changing notification behaviour: multiple recipients, but only one mail

Handler/Buy.hs

@@ -50,7 +50,7 @@ postBuyR uId bId = do
             update uId [UserBalance -=. price]
             update bId [BeverageAmount -=. quant]
             update bId [BeverageTotalBought +=. 1]
-          checkAlert bId
+          checkAlert bId (beverageAmount bev)
           master <- getYesod
           liftIO $ notifyUser user bev quant price master
           case sw of
@@ -128,7 +128,7 @@ postBuyCashR bId =
             let price = quant * (beveragePrice bev + appCashCharge (appSettings master))
             runDB $ update bId [BeverageAmount -=. quant]
             updateCashier price "Barzahlung"
-            checkAlert bId
+            checkAlert bId (beverageAmount bev)
             let currency = appCurrency $ appSettings master
             setMessageI $ MsgPurchaseSuccessCash price currency
             redirect HomeR

Handler/Common.hs

@@ -183,13 +183,14 @@ amountField = Field
     showVal = either id (pack . showI)
     showI x = show (fromIntegral x :: Integer)
 
-checkAlert :: BeverageId -> Handler ()
-checkAlert bId = do
+checkAlert :: BeverageId -> Int -> Handler ()
+checkAlert bId oldamount = do
   bev <- runDB $ getJust bId
-  if beverageAmount bev < beverageAlertAmount bev
-    then do
-      master <- getYesod
-      let to = appEmail $ appSettings master
+  let alert = beverageAlertAmount bev
+  when (beverageAmount bev < alert && oldamount > alert) $ do
+    master <- getYesod
+    let tos = appEmail $ appSettings master
+    mapM_ (\to ->
       liftIO $ sendMail to "Niedriger Bestand"
         [stext|
 Hallo,
@@ -199,10 +200,9 @@ Der momentane Bestand ist bei #{beverageAmount bev} Artikeln.
 
 Viele Grüße,
 
-der Matemat
+Dein Matemat
         |]
-    else
-      return () -- do nothing
+      ) tos
 
 sendMail :: MonadIO m => Text -> Text -> TL.Text -> m ()
 sendMail to subject body =

Settings.hs

@@ -67,7 +67,7 @@ data AppSettings = AppSettings
     -- ^ Copyright text to appear in the footer of the page
     , appAnalytics              :: Maybe Text
     -- ^ Google Analytics code
-    , appEmail                  :: Text
+    , appEmail                  :: [Text]
     -- ^ notification address
     , appCurrency               :: Text
     -- ^ Currency character

config/settings.yml

@@ -26,7 +26,8 @@ database:
   poolsize: "_env:PGPOOLSIZE:10"
 
 #analytics: UA-YOURCODE
-email: "nek0@momen"
+email:
+- "nek0@momen"
 currency: "€"
 cash_charge: 50