-- |
-- Module      :  Data.Filters.Basic
-- Copyright   :  (c) OleksandrZhabenko 2020
-- License     :  MIT
-- Stability   :  Experimental
-- Maintainer  :  olexandr543@yahoo.com
--
-- A module allows to change the structure of the function output for the functions of
-- elements from 'RealFrac' class. At the moment only the equal intervals are supported.
-- Has basic functions for the filters. Is taken from the @uniqueness-periods-vector-filters@ package
-- that is intended to be rewritten. These functions are basic for it and for its successor,
-- @phonetic-languages-filters-array@ package.

module Data.Filters.Basic (
  -- * One interval used
  intervalNRealFrac
  , zero2One
  , unsafeTransfer1I5
  , transfer1IEq3
) where

-- | Given the minimum and maximum elements, a quantity of equal intervals, and an element in between the first two arguments (or equal to one of them), finds out the
-- index of the interval, to which the element belongs (starting from 1). The minimum element belongs to the interval with the index 1.
intervalNRealFrac
  :: (RealFrac b, Integral c) => b
  -> b
  -> c
  -> b
  -> c
intervalNRealFrac minE maxE n x
 | maxE == minE = ceiling (0.5 * fromIntegral n)
 | otherwise = zero2One . ceiling $ fromIntegral n * (x - minE) / (maxE - minE)
{-# INLINE intervalNRealFrac #-}

zero2One :: Integral a => a -> a
zero2One x = if x == 0 then 1 else x
{-# INLINE zero2One #-}

-- | Moves (if needed) the given value so that its result divides the new [min..max] interval in the same proportion as the starting one. Is intended to be used
-- for the arguments satisfying some additional constraints, but they are not checked (hence, its name prefix \"unsafe\"). For example, the second argument must be
-- greater than the first one, the fourth -- than the third one, and the fifth must be located in between the first two. Then the result is also located in between
-- the third and fourth arguments similarly.
unsafeTransfer1I5
  :: RealFrac b => b
  -> b
  -> b
  -> b
  -> b
  -> b
unsafeTransfer1I5 minE0 maxE0 minE1 maxE1 x
 | minE0 == maxE0 = x
 | otherwise = minE1 + (x - minE0) * (maxE1 - minE1) / (maxE0 - minE0)
{-# INLINE unsafeTransfer1I5 #-}

-- | A variant of the 'unsafeTransfer1I5' where the lengths of the both intervals (the old and the new ones) are equal.
transfer1IEq3
  :: RealFrac b => b
  -> b
  -> b
  -> b
transfer1IEq3 minE0 minE1 = (+ (minE1 - minE0))
{-# INLINE transfer1IEq3 #-}