# Issuers and Mints

# Issuers

Issuer structure

Note: You should not create an Issuer in a deploy script. Deploy scripts are ephemeral, so any object created there dies as soon as the script stops.

Behind the scenes, an issuer maps minted digital assets to their location in a purse or payment. An issuer verifies, moves, and manipulates digital assets. Its special admin facet is a mint which it has a one-to-one relationship with. Only a mint can issue new digital assets; an issuer cannot.

An issuer also has a one-to-one relationship with a brand. So, if our brand is the imaginary currency Quatloos, only the issuer in the one-to-one relationship with the Quatloos brand can:

Create a new empty purse that can store Quatloos.
Manipulate a payment in Quatloos to be claimed, split, combined, burned, or have its amount received.

An issuer should be obtained from a trusted source and then relied upon as the authority as to whether an untrusted payment of the same brand is valid.

Issuer methods

Issuer methods:

Return information about an issuer.
Create a new issuer.
Create a new purse.
Operate on payment arguments.

The following is a brief description and example of each Issuer method. For more detail, click the method's name to go to its entry in the ERTP API Reference.

Create issuer operation

makeIssuerKit()

Create and return a new issuer and its associated mint and brand.

/* eslint-disable import/order -- https://github.com/endojs/endo/issues/1235 */
import { test } from '../../prepare-test-env-ava.js';

import { AmountMath, makeIssuerKit, AssetKind } from '@agoric/ertp';

// TODO `claim`,`combine`, `split`, and `splitMany' are deprecated.
// Stop documenting, importing, and testing them.
import {
  claim,
  combine,
  split,
  splitMany,
} from '@agoric/ertp/src/legacy-payment-helpers.js';

test('ertp guide issuers and mints makeIssuerKit', async t => {
  // #region makeIssuerKit
  const {
    issuer: quatloosIssuer,
    mint: quatloosMint,
    brand: quatloosBrand,
  } = makeIssuerKit('quatloos');
  // This is merely an amount, describing assets.
  // It does not create new assets.
  const quatloos2 = AmountMath.make(quatloosBrand, 2n);
  // Non-fungible asset, which needs an AssetKind
  // of AssetKind.SET
  const { mint: titleMint, issuer: titleIssuer } = makeIssuerKit(
    'alamedaCountyPropertyTitle',
    AssetKind.SET,
  );
  // #endregion makeIssuerKit

  t.truthy(quatloosIssuer);
  t.truthy(quatloosMint);
  t.truthy(quatloosBrand);
  t.deepEqual(quatloos2, { brand: quatloosBrand, value: 2n });
  t.truthy(titleMint);
  t.truthy(titleIssuer);
});

test('ertp guide issuers and mints getBrand', async t => {
  // #region getBrand
  const { issuer: quatloosIssuer, brand: quatloosBrand } = makeIssuerKit(
    'quatloos',
  );
  // myQuatloosBrand === quatloosBrand
  const myQuatloosBrand = quatloosIssuer.getBrand();
  // #endregion getBrand

  t.is(quatloosBrand, myQuatloosBrand);
});

test('ertp guide issuers and mints getAllegedName', async t => {
  // #region getAllegedName
  const { issuer: quatloosIssuer } = makeIssuerKit('quatloos');
  const quatloosIssuerAllegedName = quatloosIssuer.getAllegedName();
  // quatloosIssuerAllegedName === 'quatloos'
  // #endregion getAllegedName
  t.is(quatloosIssuerAllegedName, 'quatloos');
});

test('ertp guide issuers and mints getAssetKind', async t => {
  // #region getAssetKind
  const { issuer: quatloosIssuer } = makeIssuerKit('quatloos');
  const kind = quatloosIssuer.getAssetKind(); // 'nat', the default value for makeIssuerKit()
  // #endregion getAssetKind
  t.is(kind, 'nat');
});

test('ertp guide issuers and mints makeEmptyPurse', async t => {
  // #region makeEmptyPurse
  const { issuer: quatloosIssuer } = makeIssuerKit('quatloos');
  // The new empty purse contains 0 Quatloos
  const quatloosPurse = quatloosIssuer.makeEmptyPurse();
  // #endregion makeEmptyPurse
  t.deepEqual(await quatloosPurse.getCurrentAmount(), {
    brand: quatloosIssuer.getBrand(),
    value: 0n,
  });
});

test('ertp guide issuers and mints payment methods', async t => {
  const {
    issuer: quatloosIssuer,
    brand: quatloosBrand,
    mint: quatloosMint,
  } = makeIssuerKit('quatloos');

  const recoveryPurse = quatloosIssuer.makeEmptyPurse();

  // #region getAmountOf
  const quatloosPayment = quatloosMint.mintPayment(
    AmountMath.make(quatloosBrand, 100n),
  );
  // returns an amount with a value of 100 and the quatloos brand
  quatloosIssuer.getAmountOf(quatloosPayment);
  // #endregion getAmountOf

  // #region burn
  const amountToBurn = AmountMath.make(quatloosBrand, 10n);
  const paymentToBurn = quatloosMint.mintPayment(amountToBurn);
  // burntAmount is 10 quatloos
  const burntAmount = await quatloosIssuer.burn(paymentToBurn, amountToBurn);
  // #endregion burn
  t.deepEqual(burntAmount, amountToBurn);

  // #region claim
  const amountToTransfer = AmountMath.make(quatloosBrand, 2n);
  const originalPayment = quatloosMint.mintPayment(amountToTransfer);
  const newPayment = await claim(
    recoveryPurse,
    originalPayment,
    amountToTransfer,
  );
  // #endregion claim
  t.deepEqual(await quatloosIssuer.getAmountOf(newPayment), amountToTransfer);
  t.not(originalPayment, newPayment);

  // #region combine
  // create an array of 100 payments of 1 unit each
  const payments = [];
  for (let i = 0; i < 100; i += 1) {
    payments.push(quatloosMint.mintPayment(AmountMath.make(quatloosBrand, 1n)));
  }
  // combinedPayment equals 100
  const combinedPayment = combine(recoveryPurse, harden(payments));
  // #endregion combine

  t.deepEqual(await quatloosIssuer.getAmountOf(combinedPayment), {
    brand: quatloosBrand,
    value: 100n,
  });

  // #region split
  const oldPayment = quatloosMint.mintPayment(
    AmountMath.make(quatloosBrand, 30n),
  );
  const [paymentA, paymentB] = await split(
    recoveryPurse,
    oldPayment,
    AmountMath.make(quatloosBrand, 10n),
  );
  // paymentA is 10 quatloos, payment B is 20 quatloos.
  // #endregion split
  const paymentAAmount = await quatloosIssuer.getAmountOf(paymentA);
  const paymentBAmount = await quatloosIssuer.getAmountOf(paymentB);
  t.deepEqual(paymentAAmount, AmountMath.make(quatloosBrand, 10n));
  t.deepEqual(paymentBAmount, AmountMath.make(quatloosBrand, 20n));

  // #region splitMany
  // #region splitManyConcise
  const oldQuatloosPayment = quatloosMint.mintPayment(
    AmountMath.make(quatloosBrand, 100n),
  );
  const goodQuatloosAmounts = Array(10).fill(
    AmountMath.make(quatloosBrand, 10n),
  );

  const arrayOfNewPayments = await splitMany(
    recoveryPurse,
    oldQuatloosPayment,
    harden(goodQuatloosAmounts),
  );
  // #endregion splitManyConcise
  // Note that the total amount in the amountArray must equal the
  // amount in the original payment, in the above case, 100 Quatloos in each.

  const anotherQuatloosPayment = quatloosMint.mintPayment(
    AmountMath.make(quatloosBrand, 1000n),
  );
  // total amounts in badQuatloosAmounts equal 20, when it should equal 1000
  const badQuatloosAmounts = Array(2).fill(AmountMath.make(quatloosBrand, 10n));
  // throws error
  await t.throwsAsync(
    () =>
      splitMany(
        recoveryPurse,
        anotherQuatloosPayment,
        harden(badQuatloosAmounts),
      ),
    { message: /rights were not conserved/ },
  );
  // #endregion splitMany

  t.is(arrayOfNewPayments.length, 10);
  t.deepEqual(await quatloosIssuer.getAmountOf(arrayOfNewPayments[0]), {
    value: 10n,
    brand: quatloosBrand,
  });

  const payment = quatloosMint.mintPayment(
    AmountMath.make(quatloosBrand, 100n),
  );
  // #region isLive
  const isItLive = quatloosIssuer.isLive(payment);
  // #endregion isLive
  t.truthy(isItLive);

  // #region getIssuer
  const quatloosMintIssuer = quatloosMint.getIssuer();
  // returns true
  const sameIssuer = quatloosIssuer === quatloosMintIssuer;
  // #endregion

  t.truthy(sameIssuer);

  // #region isMyIssuer
  const isIssuer = quatloosBrand.isMyIssuer(quatloosIssuer);
  // #endregion isMyIssuer

  t.truthy(isIssuer);
});

test('ertp guide issuers and mints mint.getIssuer', async t => {
  // #region mintGetIssuer
  const { issuer: quatloosIssuer, mint: quatloosMint } = makeIssuerKit(
    'quatloos',
  );
  const quatloosMintIssuer = quatloosMint.getIssuer();
  // returns true
  const sameIssuer = quatloosIssuer === quatloosMintIssuer;
  // #endregion mintGetIssuer
  t.truthy(sameIssuer);
});

test('ertp guide issuers and mints mint.mintPayment', async t => {
  // #region mintMintPayment
  const { mint: quatloosMint, brand: quatloosBrand } = makeIssuerKit(
    'quatloos',
  );
  const quatloos1000 = AmountMath.make(quatloosBrand, 1000n);
  const newPayment = quatloosMint.mintPayment(quatloos1000);
  // #endregion mintMintPayment

  const issuer = quatloosMint.getIssuer();
  t.truthy(issuer.isLive(newPayment));
});

test('ertp guide mints makeIssuerKit', async t => {
  // #region makeIssuerKitMint
  const {
    issuer: quatloosIssuer,
    mint: quatloosMint,
    brand: quatloosBrand,
  } = makeIssuerKit('quatloos');
  // Mint a new 2 Quatloos payment
  const paymentQuatloos2 = quatloosMint.mintPayment(
    AmountMath.make(quatloosBrand, 2n),
  );
  // #endregion makeIssuerKitMint
  t.truthy(quatloosIssuer.isLive(paymentQuatloos2));
  t.truthy(quatloosIssuer);
  t.truthy(quatloosMint);
  t.truthy(quatloosBrand);
});

const {
  issuer: quatloosIssuer,
  mint: quatloosMint,
  brand: quatloosBrand,
} = makeIssuerKit('quatloos');
// This is merely an amount, describing assets.
// It does not create new assets.
const quatloos2 = AmountMath.make(quatloosBrand, 2n);
// Non-fungible asset, which needs an AssetKind
// of AssetKind.SET
const { mint: titleMint, issuer: titleIssuer } = makeIssuerKit(
  'alamedaCountyPropertyTitle',
  AssetKind.SET,
);

Get information about the issuer operations

anIssuer.getAllegedName()

Return the allegedName for the issuer (the non-trusted human-readable name of its associated brand).

const { issuer: quatloosIssuer } = makeIssuerKit('quatloos');
const quatloosIssuerAllegedName = quatloosIssuer.getAllegedName();
// quatloosIssuerAllegedName === 'quatloos'

anIssuer.getAssetKind()

Return the kind of the issuer's asset; either AssetKind.NAT ("nat") or AssetKind.SET ("set").

const { issuer: quatloosIssuer } = makeIssuerKit('quatloos');
const kind = quatloosIssuer.getAssetKind(); // 'nat', the default value for makeIssuerKit()

anIssuer.getBrand()

Return the brand for the issuer.

const { issuer: quatloosIssuer, brand: quatloosBrand } = makeIssuerKit(
  'quatloos',
);
// myQuatloosBrand === quatloosBrand
const myQuatloosBrand = quatloosIssuer.getBrand();

Purse operation

anIssuer.makeEmptyPurse()

Make and return an empty purse for holding assets of the brand associated with the issuer.

const { issuer: quatloosIssuer } = makeIssuerKit('quatloos');
// The new empty purse contains 0 Quatloos
const quatloosPurse = quatloosIssuer.makeEmptyPurse();

Payment operations

anIssuer.burn(payment, optAmount)

Destroy all of the digital assets in the payment.

const amountToBurn = AmountMath.make(quatloosBrand, 10n);
const paymentToBurn = quatloosMint.mintPayment(amountToBurn);
// burntAmount is 10 quatloos
const burntAmount = await quatloosIssuer.burn(paymentToBurn, amountToBurn);

anIssuer.claim(payment, optAmount)

Transfer all digital assets from payment to a new Payment.

const amountToTransfer = AmountMath.make(quatloosBrand, 2n);
const originalPayment = quatloosMint.mintPayment(amountToTransfer);
const newPayment = await claim(
  recoveryPurse,
  originalPayment,
  amountToTransfer,
);

anIssuer.combine(paymentsArray)

Combine multiple Payments into one new Payment.

// create an array of 100 payments of 1 unit each
const payments = [];
for (let i = 0; i < 100; i += 1) {
  payments.push(quatloosMint.mintPayment(AmountMath.make(quatloosBrand, 1n)));
}
// combinedPayment equals 100
const combinedPayment = combine(recoveryPurse, harden(payments));

anIssuer.getAmountOf(payment)

Describe the payment's balance as an Amount.

const quatloosPayment = quatloosMint.mintPayment(
  AmountMath.make(quatloosBrand, 100n),
);
// returns an amount with a value of 100 and the quatloos brand
quatloosIssuer.getAmountOf(quatloosPayment);

anIssuer.isLive(payment)
- Return true if the payment was created by the issuer and is available for use (has not been consumed or burned).
- ```
  const isItLive = quatloosIssuer.isLive(payment);
```

anIssuer.split(payment, paymentAmountA)

Split a single payment into two new Payments.

const oldPayment = quatloosMint.mintPayment(
  AmountMath.make(quatloosBrand, 30n),
);
const [paymentA, paymentB] = await split(
  recoveryPurse,
  oldPayment,
  AmountMath.make(quatloosBrand, 10n),
);
// paymentA is 10 quatloos, payment B is 20 quatloos.

anIssuer.splitMany(payment, paymentAmountArray)

Split a single payment into multiple Payments.

const oldQuatloosPayment = quatloosMint.mintPayment(
  AmountMath.make(quatloosBrand, 100n),
);
const goodQuatloosAmounts = Array(10).fill(
  AmountMath.make(quatloosBrand, 10n),
);

const arrayOfNewPayments = await splitMany(
  recoveryPurse,
  oldQuatloosPayment,
  harden(goodQuatloosAmounts),
);
// Note that the total amount in the amountArray must equal the
// amount in the original payment, in the above case, 100 Quatloos in each.

const anotherQuatloosPayment = quatloosMint.mintPayment(
  AmountMath.make(quatloosBrand, 1000n),
);
// total amounts in badQuatloosAmounts equal 20, when it should equal 1000
const badQuatloosAmounts = Array(2).fill(AmountMath.make(quatloosBrand, 10n));
// throws error
await t.throwsAsync(
  () =>
    splitMany(
      recoveryPurse,
      anotherQuatloosPayment,
      harden(badQuatloosAmounts),
    ),
  { message: /rights were not conserved/ },
);

Related Methods:

Note: These methods help you find the right issuer, but aren't authoritative. A mint, brand, or purse is actually associated with an issuer only if the issuer itself acknowledges the association.

aMint.getIssuer()

Return the issuer uniquely associated with the mint.

const { issuer: quatloosIssuer, mint: quatloosMint } = makeIssuerKit(
  'quatloos',
);
const quatloosMintIssuer = quatloosMint.getIssuer();
// returns true
const sameIssuer = quatloosIssuer === quatloosMintIssuer;

aBrand.isMyIssuer(issuer)
- Return true if issuer is the brand's issuer, false if not.
- ```
  const isIssuer = quatloosBrand.isMyIssuer(quatloosIssuer);
```

# Mints

Mint methods

A mint issues new digital assets of its associated brand as a new payment object. These assets may be currency-like (our imaginary Quatloos currency), goods-like valuables (magic swords for games), or electronic rights (the right to participate in a contract). Only a holder of a mint object can create new assets from it.

In other words, let's say there are 1000 Quatloos in circulation. Only holders of the Quatloos associated mint can make any more Quatloos that'd boost the amount in circulation to, say, 2000.

Since these relationships are one-to-one and unchangeable:

A mint created to make an asset brand, say Quatloos, can only create that brand asset. For example, only Quatloos, not Moola or anything else.
A mint that creates an asset brand is the only mint that can create that brand. Only the one Quatloos mint can create new Quatloos.
A mint that creates an asset brand can never be changed to create a different brand. So a Quatloos mint can never become a Moola mint, or any other non-Quatloos asset.

There are two mint methods, and the method that creates new mints. Click the method's name to go to its entry in the ERTP API Reference.

aMint.getIssuer()

Return the issuer uniquely associated with the mint.

const { issuer: quatloosIssuer, mint: quatloosMint } = makeIssuerKit(
  'quatloos',
);
const quatloosMintIssuer = quatloosMint.getIssuer();
// returns true
const sameIssuer = quatloosIssuer === quatloosMintIssuer;

aMint.mintPayment()

Create new digital assets of the mint's associated brand.

const { mint: quatloosMint, brand: quatloosBrand } = makeIssuerKit(
  'quatloos',
);
const quatloos1000 = AmountMath.make(quatloosBrand, 1000n);
const newPayment = quatloosMint.mintPayment(quatloos1000);

makeIssuerKit()

Create and return a new issuer and its associated mint and brand.

const {
  issuer: quatloosIssuer,
  mint: quatloosMint,
  brand: quatloosBrand,
} = makeIssuerKit('quatloos');
// Mint a new 2 Quatloos payment
const paymentQuatloos2 = quatloosMint.mintPayment(
  AmountMath.make(quatloosBrand, 2n),
);

← AmountMath Purses and Payments →