -> IO (Maybe FilePath)
+findImage _ (Just path) = return . Just $ absolute path
+findImage name Nothing =
+  fmap absolute . listToMaybe <$> filterM doesFileExist pathsToCheck
   where
     directories = [".", "image", "images", "pictures", "skin", "static"]
     extensions = ["ico", "gif", "jpeg", "jpg", "png", "svg"]
-    pathsToCheck = [ dir </> "favicon" <.> ext | dir <- directories, ext <- extensions ]
-    absolute ('.':path) = path
-    absolute path = "/" </> path
+    pathsToCheck = [ dir </> name <.> ext | dir <- directories, ext <- extensions ]
 
 build :: String -> Arguments -> IO Skin
 build blogName arguments = do
-  let cardImage = maybe ("/image" </> blogName <.> "png") id $ Arguments.cardImage arguments
   banner <- mapM readFile $ Arguments.bannerPath arguments
-  favicon <- findFavicon arguments
+  cardImage <- findImage blogName $ Arguments.cardImage arguments
+  favicon <- findImage "favicon" $ Arguments.favicon arguments
   head <- mapM readFile $ Arguments.headPath arguments
   return $ Skin {
         banner

src/Dom.hs

@@ -9,6 +9,7 @@ import qualified Article (preview)
 import ArticlesList (ArticlesList(..), otherUrl, pageTitle)
 import Blog (Blog(..), Path(..), Skin(..), Wording(..))
 import qualified Blog (get)
+import Control.Applicative ((<|>))
 import Control.Monad.Reader (ReaderT)
 import qualified Data.Map as Map (keys, lookup)
 import Data.Monoid ((<>))
@@ -68,10 +69,11 @@ makeCard :: String -> Text -> Maybe String -> HtmlGenerator ()
 makeCard title description image = do
   og "title" $ pack title
   og "description" description
-  og "image" =<< pack <$> maybe (Blog.get $skin.$cardImage) return image
+  maybeImage =<< ((image <|>) <$> (Blog.get $skin.$cardImage))
   og "site_name" =<< (Blog.get $name.$pack)
   where
     og attribute value = meta_ [makeAttribute "property" $ "og:" <> attribute , content_ value]
+    maybeImage = maybe (return ()) (og "image" . pack)
 
 navigationA :: Term arg result => arg -> result
 navigationA = "a" `termWith` [class_ "navigation"]