var SPENT = {};  // SPENT{sectorId}

function getSpent(sector) {
	var spent = SPENT[sector] || 0;
	return spent;
}

function updateSpent(sector, oldAmount, newAmount) {
	var diff = (newAmount || 0) - (oldAmount || 0);
	addSpent(sector, diff);
}

function setSpent(sector, amount) {
	SPENT[sector] = amount || 0;
}

function subtractSpent(sector, amount) {
	return addSpent(sector, -amount);
}

function addSpent(sector, amount) {
	var spent = getSpent(sector);
	spent += amount || 0;
	if (spent < 0) {
		spent = 0;
	}
	setSpent(sector, spent);
	return spent;
}

function getAvailableRU(sector) {
	var stockpile = getStockpile(sector);
	var spent = getSpent(sector);
	var available = stockpile - spent;
	return available;
}