-- | This module deals with information of a task which is dependent on the status.
module Taskwarrior.Status (
  Status (..),
  parseFromObject,
  toPairs,
) where

import Data.Aeson (
  FromJSON,
  Object,
  ToJSON,
  object,
  pairs,
  withObject,
  (.:),
  (.=),
 )
import qualified Data.Aeson as Aeson
import Data.Aeson.Types (
  Pair,
  Parser,
  typeMismatch,
 )
import Data.Text (Text)
import Data.Time (UTCTime)
import Taskwarrior.Mask (Mask)
import qualified Taskwarrior.Time as Time

{- | A task can be pending, deleted, completed, waiting or recurring.
 It is recommended to access the fields only by pattern matching since the getters are partial.
-}
data Status
  = Pending
  | Deleted {end :: UTCTime}
  | Completed {end :: UTCTime}
  | Recurring
      { recur :: Text
      , mask :: Mask
      }
  deriving (Eq, Show, Read, Ord)

-- | Takes all information that is dependent on the status from a JSON object.
parseFromObject :: Object -> Parser Status
parseFromObject o =
  (o .: "status") >>= \case
    "pending" -> pure Pending
    "deleted" -> Deleted <$> (o .: "end" >>= Time.parse)
    "completed" -> Completed <$> (o .: "end" >>= Time.parse)
    "recurring" -> Recurring <$> o .: "recur" <*> o .: "mask"
    str -> typeMismatch "status" (Aeson.String str)

-- | A list of Pairs can be used to construct a JSON object later. The result of 'toPairs' is supposed to be combined with the rest of the fields of a task.
toPairs :: Status -> [Pair]
toPairs = \case
  Pending -> [statusLabel "pending"]
  Deleted{..} -> [statusLabel "deleted", "end" .= Time.toValue end]
  Completed{..} -> [statusLabel "completed", "end" .= Time.toValue end]
  Recurring{..} -> [statusLabel "recurring", "recur" .= recur, "mask" .= mask]
 where
  statusLabel :: Text -> Pair
  statusLabel = ("status" .=)

instance FromJSON Status where
  parseJSON = withObject "Status" parseFromObject

instance ToJSON Status where
  toJSON = object . toPairs
  toEncoding = pairs . mconcat . map (uncurry (.=)) . toPairs