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module Fig.Web.Exchange where
import Control.Error.Util (hush)
import qualified Database.Redis as Redis
import Data.Maybe (mapMaybe)
import qualified Data.Aeson as Aeson
import qualified Data.Text.Read as Text.R
import qualified Data.ByteString.Lazy as BS.Lazy
import qualified Data.UUID as UUID
import qualified Data.UUID.V4 as UUID
import Fig.Prelude
adjustUserCurrency :: Text -> Text -> Integer -> Redis.Redis ()
adjustUserCurrency user cur amt = do
let key = "currency:" <> encodeUtf8 user
let ecur = encodeUtf8 cur
mold <- hush <$> Redis.hget key ecur
let old = case mold of
Just (Just o) -> case Text.R.decimal $ decodeUtf8 o of
Right (num, _) -> num
_else -> 0
_else -> 0
void . Redis.hset key ecur . encodeUtf8 . tshow $ old + amt
data Order = Order
{ creator :: !Text
, wantCur :: !Text
, wantAmount :: !Integer
, haveCur :: !Text
, haveAmount :: !Integer
} deriving Generic
instance Aeson.ToJSON Order
instance Aeson.FromJSON Order
createOrder :: MonadIO m => Redis.Connection -> Order -> m ByteString
createOrder c o = liftIO $ Redis.runRedis c do
let bs = Aeson.encode o
uuid <- liftIO UUID.nextRandom
let key = BS.Lazy.toStrict $ UUID.toByteString uuid
void $ Redis.hset "orders" key (BS.Lazy.toStrict bs)
pure key
getOrders :: MonadIO m => Redis.Connection -> m [Order]
getOrders c = liftIO $ Redis.runRedis c do
Redis.hvals "orders" >>= \case
Left _ -> pure []
Right orders -> pure $ mapMaybe (Aeson.decode' . BS.Lazy.fromStrict) orders
cancelOrder :: MonadIO m => Redis.Connection -> ByteString -> m ()
cancelOrder c key = liftIO $ Redis.runRedis c do
void $ Redis.hdel "orders" [key]
satisfyOrder :: MonadIO m => Redis.Connection -> ByteString -> Text -> m ()
satisfyOrder c key buyer = liftIO $ Redis.runRedis c do
Redis.hget "orders" key >>= \case
Right (Just bs) -> case Aeson.decode' $ BS.Lazy.fromStrict bs of
Nothing -> pure ()
Just (order :: Order) -> do
adjustUserCurrency buyer order.wantCur (-order.wantAmount)
adjustUserCurrency order.creator order.wantCur order.wantAmount
adjustUserCurrency buyer order.haveCur order.haveAmount
adjustUserCurrency order.creator order.haveCur (-order.haveAmount)
_else -> pure ()
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