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issuer.js
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issuer.js
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// Copyright (C) 2019 Agoric, under Apache License 2.0
// @ts-check
import { assert, details as X } from '@agoric/assert';
import { makeExternalStore } from '@agoric/store';
import { E } from '@agoric/eventual-send';
import { Far } from '@agoric/marshal';
import { makeNotifierKit } from '@agoric/notifier';
import { isPromise } from '@agoric/promise-kit';
import { makeAmountMath, MathKind } from './amountMath';
import { makeFarName, ERTPKind } from './interfaces';
import { coerceDisplayInfo } from './displayInfo';
import './types';
/**
* @type {MakeIssuerKit}
*/
function makeIssuerKit(
allegedName,
amountMathKind = MathKind.NAT,
displayInfo = undefined,
) {
assert.typeof(allegedName, 'string');
displayInfo = coerceDisplayInfo(displayInfo);
const brand = Far(makeFarName(allegedName, ERTPKind.BRAND), {
isMyIssuer: allegedIssuerP => {
return E.when(allegedIssuerP, allegedIssuer => {
// eslint-disable-next-line no-use-before-define
return allegedIssuer === issuer;
});
},
getAllegedName: () => allegedName,
// Give information to UI on how to display the amount.
getDisplayInfo: () => displayInfo,
});
const amountMath = makeAmountMath(brand, amountMathKind);
const { add } = amountMath;
const empty = amountMath.getEmpty();
const {
makeInstance: makePayment,
makeWeakStore: makePaymentWeakStore,
} = makeExternalStore('payment', () =>
Far(makeFarName(allegedName, ERTPKind.PAYMENT), {
getAllegedBrand: () => brand,
}),
);
/** @type {WeakStore<Payment, Amount>} */
const paymentLedger = makePaymentWeakStore();
function assertKnownPayment(payment) {
assert(paymentLedger.has(payment), X`payment not found for ${allegedName}`);
}
// Methods like deposit() have an optional second parameter `amount`
// which, if present, is supposed to be equal to the balance of the
// payment. This helper function does that check.
const assertAmountEqual = (paymentBalance, amount) => {
if (amount !== undefined) {
assert(
amountMath.isEqual(amount, paymentBalance),
X`payment balance ${paymentBalance} must equal amount ${amount}`,
);
}
};
const { makeInstance: makeDepositFacet } = makeExternalStore(
'depositFacet',
/**
* @param {Purse} purse
* @returns {DepositFacet}
*/
purse =>
Far(makeFarName(allegedName, ERTPKind.DEPOSIT_FACET), {
receive: purse.deposit,
}),
);
const { makeInstance: makePurse } = makeExternalStore('purse', () => {
let currentBalance = amountMath.getEmpty();
/** @type {NotifierRecord<Amount>} */
const {
notifier: balanceNotifier,
updater: balanceUpdater,
} = makeNotifierKit(currentBalance);
/** @type {Purse} */
const purse = Far(makeFarName(allegedName, ERTPKind.PURSE), {
deposit: (srcPayment, optAmount = undefined) => {
if (isPromise(srcPayment)) {
throw new TypeError(
`deposit does not accept promises as first argument. Instead of passing the promise (deposit(paymentPromise)), consider unwrapping the promise first: paymentPromise.then(actualPayment => deposit(actualPayment))`,
);
}
assertKnownPayment(srcPayment);
const srcPaymentBalance = paymentLedger.get(srcPayment);
// Note: this does not guarantee that optAmount itself is a valid stable amount
assertAmountEqual(srcPaymentBalance, optAmount);
const newPurseBalance = amountMath.add(
srcPaymentBalance,
currentBalance,
);
// Commit point
// Move the assets in `srcPayment` into this purse, using up the
// source payment, such that total assets are conserved.
paymentLedger.delete(srcPayment);
currentBalance = newPurseBalance;
balanceUpdater.updateState(currentBalance);
return srcPaymentBalance;
},
withdraw: amount => {
amount = amountMath.coerce(amount);
const newPurseBalance = amountMath.subtract(currentBalance, amount);
const payment = makePayment();
// Commit point
// Move the withdrawn assets from this purse into a new payment
// which is returned. Total assets must remain conserved.
currentBalance = newPurseBalance;
balanceUpdater.updateState(currentBalance);
paymentLedger.init(payment, amount);
return payment;
},
getCurrentAmount: () => currentBalance,
getCurrentAmountNotifier: () => balanceNotifier,
getAllegedBrand: () => brand,
// eslint-disable-next-line no-use-before-define
getDepositFacet: () => depositFacet,
});
const depositFacet = makeDepositFacet(purse);
return purse;
});
/**
* Reallocate assets from the `payments` passed in to new payments
* created and returned, with balances from `newPaymentBalances`.
* Enforces that total assets are conserved.
*
* Note that this is not the only operation that reallocates assets.
* `purse.deposit` and `purse.withdraw` move assets between a purse and
* a payment, and so must also enforce conservation there.
*
* @param {Payment[]} payments
* @param {Amount[]} newPaymentBalances
* @returns {Payment[]}
*/
const reallocate = (payments, newPaymentBalances) => {
// There may be zero, one, or many payments as input to
// reallocate. We want to protect against someone passing in
// what appears to be multiple payments that turn out to actually
// be the same payment (an aliasing issue). The `combine` method
// legitimately needs to take in multiple payments, but we don't
// need to pay the costs of protecting against aliasing for the
// other uses.
if (payments.length > 1) {
const paymentSet = new Set();
payments.forEach(payment => {
if (paymentSet.has(payment)) {
throw new Error('same payment seen twice');
}
paymentSet.add(payment);
});
}
const total = payments.map(paymentLedger.get).reduce(add, empty);
const newTotal = newPaymentBalances.reduce(add, empty);
// Invariant check
assert(amountMath.isEqual(total, newTotal), 'rights were not conserved');
// commit point
payments.forEach(payment => paymentLedger.delete(payment));
const newPayments = newPaymentBalances.map(balance => {
const newPayment = makePayment();
paymentLedger.init(newPayment, balance);
return newPayment;
});
return harden(newPayments);
};
/** @type {Issuer} */
const issuer = Far(makeFarName(allegedName, ERTPKind.ISSUER), {
getBrand: () => brand,
getAllegedName: () => allegedName,
getAmountMathKind: () => amountMathKind,
makeEmptyPurse: makePurse,
isLive: paymentP => {
return E.when(paymentP, payment => {
return paymentLedger.has(payment);
});
},
getAmountOf: paymentP => {
return E.when(paymentP, payment => {
assertKnownPayment(payment);
return paymentLedger.get(payment);
});
},
burn: (paymentP, optAmount = undefined) => {
return E.when(paymentP, payment => {
assertKnownPayment(payment);
const paymentBalance = paymentLedger.get(payment);
assertAmountEqual(paymentBalance, optAmount);
// Commit point.
paymentLedger.delete(payment);
return paymentBalance;
});
},
claim: (paymentP, optAmount = undefined) => {
return E.when(paymentP, srcPayment => {
assertKnownPayment(srcPayment);
const srcPaymentBalance = paymentLedger.get(srcPayment);
assertAmountEqual(srcPaymentBalance, optAmount);
// Commit point.
const [payment] = reallocate([srcPayment], [srcPaymentBalance]);
return payment;
});
},
// Payments in `fromPaymentsPArray` must be distinct. Alias
// checking is delegated to the `reallocate` function.
combine: (fromPaymentsPArray, optTotalAmount = undefined) => {
return Promise.all(fromPaymentsPArray).then(fromPaymentsArray => {
fromPaymentsArray.every(assertKnownPayment);
const totalPaymentsBalance = fromPaymentsArray
.map(paymentLedger.get)
.reduce(add, empty);
assertAmountEqual(totalPaymentsBalance, optTotalAmount);
// Commit point.
const [payment] = reallocate(fromPaymentsArray, [totalPaymentsBalance]);
return payment;
});
},
// payment to two payments, A and B
split: (paymentP, paymentAmountA) => {
return E.when(paymentP, srcPayment => {
paymentAmountA = amountMath.coerce(paymentAmountA);
assertKnownPayment(srcPayment);
const srcPaymentBalance = paymentLedger.get(srcPayment);
const paymentAmountB = amountMath.subtract(
srcPaymentBalance,
paymentAmountA,
);
// Commit point
const newPayments = reallocate(
[srcPayment],
[paymentAmountA, paymentAmountB],
);
return newPayments;
});
},
splitMany: (paymentP, amounts) => {
return E.when(paymentP, srcPayment => {
assertKnownPayment(srcPayment);
amounts = amounts.map(amountMath.coerce);
// Commit point
const newPayments = reallocate([srcPayment], amounts);
return newPayments;
});
},
});
/** @type {Mint} */
const mint = Far(makeFarName(allegedName, ERTPKind.MINT), {
getIssuer: () => issuer,
mintPayment: newAmount => {
newAmount = amountMath.coerce(newAmount);
const payment = makePayment();
paymentLedger.init(payment, newAmount);
return payment;
},
});
return harden({
mint,
issuer,
amountMath,
brand,
});
}
harden(makeIssuerKit);
export { makeIssuerKit };