matchOrder.js

var matchOrder = function(corp) {
	var self = this;
	self.corp = corp;
	debug('corp [%s] [%s]', self.corp.symbol, self.corp.name);

	return Promise.all([
		Order.findOne({ 
			corp: self.corp._id, 
			action: 'buy', 
			type: 'limit', 
			unfilled: { $gt: 0 }, 
			expired: { $gt: Date.now() },
			is_failed: false,
		}).sort('-price placed'),

		Order.findOne({ 
			corp: self.corp._id, 
			action: 'sell', 
			type: 'limit', 
			unfilled: { $gt: 0 }, 
			expired: { $gt: Date.now() },
			is_failed: false,
		}).sort('price placed'),
		
		Tick.findOne({
			corp: self.corp._id,
		}).sort('date'),
	]).then(results => {
		self.bid = results[0];
		self.ask = results[1];
		self.tick = results[2];

		if (!self.bid || !self.ask) {
			debug('no order');
			throw 'No Order';
		}

		debug('bid [%d] x [%d]', self.bid.price, self.bid.quantity);
		debug('ask [%d] x [%d]', self.ask.price, self.ask.quantity);
		debug('last tick [%d] - [%d]', self.tick.bid, self.tick.ask);

		if (self.bid.price < self.ask.price) {
			if (self.bid.price != self.tick.bid || self.ask.price != self.tick.price) {
				debug('new tick [%d] - [%d]', self.bid.price, self.ask.price);
				Tick.create({ bid: self.bid.price, ask: self.ask.price, date: Date.now() });
			}
			debug('no trade');
			throw 'No Trade';
		}

		return Promise.all([
			Friend.findById(self.bid.friend),
			Friend.findById(self.ask.friend),

			Stock.findOne({ friend: self.bid.friend, corp: self.corp._id }),
			Stock.findOne({ friend: self.ask.friend, corp: self.corp._id }),
		]);
	}).then(results => {
		self.buyer = results[0];
		self.seller = results[1];
		self.buyerStock = results[2];
		self.sellerStock = results[3];

		debug('buyer [%s] [%d]', self.buyer.name, self.buyer.cash);
		debug('seller [%s] [%d]', self.seller.name, self.seller.cash);
		debug('buyer stock [%d]', self.buyerStock.quantity);
		debug('seller stock [%d]', self.sellerStock.quantity);

		self.quantity = Math.min(self.bid.unfilled, self.ask.unfilled);
		self.buyAmount = self.quantity * self.bid.price;
		self.sellAmount = self.quantity * self.ask.price;
		self.makerCollect = self.buyAmount - self.sellAmount;

		debug('quantity [%d]', self.quantity);
		debug('buy amount [%d]', self.buyAmount);
		debug('sell amount [%d]', self.sellAmount);
		debug('maker collect [%d]', self.makerCollect);

		if (self.buyer.cash < self.buyAmount) {  // buyer cannot paid for the stock
			self.bid.is_failed = true;
			self.bid.save();

			debug('buyer too poor');
			throw 'Buyer Too Poor';
		}

		if (self.quantity < self.sellerStock.quantity) {  // seller cannot sell the stock
			self.ask.is_failed = true;
			self.ask.save();

			debug('seller too poor');
			throw 'Seller Too Poor';
		}
		
		self.bid.unfilled -= self.quantity;
		self.ask.unfilled -= self.quantity;

		self.buyer.cash -= self.buyAmount;
		self.seller.cash += self.sellAmount;

		self.buyerStock.quantity += self.quantity;
		self.sellerStock.quantity -= self.quantity;
		
		gskse.maker.cash += self.makerCollect;  // maket maker collect the spread

		self.bid.save();
		self.ask.save();

		self.buyer.save();
		self.seller.save();
		
		self.buyerStock.save();
		self.sellerStock.save();
		
		gskse.maker.save();

		return matchOrder(corp);
	});
};

exports.matchOrder = matchOrder;

function() {
	matchOrder(self.corp).catch(err => debug(err));
}