Add import expression

1 files changed, 41 insertions, 0 deletions

diff --git a/Data/ConfigManager/Reader.hs b/Data/ConfigManager/Reader.hs
new file mode 100644
index 0000000..9f4cc3c
--- /dev/null
+++ b/Data/ConfigManager/Reader.hs
@@ -0,0 +1,41 @@
+module Data.ConfigManager.Reader
+  ( readConfig
+  ) where
+
+import Control.Monad (foldM)
+
+import System.FilePath.Posix (dropFileName, (</>))
+
+import qualified Data.HashMap.Strict as M
+import Data.Text (Text)
+import qualified Data.Text.IO as T
+
+import Data.ConfigManager.Parser (parseConfig)
+import Data.ConfigManager.Expr
+import Data.ConfigManager.Config
+
+readConfig :: FilePath -> IO (Either Text Config)
+readConfig path = do
+  input <- T.readFile path
+  case parseConfig input of
+    Left errorMessage ->
+      return . Left $ errorMessage
+    Right exprs ->
+      foldM (go fileDir) (Right emptyConfig) exprs
+      where fileDir = dropFileName path
+            emptyConfig = Config $ M.fromList []
+
+go :: String -> Either Text Config -> Expr -> IO (Either Text Config)
+go _ errorMessage@(Left _) _ = return errorMessage
+go fileDir (Right config) expr =
+  case expr of
+    Binding name value ->
+      return . Right . Config $ M.insert name value (hashMap config)
+    Import path -> do
+      eitherConfig <- readConfig (fileDir </> path)
+      case eitherConfig of
+        Left errorMessage ->
+          return . Left $ errorMessage
+        Right importedConfig ->
+          let unionConfig = (hashMap importedConfig) `M.union` (hashMap config)
+          in  return . Right . Config $ unionConfig