Introduce application error

src/Yore/DB.hs

@@ -28,12 +28,9 @@ import GHC.Generics (Generic)
 
 import qualified Database.PostgreSQL.Opium as Opium
 
-newtype DB = DB (Pool (Either Opium.ConnectionError Opium.Connection))
+import Yore.Error (Error (..))
 
-data Error
-  = ConnectionError Opium.ConnectionError
-  | Error Opium.Error
-  deriving (Show)
+newtype DB = DB (Pool (Either Opium.ConnectionError Opium.Connection))
 
 initDB :: Text -> IO DB
 initDB connString = do
@@ -54,7 +51,7 @@ withConn (DB connPool) f =
     Left connectionError ->
       pure $ Left $ ConnectionError connectionError
     Right conn ->
-      either (Left . Error) Right <$> f conn
+      either (Left . DBError) Right <$> f conn
 
 data DayIndex = DayIndex
   { day_index_id :: Int

src/Yore/Error.hs

@@ -0,0 +1,11 @@
+module Yore.Error (Error (..)) where
+
+import Data.Text (Text)
+
+import qualified Database.PostgreSQL.Opium as Opium
+
+data Error
+  = ConnectionError Opium.ConnectionError
+  | DBError Opium.Error
+  | GenericError Text
+  deriving (Show)

src/Yore/Repl.hs

@@ -34,9 +34,9 @@ getToday = do
   print now
   let currentDay = localDay $ zonedTimeToLocalTime now
   case addYears (-100) currentDay of
-    Just then_ ->
+    Right then_ ->
       getIssuesByDay then_
-    Nothing ->
+    Left _ ->
       pure []
 
 indexDay :: Day -> IO ()

src/Yore/Time.hs

@@ -1,5 +1,6 @@
 module Yore.Time (addYears, getCurrentDay, getSecondsUntilMidnight) where
 
+import Data.Text (Text)
 import Data.Time
   ( Day
   , addGregorianYearsClip
@@ -11,13 +12,16 @@ import Data.Time
   , toGregorian
   , zonedTimeToLocalTime
   )
+import Text.Printf (printf)
 
-addYears :: Integer -> Day -> Maybe Day
+import qualified Data.Text as Text
+
+addYears :: Integer -> Day -> Either Text Day
 addYears yearOffset date
   | isFebruary29th && not (isLeapYear year') =
-      Nothing
+      Left $ Text.pack $ printf "year %d is not a leap year"
   | otherwise =
-      Just $ addGregorianYearsClip yearOffset date
+      Right $ addGregorianYearsClip yearOffset date
   where
     (year, month, day) = toGregorian date
     year' = year + yearOffset