Some refactoring in variants logic: more robust FEN handling (untested)

[vchess.git] / public / javascripts / variants / Loser.js

class LoserRules extends ChessRules
{
	static get HasFlags() { return false; }

	setOtherVariables(fen)
	{
		const parsedFen = V.ParseFen(fen);
		const epSq = parsedFen.enpassant != "-"
			? V.SquareToCoords(parsedFen.enpassant)
			: undefined;
		this.epSquares = [ epSq ];
		this.scanKingsRooks(fen);
	}

	getPotentialPawnMoves([x,y])
	{
		let moves = super.getPotentialPawnMoves([x,y]);

		// Complete with promotion(s) into king, if possible
		const color = this.turn;
		const shift = (color == "w" ? -1 : 1);
		const lastRank = (color == "w" ? 0 : V.size.x-1);
		if (x+shift == lastRank)
		{
			// Normal move
			if (this.board[x+shift][y] == V.EMPTY)
				moves.push(this.getBasicMove([x,y], [x+shift,y], {c:color,p:V.KING}));
			// Captures
			if (y>0 && this.canTake([x,y], [x+shift,y-1])
				&& this.board[x+shift][y-1] != V.EMPTY)
			{
				moves.push(this.getBasicMove([x,y], [x+shift,y-1], {c:color,p:V.KING}));
			}
			if (y<V.size.y-1 && this.canTake([x,y], [x+shift,y+1])
				&& this.board[x+shift][y+1] != V.EMPTY)
			{
				moves.push(this.getBasicMove([x,y], [x+shift,y+1], {c:color,p:V.KING}));
			}
		}

		return moves;
	}

	getPotentialKingMoves(sq)
	{
		// No castle:
		return this.getSlideNJumpMoves(sq,
			V.steps[V.ROOK].concat(V.steps[V.BISHOP]), "oneStep");
	}

	// Stop at the first capture found (if any)
	atLeastOneCapture()
	{
		const color = this.turn;
		const oppCol = this.getOppCol(color);
		for (let i=0; i<V.size.x; i++)
		{
			for (let j=0; j<V.size.y; j++)
			{
				if (this.board[i][j] != V.EMPTY && this.getColor(i,j) != oppCol)
				{
					const moves = this.getPotentialMovesFrom([i,j]);
					if (moves.length > 0)
					{
						for (let k=0; k<moves.length; k++)
						{
							if (moves[k].vanish.length==2 && this.filterValid([moves[k]]).length > 0)
								return true;
						}
					}
				}
			}
		}
		return false;
	}

	// Trim all non-capturing moves
	static KeepCaptures(moves)
	{
		return moves.filter(m => { return m.vanish.length == 2; });
	}

	getPossibleMovesFrom(sq)
	{
		let moves = this.filterValid( this.getPotentialMovesFrom(sq) );
		// This is called from interface: we need to know if a capture is possible
		if (this.atLeastOneCapture())
			moves = V.KeepCaptures(moves);
		return moves;
	}

	getAllValidMoves()
	{
		let moves = super.getAllValidMoves();
		if (moves.some(m => { return m.vanish.length == 2; }))
			moves = V.KeepCaptures(moves);
		return moves;
	}

	underCheck(move)
	{
		return false; //No notion of check
	}

	getCheckSquares(move)
	{
		return [];
	}

	// No variables update because no castling
	updateVariables(move) { }
	unupdateVariables(move) { }

	checkGameEnd()
	{
		// No valid move: you win!
		return this.turn == "w" ? "1-0" : "0-1";
	}

	static get VALUES()
	{
		// Experimental...
		return {
			'p': 1,
			'r': 7,
			'n': 3,
			'b': 3,
			'q': 5,
			'k': 5
		};
	}

	static get SEARCH_DEPTH() { return 4; }

	evalPosition()
	{
		return - super.evalPosition(); //better with less material
	}

	static GenRandInitFen()
	{
		let pieces = { "w": new Array(8), "b": new Array(8) };
		// Shuffle pieces on first and last rank
		for (let c of ["w","b"])
		{
			let positions = _.range(8);

			// Get random squares for bishops
			let randIndex = 2 * _.random(3);
			let bishop1Pos = positions[randIndex];
			// The second bishop must be on a square of different color
			let randIndex_tmp = 2 * _.random(3) + 1;
			let bishop2Pos = positions[randIndex_tmp];
			// Remove chosen squares
			positions.splice(Math.max(randIndex,randIndex_tmp), 1);
			positions.splice(Math.min(randIndex,randIndex_tmp), 1);

			// Get random squares for knights
			randIndex = _.random(5);
			let knight1Pos = positions[randIndex];
			positions.splice(randIndex, 1);
			randIndex = _.random(4);
			let knight2Pos = positions[randIndex];
			positions.splice(randIndex, 1);

			// Get random square for queen
			randIndex = _.random(3);
			let queenPos = positions[randIndex];
			positions.splice(randIndex, 1);

			// Random square for king (no castle)
			randIndex = _.random(2);
			let kingPos = positions[randIndex];
			positions.splice(randIndex, 1);

			// Rooks positions are now fixed
			let rook1Pos = positions[0];
			let rook2Pos = positions[1];

			// Finally put the shuffled pieces in the board array
			pieces[c][rook1Pos] = 'r';
			pieces[c][knight1Pos] = 'n';
			pieces[c][bishop1Pos] = 'b';
			pieces[c][queenPos] = 'q';
			pieces[c][kingPos] = 'k';
			pieces[c][bishop2Pos] = 'b';
			pieces[c][knight2Pos] = 'n';
			pieces[c][rook2Pos] = 'r';
		}
		return pieces["b"].join("") +
			"/pppppppp/8/8/8/8/PPPPPPPP/" +
			pieces["w"].join("").toUpperCase() +
			" w -"; //no en-passant
	}
}