{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
-- |
-- Module      : Data.Massiv.Array.Manifest.Vector
-- Copyright   : (c) Alexey Kuleshevich 2018-2019
-- License     : BSD3
-- Maintainer  : Alexey Kuleshevich <lehins@yandex.ru>
-- Stability   : experimental
-- Portability : non-portable
--
module Data.Massiv.Array.Manifest.Vector
  ( fromVectorM
  , fromVector'
  , castFromVector
  , toVector
  , castToVector
  , ARepr
  , VRepr
  ) where

import Control.Monad (guard, join, msum)
import Data.Massiv.Array.Manifest.Boxed
import Data.Massiv.Array.Manifest.Internal
import Data.Massiv.Array.Manifest.Primitive
import Data.Massiv.Array.Manifest.Storable
import Data.Massiv.Array.Manifest.Unboxed
import Data.Massiv.Array.Mutable
import Data.Massiv.Core.Common
import Data.Maybe (fromMaybe)
import Data.Typeable
import qualified Data.Vector as VB
import qualified Data.Vector.Generic as VG
import qualified Data.Vector.Primitive as VP
import qualified Data.Vector.Storable as VS
import qualified Data.Vector.Unboxed as VU

-- | Match vector type to array representation
type family ARepr (v :: * -> *) :: * where
  ARepr VU.Vector = U
  ARepr VS.Vector = S
  ARepr VP.Vector = P
  ARepr VB.Vector = B

-- | Match array representation to a vector type
type family VRepr r :: * -> * where
  VRepr U = VU.Vector
  VRepr S = VS.Vector
  VRepr P = VP.Vector
  VRepr B = VB.Vector
  VRepr N = VB.Vector


-- | /O(1)/ - conversion from vector to an array with a corresponding representation. Will
-- return `Nothing` if there is a size mismatch or if some non-standard vector type is
-- supplied. Is suppplied is the boxed `Data.Vector.Vector` then it's all elements will be
-- evaluated toWHNF, therefore complexity will be /O(n)/
castFromVector :: forall v r ix e. (VG.Vector v e, Typeable v, Mutable r ix e, ARepr v ~ r)
               => Comp
               -> Sz ix -- ^ Size of the result Array
               -> v e -- ^ Source Vector
               -> Maybe (Array r ix e)
castFromVector comp sz vector = do
  guard (totalElem sz == VG.length vector)
  msum
    [ do Refl <- eqT :: Maybe (v :~: VU.Vector)
         uVector <- join $ gcast1 (Just vector)
         return $ UArray {uComp = comp, uSize = sz, uData = uVector}
    , do Refl <- eqT :: Maybe (v :~: VS.Vector)
         sVector <- join $ gcast1 (Just vector)
         return $ SArray {sComp = comp, sSize = sz, sData = sVector}
    , do Refl <- eqT :: Maybe (v :~: VP.Vector)
         VP.Vector o _ ba <- join $ gcast1 (Just vector)
         return $ PArray {pComp = comp, pSize = sz, pOffset = o, pData = ba}
    , do Refl <- eqT :: Maybe (v :~: VB.Vector)
         bVector <- join $ gcast1 (Just vector)
         let ba = unsafeFromBoxedVector bVector
         ba `seqArray` pure (unsafeResize sz ba)
    ]
{-# NOINLINE castFromVector #-}


-- | In case when resulting array representation matches the one of vector's it
-- will do a /O(1)/ - conversion using `castFromVector`, otherwise Vector elements
-- will be copied into a new array. Will throw an error if length of resulting
-- array doesn't match the source vector length.
--
-- @since 0.3.0
fromVectorM ::
     ( MonadThrow m
     , Typeable v
     , VG.Vector v a
     , Mutable (ARepr v) ix a
     , Mutable r ix a
     )
  => Comp
  -> Sz ix -- ^ Resulting size of the array
  -> v a -- ^ Source Vector
  -> m (Array r ix a)
fromVectorM comp sz v =
  case castFromVector comp sz v of
    Just arr -> pure $ convert arr
    Nothing -> do
      guardNumberOfElements sz (Sz (VG.length v))
      pure (makeArrayLinear comp sz (VG.unsafeIndex v))
{-# NOINLINE fromVectorM #-}


-- | Just like `fromVectorM`, but will throw an exception on a mismatched size.
--
-- @since 0.3.0
fromVector' ::
     (Typeable v, VG.Vector v a, Mutable (ARepr v) ix a, Mutable r ix a)
  => Comp
  -> Sz ix -- ^ Resulting size of the array
  -> v a -- ^ Source Vector
  -> Array r ix a
fromVector' comp sz = either throw id . fromVectorM comp sz
{-# INLINE fromVector' #-}

-- | /O(1)/ - conversion from `Mutable` array to a corresponding vector. Will
-- return `Nothing` only if source array representation was not one of `B`, `N`,
-- `P`, `S` or `U`.
castToVector ::
     forall v r ix e. (Mutable r ix e, VRepr r ~ v)
  => Array r ix e
  -> Maybe (v e)
castToVector arr =
  msum
    [ do Refl <- eqT :: Maybe (r :~: U)
         uArr <- gcastArr arr
         return $ uData uArr
    , do Refl <- eqT :: Maybe (r :~: S)
         sArr <- gcastArr arr
         return $ sData sArr
    , do Refl <- eqT :: Maybe (r :~: P)
         pArr <- gcastArr arr
         return $ VP.Vector (pOffset pArr) (totalElem (size arr)) $ pData pArr
    , do Refl <- eqT :: Maybe (r :~: B)
         bArr <- gcastArr arr
         return $ toBoxedVector bArr
    , do Refl <- eqT :: Maybe (r :~: N)
         bArr <- gcastArr arr
         return $ toBoxedVector $ bArray bArr
    ]
{-# NOINLINE castToVector #-}


-- | Convert an array into a vector. Will perform a cast if resulting vector is
-- of compatible representation, otherwise memory copy will occur.
--
-- ==== __Examples__
--
-- In this example a `S`torable Array is created and then casted into a Storable
-- `VS.Vector` in costant time:
--
-- >>> import Data.Massiv.Array as A
-- >>> import qualified Data.Vector.Storable as VS
-- >>> toVector (makeArrayR S Par (Sz2 5 6) (\(i :. j) -> i + j)) :: VS.Vector Int
-- [0,1,2,3,4,5,1,2,3,4,5,6,2,3,4,5,6,7,3,4,5,6,7,8,4,5,6,7,8,9]
--
-- While in this example `S`torable Array will first be converted into `U`nboxed
-- representation in `Par`allel and only after that will be coverted into Unboxed
-- `VU.Vector` in constant time.
--
-- >>> import qualified Data.Vector.Unboxed as VU
-- >>> toVector (makeArrayR S Par (Sz2 5 6) (\(i :. j) -> i + j)) :: VU.Vector Int
-- [0,1,2,3,4,5,1,2,3,4,5,6,2,3,4,5,6,7,3,4,5,6,7,8,4,5,6,7,8,9]
--
toVector ::
     forall r ix e v.
     ( Manifest r ix e
     , Mutable (ARepr v) ix e
     , VG.Vector v e
     , VRepr (ARepr v) ~ v
     )
  => Array r ix e
  -> v e
toVector arr =
  fromMaybe
    (VG.generate (totalElem (size arr)) (unsafeLinearIndex arr))
    (castToVector (convert arr :: Array (ARepr v) ix e))
{-# NOINLINE toVector #-}