Constellations/js/Geometry/CellSet.js

import size from Config;
import {isSmaller, plus, zero} from Geometry.Vector;
import * as Vector from Geometry.Vector;
import {at, iter} from Grid.Util;
import * as Matrix from Grid.Util;
import Set;

var CellSet = Set.make(Vector);

return {
	CellSet: CellSet,
	union: CellSet.union,
	rectangle: rectangle,
	isochrome: isochrome,
	row: row,
	column: column
};

function rectangle(origin, delta) {
	var cellSet = new CellSet();
	iter(Matrix.make(delta), function(_, cell) {cellSet.add(plus(origin, cell));});
	return cellSet;
}

function isochrome(coloring, origin) {
	var cellSet = new CellSet();
	var color = at(coloring, origin);
	var queue = [origin];
	while(queue.length > 0) {
		var cell = queue.shift();
		cellSet.add(cell);
		for(var d = -1; d < 2; d += 2) {
			[plus(cell, Vector.vertical(d)), plus(cell, Vector.horizontal(d))].forEach(
				gateKeeper(cellSet, coloring, queue, color)
			);
		}
	}
	return cellSet;
}

function gateKeeper(cellSet, coloring, queue, color) {
	return function(cell) {
		if(isSmaller(zero(), cell)
			&& isSmaller(cell, Vector.diagonal(size-1))
			&& !cellSet.contains(cell)
			&& at(coloring, cell) == color) {
			queue.push(cell);
		}
	}
}

function row(n) {
	return rectangle(Vector.vertical(n), Vector.make(1, size));
}

function column(n) {
	return rectangle(Vector.horizontal(n), Vector.make(size, 1));
}