{-# LANGUAGE FlexibleInstances, MultiParamTypeClasses #-}
{-
	Copyright (C) 2018 Dr. Alistair Ward

	This file is part of BishBosh.

	BishBosh is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	BishBosh is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with BishBosh.  If not, see <http://www.gnu.org/licenses/>.
-}
{- |
 [@AUTHOR@]	Dr. Alistair Ward

 [@DESCRIPTION@]

	* Defines the state of the game, without regard to how it arrived there; <https://www.chessprogramming.org/Chess_Position>.

	* Games with the same /position/ may be considered to have converged, since they now have equal opportunity.

	* N.B.: /piece/s are fungible, i.e. they lack identity, so the location of identical /piece/s may be exchanged, without altering the /position/.
-}

module BishBosh.State.Position(
-- * Types
-- ** Data-types
	Position(
--		MkPosition,
--		getNextLogicalColour,
--		getMaybePieceByCoordinates,
--		getCastleableRooksByLogicalColour,
		getMaybeEnPassantAbscissa
	),
-- * Functions
-- ** Constructors
	mkPosition
) where

import qualified	BishBosh.Attribute.LogicalColour		as Attribute.LogicalColour
import qualified	BishBosh.Component.Turn				as Component.Turn
import qualified	BishBosh.Component.Zobrist			as Component.Zobrist
import qualified	BishBosh.Property.Opposable			as Property.Opposable
import qualified	BishBosh.Property.Reflectable			as Property.Reflectable
import qualified	BishBosh.State.CastleableRooksByLogicalColour	as State.CastleableRooksByLogicalColour
import qualified	BishBosh.State.EnPassantAbscissa		as State.EnPassantAbscissa
import qualified	BishBosh.State.MaybePieceByCoordinates		as State.MaybePieceByCoordinates
import qualified	BishBosh.Type.Length				as Type.Length
import qualified	Control.DeepSeq
import qualified	Data.Array.IArray
import qualified	Data.Maybe

-- | The state of the game, without regard to how it arrived there.
data Position x y	= MkPosition {
	Position x y -> LogicalColour
getNextLogicalColour			:: Attribute.LogicalColour.LogicalColour,	-- ^ The next player to move.
	Position x y -> MaybePieceByCoordinates x y
getMaybePieceByCoordinates		:: State.MaybePieceByCoordinates.MaybePieceByCoordinates x y,
	Position x y -> CastleableRooksByLogicalColour x
getCastleableRooksByLogicalColour	:: State.CastleableRooksByLogicalColour.CastleableRooksByLogicalColour x,
	Position x y -> Maybe (EnPassantAbscissa x)
getMaybeEnPassantAbscissa		:: Maybe (State.EnPassantAbscissa.EnPassantAbscissa x)
} deriving Position x y -> Position x y -> Bool
(Position x y -> Position x y -> Bool)
-> (Position x y -> Position x y -> Bool) -> Eq (Position x y)
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
forall x y.
(Enum x, Enum y, Ord x, Ord y) =>
Position x y -> Position x y -> Bool
/= :: Position x y -> Position x y -> Bool
$c/= :: forall x y.
(Enum x, Enum y, Ord x, Ord y) =>
Position x y -> Position x y -> Bool
== :: Position x y -> Position x y -> Bool
$c== :: forall x y.
(Enum x, Enum y, Ord x, Ord y) =>
Position x y -> Position x y -> Bool
Eq

instance (
	Enum	x,
	Enum	y,
	Ord	x,
	Ord	y
 ) => Ord (Position x y) where
	{-# SPECIALISE instance Ord (Position Type.Length.X Type.Length.Y) #-}
	position :: Position x y
position@MkPosition {
		getNextLogicalColour :: forall x y. Position x y -> LogicalColour
getNextLogicalColour		= LogicalColour
nextLogicalColour,
		getMaybePieceByCoordinates :: forall x y. Position x y -> MaybePieceByCoordinates x y
getMaybePieceByCoordinates	= MaybePieceByCoordinates x y
maybePieceByCoordinates
	} compare :: Position x y -> Position x y -> Ordering
`compare` position' :: Position x y
position'@MkPosition {
		getNextLogicalColour :: forall x y. Position x y -> LogicalColour
getNextLogicalColour		= LogicalColour
nextLogicalColour',
		getMaybePieceByCoordinates :: forall x y. Position x y -> MaybePieceByCoordinates x y
getMaybePieceByCoordinates	= MaybePieceByCoordinates x y
maybePieceByCoordinates'
	} = (
		LogicalColour
nextLogicalColour,
		MaybePieceByCoordinates x y
maybePieceByCoordinates,
		Position x y -> CastleableRooksByLogicalColour x
forall x y. Position x y -> CastleableRooksByLogicalColour x
getCastleableRooksByLogicalColour Position x y
position,
		Position x y -> Maybe (EnPassantAbscissa x)
forall x y. Position x y -> Maybe (EnPassantAbscissa x)
getMaybeEnPassantAbscissa Position x y
position
	 ) (LogicalColour, MaybePieceByCoordinates x y,
 CastleableRooksByLogicalColour x, Maybe (EnPassantAbscissa x))
-> (LogicalColour, MaybePieceByCoordinates x y,
    CastleableRooksByLogicalColour x, Maybe (EnPassantAbscissa x))
-> Ordering
forall a. Ord a => a -> a -> Ordering
`compare` (
		LogicalColour
nextLogicalColour',
		MaybePieceByCoordinates x y
maybePieceByCoordinates',
		Position x y -> CastleableRooksByLogicalColour x
forall x y. Position x y -> CastleableRooksByLogicalColour x
getCastleableRooksByLogicalColour Position x y
position',
		Position x y -> Maybe (EnPassantAbscissa x)
forall x y. Position x y -> Maybe (EnPassantAbscissa x)
getMaybeEnPassantAbscissa Position x y
position'
	 )

instance (
	Control.DeepSeq.NFData	x,
	Control.DeepSeq.NFData	y
 ) => Control.DeepSeq.NFData (Position x y) where
	rnf :: Position x y -> ()
rnf MkPosition {
		getNextLogicalColour :: forall x y. Position x y -> LogicalColour
getNextLogicalColour			= LogicalColour
nextLogicalColour,
		getMaybePieceByCoordinates :: forall x y. Position x y -> MaybePieceByCoordinates x y
getMaybePieceByCoordinates		= MaybePieceByCoordinates x y
maybePieceByCoordinates,
		getCastleableRooksByLogicalColour :: forall x y. Position x y -> CastleableRooksByLogicalColour x
getCastleableRooksByLogicalColour	= CastleableRooksByLogicalColour x
castleableRooksByLogicalColour,
		getMaybeEnPassantAbscissa :: forall x y. Position x y -> Maybe (EnPassantAbscissa x)
getMaybeEnPassantAbscissa		= Maybe (EnPassantAbscissa x)
maybeEnPassantAbscissa
	} = (LogicalColour, MaybePieceByCoordinates x y,
 CastleableRooksByLogicalColour x, Maybe (EnPassantAbscissa x))
-> ()
forall a. NFData a => a -> ()
Control.DeepSeq.rnf (LogicalColour
nextLogicalColour, MaybePieceByCoordinates x y
maybePieceByCoordinates, CastleableRooksByLogicalColour x
castleableRooksByLogicalColour, Maybe (EnPassantAbscissa x)
maybeEnPassantAbscissa)

instance (
	Enum	x,
	Enum	y,
	Ord	x,
	Ord	y
 ) => Property.Reflectable.ReflectableOnX (Position x y) where
	reflectOnX :: Position x y -> Position x y
reflectOnX position :: Position x y
position@MkPosition {
		getNextLogicalColour :: forall x y. Position x y -> LogicalColour
getNextLogicalColour			= LogicalColour
nextLogicalColour,
		getMaybePieceByCoordinates :: forall x y. Position x y -> MaybePieceByCoordinates x y
getMaybePieceByCoordinates		= MaybePieceByCoordinates x y
maybePieceByCoordinates,
		getCastleableRooksByLogicalColour :: forall x y. Position x y -> CastleableRooksByLogicalColour x
getCastleableRooksByLogicalColour	= CastleableRooksByLogicalColour x
castleableRooksByLogicalColour
	} = Position x y
position {
		getNextLogicalColour :: LogicalColour
getNextLogicalColour			= LogicalColour -> LogicalColour
forall a. Opposable a => a -> a
Property.Opposable.getOpposite LogicalColour
nextLogicalColour,
		getMaybePieceByCoordinates :: MaybePieceByCoordinates x y
getMaybePieceByCoordinates		= MaybePieceByCoordinates x y -> MaybePieceByCoordinates x y
forall a. ReflectableOnX a => a -> a
Property.Reflectable.reflectOnX MaybePieceByCoordinates x y
maybePieceByCoordinates,
		getCastleableRooksByLogicalColour :: CastleableRooksByLogicalColour x
getCastleableRooksByLogicalColour	= CastleableRooksByLogicalColour x
-> CastleableRooksByLogicalColour x
forall a. ReflectableOnX a => a -> a
Property.Reflectable.reflectOnX CastleableRooksByLogicalColour x
castleableRooksByLogicalColour
	}

instance (Data.Array.IArray.Ix x, Enum x, Enum y, Ord y) => Component.Zobrist.Hashable2D Position x y {-CAVEAT: FlexibleInstances, MultiParamTypeClasses-} where
	listRandoms2D :: Position x y -> Zobrist x y positionHash -> [positionHash]
listRandoms2D MkPosition {
		getNextLogicalColour :: forall x y. Position x y -> LogicalColour
getNextLogicalColour			= LogicalColour
nextLogicalColour,
		getMaybePieceByCoordinates :: forall x y. Position x y -> MaybePieceByCoordinates x y
getMaybePieceByCoordinates		= MaybePieceByCoordinates x y
maybePieceByCoordinates,
		getCastleableRooksByLogicalColour :: forall x y. Position x y -> CastleableRooksByLogicalColour x
getCastleableRooksByLogicalColour	= CastleableRooksByLogicalColour x
castleableRooksByLogicalColour,
		getMaybeEnPassantAbscissa :: forall x y. Position x y -> Maybe (EnPassantAbscissa x)
getMaybeEnPassantAbscissa		= Maybe (EnPassantAbscissa x)
maybeEnPassantAbscissa
	} Zobrist x y positionHash
zobrist	= (
		if LogicalColour -> Bool
Attribute.LogicalColour.isBlack LogicalColour
nextLogicalColour
			then (Zobrist x y positionHash -> positionHash
forall x y positionHash. Zobrist x y positionHash -> positionHash
Component.Zobrist.getRandomForBlacksMove Zobrist x y positionHash
zobrist positionHash -> [positionHash] -> [positionHash]
forall a. a -> [a] -> [a]
:)
			else [positionHash] -> [positionHash]
forall a. a -> a
id
	 ) ([positionHash] -> [positionHash])
-> ([positionHash] -> [positionHash])
-> [positionHash]
-> [positionHash]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ([positionHash] -> [positionHash])
-> (EnPassantAbscissa x -> [positionHash] -> [positionHash])
-> Maybe (EnPassantAbscissa x)
-> [positionHash]
-> [positionHash]
forall b a. b -> (a -> b) -> Maybe a -> b
Data.Maybe.maybe [positionHash] -> [positionHash]
forall a. a -> a
id (
		[positionHash] -> [positionHash] -> [positionHash]
forall a. [a] -> [a] -> [a]
(++) ([positionHash] -> [positionHash] -> [positionHash])
-> (EnPassantAbscissa x -> [positionHash])
-> EnPassantAbscissa x
-> [positionHash]
-> [positionHash]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (EnPassantAbscissa x -> Zobrist x y positionHash -> [positionHash]
forall (hashable :: * -> *) x y positionHash.
Hashable1D hashable x =>
hashable x -> Zobrist x y positionHash -> [positionHash]
`Component.Zobrist.listRandoms1D` Zobrist x y positionHash
zobrist)
	 ) Maybe (EnPassantAbscissa x)
maybeEnPassantAbscissa ([positionHash] -> [positionHash])
-> [positionHash] -> [positionHash]
forall a b. (a -> b) -> a -> b
$ CastleableRooksByLogicalColour x
-> Zobrist x y positionHash -> [positionHash]
forall (hashable :: * -> *) x y positionHash.
Hashable1D hashable x =>
hashable x -> Zobrist x y positionHash -> [positionHash]
Component.Zobrist.listRandoms1D CastleableRooksByLogicalColour x
castleableRooksByLogicalColour Zobrist x y positionHash
zobrist [positionHash] -> [positionHash] -> [positionHash]
forall a. [a] -> [a] -> [a]
++ MaybePieceByCoordinates x y
-> Zobrist x y positionHash -> [positionHash]
forall (hashable :: * -> * -> *) x y positionHash.
Hashable2D hashable x y =>
hashable x y -> Zobrist x y positionHash -> [positionHash]
Component.Zobrist.listRandoms2D MaybePieceByCoordinates x y
maybePieceByCoordinates Zobrist x y positionHash
zobrist

-- | Constructor.
mkPosition :: (
	Enum	x,
	Enum	y,
	Ord	x,
	Ord	y
 )
	=> Attribute.LogicalColour.LogicalColour	-- ^ The logical colour of the next player to move.
	-> State.MaybePieceByCoordinates.MaybePieceByCoordinates x y
	-> State.CastleableRooksByLogicalColour.CastleableRooksByLogicalColour x
	-> Maybe (Component.Turn.Turn x y)		-- ^ The last /turn/ made.
	-> Position x y
{-# SPECIALISE mkPosition :: Attribute.LogicalColour.LogicalColour -> State.MaybePieceByCoordinates.MaybePieceByCoordinates Type.Length.X Type.Length.Y -> State.CastleableRooksByLogicalColour.CastleableRooksByLogicalColour Type.Length.X -> Maybe (Component.Turn.Turn Type.Length.X Type.Length.Y) -> Position Type.Length.X Type.Length.Y #-}
mkPosition :: LogicalColour
-> MaybePieceByCoordinates x y
-> CastleableRooksByLogicalColour x
-> Maybe (Turn x y)
-> Position x y
mkPosition LogicalColour
nextLogicalColour MaybePieceByCoordinates x y
maybePieceByCoordinates CastleableRooksByLogicalColour x
castleableRooksByLogicalColour Maybe (Turn x y)
maybeLastTurn	= MkPosition :: forall x y.
LogicalColour
-> MaybePieceByCoordinates x y
-> CastleableRooksByLogicalColour x
-> Maybe (EnPassantAbscissa x)
-> Position x y
MkPosition {
	getNextLogicalColour :: LogicalColour
getNextLogicalColour			= LogicalColour
nextLogicalColour,
	getMaybePieceByCoordinates :: MaybePieceByCoordinates x y
getMaybePieceByCoordinates		= MaybePieceByCoordinates x y
maybePieceByCoordinates,	-- N.B.: one could have used 'State.CoordinatesByRankByLogicalColour.CoordinatesByRankByLogicalColour', except that the coordinates have an undefined order.
	getCastleableRooksByLogicalColour :: CastleableRooksByLogicalColour x
getCastleableRooksByLogicalColour	= CastleableRooksByLogicalColour x
castleableRooksByLogicalColour,
	getMaybeEnPassantAbscissa :: Maybe (EnPassantAbscissa x)
getMaybeEnPassantAbscissa		= Maybe (Turn x y)
maybeLastTurn Maybe (Turn x y)
-> (Turn x y -> Maybe (EnPassantAbscissa x))
-> Maybe (EnPassantAbscissa x)
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= LogicalColour
-> MaybePieceByCoordinates x y
-> Turn x y
-> Maybe (EnPassantAbscissa x)
forall x y.
(Enum x, Enum y, Ord x, Ord y) =>
LogicalColour
-> MaybePieceByCoordinates x y
-> Turn x y
-> Maybe (EnPassantAbscissa x)
State.EnPassantAbscissa.mkMaybeEnPassantAbscissa LogicalColour
nextLogicalColour MaybePieceByCoordinates x y
maybePieceByCoordinates
}