Taker's order criteria

[D4nte]

Problem

To get an order, the taker needs to go through several hoops:

1. Get orders from maker by doing TakerNegotiator.getOrderByTradingPair("ETH-BTC")
2. Do manual sanity checks on the order: https://github.com/comit-network/create-comit-app/blob/e2718a60bf7319e2504bb355c0406b00da0ae055/create/new_project/examples/separate_apps/src/taker.ts#L49
3. Manually check that the rate is acceptable: https://github.com/comit-network/create-comit-app/blob/e2718a60bf7319e2504bb355c0406b00da0ae055/create/new_project/examples/separate_apps/src/taker.ts#L67
4. Take the order using TakerNegotiator.takeOrder(order): https://github.com/comit-network/create-comit-app/blob/e2718a60bf7319e2504bb355c0406b00da0ae055/create/new_project/examples/separate_apps/src/taker.ts#L73

The downsides are:

• The taker needs to specify the criteria in several steps (first pair, then check itself)
• Validation of the order is manual, a dev would expect to be able to do Order.validate() or even only return valid orders from the TakerNegotiator.getOrderByTradingPair call by filtering
• The filtering is quite manual and forces the dev to work through the properties of the order

Goal

Provide a straightforward, function based, API to the developer. Alleviate the work.

Recommendation

Re-think the API describe above to simplify it.
A better flow would be:

const criteria = {
	buy: "BTC",
	sell: "ETH",
	btcAmount: 0.5,
	allowOffersWithLesserAmount: false,
	maximumRate: 10
}

// Probably revise the `TakerNegotiator` terminology
const order = await takerNegotiator.getOffer(criteria);

if (!order.isValid()) { // This is an optional call and could/should be done already by `getOffer`
	// Ban this maker
}

if (!order.matches()) {  // This is an optional call and could/should be done already by `getOffer`
	// Tell the user why we cannot find an appropriate order
	console.log("Order found but does not match criteria", order.matchFailReason());
	// -> "Order found but does not match criteria { reason: 'maximumRate exceeded', expected: 10, actual: 15 }"
	// -> "Order found but does not match criteria { reason: 'lesser amount provided and not allowed', expected: 0.5, actual: 0.1 }"
}

const swap = await order.take();

[D4nte]

@yosriady what do you think about the proposed flow?

[yosriady]

@D4nte

Looks better! The core idea is to automatically give users a pre-filtered list of acceptable orders to take from.

const order = await takerNegotiator.getOffer(criteria);

What's an 'offer'? Would this function return one or a list of valid offers?

[bonomat]

const criteria = {
  buy: "BTC",
  sell: "ETH",
  btcAmount: 0.5,
  allowOffersWithLesserAmount: false,
  maximumRate: 10
}
// Probably revise the `TakerNegotiator` terminology
const order = await takerNegotiator.getOffer(criteria);
...

Are these fields optional?

//Ignore what was written here before :) //

[D4nte]

const criteria = {
  buy: "BTC",
  sell: "ETH",
  btcAmount: 0.5,
  allowOffersWithLesserAmount: false,
  maximumRate: 10
}
// Probably revise the `TakerNegotiator` terminology
const order = await takerNegotiator.getOffer(criteria);
...

Are these fields optional?

//Ignore what was written here before :) //

Some field are likely to be optional while other are mandatory.