-- |
-- Module      :  Phonetic.Languages.Permutations.Arr
-- Copyright   :  (c) OleksandrZhabenko 2020-2021
-- License     :  MIT
-- Stability   :  Experimental
-- Maintainer  :  olexandr543@yahoo.com
--
-- Permutations and universal set functions for the phonetic-languages series of packages. This
-- module uses no vectors, but instead uses arrays.

module Phonetic.Languages.Permutations.Arr (
  universalSetGL
  , genPermutations
  , genPermutationsArr
  , genPermutationsL
  , genPermutationsArrL
) where

import GHC.Arr
import qualified Data.List as L (permutations)
import Data.SubG
import qualified Data.Foldable as F (concat,foldr',foldl')
import Data.Monoid

-- | A key point of the evaluation -- the universal set of the task represented as a @[[a]]@.
universalSetGL ::
  (Eq a, Foldable t, InsertLeft t a, Monoid (t a), Monoid (t (t a))) => t a
  -> t (t a)
  -> (t a -> [a]) -- ^ The function that is used internally to convert to the @[a]@ so that the function can process further the permutations
  -> ((t (t a)) -> [[a]]) -- ^ The function that is used internally to convert to the needed representation so that the function can process further
  -> [Array Int Int] -- ^ The list of permutations of 'Int' indices starting from 0 and up to n (n is probably less than 7).
  -> Array Int [a]
  -> [[a]]
universalSetGL ts uss f1 f2 permsL baseArr = map (F.concat . F.foldr' (:) [] . (f1 ts:) . (`mappend` f2 uss) . elems . amap (unsafeAt baseArr)) permsL
{-# INLINE universalSetGL #-}

-- | One of the popular examples:  realization of the factorial function using 'F.foldl''. Is taken from some
-- teaching material.
factorial n = F.foldl' (*) 1 [1..n]

genPermutations :: Int -> Array Int [Int]
genPermutations n = listArray (0,factorial n - 1) . L.permutations . take n $ [0..]
{-# INLINE genPermutations #-}

genPermutationsArr :: Array Int (Array Int [Int])
genPermutationsArr = amap genPermutations . listArray (0,5) $ [2..7]
{-# INLINE genPermutationsArr #-}

genPermutationsL :: Int -> [Array Int Int]
genPermutationsL n = map (\xs -> listArray (0,n - 1) xs) . L.permutations . take n $ [0..]
{-# INLINE genPermutationsL #-}

genPermutationsArrL :: Array Int [Array Int Int]
genPermutationsArrL = amap genPermutationsL . listArray (0,5) $ [2..7]
{-# INLINE genPermutationsArrL #-}