xchess/lib/dead-position.js

Chess Engine

export {DeadPositionTest, CheckmateChanceTest}

import {King, Queen, Bishop, Rook, Knight, Pawn} from './piece.js'
import {Color} from './color.js'

function CheckmateChanceTest(context, color){
	return true;
}

function DeadPositionTest(board){

	let WhiteKing = null;
	let BlackKing = null;
	let WhiteBishop = null;
	let BlackBishop = null;
	let AnyKnight = null;

	function KingTest(king){
		if(Color.isWhite(king.color)){
			if(WhiteKing)
				return false;
			WhiteKing = king;
			return true;
		}
		if(BlackKing)
			return false;
		BlackKing = king;
		return true;
	}

	function BishopTest(bishop, color){
		if(AnyKnight)
			return false;
		if(Color.isWhite(bishop.color)){
			if(WhiteBishop)
				return WhiteBishop.eq(color);
			WhiteBishop = color;
			return true;
		}
		if(BlackBishop)
			return BlackBishop.eq(color);
		BlackBishop = color;
		return true;
	}

	function KnightTest(knight){
		if(AnyKnight || WhiteBishop || BlackBishop)
			return false;
		AnyKnight = knight;
		return true;
	}

	function Test(piece, color){
		if(King.is(piece))
			return KingTest(piece);
		if(Knight.is(piece))
			return KnightTest(piece);
		if(Bishop.is(piece))
			return BishopTest(piece, color);
		return false;
	}

	for(const [square, piece] of board)
		if(!Test(piece, square.color))
			return false;

	return Boolean(WhiteKing && BlackKing);
}