-- | This module provides the type for the 'Priority' of a task.
module Taskwarrior.Priority (
  parseMay,
  Priority (..),
) where

import qualified Data.Aeson as Aeson
import Data.Aeson.Types (Parser)

-- | A 'Taskwarrior.Task.Task' can have the priorities 'High', 'Medium', 'Low' or none, which is modeled via a 'Maybe' 'Priority'.
data Priority = High | Medium | Low
  deriving (Priority -> Priority -> Bool
(Priority -> Priority -> Bool)
-> (Priority -> Priority -> Bool) -> Eq Priority
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
/= :: Priority -> Priority -> Bool
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[Priority] -> ShowS
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Bounded)

instance Aeson.ToJSON Priority where
  toJSON :: Priority -> Value
toJSON = \case
    Priority
High -> Value
"H"
    Priority
Medium -> Value
"M"
    Priority
Low -> Value
"L"

-- | Parses a JSON string to a 'Maybe' 'Priority', fails on anything else.
parseMay :: Aeson.Value -> Parser (Maybe Priority)
parseMay :: Value -> Parser (Maybe Priority)
parseMay = String
-> (Text -> Parser (Maybe Priority))
-> Value
-> Parser (Maybe Priority)
forall a. String -> (Text -> Parser a) -> Value -> Parser a
Aeson.withText String
"Priority" ((Text -> Parser (Maybe Priority))
 -> Value -> Parser (Maybe Priority))
-> (Text -> Parser (Maybe Priority))
-> Value
-> Parser (Maybe Priority)
forall a b. (a -> b) -> a -> b
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  Text
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$ Priority -> Maybe Priority
forall a. a -> Maybe a
Just Priority
High
  Text
"M" -> Maybe Priority -> Parser (Maybe Priority)
forall (f :: * -> *) a. Applicative f => a -> f a
pure (Maybe Priority -> Parser (Maybe Priority))
-> Maybe Priority -> Parser (Maybe Priority)
forall a b. (a -> b) -> a -> b
$ Priority -> Maybe Priority
forall a. a -> Maybe a
Just Priority
Medium
  Text
"L" -> Maybe Priority -> Parser (Maybe Priority)
forall (f :: * -> *) a. Applicative f => a -> f a
pure (Maybe Priority -> Parser (Maybe Priority))
-> Maybe Priority -> Parser (Maybe Priority)
forall a b. (a -> b) -> a -> b
$ Priority -> Maybe Priority
forall a. a -> Maybe a
Just Priority
Low
  Text
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Nothing
  Text
s ->
    String -> Parser (Maybe Priority)
forall (m :: * -> *) a. MonadFail m => String -> m a
fail (String -> Parser (Maybe Priority))
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forall a b. (a -> b) -> a -> b
$
      String
"parsing Priority failed, unexpected "
        String -> ShowS
forall a. [a] -> [a] -> [a]
++ Text -> String
forall a. Show a => a -> String
show Text
s
        String -> ShowS
forall a. [a] -> [a] -> [a]
++ String
" (expected \"H\", \"M\", \"L\", or \"\")"

instance Aeson.FromJSON Priority where
  parseJSON :: Value -> Parser Priority
parseJSON Value
val =
    Value -> Parser (Maybe Priority)
parseMay Value
val Parser (Maybe Priority)
-> (Maybe Priority -> Parser Priority) -> Parser Priority
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= \case
      Maybe Priority
Nothing ->
        String -> Parser Priority
forall (m :: * -> *) a. MonadFail m => String -> m a
fail
          String
"parsing Priority failed, unexpected null (expected \"H\", \"M\", or \"L\")"
      Just Priority
p -> Priority -> Parser Priority
forall (f :: * -> *) a. Applicative f => a -> f a
pure Priority
p