xchess/lib/geo.js

Chess Engine

export {geo as default}

import {Square} from './square.js'
import {Move, Capture} from './move.js'

let board, piece, from, to, moves;

function crossInit(PIECE, TO, BOARD){
	piece = PIECE;
	board = BOARD;
	from = board.find(piece);
	to = Square.from(TO);
}

function traceInit(PIECE, BOARD){
	piece = PIECE;
	board = BOARD;
	from = board.find(piece);
	moves = [];
}

const geo = {

	crossT(piece, to, board){
		crossInit(piece, to, board);
		if(from) return crossT();
		return false;
	},

	crossX(piece, to, board){
		crossInit(piece, to, board);
		if(from) return crossX();
		return false;
	},

	crossAny(piece, to, board){
		crossInit(piece, to, board);
		if(from) return crossAny();
		return false;
	},

	isNear(piece, to, board){
		const from = board.find(piece);
		if(from) return from.isNear(to);
		return false;
	},

	isL(piece, to, board){
		const from = board.find(piece);
		if(from) return from.isL(to);
		return false;
	},

	traceT(piece, board){
		traceInit(piece, board);
		if(from) traceT();
		return moves;
	},

	traceX(piece, board){
		traceInit(piece, board);
		if(from) traceX();
		return moves;
	},

	traceAll(piece, board){
		traceInit(piece, board);
		if(from) traceAll();
		return moves;
	},

	near(piece, board){
		traceInit(piece, board);
		if(from) search(from.near);
		return moves;
	},

	L(piece, board){
		traceInit(piece, board);
		if(from) search(from.L);
		return moves;
	},
};

function crossAny(){
	return crossT() || crossX();
}

function crossX(){
	if(from.a === to.a)
		return crossZ();
	if(from.b === to.b)
		return crossN();
	return false;
}

function crossT(){
	if(from.x === to.x)
		return crossV();
	if(from.y === to.y)
		return crossH();
	return false;
}

function crossV(){
	if(from.y < to.y)
		return gap(from.walkBottom());
	if(from.y > to.y)
		return gap(from.walkTop());
	return false;
}

function crossH(){
	if(from.x < to.x)
		return gap(from.walkRight())
	if(from.x > to.x)
		return gap(from.walkLeft())
	return false;
}

function crossZ(){
	if(from.b < to.b)
		return gap(from.walkTopRight())
	if(from.b > to.b)
		return gap(from.walkBottomLeft())
	return false;
}

function crossN(){
	if(from.a < to.a)
		return gap(from.walkBottomRight())
	if(from.a > to.a)
		return gap(from.walkTopLeft())
	return false;
}

function gap(squares){
	for(const square of squares){
		if(square == to)
			return true;
		if(board.has(square))
			return false;
	} return false;
}

function traceT(){
	for(const squareSeq of from.walkT())
		trace(squareSeq);
}

function traceX(){
	for(const squareSeq of from.walkX())
		trace(squareSeq);
}

function traceAll(){
	for(const squareSeq of from.walkAll())
		trace(squareSeq);
}

function trace(squareSeq){
	for(const to of squareSeq){
		const capture = board.get(to);
		if(capture){
			if(piece.opposite(capture))
				moves.push(new Capture(piece, from, to, capture));
			break;
		} moves.push(new Move(piece, from, to));
	}
}

function search(squares){
	for(const to of squares){
		const capture = board.get(to);
		if(capture){
			if(piece.opposite(capture))
				moves.push(new Capture(piece, from, to, capture));
			continue;
		} moves.push(new Move(piece, from, to));
	}
}