{-|
Module      : Z.Data.Vector.FlatSet
Description : Fast set based on sorted vector
Copyright   : (c) Dong Han, 2017-2019
              (c) Tao He, 2018-2019
License     : BSD
Maintainer  : winterland1989@gmail.com
Stability   : experimental
Portability : non-portable

This module provides a simple value set based on sorted vector and binary search. It's particularly
suitable for small sized value collections such as deserializing intermediate representation.
But can also used in various place where insertion and deletion is rare but require fast elem.

-}

module Z.Data.Vector.FlatSet
  ( -- * FlatSet backed by sorted vector
    FlatSet, sortedValues, size, null, empty, map'
  , pack, packN, packR, packRN
  , unpack, unpackR, packVector, packVectorR
  , elem
  , delete
  , insert
  , merge
    -- * search on vectors
  , binarySearch
  ) where

import           Control.DeepSeq
import           Control.Monad
import           Control.Monad.ST
import qualified Data.Primitive.SmallArray  as A
import qualified Data.Semigroup             as Semigroup
import qualified Data.Monoid                as Monoid
import qualified Z.Data.Vector.Base         as V
import qualified Z.Data.Vector.Sort         as V
import qualified Z.Data.Text.ShowT          as T
import           Data.Bits                   (shiftR)
import           Data.Data
import           Prelude hiding (elem, null)
import           Test.QuickCheck.Arbitrary (Arbitrary(..), CoArbitrary(..))

--------------------------------------------------------------------------------

newtype FlatSet v = FlatSet { sortedValues :: V.Vector v }
    deriving (Show, Eq, Ord, Typeable, Foldable)

instance T.ShowT v => T.ShowT (FlatSet v) where
    {-# INLINE toUTF8BuilderP #-}
    toUTF8BuilderP p (FlatSet vec) = T.parenWhen (p > 10) $ do
        "FlatSet{"
        T.intercalateVec T.comma T.toUTF8Builder vec
        T.char7 '}'

instance Ord v => Semigroup.Semigroup (FlatSet v) where
    {-# INLINE (<>) #-}
    (<>) = merge

instance Ord v => Monoid.Monoid (FlatSet v) where
    {-# INLINE mappend #-}
    mappend = merge
    {-# INLINE mempty #-}
    mempty = empty

instance NFData v => NFData (FlatSet v) where
    {-# INLINE rnf #-}
    rnf (FlatSet vs) = rnf vs

instance (Ord v, Arbitrary v) => Arbitrary (FlatSet v) where
    arbitrary = pack <$> arbitrary
    shrink v = pack <$> shrink (unpack v)

instance (CoArbitrary v) => CoArbitrary (FlatSet v) where
    coarbitrary = coarbitrary . unpack

size :: FlatSet v -> Int
{-# INLINE size #-}
size = V.length . sortedValues

null :: FlatSet v -> Bool
{-# INLINE null #-}
null = V.null . sortedValues

-- | Mapping values of within a set, the result size may change if there're duplicated values
-- after mapping.
map' :: forall v. Ord v => (v -> v) -> FlatSet v -> FlatSet v
{-# INLINE map' #-}
map' f (FlatSet vs) = packVector (V.map' f vs :: V.Vector v)

-- | /O(1)/ empty flat set.
empty :: FlatSet v
{-# INLINE empty #-}
empty = FlatSet V.empty

-- | /O(N*logN)/ Pack list of values, on duplication prefer left one.
pack :: Ord v => [v] -> FlatSet v
{-# INLINE pack #-}
pack vs = FlatSet (V.mergeDupAdjacentLeft (==) (V.mergeSort (V.pack vs)))

-- | /O(N*logN)/ Pack list of values with suggested size, on duplication prefer left one.
packN :: Ord v => Int -> [v] -> FlatSet v
{-# INLINE packN #-}
packN n vs = FlatSet (V.mergeDupAdjacentLeft (==) (V.mergeSort (V.packN n vs)))

-- | /O(N*logN)/ Pack list of values, on duplication prefer right one.
packR :: Ord v => [v] -> FlatSet v
{-# INLINE packR #-}
packR vs = FlatSet (V.mergeDupAdjacentRight (==) (V.mergeSort (V.pack vs)))

-- | /O(N*logN)/ Pack list of values with suggested size, on duplication prefer right one.
packRN :: Ord v => Int -> [v] -> FlatSet v
{-# INLINE packRN #-}
packRN n vs = FlatSet (V.mergeDupAdjacentRight (==) (V.mergeSort (V.packN n vs)))

-- | /O(N)/ Unpack a set of values to a list s in ascending order.
--
-- This function works with @foldr/build@ fusion in base.
unpack :: FlatSet v -> [v]
{-# INLINE unpack #-}
unpack = V.unpack . sortedValues

-- | /O(N)/ Unpack a set of values to a list s in descending order.
--
-- This function works with @foldr/build@ fusion in base.
unpackR :: FlatSet v -> [v]
{-# INLINE unpackR #-}
unpackR = V.unpackR . sortedValues

-- | /O(N*logN)/ Pack vector of values, on duplication prefer left one.
packVector :: Ord v => V.Vector v -> FlatSet v
{-# INLINE packVector #-}
packVector vs = FlatSet (V.mergeDupAdjacentLeft (==) (V.mergeSort vs))

-- | /O(N*logN)/ Pack vector of values, on duplication prefer right one.
packVectorR :: Ord v => V.Vector v -> FlatSet v
{-# INLINE packVectorR #-}
packVectorR vs = FlatSet (V.mergeDupAdjacentRight (==) (V.mergeSort vs))

-- | /O(logN)/ Binary search on flat set.
elem :: Ord v => v -> FlatSet v -> Bool
{-# INLINE elem #-}
elem v (FlatSet vec) = case binarySearch vec v of Left _ -> False
                                                  _      -> True

-- | /O(N)/ Insert new value into set.
insert :: Ord v => v -> FlatSet v -> FlatSet v
{-# INLINE insert #-}
insert v m@(FlatSet vec@(V.Vector arr s l)) =
    case binarySearch vec v of
        Left i -> FlatSet (V.create (l+1) (\ marr -> do
            when (i>0) $ A.copySmallArray marr 0 arr s i
            A.writeSmallArray marr i v
            when (i<l) $ A.copySmallArray marr (i+1) arr (i+s) (l-i)))
        Right _ -> m

-- | /O(N)/ Delete a value from set.
delete :: Ord v => v -> FlatSet v -> FlatSet v
{-# INLINE delete #-}
delete v m@(FlatSet vec@(V.Vector arr s l)) =
    case binarySearch vec v of
        Left _ -> m
        Right i -> FlatSet $ V.create (l-1) (\ marr -> do
            when (i>0) $ A.copySmallArray marr 0 arr s i
            let i' = i+1
            when (i'<l) $ A.copySmallArray marr i arr (i'+s) (l-i'))

-- | /O(n+m)/ Merge two 'FlatSet', prefer right value on value duplication.
merge :: forall v . Ord v => FlatSet v -> FlatSet v -> FlatSet v
{-# INLINE merge #-}
merge fmL@(FlatSet (V.Vector arrL sL lL)) fmR@(FlatSet (V.Vector arrR sR lR))
    | null fmL = fmR
    | null fmR = fmL
    | otherwise = FlatSet (V.createN (lL+lR) (go sL sR 0))
  where
    endL = sL + lL
    endR = sR + lR
    go :: Int -> Int -> Int -> A.SmallMutableArray s v -> ST s Int
    go !i !j !k marr
        | i >= endL = do
            A.copySmallArray marr k arrR j (lR-j)
            return $! k+lR-j
        | j >= endR = do
            A.copySmallArray marr k arrL i (lL-i)
            return $! k+lL-i
        | otherwise = do
            vL <- arrL `A.indexSmallArrayM` i
            vR <- arrR `A.indexSmallArrayM` j
            case vL `compare` vR of LT -> do A.writeSmallArray marr k vL
                                             go (i+1) j (k+1) marr
                                    EQ -> do A.writeSmallArray marr k vR
                                             go (i+1) (j+1) (k+1) marr
                                    _  -> do A.writeSmallArray marr k vR
                                             go i (j+1) (k+1) marr

--------------------------------------------------------------------------------

-- | Find the value's index in the vector, if value exists return 'Right',
-- otherwise 'Left', i.e. the insert index
--
-- This function only works on ascending sorted vectors.
binarySearch :: Ord v => V.Vector v -> v -> Either Int Int
{-# INLINABLE binarySearch #-}
binarySearch (V.Vector _ _ 0) _   = Left 0
binarySearch (V.Vector arr s0 l) !v' = go s0 (s0+l-1)
  where
    go !s !e
        | s == e =
            let v = arr `A.indexSmallArray` s
            in case v' `compare` v of LT -> Left (s-s0)
                                      GT -> let !s' = s+1 in Left (s'-s0)
                                      _  -> Right (s-s0)
        | s >  e = Left s
        | otherwise =
            let !mid = (s+e) `shiftR` 1
                v = arr `A.indexSmallArray` mid
            in case v' `compare` v of LT -> go s (mid-1)
                                      GT -> go (mid+1) e
                                      _  -> Right (mid-s0)