{-# Language TemplateHaskell #-}

{-|
Module:             Network.AWS.Machines.SpotPrices
Description:        Stream the spot price history.
Copyright:          © 2017 All rights reserved.
License:            GPL-3
Maintainer:         Evan Cofsky <evan@theunixman.com>
Stability:          experimental
Portability:        POSIX
-}

module Network.AWS.Machines.SpotPrices where

import Lawless hiding (filtered, mapping)
import Network.AWS.EC2
import Network.AWS.Machines.AWS
import Network.AWS.Data.Text (toText)

import Time
import Data.Fixed
import Textual (Textual(..), Printable(..), fromText, hcat, fsep)
import Text

-- | An 'AWSSourceT' for 'SpotPrice's.
type SpotPriceSourceT m = AWSSourceT m SpotPrice

-- | A 'Process' for transducing 'SpotPrice's to something else.
type SpotPriceProcess b = Process SpotPrice b

-- | A 'Num' instance for representing US Dollars.
newtype Dollars = Dollars {unDollars ∷ Centi}
    deriving (Eq, Show, Ord, Enum, Num, Real)

instance Printable Dollars where
    print d = hcat ["$",  print (unDollars d)]

instance Textual Dollars where
    textual = Dollars <$> textual

-- | The hourly spot price at a specific 'Time', 'InstanceType', and
-- 'Zone'.
data PricePoint = PricePoint {
    _ppTime ∷ Time -- ^ The time for this price
    , _ppInstanceType ∷ InstanceType -- ^ The instance type of this price
    , _ppZone ∷ Text -- ^ The zone of this price
    , _ppDollars ∷ Dollars -- ^ The hourly price in USD
    } deriving (Eq, Ord, Show)
makeLenses ''PricePoint

instance Printable PricePoint where
    print (PricePoint {..}) = fsep "\t" [
        print _ppTime,
        print ∘ toText $ _ppInstanceType,
        print _ppZone,
        print _ppDollars]

pricePoint ∷ SpotPrice → Maybe PricePoint
pricePoint sp = PricePoint
                <$> (review _Time <$> sp ^. sTimestamp)
                <*> sp ^. sInstanceType
                <*> sp ^. sAvailabilityZone
                <*> (sp ^. sSpotPrice >>= fromText)

-- | Streams the historic spot price history for a region.
spotPriceHistory ∷
    [RequestMod DescribeSpotPriceHistory]
    → SpotPriceSourceT m -- ^ The spot price history
spotPriceHistory ms =
    pagedSource dsphrsSpotPriceHistory ms describeSpotPriceHistory

pricePoints ∷ SpotPriceProcess PricePoint
pricePoints = mapping pricePoint
    ~> filtered (has _Just)
    ~> mapping (\(Just m) → m)