{-# LANGUAGE OverloadedStrings          #-}
{-# LANGUAGE DeriveDataTypeable         #-}
{-# LANGUAGE DeriveGeneric              #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}

-- |
-- Module      : Network.Google.Data.Time
-- Copyright   : (c) 2015-2016 Brendan Hay <brendan.g.hay@gmail.com>
-- License     : Mozilla Public License, v. 2.0.
-- Maintainer  : Brendan Hay <brendan.g.hay@gmail.com>
-- Stability   : provisional
-- Portability : non-portable (GHC extensions)
--
module Network.Google.Data.Time
    ( Time'
    , Date'
    , DateTime'
    , Duration

    , _Time
    , _Date
    , _DateTime
    , _Duration
    ) where

import           Data.Monoid                      ((<>))
import           Control.Lens
import           Data.Aeson
import qualified Data.Aeson.Types                  as Aeson
import           Data.Attoparsec.Text
import           Data.Bifunctor                    (first, second)
import           Data.Bits                         ((.&.))
import           Data.Char                         (ord)
import           Data.Data                         (Data, Typeable)
import           Data.Scientific                   (Scientific)
import qualified Data.Scientific                   as Sci
import           Data.Text                         (Text)
import qualified Data.Text                         as Text
import qualified Data.Text.Lazy                    as LText
import qualified Data.Text.Lazy.Builder            as Build
import qualified Data.Text.Lazy.Builder.Scientific as Sci
import           Data.Time
import           GHC.Generics
import           Web.HttpApiData                   (FromHttpApiData (..),
                                                    ToHttpApiData (..))

-- | This SHOULD be a time in the format of hh:mm:ss.  It is
-- recommended that you use the "date-time" format instead of "time"
-- unless you need to transfer only the time part.
newtype Time' = Time' { unTime :: TimeOfDay }
    deriving (Eq, Ord, Show, Read, Generic, Data, Typeable)

_Time :: Iso' Time' TimeOfDay
_Time = iso unTime Time'

instance ToHttpApiData Time' where
    toQueryParam = Text.pack . show . unTime

instance FromHttpApiData Time' where
    parseQueryParam = second Time' . parseText timeParser

-- | This SHOULD be a date in the format of YYYY-MM-DD.  It is
-- recommended that you use the "date-time" format instead of "date"
-- unless you need to transfer only the date part.
newtype Date' = Date' { unDate :: Day }
    deriving (Eq, Ord, Show, Read, Generic, Data, Typeable, ToHttpApiData, FromHttpApiData)

_Date :: Iso' Date' Day
_Date = iso unDate Date'

-- | This SHOULD be a date in ISO 8601 format of YYYY-MM-
-- DDThh:mm:ssZ in UTC time. This is the recommended form of date/timestamp.
newtype DateTime' = DateTime' { unDateTime :: UTCTime }
    deriving (Eq, Ord, Show, Read, Generic, Data, Typeable, ToHttpApiData, FromHttpApiData)

_DateTime :: Iso' DateTime' UTCTime
_DateTime = iso unDateTime DateTime'

-- | A duration in seconds with up to nine fractional digits, terminated by 's'.
--
-- /Example/: @"3.5s"@.
newtype Duration = Duration { unDuration :: Scientific }
    deriving (Eq, Ord, Show, Read, Generic, Data, Typeable)

_Duration :: Iso' Duration Scientific
_Duration = iso unDuration Duration

instance ToHttpApiData Duration where
    toQueryParam =
          LText.toStrict
        . (\seconds -> Build.toLazyText seconds <> "s")
        . Sci.formatScientificBuilder Sci.Fixed (Just 9)
        . unDuration

instance FromHttpApiData Duration where
    parseQueryParam = second Duration . parseText durationParser

instance ToJSON Time'     where toJSON = String . toQueryParam
instance ToJSON Date'     where toJSON = String . toQueryParam
instance ToJSON DateTime' where toJSON = toJSON . unDateTime
instance ToJSON Duration  where toJSON = String . toQueryParam

instance FromJSON Time' where
    parseJSON = fmap Time' . withText "time" (run timeParser)

instance FromJSON Date' where
    parseJSON = fmap Date' . withText "date" (run dayParser)

instance FromJSON DateTime' where
    parseJSON = fmap DateTime' . parseJSON

instance FromJSON Duration where
    parseJSON = fmap Duration . withText "duration" (run durationParser)

parseText :: Parser a -> Text -> Either Text a
parseText p = first Text.pack . parseOnly p

-- | Parse a time of the form @HH:MM:SS@.
timeParser :: Parser TimeOfDay
timeParser = do
    h <- twoDigits <* char ':'
    m <- twoDigits <* char ':'
    s <- twoDigits <&> fromIntegral
    if h < 24 && m < 60 && s < 61
        then pure (TimeOfDay h m s)
        else fail "invalid time"

-- | Parse a date of the form @YYYY-MM-DD@.
dayParser :: Parser Day
dayParser = do
    y <- decimal   <* char '-'
    m <- twoDigits <* char '-'
    d <- twoDigits
    maybe (fail "invalid date") pure (fromGregorianValid y m d)

durationParser :: Parser Scientific
durationParser = Sci.fromFloatDigits <$> (double <* char 's')

-- | Parse a two-digit integer (e.g. day of month, hour).
twoDigits :: Parser Int
twoDigits = do
    a <- digit
    b <- digit
    let c2d c = ord c .&. 15
    pure $! c2d a * 10 + c2d b

-- | Run an attoparsec parser as an aeson parser.
run :: Parser a -> Text -> Aeson.Parser a
run p t =
    case parseOnly (p <* endOfInput) t of
        Left err -> fail $ "could not parse date: " ++ err
        Right r  -> pure r