xchess/lib/piece-stat.js

Chess Engine

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

export function Weight(pieceList){
	let weight = 0;
	for(const piece of pieceList)
		weight += piece.weight;
	return weight;
}

export function Advantage(pieceList, colorArg = Color.white){
	const color = Color.from(colorArg);
	let advantage = 0;
	for(const piece of pieceList){
		if(color.eq(piece.color))
			advantage += piece.weight;
		else
			advantage -= piece.weight;
	}
	return advantage;
}

function CreateStat(){
	return {
		count: 0,
		weight: 0,
		kings: 0,
		queens: 0,
		rooks: 0,
		bishops: 0,
		knights: 0,
		pawns: 0,
	};
}

function AddToStat(stat, piece){
	stat.count ++;
	stat.weight += piece.weight;
	if(King.is(piece))
		stat.kings ++;
	if(Queen.is(piece))
		stat.queens ++;
	if(Rook.is(piece))
		stat.rooks ++;
	if(Bishop.is(piece))
		stat.bishops ++;
	if(Knight.is(piece))
		stat.knights ++;
	if(Pawn.is(piece))
		stat.pawns ++;
}

export function PiecesStat(pieceList){
	const white = CreateStat();
	const black = CreateStat();
	const advantage = 0;
	const stat = {... CreateStat(), advantage, white, black};
	for(const piece of pieceList){
		AddToStat(stat, piece);
		if(Color.isWhite(piece.color)){
			AddToStat(white, piece);
			stat.advantage += piece.weight;
		} else {
			AddToStat(black, piece);
			stat.advantage -= piece.weight;
		}
	}
	return stat;
}