Cryptsy/API/Public/MarketData/New.hs

   1 {-# LANGUAGE ViewPatterns #-}
   2 module Cryptsy.API.Public.MarketData.New
   3         ( GMarketData(..), MarketData
   4         , withComponents, withMarket
   5         , getMarketData, marketData
   6         , module Cryptsy.API.Public.Market
   7         -- |Re-exported from Data.Text
   8         , Text
   9         -- |Re-exported from Data.Aeson
  10         , Value, Object, FromJSON(..)
  11         -- |Re-exported from Data.Aeson.Types
  12         , Parser
  13         )
  14 where
  15
  16 -- aeson
  17 import Data.Aeson ( FromJSON(..), Value(Object), Object, withObject )
  18 import Data.Aeson.Types (Parser, Result(..), parse)
  19
  20 -- base
  21 import Data.Function ( ($) )
  22 import Data.Functor ( fmap, (<$>) )
  23 import Data.Maybe (Maybe(..))
  24 import Data.Traversable (mapM)
  25 import Prelude ( Show, String )
  26
  27 -- either
  28 import Control.Monad.Trans.Either (left, right)
  29
  30 -- text
  31 import Data.Text (Text, pack)
  32
  33 -- unordered-containers
  34 import           Data.HashMap.Strict (HashMap)
  35 import qualified Data.HashMap.Strict as HM (lookup)
  36
  37 -- this pacakge
  38 import Cryptsy.API.Public
  39 import Cryptsy.API.Public.Market
  40         ( GMarket(..), Market
  41         , GOrder(Order) -- for re-export
  42         , GTrade(Trade, time) -- for re-export
  43         )
  44
  45 marketdatav2URL :: String
  46 marketdatav2URL = "http://pubapi.cryptsy.com/api.php?method=marketdatav2"
  47
  48 newtype GMarketData p q dt t =
  49         MarketData { markets :: (HashMap Text (GMarket p q dt t)) }
  50         deriving Show
  51 type MarketData = GMarketData Text Text Text Text
  52
  53 instance (FromJSON p, FromJSON q, FromJSON dt, FromJSON t) =>
  54         FromJSON (GMarketData p q dt t)
  55  where
  56         parseJSON = withObject "markets" $ withComponents parseJSON
  57
  58 -- |Build parser for multiple markets from parser for single market.
  59 withComponents :: (Value -> Parser (GMarket p q dt t)) -- ^ market parser
  60                -> Object -> Parser (GMarketData p q dt t)
  61 withComponents parseMarket = fmap MarketData <$> mapM parseMarket
  62
  63 -- |Build parser for multiple markets from parser for single market object.
  64 withMarket :: (Object -> Parser (GMarket p q dt t)) -- ^ market parser
  65            -> Object -> Parser (GMarketData p q dt t)
  66 withMarket parseMarket = withComponents (withObject "market" parseMarket)
  67
  68 {-|
  69 "Raw" request, does not convert the JSON value, but simply returns the JSON
  70 value bound to the "return" key from the response body.
  71 -}
  72 getMarketData :: PubCryptsy Value
  73 getMarketData = pubCryptsy marketdatav2URL
  74
  75 marketsKey :: Text
  76 marketsKey = pack "markets"
  77
  78 {-|
  79 "Cooked" request, extracts the JSON object bound to the "market" key of the
  80 object boudn to the "return" key and converts it.
  81 -}
  82 marketData :: (Object -> Parser (GMarketData p q dt t)) -- ^ market data parser
  83              -> PubCryptsy (GMarketData p q dt t)
  84 marketData parseMarkets = do
  85         ret <- getMarketData
  86         mkts <- case ret of
  87                 Object (HM.lookup marketsKey -> Just m) -> right m
  88                 _ -> left $ FailParseReturn ret "Missing 'markets' key."
  89         case parse (withObject "markets" parseMarkets) mkts of
  90                 Error err -> left $ FailParseReturn ret err
  91                 Success v -> right v