Cryptsy/API/Public/Trade.hs

   1 module Cryptsy.API.Public.Trade
   2         ( GTrade(..), Trade
   3         , withComponents, withText
   4         , module Cryptsy.API.Public
   5         -- |Re-exported from Data.Text
   6         , Text
   7         -- |Re-exported from Data.Aeson
   8         , Value, Object, FromJSON(..)
   9         -- |Re-exported from Data.Aeson.Types
  10         , Parser
  11         )
  12 where
  13
  14 -- base
  15 import Control.Applicative ((<$>), (<*>))
  16
  17 -- text
  18 import Data.Text (Text, pack)
  19
  20 -- aeson
  21 import qualified Data.Aeson as Aeson
  22 import Data.Aeson
  23         ( FromJSON(..), Value, Object, withObject, (.:)
  24         )
  25 import Data.Aeson.Types (Parser)
  26
  27 -- this package
  28 import Cryptsy.API.Public (CryptsyNum(..))
  29
  30 data GTrade dt p q t = Trade
  31         { id :: Text
  32         , time :: dt
  33         , price :: p
  34         , quantity :: q
  35         , total :: t
  36         } deriving Show
  37 type Trade = GTrade Text CryptsyNum CryptsyNum CryptsyNum
  38
  39 instance (FromJSON dt, FromJSON p, FromJSON q, FromJSON t) =>
  40         FromJSON (GTrade dt p q t)
  41  where
  42         parseJSON = withObject "trade"
  43                   $ withComponents parseJSON parseJSON parseJSON parseJSON
  44
  45 -- |Combine component parsers into JSON Object parser, for use with
  46 -- |'Aeson.withObject'.
  47 withComponents :: (Value -> Parser dt) -- ^ date/time parser
  48                -> (Value -> Parser p)  -- ^ price parser
  49                -> (Value -> Parser q)  -- ^ quantity parser
  50                -> (Value -> Parser t)  -- ^ total parser
  51                -> Object -> Parser (GTrade dt p q t)
  52 withComponents parseDatetime parsePrice parseQuantity parseTotal o =
  53         Trade                                <$>
  54                  o .: pack "id"                          <*>
  55                 (o .: pack "time"     >>= parseDatetime) <*>
  56                 (o .: pack "price"    >>= parsePrice   ) <*>
  57                 (o .: pack "quantity" >>= parseQuantity) <*>
  58                 (o .: pack "total"    >>= parseTotal   )
  59
  60 -- |Special from of 'withComponents', since API delivers components as JSON
  61 -- |Strings.
  62 withText :: (Text -> Parser dt) -- ^ date/time parser
  63          -> (Text -> Parser p)  -- ^ price parser
  64          -> (Text -> Parser q)  -- ^ quantity parser
  65          -> (Text -> Parser t)  -- ^ total parser
  66          -> Object -> Parser (GTrade dt p q t)
  67 withText parseDatetime parsePrice parseQuantity parseTotal =
  68         withComponents
  69                 (Aeson.withText "time"     parseDatetime)
  70                 (Aeson.withText "price"    parsePrice   )
  71                 (Aeson.withText "quantity" parseQuantity)
  72                 (Aeson.withText "total"    parseTotal   )