mateamt/src/Control/Buy.hs

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{-# LANGUAGE OverloadedStrings #-}
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module Control.Buy where
import Control.Monad (void, foldM)
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import Control.Monad.Reader (asks)
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-- internal imports
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import Control.User
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import Types
import Model
buy
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:: Maybe (Int, AuthMethod)
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-> [PurchaseDetail]
-> MateHandler PurchaseResult
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buy auth pds = do
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conn <- asks rsConnection
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(missing, real) <- foldM (\(ms, rs) pd -> do
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mmiss <- checkProductAvailability pd conn
case mmiss of
Just miss -> return
( (pd {purchaseDetailAmount = miss}):ms
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, pd {purchaseDetailAmount = max 0 (purchaseDetailAmount pd - miss)}:rs
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)
Nothing -> return
( ms
, pd:rs
)
)
([], [])
pds
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mapM_ (`postBuyProductAmountUpdate` conn) real
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price <- foldM
(\total pd ->
fmap (+ total) (getLatestTotalPrice pd conn)
)
0
real
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case auth of
Just (auid, _) -> do
void $ addToUserBalance auid (-price) conn
newBalance <- userBalanceSelect conn auid
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userUpdateTimestamp auth
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return $ PurchaseResult
( if newBalance < 0
then PurchaseDebtful
else PurchaseOK
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)
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missing
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Nothing -> do
void $ insertNewJournalEntry
(JournalSubmit
("Cash purchase")
price
)
conn
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return $ PurchaseResult
(PayAmount price)
missing