NonEmpty.hs

{- |
Module      : Antelude.List.NonEmpty
Description : Contains some functions for NonEmptys, and reexports the Data.List.NonEmpty module.
Maintainer  : dneavesdev@pm.me
-}
module Antelude.List.NonEmpty
    ( -- * Rexports
      module NEExport
      -- * New and Reconstructed for safety
    , append
    , appendList
    , atIndex
    , fromList
    , prepend
    ) where

import safe           Antelude.Function              ( flip, (|>) )
import safe           Antelude.Internal.TypesClasses
    ( Int
    , List
    , Maybe (..)
    , Ordering (..)
    )
import safe           Antelude.List                  as AL ( head )

import safe           Data.List.NonEmpty             as NEExport hiding
    ( append
    , appendList
    , fromList
    )
import safe qualified Data.List.NonEmpty             as NE

import safe           Prelude                        ( Ord (compare) )


-- | Obtain the element at the given index, starting at 0. 'Nothing' if the index is not valid.
atIndex :: Int -> NonEmpty a -> Maybe a
atIndex index lst = case compare index 0 of
  LT ->
    Nothing
  _ ->
    lst
      |> NE.drop
        index
      |> AL.head


-- | Convert a `List a` to a `NonEmpty a`
fromList :: List a -> Maybe (NonEmpty a)
fromList = NE.nonEmpty

-- | Add an item to the beginning of a 'NonEmpty'.
prepend :: NonEmpty a -> NonEmpty a -> NonEmpty a
prepend = flip NE.append


-- | Add an item to the end of a 'NonEmpty'.
append :: NonEmpty a -> NonEmpty a -> NonEmpty a
append = NE.append


-- | Add a 'List' to the end of a 'NonEmpty'.
appendList :: List a -> NonEmpty a -> NonEmpty a
appendList = flip NE.appendList