{-# LANGUAGE FlexibleContexts    #-}
{-# LANGUAGE FlexibleInstances   #-}
{-# LANGUAGE InstanceSigs        #-}
{-# LANGUAGE ScopedTypeVariables #-}

module HaskellWorks.Data.BalancedParens.Broadword.Word16
  ( findUnmatchedCloseFar
  ) where

import Data.Int
import Data.Word
import HaskellWorks.Data.Bits.BitWise
import HaskellWorks.Data.Bits.Broadword.Word16

muk1 :: Word16
muk1 = 0x3333
{-# INLINE muk1 #-}

muk2 :: Word16
muk2 = 0x0f0f
{-# INLINE muk2 #-}

muk3 :: Word16
muk3 = 0x00ff
{-# INLINE muk3 #-}

-- | Find the position of the first unmatch parenthesis.
--
-- This is the broadword implementation of 'HaskellWorks.Data.BalancedParens.Internal.Slow.Word16.findCloseFor'.
--
-- See [Broadword Implementation of Parenthesis Queries](https://arxiv.org/pdf/1301.5468.pdf), Sebastiano Vigna, 2013
findUnmatchedCloseFar :: Word16 -> Word16 -> Word16
findUnmatchedCloseFar p w =
  let x     = w .>. fromIntegral p                                                        in
  let wsz   = 16 :: Int16                                                                 in
  let k1    = 1                                                                           in
  let k2    = 2                                                                           in
  let k3    = 3                                                                           in
  let k4    = 4                                                                           in
  let mask1 = (1 .<. (1 .<. k1)) - 1                                                      in
  let mask2 = (1 .<. (1 .<. k2)) - 1                                                      in
  let mask3 = (1 .<. (1 .<. k3)) - 1                                                      in
  let mask4 = (1 .<. (1 .<. k4)) - 1                                                      in
  let t64k1 = 1 .<. k1 :: Word64                                                          in
  let t64k2 = 1 .<. k2 :: Word64                                                          in
  let t64k3 = 1 .<. k3 :: Word64                                                          in
  let t8k1  = 1 .<. k1 :: Word16                                                          in
  let t8k2  = 1 .<. k2 :: Word16                                                          in
  let t8k3  = 1 .<. k3 :: Word16                                                          in
  let t8k4  = 1 .<. k4 :: Word16                                                          in

  let b0    =      x .&. 0x5555                                                           in
  let b1    =    ( x .&. 0xaaaa) .>. 1                                                    in
  let ll    =   (b0  .^. b1  ) .&. b1                                                     in
  let ok1   = ( (b0  .&. b1  )             .<. 1) .|. ll                                  in
  let ck1   = (((b0  .|. b1  ) .^. 0x5555) .<. 1) .|. ll                                  in

  let eok1 =   ok1 .&.  muk1                                                              in
  let eck1 =  (ck1 .&. (muk1 .<. t64k1)) .>. t64k1                                        in
  let ok2L =  (ok1 .&. (muk1 .<. t64k1)) .>. t64k1                                        in
  let ok2R = kBitDiffPos 4 eok1 eck1                                                      in
  let ok2  = ok2L + ok2R                                                                  in
  let ck2  =  (ck1 .&.  muk1) + kBitDiffPos 4 eck1 eok1                                   in

  let eok2 =   ok2 .&.  muk2                                                              in
  let eck2 =  (ck2 .&. (muk2 .<. t64k2)) .>. t64k2                                        in
  let ok3L =  (ok2 .&. (muk2 .<. t64k2)) .>. t64k2                                        in
  let ok3R = kBitDiffPos 8 eok2 eck2                                                      in
  let ok3  = ok3L + ok3R                                                                  in
  let ck3  =  (ck2 .&.  muk2) + kBitDiffPos 8 eck2 eok2                                   in

  let eok3 =   ok3 .&.  muk3                                                              in
  let eck3 =  (ck3 .&. (muk3 .<. t64k3)) .>. t64k3                                        in
  let ok4L =  (ok3 .&. (muk3 .<. t64k3)) .>. t64k3                                        in
  let ok4R = kBitDiffPos 16 eok3 eck3                                                     in
  let ok4  = ok4L + ok4R                                                                  in
  let ck4  =  (ck3 .&.  muk3) + kBitDiffPos 16 eck3 eok3                                  in

  let pak4  = 0                                                                           in
  let sak4  = 0                                                                           in

  let fk4   = (ck4 .>. fromIntegral sak4) .&. mask4                                       in
  let bk4   = ((pak4 - fk4) .>. fromIntegral (wsz - 1)) - 1                               in
  let mk4   = bk4 .&. mask4                                                               in
  let pbk4  = pak4 - ((ck4 .>. fromIntegral sak4) .&. mk4)                                in
  let pck4  = pbk4 + ((ok4 .>. fromIntegral sak4) .&. mk4)                                in
  let sbk4  = sak4 + (t8k4 .&. bk4)                                                       in

  let pak3  = pck4                                                                        in
  let sak3  = sbk4                                                                        in

  let ek3   = 0x0808 .&. comp (0xffff .>. fromIntegral sak3)                              in
  let fk3   = ((ck3 .>. fromIntegral sak3) .|. ek3) .&. mask3                             in
  let bk3   = ((pak3 - fk3) .>. fromIntegral (wsz - 1)) - 1                               in
  let mk3   = bk3 .&. mask3                                                               in
  let pbk3  = pak3 - (((ck3 .>. fromIntegral sak3) .|. ek3) .&. mk3)                      in
  let pck3  = pbk3 + ( (ok3 .>. fromIntegral sak3)          .&. mk3)                      in
  let sbk3  = sak3 + (t8k3 .&. bk3)                                                       in

  let pak2  = pck3                                                                        in
  let sak2  = sbk3                                                                        in

  let ek2   = 0xaaaa .&. comp (0xffff .>. fromIntegral sak2)                              in
  let fk2   = ((ck2 .>. fromIntegral sak2) .|. ek2) .&. mask2                             in
  let bk2   = ((pak2 - fk2) .>. fromIntegral (wsz - 1)) - 1                               in
  let mk2   = bk2 .&. mask2                                                               in
  let pbk2  = pak2 - (((ck2 .>. fromIntegral sak2) .|. ek2) .&. mk2)                      in
  let pck2  = pbk2 + ( (ok2 .>. fromIntegral sak2)          .&. mk2)                      in
  let sbk2  = sak2 + (t8k2 .&. bk2)                                                       in

  let pak1  = pck2                                                                        in
  let sak1  = sbk2                                                                        in

  let ek1   = 0xaaaa .&. comp (0xffff .>. fromIntegral sak1)                              in
  let fk1   = ((ck1 .>. fromIntegral sak1) .|. ek1) .&. mask1                             in
  let bk1   = ((pak1 - fk1) .>. fromIntegral (wsz - 1)) - 1                               in
  let mk1   = bk1  .&. mask1                                                              in
  let pbk1  = pak1 - (((ck1 .>. fromIntegral sak1) .|. ek1) .&. mk1)                      in
  let pck1  = pbk1 + ( (ok1 .>. fromIntegral sak1)          .&. mk1)                      in
  let sbk1  = sak1 + (t8k1 .&. bk1)                                                       in

  let rrr   = sbk1 + pck1 + (((x .>. fromIntegral sbk1) .&. ((pck1 .<. 1) .|. 1)) .<. 1)  in

  rrr + p
{-# INLINE findUnmatchedCloseFar #-}