feat: implement DeflectionEval
#579
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,237 @@ | ||
| <?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\Color; | ||
| use Chess\Variant\Classical\PGN\AN\Piece; | ||
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| class DeflectionEval extends AbstractEval implements | ||
| ElaborateEvalInterface, | ||
| InverseEvalInterface | ||
| { | ||
| 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; | ||
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| $this->result = [ | ||
| Color::W => [], | ||
| Color::B => [], | ||
| ]; | ||
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| $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; | ||
| $this->result[$piece->color][] = $piece->sq; | ||
| $this->elaborateAdvantage($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, $attackingPieces) | ||
| { | ||
| usort($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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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.