feat: contract code to mint tickets

[LuqiPan]

My first stab at updating the contract to mint tickets, notably, update contract terms to accept inventory then check want against inventory to make sure we have enough inventory and check give against total price to make sure user offers enough tokens.

This is still pretty rough so any and all feedbacks are welcomed.

TODOs:

• make the last test case in test-contract.js pass, it's using mockBootstrap and I don't know quite understand how it works
• update comments and JSDocs accordingly

[LuqiPan]

Posting my open questions with current code

[LuqiPan]

question

I didn't see a AmountMath.multiply function so I implemented it myself

[dckc]

import {
  makeRatio,
  multiplyBy,
} from '@agoric/zoe/src/contractSupport/ratio.js';
import { Nat } from '@endo/nat';

/**
 *
 * @param {Amount<'nat'>} amount
 * @param {number} n
 * @returns {Amount}
 */
const multiply = (amount, n) => {
  const r = makeRatio(Nat(n), amount.brand, 1n);
  return multiplyBy(amount, r);
};

[LuqiPan]

I seem to have some trouble making multiply work for Amount<AssetKind> instead of Amount<'nat'>, am I missing something?

[dckc]

Our ratio library doesn't support non-fungible amounts and says so in its type annotations... which means you may have to trace thru all the callers and update their types to Amount<'nat'>.

In some places, a typecast is called for. For example, zcf.getTerms() doesn't know whether the brands are for fungible assets or not. And you're not in a position to doubt the caller that started the contract - that's part of the reliance set. You could ask the brand what its AssetKind is, but it could lie, so it's not worth the bother.

[dckc]

thanks for sharing in draft form. good stuff here.

[dckc]

import {
  makeRatio,
  multiplyBy,
} from '@agoric/zoe/src/contractSupport/ratio.js';
import { Nat } from '@endo/nat';

/**
 *
 * @param {Amount<'nat'>} amount
 * @param {number} n
 * @returns {Amount}
 */
const multiply = (amount, n) => {
  const r = makeRatio(Nat(n), amount.brand, 1n);
  return multiplyBy(amount, r);
};

[dckc]

update UI code and tests accordingly

updating the UI code seems to fit more comfortably in a separate PR

[LuqiPan]

I seem to have some trouble making multiply work for Amount<AssetKind> instead of Amount<'nat'>, am I missing something?

[LuqiPan]

question, for my learning

What to do with proceeds and inventorySeat?

Seems like we could get the proceeds when contract is closed by the creator via creatorFacet. Should we keep inventorySeat open even in the case when all tickets are sold?

[dckc]

yes, a creatorFacet method is a typical way to collect the proceeds. (Seems fine to postpone to a later PR, if we bother to do it at all)
See, for example, collectFees.js and the contracts that import it.

as to inventorySeat... when they're all sold, we could shut the contract down (there's a shutdown method on zcf)

Or we could have a creatorFacet method to resupply it for the next event or something. But that seems like over-kill.

[LuqiPan]

question

Not sure why M.splitRecord(...) doesn't work here- inventory has tradePrice and maxTickets in the values

[dckc]

I took the liberty of pushing a fix

[dckc]

good stuff!

[aj-agoric]

Marking this PR as done in the project board since this is merged.