1 files changed, 23 insertions, 0 deletions
diff --git a/src/server/Validation.hs b/src/server/Validation.hs
new file mode 100644
index 0000000..9035be7
--- /dev/null
+++ b/src/server/Validation.hs
@@ -0,0 +1,23 @@
+module Validation
+  ( nonEmpty
+  , number
+  ) where
+
+import Data.Text (Text)
+import qualified Data.Text as T
+
+nonEmpty :: a -> Text -> Either a Text
+nonEmpty x str =
+  if T.null str
+   then Left x
+   else Right str
+
+number :: x -> (Int -> Bool) -> Text -> Either x Int
+number x numberForm str =
+  case reads (T.unpack str) :: [(Int, String)] of
+    (number, _) : _ ->
+      if numberForm number
+        then Right number
+        else Left x
+    _ ->
+      Left x