{-# LANGUAGE CPP                 #-}
{-# LANGUAGE ConstraintKinds     #-}
{-# LANGUAGE DefaultSignatures   #-}
{-# LANGUAGE FlexibleContexts    #-}
{-# LANGUAGE GADTs               #-}
{-# LANGUAGE RankNTypes          #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeOperators       #-}
#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 708
{-# LANGUAGE EmptyCase           #-}
#endif
-- | A 'ToExpr' class.
module Data.TreeDiff.Class (
    ediff,
    ediff',
    ToExpr (..),
    defaultExprViaShow,
    -- * Generics
    genericToExpr,
    GToExpr,
    ) where

import Data.Foldable    (toList)
import Data.List.Compat (uncons)
import Data.Proxy       (Proxy (..))
import GHC.Generics
       (Constructor (..), Generic (..), K1 (..), M1 (..), Selector (..),
       U1 (..), V1, (:*:) (..), (:+:) (..))

import qualified Data.Map           as Map
import qualified Data.TreeDiff.OMap as OMap

import Data.TreeDiff.Expr

-- Instances
import Control.Applicative   (Const (..), ZipList (..))
import Data.Fixed            (Fixed, HasResolution)
import Data.Functor.Identity (Identity (..))
import Data.Int
import Data.List.NonEmpty    (NonEmpty (..))
import Data.Void             (Void)
import Data.Word
import Numeric.Natural       (Natural)

#ifdef MIN_VERSION_generic_deriving
import Generics.Deriving.Instances ()
#endif

import qualified Data.Monoid    as Mon
import qualified Data.Ratio     as Ratio
import qualified Data.Semigroup as Semi

-- containers
import qualified Data.IntMap   as IntMap
import qualified Data.IntSet   as IntSet
import qualified Data.Sequence as Seq
import qualified Data.Set      as Set
import qualified Data.Tree     as Tree

-- text
import qualified Data.Text      as T
import qualified Data.Text.Lazy as LT

-- time
import qualified Data.Time as Time

-- bytestring
import qualified Data.ByteString      as BS
import qualified Data.ByteString.Lazy as LBS

import qualified Data.ByteString.Short as SBS

-- scientific
import qualified Data.Scientific as Sci

-- uuid-types
import qualified Data.UUID.Types as UUID

-- vector
import qualified Data.Vector           as V
import qualified Data.Vector.Primitive as VP
import qualified Data.Vector.Storable  as VS
import qualified Data.Vector.Unboxed   as VU

-- tagged
import Data.Tagged (Tagged (..))

-- hashable
import Data.Hashable (Hashed, unhashed)

-- unordered-containers
import qualified Data.HashMap.Strict as HM
import qualified Data.HashSet        as HS

-- aeson
import qualified Data.Aeson as Aeson
#if MIN_VERSION_aeson(2,0,0)
import qualified Data.Aeson.Key    as Key
import qualified Data.Aeson.KeyMap as KM
#endif

-- strict
import qualified Data.Strict as Strict

-- these
import Data.These (These (..))

-- primitive
import qualified Data.Primitive as Prim

#if MIN_VERSION_base(4,17,0)
import Data.Array.Byte (ByteArray (..))
#endif

-- $setup
-- >>> :set -XDeriveGeneric
-- >>> import Data.Foldable (traverse_)
-- >>> import Data.Ratio ((%))
-- >>> import Data.Time (Day (..))
-- >>> import Data.Scientific (Scientific)
-- >>> import GHC.Generics (Generic)
-- >>> import qualified Data.ByteString.Char8 as BS8
-- >>> import qualified Data.ByteString.Lazy.Char8 as LBS8
-- >>> import Data.TreeDiff.Pretty

-------------------------------------------------------------------------------
-- Code
-------------------------------------------------------------------------------

-- | Difference between two 'ToExpr' values.
--
-- >>> let x = (1, Just 2) :: (Int, Maybe Int)
-- >>> let y = (1, Nothing)
-- >>> prettyEditExpr (ediff x y)
-- _×_ 1 -(Just 2) +Nothing
--
-- >>> data Foo = Foo { fooInt :: Either Char Int, fooBool :: [Maybe Bool], fooString :: String } deriving (Eq, Generic)
-- >>> instance ToExpr Foo
--
-- >>> prettyEditExpr $ ediff (Foo (Right 2) [Just True] "fo") (Foo (Right 3) [Just True] "fo")
-- Foo {fooInt = Right -2 +3, fooBool = [Just True], fooString = "fo"}
--
-- >>> prettyEditExpr $ ediff (Foo (Right 42) [Just True, Just False] "old") (Foo (Right 42) [Nothing, Just False, Just True] "new")
-- Foo {
--   fooInt = Right 42,
--   fooBool = [-Just True, +Nothing, Just False, +Just True],
--   fooString = -"old" +"new"}
--
ediff :: ToExpr a => a -> a -> Edit EditExpr
ediff x y = exprDiff (toExpr x) (toExpr y)

-- | Compare different types.
--
-- /Note:/ Use with care as you can end up comparing apples with oranges.
--
-- >>> prettyEditExpr $ ediff' ["foo", "bar"] [Just "foo", Nothing]
-- [-"foo", +Just "foo", -"bar", +Nothing]
--
ediff' :: (ToExpr a, ToExpr b) => a -> b -> Edit EditExpr
ediff' x y = exprDiff (toExpr x) (toExpr y)

-- | 'toExpr' converts a Haskell value into
-- untyped Haskell-like syntax tree, 'Expr'.
--
-- >>> toExpr ((1, Just 2) :: (Int, Maybe Int))
-- App "_\215_" [App "1" [],App "Just" [App "2" []]]
--
class ToExpr a where
    toExpr :: a -> Expr
    default toExpr
        :: (Generic a, GToExpr (Rep a))
        => a -> Expr
    toExpr = genericToExpr

    listToExpr :: [a] -> Expr
    listToExpr = Lst . map toExpr

instance ToExpr Expr where
    toExpr = id

-- | An alternative implementation for literal types. We use 'show'
-- representation of them.
defaultExprViaShow :: Show a => a -> Expr
defaultExprViaShow x = App (show x) []

-------------------------------------------------------------------------------
-- Generics
-------------------------------------------------------------------------------

class GToExpr f where
    gtoExpr :: f x -> Expr

instance GSumToExpr f => GToExpr (M1 i c f) where
    gtoExpr (M1 x) = gsumToExpr x

class GSumToExpr f where
    gsumToExpr :: f x -> Expr

instance (GSumToExpr f, GSumToExpr g) => GSumToExpr (f :+: g) where
    gsumToExpr (L1 x) = gsumToExpr x
    gsumToExpr (R1 x) = gsumToExpr x

instance GSumToExpr V1 where
#if __GLASGOW_HASKELL__ >= 708
    gsumToExpr x = case x of {}
#else
    gsumToExpr x = x `seq` error "panic: V1 value"
#endif

instance (Constructor c, GProductToExpr f) => GSumToExpr (M1 i c f) where
    gsumToExpr z@(M1 x) = case gproductToExpr x of
        App' exprs   -> App cn exprs
        Rec' []      -> App cn []
        Rec' [(_,e)] -> App cn [e]
        Rec' pairs   -> Rec cn (OMap.fromList pairs)
      where
        cn = conName z

class GProductToExpr f where
    gproductToExpr :: f x -> AppOrRec

instance (GProductToExpr f, GProductToExpr g) => GProductToExpr (f :*: g) where
    gproductToExpr (f :*: g) = gproductToExpr f `combine` gproductToExpr g

instance GProductToExpr U1 where
    gproductToExpr _ = Rec' []

instance (Selector s, GLeafToExpr f) => GProductToExpr (M1 i s f) where
    gproductToExpr z@(M1 x) = case selName z of
        [] -> App' [gleafToExpr x]
        sn -> Rec' [(sn, gleafToExpr x)]

class GLeafToExpr f where
    gleafToExpr :: f x -> Expr

instance ToExpr x => GLeafToExpr (K1 i x) where
    gleafToExpr (K1 x) = toExpr x

data AppOrRec = App' [Expr] | Rec' [(FieldName, Expr)]
  deriving Show

combine :: AppOrRec -> AppOrRec -> AppOrRec
combine (Rec' xs) (Rec' ys) = Rec' (xs ++ ys)
combine xs        ys        = App' (exprs xs ++ exprs ys)
  where
    exprs (App' zs) = zs
    exprs (Rec' zs) = map snd zs

-- | Generic 'toExpr'.
--
-- >>> data Foo = Foo Int Char deriving Generic
-- >>> genericToExpr (Foo 42 'x')
-- App "Foo" [App "42" [],App "'x'" []]
--
genericToExpr :: (Generic a, GToExpr (Rep a)) => a -> Expr
genericToExpr = gtoExpr . from

-------------------------------------------------------------------------------
-- Instances
-------------------------------------------------------------------------------

instance ToExpr () where toExpr = defaultExprViaShow
instance ToExpr Bool where toExpr = defaultExprViaShow
instance ToExpr Ordering where toExpr = defaultExprViaShow

instance ToExpr Integer where toExpr = defaultExprViaShow
instance ToExpr Natural where toExpr = defaultExprViaShow

instance ToExpr Float where toExpr = defaultExprViaShow
instance ToExpr Double where toExpr = defaultExprViaShow

instance ToExpr Int where toExpr = defaultExprViaShow
instance ToExpr Int8 where toExpr = defaultExprViaShow
instance ToExpr Int16 where toExpr = defaultExprViaShow
instance ToExpr Int32 where toExpr = defaultExprViaShow
instance ToExpr Int64 where toExpr = defaultExprViaShow

instance ToExpr Word where toExpr = defaultExprViaShow
instance ToExpr Word8 where toExpr = defaultExprViaShow
instance ToExpr Word16 where toExpr = defaultExprViaShow
instance ToExpr Word32 where toExpr = defaultExprViaShow
instance ToExpr Word64 where toExpr = defaultExprViaShow

instance ToExpr (Proxy a) where toExpr = defaultExprViaShow

-- | >>> prettyExpr $ toExpr 'a'
-- 'a'
--
-- >>> prettyExpr $ toExpr "Hello world"
-- "Hello world"
--
-- >>> prettyExpr $ toExpr "Hello\nworld"
-- concat ["Hello\n", "world"]
--
-- >>> traverse_ (print . prettyExpr . toExpr) ["", "\n", "foo", "foo\n", "foo\nbar", "foo\nbar\n"]
-- ""
-- "\n"
-- "foo"
-- "foo\n"
-- concat ["foo\n", "bar"]
-- concat ["foo\n", "bar\n"]
--
instance ToExpr Char where
    toExpr = defaultExprViaShow
    listToExpr = stringToExpr "concat" . unconcat uncons

stringToExpr
    :: Show a
    => String -- ^ name of concat
    -> [a]
    -> Expr
stringToExpr _  []  = App "\"\"" []
stringToExpr _  [l] = defaultExprViaShow l
stringToExpr cn ls  = App cn [Lst (map defaultExprViaShow ls)]

-- | Split on '\n'.
--
-- prop> \xs -> xs == concat (unconcat uncons xs)
unconcat :: forall a. (a -> Maybe (Char, a)) -> a -> [String]
unconcat uncons_ = go where
    go :: a -> [String]
    go xs = case span_ xs of
        ~(ys, zs)
            | null ys   -> []
            | otherwise -> ys : go zs

    span_ :: a -> (String, a)
    span_ xs = case uncons_ xs of
        Nothing         -> ("", xs)
        Just ~(x, xs')
            | x == '\n' -> ("\n", xs')
            | otherwise -> case span_ xs' of
            ~(ys, zs) -> (x : ys, zs)

instance ToExpr a => ToExpr (Maybe a) where
    toExpr Nothing  = App "Nothing" []
    toExpr (Just x) = App "Just" [toExpr x]

instance (ToExpr a, ToExpr b) => ToExpr (Either a b) where
    toExpr (Left x)  = App "Left"  [toExpr x]
    toExpr (Right y) = App "Right" [toExpr y]

instance ToExpr a => ToExpr [a] where
    toExpr = listToExpr

instance (ToExpr a, ToExpr b) => ToExpr (a, b) where
    toExpr (a, b) = App "_×_" [toExpr a, toExpr b]
instance (ToExpr a, ToExpr b, ToExpr c) => ToExpr (a, b, c) where
    toExpr (a, b, c) = App "_×_×_" [toExpr a, toExpr b, toExpr c]
instance (ToExpr a, ToExpr b, ToExpr c, ToExpr d) => ToExpr (a, b, c, d) where
    toExpr (a, b, c, d) = App "_×_×_×_" [toExpr a, toExpr b, toExpr c, toExpr d]
instance (ToExpr a, ToExpr b, ToExpr c, ToExpr d, ToExpr e) => ToExpr (a, b, c, d, e) where
    toExpr (a, b, c, d, e) = App "_×_×_×_×_" [toExpr a, toExpr b, toExpr c, toExpr d, toExpr e]

-- | >>> prettyExpr $ toExpr (3 % 12 :: Rational)
-- _%_ 1 4
instance (ToExpr a, Integral a) => ToExpr (Ratio.Ratio a) where
    toExpr r = App "_%_" [ toExpr $ Ratio.numerator r, toExpr $ Ratio.denominator r ]
instance HasResolution a => ToExpr (Fixed a) where toExpr = defaultExprViaShow

-- | >>> prettyExpr $ toExpr $ Identity 'a'
-- Identity 'a'
instance ToExpr a => ToExpr (Identity a) where
    toExpr (Identity x) = App "Identity" [toExpr x]

instance ToExpr a => ToExpr (Const a b)
instance ToExpr a => ToExpr (ZipList a)

instance ToExpr a => ToExpr (NonEmpty a) where
    toExpr (x :| xs) = App "NE.fromList" [toExpr (x : xs)]

instance ToExpr Void where
    toExpr _ = App "error" [toExpr "Void"]

-------------------------------------------------------------------------------
-- Monoid/semigroups
-------------------------------------------------------------------------------

instance ToExpr a => ToExpr (Mon.Dual a) where
instance ToExpr a => ToExpr (Mon.Sum a) where
instance ToExpr a => ToExpr (Mon.Product a) where
instance ToExpr a => ToExpr (Mon.First a) where
instance ToExpr a => ToExpr (Mon.Last a) where

-- ...
#if !MIN_VERSION_base(4,16,0)
instance ToExpr a => ToExpr (Semi.Option a) where
    toExpr (Semi.Option x) = App "Option" [toExpr x]
#endif
instance ToExpr a => ToExpr (Semi.Min a) where
    toExpr (Semi.Min x) = App "Min" [toExpr x]
instance ToExpr a => ToExpr (Semi.Max a) where
    toExpr (Semi.Max x) = App "Max" [toExpr x]
instance ToExpr a => ToExpr (Semi.First a) where
    toExpr (Semi.First x) = App "First" [toExpr x]
instance ToExpr a => ToExpr (Semi.Last a) where
    toExpr (Semi.Last x) = App "Last" [toExpr x]

-------------------------------------------------------------------------------
-- containers
-------------------------------------------------------------------------------

instance ToExpr a => ToExpr (Tree.Tree a) where
    toExpr (Tree.Node x xs) = App "Node" [toExpr x, toExpr xs]

instance (ToExpr k, ToExpr v) => ToExpr (Map.Map k v) where
    toExpr x = App "Map.fromList" [ toExpr $ Map.toList x ]
instance (ToExpr k) => ToExpr (Set.Set k) where
    toExpr x = App "Set.fromList" [ toExpr $ Set.toList x ]
instance (ToExpr v) => ToExpr (IntMap.IntMap v) where
    toExpr x = App "IntMap.fromList" [ toExpr $ IntMap.toList x ]
instance ToExpr IntSet.IntSet where
    toExpr x = App "IntSet.fromList" [ toExpr $ IntSet.toList x ]
instance (ToExpr v) => ToExpr (Seq.Seq v) where
    toExpr x = App "Seq.fromList" [ toExpr $ toList x ]

-------------------------------------------------------------------------------
-- text
-------------------------------------------------------------------------------

-- | >>> traverse_ (print . prettyExpr . toExpr . LT.pack) ["", "\n", "foo", "foo\n", "foo\nbar", "foo\nbar\n"]
-- ""
-- "\n"
-- "foo"
-- "foo\n"
-- LT.concat ["foo\n", "bar"]
-- LT.concat ["foo\n", "bar\n"]
instance ToExpr LT.Text where
    toExpr = stringToExpr "LT.concat" . unconcat LT.uncons

-- | >>> traverse_ (print . prettyExpr . toExpr . T.pack) ["", "\n", "foo", "foo\n", "foo\nbar", "foo\nbar\n"]
-- ""
-- "\n"
-- "foo"
-- "foo\n"
-- T.concat ["foo\n", "bar"]
-- T.concat ["foo\n", "bar\n"]
instance ToExpr T.Text where
    toExpr = stringToExpr "T.concat" . unconcat T.uncons

-------------------------------------------------------------------------------
-- time
-------------------------------------------------------------------------------

-- | >>> prettyExpr $ toExpr $ ModifiedJulianDay 58014
-- Day "2017-09-18"
instance ToExpr Time.Day where
    toExpr d = App "Day" [ toExpr (show d) ]

instance ToExpr Time.UTCTime where
    toExpr t = App "UTCTime" [ toExpr (show t) ]

-------------------------------------------------------------------------------
-- bytestring
-------------------------------------------------------------------------------

-- | >>> traverse_ (print . prettyExpr . toExpr . LBS8.pack) ["", "\n", "foo", "foo\n", "foo\nbar", "foo\nbar\n"]
-- ""
-- "\n"
-- "foo"
-- "foo\n"
-- LBS.concat ["foo\n", "bar"]
-- LBS.concat ["foo\n", "bar\n"]
instance ToExpr LBS.ByteString where
    toExpr = stringToExpr "LBS.concat" . bsUnconcat LBS.null LBS.elemIndex LBS.splitAt

-- | >>> traverse_ (print . prettyExpr . toExpr . BS8.pack) ["", "\n", "foo", "foo\n", "foo\nbar", "foo\nbar\n"]
-- ""
-- "\n"
-- "foo"
-- "foo\n"
-- BS.concat ["foo\n", "bar"]
-- BS.concat ["foo\n", "bar\n"]
instance ToExpr BS.ByteString where
    toExpr = stringToExpr "BS.concat" . bsUnconcat BS.null BS.elemIndex BS.splitAt

-- | >>> traverse_ (print . prettyExpr . toExpr . SBS.toShort . BS8.pack) ["", "\n", "foo", "foo\n", "foo\nbar", "foo\nbar\n"]
-- ""
-- "\n"
-- "foo"
-- "foo\n"
-- mconcat ["foo\n", "bar"]
-- mconcat ["foo\n", "bar\n"]
instance ToExpr SBS.ShortByteString where
    toExpr = stringToExpr "mconcat" . bsUnconcat BS.null BS.elemIndex BS.splitAt . SBS.fromShort

bsUnconcat
    :: forall bs int. Num int
    => (bs -> Bool)
    -> (Word8 -> bs -> Maybe int)
    -> (int -> bs -> (bs, bs))
    -> bs
    -> [bs]
bsUnconcat null_ elemIndex_ splitAt_ = go where
    go :: bs -> [bs]
    go bs
        | null_ bs  = []
        | otherwise = case elemIndex_ 10 bs of
            Nothing -> [bs]
            Just i  -> case splitAt_ (i + 1) bs of
                (bs0, bs1) -> bs0 : go bs1

-------------------------------------------------------------------------------
-- scientific
-------------------------------------------------------------------------------

-- | >>> prettyExpr $ toExpr (123.456 :: Scientific)
-- scientific 123456 `-3`
instance ToExpr Sci.Scientific where
    toExpr s = App "scientific" [ toExpr $ Sci.coefficient s, toExpr $ Sci.base10Exponent s ]

-------------------------------------------------------------------------------
-- uuid-types
-------------------------------------------------------------------------------

-- | >>> prettyExpr $ toExpr UUID.nil
-- UUID "00000000-0000-0000-0000-000000000000"
instance ToExpr UUID.UUID where
    toExpr u = App "UUID" [ toExpr $ UUID.toString u ]

-------------------------------------------------------------------------------
-- vector
-------------------------------------------------------------------------------

instance ToExpr a => ToExpr (V.Vector a) where
    toExpr x = App "V.fromList" [ toExpr $ V.toList x ]
instance (ToExpr a, VU.Unbox a) => ToExpr (VU.Vector a) where
    toExpr x = App "VU.fromList" [ toExpr $ VU.toList x ]
instance (ToExpr a, VS.Storable a) => ToExpr (VS.Vector a) where
    toExpr x = App "VS.fromList" [ toExpr $ VS.toList x ]
instance (ToExpr a, VP.Prim a) => ToExpr (VP.Vector a) where
    toExpr x = App "VP.fromList" [ toExpr $ VP.toList x ]

-------------------------------------------------------------------------------
-- tagged
-------------------------------------------------------------------------------

instance ToExpr a => ToExpr (Tagged t a) where
    toExpr (Tagged x) = App "Tagged" [ toExpr x ]

-------------------------------------------------------------------------------
-- hashable
-------------------------------------------------------------------------------

instance ToExpr a => ToExpr (Hashed a) where
    toExpr x = App "hashed" [ toExpr $ unhashed x ]

-------------------------------------------------------------------------------
-- unordered-containers
-------------------------------------------------------------------------------

instance (ToExpr k, ToExpr v) => ToExpr (HM.HashMap k v) where
    toExpr x = App "HM.fromList" [ toExpr $ HM.toList x ]
instance (ToExpr k) => ToExpr (HS.HashSet k) where
    toExpr x = App "HS.fromList" [ toExpr $ HS.toList x ]

-------------------------------------------------------------------------------
-- aeson
-------------------------------------------------------------------------------

instance ToExpr Aeson.Value

#if MIN_VERSION_aeson(2,0,0)
instance ToExpr Key.Key where
    toExpr = stringToExpr "Key.concat" . unconcat T.uncons . Key.toText

instance ToExpr a => ToExpr (KM.KeyMap a) where
    toExpr x = App "KM.fromList" [ toExpr $ KM.toList x ]
#endif

-------------------------------------------------------------------------------
-- strict
-------------------------------------------------------------------------------

instance ToExpr a => ToExpr (Strict.Maybe a) where
    toExpr = toExpr . Strict.toLazy

instance (ToExpr a, ToExpr b) => ToExpr (Strict.Either a b) where
    toExpr = toExpr . Strict.toLazy

instance (ToExpr a, ToExpr b) => ToExpr (Strict.These a b) where
    toExpr = toExpr . Strict.toLazy

instance (ToExpr a, ToExpr b) => ToExpr (Strict.Pair a b) where
    toExpr = toExpr . Strict.toLazy

-------------------------------------------------------------------------------
-- these
-------------------------------------------------------------------------------

instance (ToExpr a, ToExpr b) => ToExpr (These a b) where
    toExpr (This x)    = App "This" [toExpr x]
    toExpr (That y)    = App "That" [toExpr y]
    toExpr (These x y) = App "These " [toExpr x, toExpr y]

-------------------------------------------------------------------------------
-- primitive
-------------------------------------------------------------------------------

-- | @since 0.2.2
instance ToExpr Prim.ByteArray where
    toExpr ba = App "Prim.byteArrayFromList" [toExpr (Prim.foldrByteArray (:) [] ba :: [Word8])]

#if MIN_VERSION_base(4,17,0)
-- | @since 0.2.2
instance ToExpr ByteArray where
    toExpr (ByteArray ba) = App "byteArrayFromList" [toExpr (Prim.foldrByteArray (:) [] (Prim.ByteArray ba) :: [Word8])]
#endif

-- TODO: add more instances