{-
	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@]

	* Constructs a tree in which each node contains,
	a zobrist-hash,
	a /quantifiedGame/ with one of the moves available to its parent node applied & evaluation of the fitness of the resulting position.

	* Each forest in the tree is sorted, before evaluation of its fitness is performed.

	* CAVEAT: promotions are insufficiently frequent to be treated specially when sorting.
-}

module BishBosh.Evaluation.PositionHashQuantifiedGameTree(
-- * Types
-- ** Type-synonyms
--	BarePositionHashQuantifiedGameTree,
	Forest,
-- ** Data-types
	NodeLabel(
--		MkNodeLabel,
		getPositionHash,
		getQuantifiedGame
	),
	PositionHashQuantifiedGameTree(
		MkPositionHashQuantifiedGameTree,
		deconstruct
	),
-- * Functions
	reduce,
	traceRoute,
	resign,
	traceMatchingMoves,
	promoteMatchingMoves,
	sortNonCaptureMoves,
-- ** Accessors
	getRootQuantifiedGame',
	getRootPositionHash,
	getRootQuantifiedGame,
-- ** Constructor
	fromBarePositionHashQuantifiedGameTree,
	mkPositionHashQuantifiedGameTree
-- ** Predicates
--	equalsLastMove
 ) where

import			Control.Arrow((&&&))
import qualified	BishBosh.Attribute.RankValues				as Attribute.RankValues
import qualified	BishBosh.Attribute.WeightedMeanAndCriterionValues	as Attribute.WeightedMeanAndCriterionValues
import qualified	BishBosh.Component.Move					as Component.Move
import qualified	BishBosh.Component.QualifiedMove			as Component.QualifiedMove
import qualified	BishBosh.Component.Turn					as Component.Turn
import qualified	BishBosh.Component.Zobrist				as Component.Zobrist
import qualified	BishBosh.Data.RoseTree					as Data.RoseTree
import qualified	BishBosh.Evaluation.Fitness				as Evaluation.Fitness
import qualified	BishBosh.Evaluation.QuantifiedGame			as Evaluation.QuantifiedGame
import qualified	BishBosh.Input.EvaluationOptions			as Input.EvaluationOptions
import qualified	BishBosh.Input.SearchOptions				as Input.SearchOptions
import qualified	BishBosh.Model.Game					as Model.Game
import qualified	BishBosh.Model.GameTree					as Model.GameTree
import qualified	BishBosh.Notation.MoveNotation				as Notation.MoveNotation
import qualified	BishBosh.Property.Null					as Property.Null
import qualified	BishBosh.Property.Tree					as Property.Tree
import qualified	BishBosh.Types						as T
import qualified	Control.Arrow
import qualified	Control.Monad.Reader
import qualified	Data.Array.IArray
import qualified	Data.Bits
import qualified	Data.Maybe
import qualified	Data.Tree

-- | Define a node in the tree to contain the hash of a /game/ & an evaluation of the fitness of that /game/.
data NodeLabel x y positionHash criterionValue weightedMean	= MkNodeLabel {
	getPositionHash		:: positionHash,	-- ^ The hash of the /game/ contained in 'getQuantifiedGame'.
	getQuantifiedGame	:: Evaluation.QuantifiedGame.QuantifiedGame x y criterionValue weightedMean
} deriving (Eq, Show)

instance (Enum x, Enum y, Real weightedMean) => Notation.MoveNotation.ShowNotationFloat (NodeLabel x y positionHash criterionValue weightedMean) where
	showsNotationFloat moveNotation showsDouble MkNodeLabel { getQuantifiedGame = quantifiedGame }	= Notation.MoveNotation.showsNotation moveNotation (
		Evaluation.QuantifiedGame.getLastTurn quantifiedGame
	 ) . showString "\t=> " . showsDouble (
		realToFrac . Attribute.WeightedMeanAndCriterionValues.getWeightedMean $ Evaluation.QuantifiedGame.getWeightedMeanAndCriterionValues quantifiedGame
	 )

instance Property.Null.Null (NodeLabel x y positionHash criterionValue weightedMean) where
	isNull MkNodeLabel { getQuantifiedGame = quantifiedGame }	= Property.Null.isNull quantifiedGame

-- | Whether the last move of the /game/ in a node, matches a specified /move/.
equalsLastMove :: (Eq x, Eq y) => Component.Move.Move x y -> Data.RoseTree.IsMatch (NodeLabel x y positionHash criterionValue weightedMean)
equalsLastMove move MkNodeLabel { getQuantifiedGame = quantifiedGame }	= (== move) . Component.QualifiedMove.getMove . Component.Turn.getQualifiedMove $ Evaluation.QuantifiedGame.getLastTurn quantifiedGame

-- | The tree resulting from each possible move-choice applied to a /game/, including a position-hash & an evaluation of the resulting fitness.
type BarePositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean	= Data.Tree.Tree (NodeLabel x y positionHash criterionValue weightedMean)

-- | Accessor.
getRootQuantifiedGame' :: BarePositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean -> Evaluation.QuantifiedGame.QuantifiedGame x y criterionValue weightedMean
getRootQuantifiedGame' Data.Tree.Node {
	Data.Tree.rootLabel	= MkNodeLabel { getQuantifiedGame = quantifiedGame }
} = quantifiedGame

-- | Wrap the bare tree.
newtype PositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean	= MkPositionHashQuantifiedGameTree {
	deconstruct	:: BarePositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean
} deriving Eq

instance Property.Tree.Prunable (PositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean) where
	prune depth MkPositionHashQuantifiedGameTree { deconstruct = barePositionHashQuantifiedGameTree }	= MkPositionHashQuantifiedGameTree $ Property.Tree.prune depth barePositionHashQuantifiedGameTree

instance (
	Enum	x,
	Enum	y,
	Real	weightedMean
 ) => Notation.MoveNotation.ShowNotationFloat (PositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean) where
	showsNotationFloat moveNotation showsDouble MkPositionHashQuantifiedGameTree { deconstruct = barePositionHashQuantifiedGameTree } = showString $ (
		if Property.Null.isNull . Data.Tree.rootLabel $ barePositionHashQuantifiedGameTree
			then Data.RoseTree.drawForest toString . Data.Tree.subForest
			else Data.RoseTree.drawTree toString
	 ) barePositionHashQuantifiedGameTree where
		toString nodeLabel	= Notation.MoveNotation.showsNotationFloat moveNotation showsDouble nodeLabel ""

-- | Constructor.
fromBarePositionHashQuantifiedGameTree :: BarePositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean -> PositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean
fromBarePositionHashQuantifiedGameTree	= MkPositionHashQuantifiedGameTree

-- | Constructor.
mkPositionHashQuantifiedGameTree :: (
	Data.Array.IArray.Ix	x,
	Data.Bits.Bits		positionHash,
	Fractional		criterionValue,
	Fractional		pieceSquareValue,
	Fractional		rankValue,
	Fractional		weightedMean,
	Integral		x,
	Integral		y,
	Real			criterionValue,
	Real			criterionWeight,
	Real			pieceSquareValue,
	Real			rankValue,
	Show			x,
	Show			y
 )
	=> Input.EvaluationOptions.EvaluationOptions criterionWeight pieceSquareValue rankValue x y
	-> Input.SearchOptions.SearchOptions
	-> Component.Zobrist.Zobrist x y positionHash
	-> Model.GameTree.MoveFrequency x y
	-> Model.Game.Game x y	-- ^ The current state of the /game/.
	-> PositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean
{-# SPECIALISE mkPositionHashQuantifiedGameTree
	:: Input.EvaluationOptions.EvaluationOptions T.CriterionWeight T.PieceSquareValue T.RankValue T.X T.Y
	-> Input.SearchOptions.SearchOptions
	-> Component.Zobrist.Zobrist T.X T.Y T.PositionHash
	-> Model.GameTree.MoveFrequency T.X T.Y
	-> Model.Game.Game T.X T.Y
	-> PositionHashQuantifiedGameTree T.X T.Y T.PositionHash T.CriterionValue T.WeightedMean
 #-}
mkPositionHashQuantifiedGameTree evaluationOptions searchOptions zobrist moveFrequency seedGame	= MkPositionHashQuantifiedGameTree (
	if Input.EvaluationOptions.getIncrementalEvaluation evaluationOptions
		then let
			apexPositionHash	= Component.Zobrist.hash2D seedGame zobrist
		in Data.Tree.Node {
			Data.Tree.rootLabel	= MkNodeLabel apexPositionHash $ Control.Monad.Reader.runReader (
				Evaluation.QuantifiedGame.fromGame Nothing seedGame
			) evaluationOptions,	-- Neither the previous positionHash nor the previous pieceSquareValue, are available to support incremental construction.
			Data.Tree.subForest	= map (
				Data.Maybe.maybe (
					let
						slave positionHash game Data.Tree.Node {
							Data.Tree.rootLabel	= game',
							Data.Tree.subForest	= gameForest'
						} = Data.Tree.Node {
							Data.Tree.rootLabel	= MkNodeLabel positionHash' $ Control.Monad.Reader.runReader (
								Evaluation.QuantifiedGame.fromGame Nothing game'
							) evaluationOptions,
							Data.Tree.subForest	= map (slave positionHash' game') gameForest'	-- Recurse.
						} where
							positionHash'	= Model.Game.incrementalHash game positionHash game' zobrist
					in slave
				) (
					\pieceSquareArray -> let
						slave pieceSquareValue positionHash game Data.Tree.Node {
							Data.Tree.rootLabel	= game',
							Data.Tree.subForest	= gameForest'
						} = Data.Tree.Node {
							Data.Tree.rootLabel	= MkNodeLabel positionHash' $ Control.Monad.Reader.runReader (
								Evaluation.QuantifiedGame.fromGame (Just pieceSquareValue') game'
							) evaluationOptions,
							Data.Tree.subForest	= map (slave pieceSquareValue' positionHash' game') gameForest'	-- Recurse.
						} where
							pieceSquareValue'	= Evaluation.Fitness.measurePieceSquareValueIncrementally pieceSquareValue pieceSquareArray game'
							positionHash'		= Model.Game.incrementalHash game positionHash game' zobrist
					in slave $ Evaluation.Fitness.measurePieceSquareValue pieceSquareArray seedGame
				) (
					Input.EvaluationOptions.getMaybePieceSquareArray evaluationOptions
				) apexPositionHash seedGame
			) $ Data.Tree.subForest bareGameTree
		}
		else fmap (
			uncurry MkNodeLabel . (
				(`Component.Zobrist.hash2D` zobrist) &&& (`Control.Monad.Reader.runReader` evaluationOptions) . Evaluation.QuantifiedGame.fromGame Nothing
			)
		) bareGameTree
 ) where
	bareGameTree	= Model.GameTree.deconstruct . uncurry Model.GameTree.sortGameTree (
		Input.SearchOptions.getPreferMovesTowardsCentre &&& Input.SearchOptions.getMaybeCaptureMoveSortAlgorithm $ searchOptions
	 ) (
		`Attribute.RankValues.findRankValue` Input.EvaluationOptions.getRankValues evaluationOptions
	 ) moveFrequency $ Model.GameTree.fromGame seedGame

-- | Accessor.
getRootPositionHash :: PositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean -> positionHash
getRootPositionHash MkPositionHashQuantifiedGameTree {
	deconstruct = Data.Tree.Node {
		Data.Tree.rootLabel	= MkNodeLabel { getPositionHash = positionHash }
	}
} = positionHash

-- | Accessor.
getRootQuantifiedGame :: PositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean -> Evaluation.QuantifiedGame.QuantifiedGame x y criterionValue weightedMean
getRootQuantifiedGame MkPositionHashQuantifiedGameTree {
	deconstruct = Data.Tree.Node {
		Data.Tree.rootLabel	= MkNodeLabel { getQuantifiedGame = quantifiedGame }
	}
} = quantifiedGame

-- | Forward request.
reduce
	:: Data.RoseTree.IsMatch (NodeLabel x y positionHash criterionValue weightedMean)
	-> PositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean
	-> Maybe (PositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean)
reduce isMatch MkPositionHashQuantifiedGameTree { deconstruct = barePositionHashQuantifiedGameTree }	= MkPositionHashQuantifiedGameTree `fmap` Data.RoseTree.reduce isMatch barePositionHashQuantifiedGameTree

-- | Forward request.
traceRoute
	:: (Component.Turn.Turn x y -> Data.RoseTree.IsMatch (NodeLabel x y positionHash criterionValue weightedMean))
	-> PositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean
	-> [Component.Turn.Turn x y]
	-> Maybe [NodeLabel x y positionHash criterionValue weightedMean]
traceRoute isMatch MkPositionHashQuantifiedGameTree { deconstruct = barePositionHashQuantifiedGameTree }	= Data.RoseTree.traceRoute isMatch barePositionHashQuantifiedGameTree

-- | Follow the specified move-sequence down the /positionHashQuantifiedGameTree/.
traceMatchingMoves
	:: (Eq x, Eq y)
	=> PositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean
	-> [Component.Move.Move x y]
	-> Maybe [NodeLabel x y positionHash criterionValue weightedMean]	-- ^ Returns 'Nothing' on failure to match a move.
traceMatchingMoves MkPositionHashQuantifiedGameTree { deconstruct = barePositionHashQuantifiedGameTree }	= Data.RoseTree.traceRoute equalsLastMove barePositionHashQuantifiedGameTree

-- | Amend the apex-game to reflect the resignation of the next player.
resign :: PositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean -> PositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean
resign MkPositionHashQuantifiedGameTree {
	deconstruct	= barePositionHashQuantifiedGameTree@Data.Tree.Node {
		Data.Tree.rootLabel	= nodeLabel@MkNodeLabel { getQuantifiedGame = quantifiedGame }
	}
} = MkPositionHashQuantifiedGameTree $ barePositionHashQuantifiedGameTree {
	Data.Tree.rootLabel	= nodeLabel {
		getQuantifiedGame	= quantifiedGame { Evaluation.QuantifiedGame.getGame = Model.Game.resign $ Evaluation.QuantifiedGame.getGame quantifiedGame }
	}
}

-- | Self-documentation.
type Forest x y positionHash criterionValue weightedMean	= [BarePositionHashQuantifiedGameTree x y positionHash criterionValue weightedMean]

{- |
	* Promotes the first matching /move/ to the head of the forest, then descends & recursively promotes the next matching move in the sub-forest.

	* N.B.: this can be used to dynamically re-order the forest when a transposition is detected.
-}
promoteMatchingMoves
	:: (Eq x, Eq y)
	=> [Component.Move.Move x y]					-- ^ The list of moves, which should be promoted at successively deeper levels in the tree.
	-> Forest x y positionHash criterionValue weightedMean
	-> Maybe (Forest x y positionHash criterionValue weightedMean)	-- ^ Returns 'Nothing' on failure to match a move.
promoteMatchingMoves	= Data.RoseTree.promote equalsLastMove

{- |
	* Sorts the forest, starting just after any initial capture-moves.

	* N.B.: this can be used to dynamically re-order the forest using the killer heuristic.
-}
sortNonCaptureMoves
	:: (Forest x y positionHash criterionValue weightedMean -> Forest x y positionHash criterionValue weightedMean)
	-> Forest x y positionHash criterionValue weightedMean
	-> Forest x y positionHash criterionValue weightedMean
sortNonCaptureMoves sortForest	= uncurry (++) . Control.Arrow.second sortForest . span (
	Component.Turn.isCapture . Evaluation.QuantifiedGame.getLastTurn . getRootQuantifiedGame'	-- Shield any capture-moves, which were previously advanced by static sorting, from the sort.
 )