feat: implement DeflectionEval
#579
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| <?php | ||
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| namespace Chess\Eval; | ||
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| use Chess\Tutor\PiecePhrase; | ||
| use Chess\Variant\AbstractBoard; | ||
| use Chess\Variant\AbstractPiece; | ||
| use Chess\Variant\Classical\PGN\AN\Piece; | ||
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| class DeflectionEval extends AbstractEval implements ElaborateEvalInterface | ||
| { | ||
| use ElaborateEvalTrait; | ||
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| const NAME = 'Deflection'; | ||
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| protected bool $deflectionExists = false; | ||
| protected bool $checkExists = false; | ||
| protected bool $mateExists = false; | ||
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| public function __construct(AbstractBoard $board) | ||
| { | ||
| $this->board = $board; | ||
| $checkingPieces = $this->board->piece($this->board->turn, Piece::K)->attacking(); | ||
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| foreach ($this->board->pieces($this->board->turn) as $piece) { | ||
| $legalMoveSquares = $this->board->legal($piece->sq); | ||
| $defendedSquares = $this->board->pieceBySq($piece->sq)->defendedSqs(); | ||
| // considering deflection due to pieces checking the king or attacking the piece | ||
| $attackingPieces = $checkingPieces + $piece->attacking(); | ||
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| // for optimisation, sorting legal moves to check cases of capturing attacking pieces first, as they would majorly lead to deflection cases | ||
| $this->sortLegalMoves($legalMoveSquares, $attackingPieces); | ||
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| if (!empty($legalMoveSquares) && !empty($attackingPieces)) { | ||
| $legalMovesCount = count($legalMoveSquares); | ||
| $primaryDeflectionPhrase = $this->primaryPhrase($piece, $attackingPieces, $legalMovesCount); | ||
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| foreach ($legalMoveSquares as $square) { | ||
| $clone = $this->board->clone(); | ||
| $clone->playLan($clone->turn, $piece->sq . $square); | ||
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| // checks for exposed pieces and protected pawns to ensure deflection | ||
| $exposedPieceList = $this->checkExposedPieceAdvantage($clone, $defendedSquares, $square); | ||
| $protectedPawnsList = $this->checkAdvancedPawnAdvantage($clone, $piece); | ||
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| if (!empty($exposedPieceList) || !empty($protectedPawnsList)) { | ||
| $this->deflectionExists = true; | ||
| $this->elaborateAdvantage($primaryDeflectionPhrase, $exposedPieceList, $protectedPawnsList, $legalMovesCount); | ||
| break; | ||
| } | ||
| } | ||
| } | ||
| if ($this->deflectionExists) { | ||
| break; | ||
| } | ||
| } | ||
| } | ||
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| /** | ||
| * sorts the legal moves array, so that it arranges the moves for capturing the attacking pieces on top | ||
| */ | ||
| private function sortLegalMoves(&$legalMoveSquares, $attackingPieces) | ||
|
Comment on lines
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+72
There was a problem hiding this comment. sorting the legal moves to arrange the moves for capturing the attacking pieces on top. As during testing, I realized, that in most cases, deflection usually happens for these moves, also are more practical. |
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| { | ||
| usort($legalMoveSquares, function ($a, $b) use ($attackingPieces) { | ||
| $aInAttacking = array_key_exists($a, $attackingPieces); | ||
| $bInAttacking = array_key_exists($b, $attackingPieces); | ||
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| if ($aInAttacking && !$bInAttacking) { | ||
| return -1; | ||
| } elseif (!$aInAttacking && $bInAttacking) { | ||
| return 1; | ||
| } else { | ||
| return 0; | ||
| } | ||
| }); | ||
| } | ||
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| private function primaryPhrase(AbstractPiece $piece, array $attackingPieces, int $legalMovesCount): string | ||
| { | ||
| $piecePhrase = PiecePhrase::create($piece); | ||
| $basePhrase = $piecePhrase . " is deflected"; | ||
| $attackedByPhrase = $this->attackedByPhrase($attackingPieces); | ||
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| return ($legalMovesCount > 1 ? "If " : "") . $basePhrase . $attackedByPhrase . ", "; | ||
| } | ||
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| private function attackedByPhrase(array $attackingPieces): string | ||
| { | ||
| $basePhrase = " due to "; | ||
| if (count($attackingPieces) === 1) { | ||
| return $basePhrase . PiecePhrase::create($attackingPieces[0]); | ||
| } elseif (count($attackingPieces) > 1) { | ||
| $squares = array_map(fn($attacking) => PiecePhrase::create($attacking), $attackingPieces); | ||
| $lastSquare = array_pop($squares); | ||
| return $basePhrase . implode(', ', $squares) . ' and ' . $lastSquare; | ||
| } | ||
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| return ""; | ||
| } | ||
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| /** | ||
| * checks for exposed pieces due to deflection, also checks for possibility of check or mate to the king | ||
| */ | ||
| private function checkExposedPieceAdvantage(AbstractBoard $clone, array $defendedSquares, string $square): array | ||
| { | ||
| $piecePhrase = []; | ||
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| $updatedDefendedSquares = $clone->pieceBySq($square)->defendedSqs(); | ||
| $undefendedSquares = array_diff($defendedSquares, $updatedDefendedSquares); | ||
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| if (!empty($undefendedSquares)) { | ||
| foreach ($undefendedSquares as $undefendedSquare) { | ||
| $attackers = $clone->pieceBySq($undefendedSquare)->attacking(); | ||
| if (!empty($attackers)) { | ||
| $piecePhrase[] = PiecePhrase::create($clone->pieceBySq($undefendedSquare)); | ||
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| foreach ($attackers as $attacker) { | ||
| $clone->playLan($clone->turn, $attacker->sq . $undefendedSquare); | ||
| if ($clone->isMate()) { | ||
| $this->mateExists = true; | ||
| } else if ($clone->isCheck()) { | ||
| $this->checkExists = true; | ||
| } | ||
| $clone->undo(); | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| return $piecePhrase; | ||
| } | ||
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| /** | ||
| * checks for the advanced pawns that become protected due to deflection | ||
| */ | ||
| private function checkAdvancedPawnAdvantage(AbstractBoard $clone, AbstractPiece $piece): array | ||
| { | ||
| $pawnsList = []; | ||
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| $advancedPawnEval = new FarAdvancedPawnEval($clone); | ||
| $advancedPawns = $advancedPawnEval->getResult()[$clone->turn]; | ||
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| if (!empty($advancedPawns)) { | ||
| foreach ($advancedPawns as $pawn) { | ||
| $attackersDiff = array_udiff_assoc( | ||
| $this->board->pieceBySq($pawn)->attacking(), | ||
| $clone->pieceBySq($pawn)->attacking(), | ||
| function ($obj1, $obj2) { | ||
| return strcmp($obj1->sq, $obj2->sq); | ||
| } | ||
| ); | ||
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| foreach ($attackersDiff as $attacker) { | ||
| if ($attacker->sq === $piece->sq) { | ||
| $pawnsList[] = PiecePhrase::create($this->board->pieceBySq($pawn)); | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| return $pawnsList; | ||
| } | ||
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| private function elaborateAdvantage(String $primaryDeflectionPhrase, array $exposedPieceList, array $protectedPawnsList, int $legalMovesCount) | ||
| { | ||
| if (!$this->deflectionExists) { | ||
| return; | ||
| } | ||
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| $exposedPiecePhrase = $this->elaborateExposedPieceAdvantage($exposedPieceList); | ||
| $protectedPawnPhrase = $this->elaborateProtectedPawnAdvantage($protectedPawnsList); | ||
| $elaborationPhrase = $primaryDeflectionPhrase . $exposedPiecePhrase . $protectedPawnPhrase; | ||
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| // in case of only moves, also presenting more details | ||
| if ($legalMovesCount == 1) { | ||
| $elaborationPhrase = str_replace("may well", "will", $elaborationPhrase); | ||
| if ($this->mateExists) { | ||
| $elaborationPhrase .= "; threatning checkmate"; | ||
| } | ||
| if ($this->checkExists) { | ||
| $elaborationPhrase .= "; threatning a check"; | ||
| } | ||
| } | ||
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| $elaborationPhrase .= "."; | ||
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| $this->elaboration[] = $elaborationPhrase; | ||
| } | ||
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| private function elaborateAdvantageText(array $itemList, string $singularMessage, string $pluralPrefix): string | ||
| { | ||
| $rephrase = ""; | ||
| $count = count($itemList); | ||
| if ($count === 1) { | ||
| $item = mb_strtolower($itemList[0]); | ||
| $rephrase = $item . ' ' . $singularMessage; | ||
| } elseif ($count > 1) { | ||
| $rephrase .= $pluralPrefix; | ||
| foreach ($itemList as $item) { | ||
| $rephrase .= $item . ', '; | ||
| } | ||
| $rephrase = substr_replace(trim($rephrase), '', -1); | ||
| } | ||
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| return $rephrase; | ||
| } | ||
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| private function elaborateExposedPieceAdvantage(array $exposedPieceList): string | ||
| { | ||
| return $this->elaborateAdvantageText( | ||
| $exposedPieceList, | ||
| 'may well be exposed to attack', | ||
| 'these pieces may well be exposed to attack: ', | ||
| '' | ||
| ); | ||
| } | ||
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| private function elaborateProtectedPawnAdvantage(array $protectedPawnsList): string | ||
| { | ||
| return $this->elaborateAdvantageText( | ||
| $protectedPawnsList, | ||
| 'is not attacked by it and may well be advanced for promotion', | ||
| 'these pawns are not attacked by it and may well be advanced for promotion: ', | ||
| '' | ||
| ); | ||
| } | ||
| } | ||
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In case deflection exists, the optimal result for the first case for that piece and move found will be returned to keep things simple, if we rather want to evaluate for all the pieces, we can extend onto it, which would require a few updates, but for simplicity and optimization, I limited it to a single case, looks fine to me.