{-# LANGUAGE DefaultSignatures, ScopedTypeVariables #-}

-- From http://stackoverflow.com/a/15911213

module Data.Text.ICU.BitMask
       (
    -- * Bit mask twiddling API
    -- $api
    -- * Types
      ToBitMask(..)
    -- * Functions
    , fromBitMask
    , highestValueInBitMask
    ) where

import Data.Bits ((.&.), (.|.))
import Data.Maybe (listToMaybe)

-- $api
-- Conversion to and from enumerated types representable as
-- a compact bitmask.

class ToBitMask a where
  toBitMask :: a -> Int

instance (ToBitMask a) => ToBitMask [a] where
  toBitMask :: [a] -> Int
toBitMask = (a -> Int -> Int) -> Int -> [a] -> Int
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (Int -> Int -> Int
forall a. Bits a => a -> a -> a
(.|.) (Int -> Int -> Int) -> (a -> Int) -> a -> Int -> Int
forall b c a. (b -> c) -> (a -> b) -> a -> c
. a -> Int
forall a. ToBitMask a => a -> Int
toBitMask) Int
0

fromBitMask :: (Enum a, Bounded a, ToBitMask a) => Int -> [a]
fromBitMask :: forall a. (Enum a, Bounded a, ToBitMask a) => Int -> [a]
fromBitMask Int
bm = (a -> Bool) -> [a] -> [a]
forall a. (a -> Bool) -> [a] -> [a]
filter a -> Bool
forall {a}. ToBitMask a => a -> Bool
inBitMask ([a] -> [a]) -> [a] -> [a]
forall a b. (a -> b) -> a -> b
$ a -> [a]
forall a. Enum a => a -> [a]
enumFrom a
forall a. Bounded a => a
minBound
  where inBitMask :: a -> Bool
inBitMask a
val = (Int
bm Int -> Int -> Int
forall a. Bits a => a -> a -> a
.&. a -> Int
forall a. ToBitMask a => a -> Int
toBitMask a
val) Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== a -> Int
forall a. ToBitMask a => a -> Int
toBitMask a
val

highestValueInBitMask :: (Enum a, Bounded a, ToBitMask a) => Int -> Maybe a
highestValueInBitMask :: forall a. (Enum a, Bounded a, ToBitMask a) => Int -> Maybe a
highestValueInBitMask = [a] -> Maybe a
forall a. [a] -> Maybe a
listToMaybe ([a] -> Maybe a) -> (Int -> [a]) -> Int -> Maybe a
forall b c a. (b -> c) -> (a -> b) -> a -> c
. [a] -> [a]
forall a. [a] -> [a]
reverse ([a] -> [a]) -> (Int -> [a]) -> Int -> [a]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Int -> [a]
forall a. (Enum a, Bounded a, ToBitMask a) => Int -> [a]
fromBitMask