{-
	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@]	Records the number of times each /position/ has been encountered.
-}

module BishBosh.State.InstancesByPosition(
-- * Types
-- ** Type-synonyms
--	NBoardsByPosition,
--	Transformation.
-- * Constants
	leastCyclicPlies,
-- ** Data-types
	InstancesByPosition(),
-- * Functions
	countConsecutiveRepeatablePlies,
	countPositionRepetitions,
	getNDistinctPositions,
-- ** Constructors
	mkInstancesByPosition,
	mkSingleton,
-- ** Mutators
	insertPosition,
	deletePosition,
-- ** Predicates
	anyInstancesByPosition
) where

import qualified	BishBosh.Component.Move		as Component.Move
import qualified	BishBosh.Data.Exception		as Data.Exception
import qualified	BishBosh.Property.Reflectable	as Property.Reflectable
import qualified	BishBosh.State.Board		as State.Board
import qualified	Control.DeepSeq
import qualified	Control.Exception
import qualified	Data.Foldable
import qualified	Data.Map
import qualified	Data.Map.Strict

-- | The smallast number of repeatable plies required to form a cycle.
leastCyclicPlies :: Component.Move.NMoves
leastCyclicPlies :: NMoves
leastCyclicPlies	= NMoves
4

{- |
	* The number of times each /position/ has been encountered.

	* The /position/ can either be represented by a physical 'State.Position.Position', or by proxy using a hash.
-}
type NBoardsByPosition position	= Data.Map.Map position State.Board.NBoards

{- |
	* A count of the number of instances of /position/s which have occurred.

	* Greater than '1' represents a repetition.
-}
newtype InstancesByPosition position	= MkInstancesByPosition {
	InstancesByPosition position -> NBoardsByPosition position
getNBoardsByPosition	:: NBoardsByPosition position
} deriving InstancesByPosition position
-> InstancesByPosition position -> Bool
(InstancesByPosition position
 -> InstancesByPosition position -> Bool)
-> (InstancesByPosition position
    -> InstancesByPosition position -> Bool)
-> Eq (InstancesByPosition position)
forall position.
Eq position =>
InstancesByPosition position
-> InstancesByPosition position -> Bool
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
/= :: InstancesByPosition position
-> InstancesByPosition position -> Bool
$c/= :: forall position.
Eq position =>
InstancesByPosition position
-> InstancesByPosition position -> Bool
== :: InstancesByPosition position
-> InstancesByPosition position -> Bool
$c== :: forall position.
Eq position =>
InstancesByPosition position
-> InstancesByPosition position -> Bool
Eq

instance Control.DeepSeq.NFData position => Control.DeepSeq.NFData (InstancesByPosition position) where
	rnf :: InstancesByPosition position -> ()
rnf MkInstancesByPosition { getNBoardsByPosition :: forall position.
InstancesByPosition position -> NBoardsByPosition position
getNBoardsByPosition = NBoardsByPosition position
m }	= NBoardsByPosition position -> ()
forall a. NFData a => a -> ()
Control.DeepSeq.rnf NBoardsByPosition position
m

instance (
	Ord					position,
	Property.Reflectable.ReflectableOnX	position
 ) => Property.Reflectable.ReflectableOnX (InstancesByPosition position) where
	reflectOnX :: InstancesByPosition position -> InstancesByPosition position
reflectOnX MkInstancesByPosition { getNBoardsByPosition :: forall position.
InstancesByPosition position -> NBoardsByPosition position
getNBoardsByPosition = NBoardsByPosition position
m }	= NBoardsByPosition position -> InstancesByPosition position
forall position.
NBoardsByPosition position -> InstancesByPosition position
MkInstancesByPosition (NBoardsByPosition position -> InstancesByPosition position)
-> NBoardsByPosition position -> InstancesByPosition position
forall a b. (a -> b) -> a -> b
$ (position -> position)
-> NBoardsByPosition position -> NBoardsByPosition position
forall k2 k1 a. Ord k2 => (k1 -> k2) -> Map k1 a -> Map k2 a
Data.Map.mapKeys position -> position
forall a. ReflectableOnX a => a -> a
Property.Reflectable.reflectOnX NBoardsByPosition position
m

-- | Smart constructor.
mkInstancesByPosition :: NBoardsByPosition position -> InstancesByPosition position
mkInstancesByPosition :: NBoardsByPosition position -> InstancesByPosition position
mkInstancesByPosition NBoardsByPosition position
nBoardsByPosition
	| (NMoves -> Bool) -> NBoardsByPosition position -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
Data.Foldable.any (NMoves -> NMoves -> Bool
forall a. Ord a => a -> a -> Bool
< NMoves
1) NBoardsByPosition position
nBoardsByPosition	= Exception -> InstancesByPosition position
forall a e. Exception e => e -> a
Control.Exception.throw (Exception -> InstancesByPosition position)
-> Exception -> InstancesByPosition position
forall a b. (a -> b) -> a -> b
$ String -> Exception
Data.Exception.mkOutOfBounds String
"BishBosh.State.InstancesByPosition.mkInstancesByPosition:\teach specified position must have been visited at least once."
	| Bool
otherwise					= NBoardsByPosition position -> InstancesByPosition position
forall position.
NBoardsByPosition position -> InstancesByPosition position
MkInstancesByPosition NBoardsByPosition position
nBoardsByPosition

-- | Constructor.
mkSingleton :: position -> InstancesByPosition position
mkSingleton :: position -> InstancesByPosition position
mkSingleton position
position	= NBoardsByPosition position -> InstancesByPosition position
forall position.
NBoardsByPosition position -> InstancesByPosition position
MkInstancesByPosition (NBoardsByPosition position -> InstancesByPosition position)
-> NBoardsByPosition position -> InstancesByPosition position
forall a b. (a -> b) -> a -> b
$ position -> NMoves -> NBoardsByPosition position
forall k a. k -> a -> Map k a
Data.Map.singleton position
position NMoves
1

-- | Count the total number of consecutive repeatable plies amongst recent moves.
countConsecutiveRepeatablePlies :: InstancesByPosition position -> Component.Move.NMoves
countConsecutiveRepeatablePlies :: InstancesByPosition position -> NMoves
countConsecutiveRepeatablePlies MkInstancesByPosition { getNBoardsByPosition :: forall position.
InstancesByPosition position -> NBoardsByPosition position
getNBoardsByPosition = NBoardsByPosition position
m }	= (NMoves -> NMoves -> NMoves)
-> NMoves -> NBoardsByPosition position -> NMoves
forall a b k. (a -> b -> a) -> a -> Map k b -> a
Data.Map.foldl' NMoves -> NMoves -> NMoves
forall a. Num a => a -> a -> a
(+) (
	NMoves -> NMoves
forall a. Num a => a -> a
negate NMoves
1	-- The map is never empty, since before the first move a singleton is constructed with the initial position.
 ) NBoardsByPosition position
m

-- | Count the total number of repetitions of /position/s.
countPositionRepetitions :: InstancesByPosition position -> State.Board.NBoards
countPositionRepetitions :: InstancesByPosition position -> NMoves
countPositionRepetitions MkInstancesByPosition { getNBoardsByPosition :: forall position.
InstancesByPosition position -> NBoardsByPosition position
getNBoardsByPosition = NBoardsByPosition position
m }	= (NMoves -> NMoves -> NMoves)
-> NMoves -> NBoardsByPosition position -> NMoves
forall a b k. (a -> b -> a) -> a -> Map k b -> a
Data.Map.foldl' (
	NMoves -> NMoves -> NMoves
forall a. Num a => a -> a -> a
(+) (NMoves -> NMoves -> NMoves)
-> (NMoves -> NMoves) -> NMoves -> NMoves -> NMoves
forall b c a. (b -> c) -> (a -> b) -> a -> c
. NMoves -> NMoves
forall a. Enum a => a -> a
pred	-- The initial instance isn't a repetition.
 ) NMoves
0 NBoardsByPosition position
m

-- | The number of distinct /position/s.
getNDistinctPositions :: InstancesByPosition position -> State.Board.NBoards
getNDistinctPositions :: InstancesByPosition position -> NMoves
getNDistinctPositions MkInstancesByPosition { getNBoardsByPosition :: forall position.
InstancesByPosition position -> NBoardsByPosition position
getNBoardsByPosition = NBoardsByPosition position
m }	= NBoardsByPosition position -> NMoves
forall k a. Map k a -> NMoves
Data.Map.size NBoardsByPosition position
m

-- | Predicate: apply the specified predicate to the map.
anyInstancesByPosition
	:: (State.Board.NBoards -> Bool)
	-> InstancesByPosition position
	-> Bool
anyInstancesByPosition :: (NMoves -> Bool) -> InstancesByPosition position -> Bool
anyInstancesByPosition NMoves -> Bool
predicate MkInstancesByPosition { getNBoardsByPosition :: forall position.
InstancesByPosition position -> NBoardsByPosition position
getNBoardsByPosition = NBoardsByPosition position
m }	= (NMoves -> Bool) -> NBoardsByPosition position -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
Data.Foldable.any NMoves -> Bool
predicate NBoardsByPosition position
m

-- | The type of a function which transforms the collection.
type Transformation position	= InstancesByPosition position -> InstancesByPosition position

-- | Insert a /position/ into the collection.
insertPosition
	:: Ord position
	=> Bool	-- ^ Whether the /turn/ which led to the specified /position/, was repeatable.
	-> position
	-> Transformation position
insertPosition :: Bool -> position -> Transformation position
insertPosition Bool
isRepeatable position
position MkInstancesByPosition { getNBoardsByPosition :: forall position.
InstancesByPosition position -> NBoardsByPosition position
getNBoardsByPosition = NBoardsByPosition position
m }	= NBoardsByPosition position -> InstancesByPosition position
forall position.
NBoardsByPosition position -> InstancesByPosition position
MkInstancesByPosition (NBoardsByPosition position -> InstancesByPosition position)
-> NBoardsByPosition position -> InstancesByPosition position
forall a b. (a -> b) -> a -> b
$ if Bool
isRepeatable
	then (NMoves -> NMoves -> NMoves)
-> position
-> NMoves
-> NBoardsByPosition position
-> NBoardsByPosition position
forall k a. Ord k => (a -> a -> a) -> k -> a -> Map k a -> Map k a
Data.Map.Strict.insertWith ((NMoves -> NMoves) -> NMoves -> NMoves -> NMoves
forall a b. a -> b -> a
const NMoves -> NMoves
forall a. Enum a => a -> a
succ) position
position NMoves
1 NBoardsByPosition position
m	-- Include this position.
	else position -> NMoves -> NBoardsByPosition position
forall k a. k -> a -> Map k a
Data.Map.singleton position
position NMoves
1				-- The previous position can't be revisited without rolling-back.

-- | Remove a /position/ from the collection, as required to implement rollback.
deletePosition :: Ord position => position -> Transformation position
deletePosition :: position -> Transformation position
deletePosition position
position MkInstancesByPosition { getNBoardsByPosition :: forall position.
InstancesByPosition position -> NBoardsByPosition position
getNBoardsByPosition = NBoardsByPosition position
m }	= Bool -> Transformation position
forall a. (?callStack::CallStack) => Bool -> a -> a
Control.Exception.assert (position -> NBoardsByPosition position -> Bool
forall k a. Ord k => k -> Map k a -> Bool
Data.Map.member position
position NBoardsByPosition position
m) Transformation position
-> (NBoardsByPosition position -> InstancesByPosition position)
-> NBoardsByPosition position
-> InstancesByPosition position
forall b c a. (b -> c) -> (a -> b) -> a -> c
. NBoardsByPosition position -> InstancesByPosition position
forall position.
NBoardsByPosition position -> InstancesByPosition position
MkInstancesByPosition (NBoardsByPosition position -> InstancesByPosition position)
-> NBoardsByPosition position -> InstancesByPosition position
forall a b. (a -> b) -> a -> b
$ (NMoves -> Maybe NMoves)
-> position
-> NBoardsByPosition position
-> NBoardsByPosition position
forall k a. Ord k => (a -> Maybe a) -> k -> Map k a -> Map k a
Data.Map.update (
		\NMoves
n -> if NMoves
n NMoves -> NMoves -> Bool
forall a. Eq a => a -> a -> Bool
== NMoves
1
			then Maybe NMoves
forall a. Maybe a
Nothing		-- Delete the entry.
			else NMoves -> Maybe NMoves
forall a. a -> Maybe a
Just (NMoves -> Maybe NMoves) -> NMoves -> Maybe NMoves
forall a b. (a -> b) -> a -> b
$ NMoves -> NMoves
forall a. Enum a => a -> a
pred NMoves
n	-- Decrement the number of instances.
	) position
position NBoardsByPosition position
m