-----------------------------------------------------------------------------
-- |
-- Module      :  Data.Enum
-- Copyright   :  (c) 2020-2021 EMQ Technologies Co., Ltd.
-- License     :  BSD-style (see the LICENSE file)
--
-- Maintainer  :  Feng Lee, feng@emqx.io
--                Yang M, yangm@emqx.io
-- Stability   :  experimental
-- Portability :  portable
--
-- The Enum typeclass.
--
-----------------------------------------------------------------------------
module Data.Enum
  ( class Enum
  , succ
  , pred
  , range
  , rangeStep
  ) where

import Data.Function (error)
import Data.Eq ((==))

class Enum a where
  succ      :: a -> a
  pred      :: a -> a
  range     :: a -> a -> [a]
  rangeStep :: a -> a -> a -> [a]

instance Enum Char where
  succ = enumCharSucc
  pred = enumCharPred
  range = enumCharRange
  rangeStep = enumCharRangeStep

foreign import enumCharSucc :: Char -> Char
foreign import enumCharPred :: Char -> Char
foreign import enumCharRange :: Char -> Char -> [Char]
foreign import enumCharRangeStep :: Char -> Char -> Char -> [Char]

instance Enum Integer where
  succ = enumIntegerSucc
  pred = enumIntegerPred
  range = enumIntegerRange
  rangeStep = enumIntegerRangeStep

foreign import enumIntegerSucc :: Integer -> Integer
foreign import enumIntegerPred :: Integer -> Integer
foreign import enumIntegerRange :: Integer -> Integer -> [Integer]
foreign import enumIntegerRangeStep :: Integer -> Integer -> Integer -> [Integer]

instance Enum Boolean where
  succ false = true
  succ true  = error "bad argument"
  pred false = error "bad argument"
  pred true  = false
  range x y | x == y = [x]
  range true false = []
  range x y = [x, y]
  rangeStep x y _ | x == y = error "bad argument"
  rangeStep x _ y | x == y = [x]
  rangeStep x _ y = [x, y]

instance Enum Float where
  succ = enumFloatSucc
  pred = enumFloatPred
  range = enumFloatRange
  rangeStep = enumFloatRangeStep

foreign import enumFloatSucc :: Float -> Float
foreign import enumFloatPred :: Float -> Float
foreign import enumFloatRange :: Float -> Float -> [Float]
foreign import enumFloatRangeStep :: Float -> Float -> Float -> [Float]