Mask.hs

-- | The Mask module models the state a recurring parent saves about its child tasks.
module Taskwarrior.Mask (
  Mask (..),
  MaskState,
) where

import qualified Data.Aeson as Aeson
import qualified Data.Aeson.Types as Aeson.Types
import qualified Data.Text as Text

-- | Represents the state of a child in a 'Status.Recurring' 'Task.Task'.
data MaskState = Pending | Completed | Deleted | Waiting deriving (Eq, Show, Enum, Read, Ord, Bounded)

-- | The mask is a newtype to provide 'Data.Aeson' instances from and to a JSON string.
newtype Mask = Mask {mask :: [MaskState]} deriving (Eq, Read, Ord, Show)

toChar :: MaskState -> Char
toChar = \case
  Pending -> '-'
  Completed -> '+'
  Deleted -> 'X'
  Waiting -> 'W'

instance Aeson.FromJSON Mask where
  parseJSON =
    Aeson.withText "Mask" $ fmap Mask . traverse parseChar . Text.unpack

parseChar :: Char -> Aeson.Types.Parser MaskState
parseChar = \case
  '-' -> pure Pending
  '+' -> pure Completed
  'X' -> pure Deleted
  'W' -> pure Waiting
  char -> fail $ "Not a Mask Char: '" ++ [char] ++ "'"

instance Aeson.ToJSON Mask where
  toJSON = Aeson.String . Text.pack . fmap toChar . mask