First attempt at exporting to JSON

src/JSON.hs

@@ -1,16 +1,51 @@
+{-# LANGUAGE DeriveGeneric #-}
 module JSON (
     generate
   ) where
 
-import Blog (Blog(..))
+import Article (Article)
+import qualified Article (Article(..))
+import Blog (Blog)
+import qualified Blog (Blog(..), get)
 import Control.Monad.IO.Class (MonadIO(..))
-import Control.Monad.Reader (MonadReader(..), ReaderT)
+import Control.Monad.Reader (ReaderT)
-import Data.Aeson
+import Data.Aeson (ToJSON(..), genericToEncoding, defaultOptions, encode)
 import Data.ByteString.Lazy (writeFile)
-import System.FilePath.Posix ((</>))
+import qualified Data.Map as Map (elems)
+import System.FilePath.Posix ((</>), (<.>))
 import Prelude hiding (writeFile)
+import GHC.Generics
+
+data ArticleExport = ArticleExport {
+      source :: String
+    , title :: String
+  } deriving (Generic)
+
+instance ToJSON ArticleExport where
+  toEncoding = genericToEncoding defaultOptions
+
+data BlogDB = BlogDB {
+    articles :: [ArticleExport]
+  } deriving (Generic)
+
+instance ToJSON BlogDB where
+  toEncoding = genericToEncoding defaultOptions
+
+export :: Article -> ArticleExport
+export article = ArticleExport {
+      source = "/" </> Article.urlPath article <.> "md"
+    , title = Article.title article
+  }
+
+exportBlog :: ReaderT Blog IO BlogDB
+exportBlog = do
+  allArticles <- Blog.get Blog.articles
+  return $ BlogDB {
+      articles = export <$> Map.elems allArticles
+    }
 
 generate :: ReaderT Blog IO ()
 generate = do
-  path <- root <$> ask
+  path <- Blog.get Blog.root
-  liftIO $ writeFile (path </> "articles.json") (encode $ object [])
+  jsonContent <- exportBlog
+  liftIO $ writeFile (path </> "articles.json") (encode jsonContent)