Using incomes to compute a fair computation to designate the payer

1 files changed, 22 insertions, 0 deletions

diff --git a/src/server/Model/Payer/Income.hs b/src/server/Model/Payer/Income.hs
new file mode 100644
index 0000000..f4bc9fd
--- /dev/null
+++ b/src/server/Model/Payer/Income.hs
@@ -0,0 +1,22 @@
+module Model.Payer.Income
+  ( incomeDefinedForAll
+  ) where
+
+import Data.Time.Clock (UTCTime)
+import Data.List (sort)
+import Data.Maybe
+
+import Database.Persist
+
+import Model.Database
+import Model.User (getUsers)
+import Model.Income (getFirstIncome)
+
+incomeDefinedForAll :: Persist (Maybe UTCTime)
+incomeDefinedForAll = do
+  userIds <- map entityKey <$> getUsers
+  firstIncomes <- mapM getFirstIncome userIds
+  return $
+    if all isJust firstIncomes
+      then listToMaybe . reverse . sort . map incomeCreation . catMaybes $ firstIncomes
+      else Nothing