src/Cryptsy/API/Public/Types/Order.hs

   1 -- |Type for individual orders (order book entries) from the API.
   2 module Cryptsy.API.Public.Types.Order
   3         ( module Cryptsy.API.Public.Types.Order
   4         , module Cryptsy.API.Public.Types.Num
   5         )
   6 where
   7
   8 -- base
   9 import Control.Applicative ((<$>), (<*>))
  10
  11 -- text
  12 import Data.Text (pack)
  13
  14 -- aeson
  15 import Data.Aeson (FromJSON(..), Value, withObject, (.:))
  16 import Data.Aeson.Types (Parser)
  17
  18 -- this package
  19 import Cryptsy.API.Public.Types.Num
  20
  21 -- |generalized order
  22 data GOrder p q t = Order
  23         { orderPrice :: p
  24         , orderQuantity :: q
  25         , orderTotal :: t
  26         } deriving Show
  27
  28 -- |default order
  29 type Order = GOrder CryptsyNum CryptsyNum CryptsyNum
  30
  31 instance (FromJSON p, FromJSON q, FromJSON t) =>
  32         FromJSON (GOrder p q t)
  33  where
  34         parseJSON = parseOrder parseJSON parseJSON parseJSON
  35
  36 -- |Combine component parsers into JSON Object parser.
  37 parseOrder :: (Value -> Parser p) -- ^ price parser
  38            -> (Value -> Parser q) -- ^ quantity parser
  39            -> (Value -> Parser t) -- ^ total parser
  40            -> Value -> Parser (GOrder p q t)
  41 parseOrder parsePrice parseQuantity parseTotal =
  42         withObject "Order" $ \o -> Order         <$>
  43         (o .: pack "price"    >>= parsePrice   ) <*>
  44         (o .: pack "quantity" >>= parseQuantity) <*>
  45         (o .: pack "total"    >>= parseTotal   )