{-# LANGUAGE NoImplicitPrelude #-}

-- |
-- Module      :  Phladiprelio.PermutationsArrMini
-- Copyright   :  (c) OleksandrZhabenko 2021-2024
-- License     :  MIT
-- Stability   :  Experimental
-- Maintainer  :  oleksandr.zhabenko@yahoo.com
--
-- Special permutations functions for the phonetic-languages and phladiprelio series of packages. This
-- module uses no vectors, but instead uses arrays.

module Phladiprelio.PermutationsArrMini (
  genPairwisePermutations
  , pairsSwapP
  , genPairwisePermutationsArrN
  , genPairwisePermutationsArr
  , genPairwisePermutationsLN
  , genPairwisePermutationsL
  , genPairwisePermutationsArrLN
  , genPairwisePermutationsArrL
) where

import GHC.Enum
import Data.Bits (shiftR)
import GHC.Base
import GHC.Num
import GHC.List
import GHC.Arr

genPairwisePermutations :: (Ord a, Enum a, Num a) => Int -> Array Int [a]
genPairwisePermutations n = listArray (0, shiftR (n*(n-1)) 1) . pairsSwapP . take n $ [0..]
{-# INLINE genPairwisePermutations #-}
{-# SPECIALIZE genPairwisePermutations :: Int -> Array Int [Int] #-}

pairsSwapP :: (Ord a, Enum a, Num a) => [a] -> [[a]]
pairsSwapP xs = xs:[swap2Ls k m xs | k <- xs, m <- xs , k < m]
{-# SPECIALIZE pairsSwapP :: [Int] -> [[Int]] #-}

-- | The first two arguments are considered not equal, though it is not checked.
swap2ns :: (Eq a) => a -> a -> a -> a
swap2ns k m n
 | n /= k = if n /= m then n else k
 | otherwise = m
{-# INLINE swap2ns #-}
{-# SPECIALIZE swap2ns :: Int -> Int -> Int -> Int #-}

swap2Ls :: (Eq a) => a -> a -> [a] -> [a]
swap2Ls k m = map (swap2ns k m)
{-# INLINE swap2Ls #-}
{-# SPECIALIZE swap2Ls :: Int -> Int -> [Int] -> [Int] #-}

genPairwisePermutationsArrN ::  (Ord a, Enum a, Num a) => Int -> Array Int (Array Int [a])
genPairwisePermutationsArrN n = amap genPairwisePermutations . listArray (0,n - 2) $ [2..n]
{-# INLINE genPairwisePermutationsArrN #-}
{-# SPECIALIZE genPairwisePermutationsArrN :: Int -> Array Int (Array Int [Int]) #-}

genPairwisePermutationsArr ::  (Ord a, Enum a, Num a) => Array Int (Array Int [a])
genPairwisePermutationsArr = genPairwisePermutationsArrN 10
{-# INLINE genPairwisePermutationsArr #-}
{-# SPECIALIZE genPairwisePermutationsArr :: Array Int (Array Int [Int]) #-}

genPairwisePermutationsLN ::  (Ord a, Enum a, Num a) => Int -> [Array Int a]
genPairwisePermutationsLN n = map (\xs -> listArray (0,n - 1) xs) . pairsSwapP . take n $ [0..]
{-# INLINE genPairwisePermutationsLN #-}
{-# SPECIALIZE genPairwisePermutationsLN :: Int -> [Array Int Int] #-}

genPairwisePermutationsL ::  (Ord a, Enum a, Num a) => [Array Int a]
genPairwisePermutationsL = genPairwisePermutationsLN 10
{-# INLINE genPairwisePermutationsL #-}
{-# SPECIALIZE genPairwisePermutationsL :: [Array Int Int] #-}

genPairwisePermutationsArrLN ::  (Ord a, Enum a, Num a) => Int -> Array Int [Array Int a]
genPairwisePermutationsArrLN n = amap genPairwisePermutationsLN . listArray (0,n - 2) $ [2..n]
{-# INLINE genPairwisePermutationsArrLN #-}
{-# SPECIALIZE genPairwisePermutationsArrLN :: Int -> Array Int [Array Int Int] #-}

genPairwisePermutationsArrL ::  (Ord a, Enum a, Num a) => Array Int [Array Int a]
genPairwisePermutationsArrL = genPairwisePermutationsArrLN 10
{-# INLINE genPairwisePermutationsArrL #-}
{-# SPECIALIZE genPairwisePermutationsArrL :: Array Int [Array Int Int] #-}