refactor(scaledPriceAuthority): factor out mintQuote()

- clarify priceOutPerIn - clarify mintCurrentQuote
Agoric · Feb 17, 2023 · b5820be · b5820be
1 parent fdc8582
commit b5820be
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Showing 2 changed files with 57 additions and 35 deletions.
diff --git a/packages/zoe/src/contractSupport/priceAuthorityInitial.js b/packages/zoe/src/contractSupport/priceAuthorityInitial.js
@@ -6,6 +6,7 @@ import { makeNotifier } from '@agoric/notifier';
 import { AmountMath } from '@agoric/ertp';
 
 import { multiplyBy } from './ratio.js';
+import { mintQuote } from './priceAuthorityTransform.js';
 
 /** @template T @typedef {import('@endo/eventual-send').EOnly<T>} EOnly */
 
@@ -15,22 +16,22 @@ import { multiplyBy } from './ratio.js';
  *
  * Mainly for testing vaults without waiting for oracle operators to PushPrice.
  *
- * @param {Ratio} initialPrice
+ * @param {Ratio} priceOutPerIn
  * @param {PriceAuthority} priceAuthority
  * @param {ERef<Mint<'set'>>} quoteMint
  * @param {Brand<'nat'>} brandIn
  * @param {Brand<'nat'>} brandOut
  * @returns {PriceAuthority}
  */
 export const makeInitialTransform = (
-  initialPrice,
+  priceOutPerIn,
   priceAuthority,
   quoteMint,
   brandIn,
   brandOut,
 ) => {
-  assert.equal(initialPrice.numerator.brand, brandOut);
-  assert.equal(initialPrice.denominator.brand, brandIn);
+  assert.equal(priceOutPerIn.numerator.brand, brandOut);
+  assert.equal(priceOutPerIn.denominator.brand, brandIn);
   let initialMode = true;
 
   const quoteBrandP = E(E(quoteMint).getIssuer()).getBrand();
@@ -41,34 +42,22 @@ export const makeInitialTransform = (
    * @param {Amount<'nat'>} amountOut
    * @returns {Promise<PriceQuote>}
    */
-  const oneQuote = async (amountIn, amountOut) => {
+  const mintCurrentQuote = async (amountIn, amountOut) => {
     const [quoteBrand, timer, timestamp] = await Promise.all([
       quoteBrandP,
       timerP,
       E(timerP).getCurrentTimestamp(),
     ]);
 
-    const quoteAmount = harden({
-      brand: quoteBrand,
-      value: [
-        {
-          amountIn,
-          amountOut,
-          timer,
-          timestamp,
-        },
-      ],
-    });
-    const quotePayment = await E(quoteMint).mintPayment({
-      brand: quoteBrand,
-      value: [quoteAmount],
-    });
-    return harden({ quoteAmount, quotePayment });
+    return mintQuote(
+      quoteBrand,
+      amountIn,
+      amountOut,
+      timer,
+      timestamp,
+      quoteMint,
+    );
   };
-  const initialUpdateP = oneQuote(
-    initialPrice.denominator,
-    initialPrice.numerator,
-  ).then(value => harden({ value, updateCount: 0n }));
 
   /** @type {PriceAuthority['makeQuoteNotifier']} */
   const makeQuoteNotifier = (amountIn, bOut) => {
@@ -77,6 +66,11 @@ export const makeInitialTransform = (
 
     const notifier = E(priceAuthority).makeQuoteNotifier(amountIn, brandOut);
 
+    const initialUpdateP = mintCurrentQuote(
+      priceOutPerIn.denominator,
+      priceOutPerIn.numerator,
+    ).then(value => harden({ value, updateCount: 0n }));
+
     // Wrap our underlying notifier.
     const prefixedNotifier = harden({
       async getUpdateSince(updateCount = -1n) {
@@ -106,7 +100,7 @@ export const makeInitialTransform = (
     const quoteP = E(priceAuthority).quoteGiven(amountIn, brandOut);
     quoteP.then(() => (initialMode = false));
     return initialMode
-      ? oneQuote(amountIn, multiplyBy(amountIn, initialPrice))
+      ? mintCurrentQuote(amountIn, multiplyBy(amountIn, priceOutPerIn))
       : quoteP;
   };
 

diff --git a/packages/zoe/src/contractSupport/priceAuthorityTransform.js b/packages/zoe/src/contractSupport/priceAuthorityTransform.js
@@ -6,6 +6,35 @@ import { makeNotifier } from '@agoric/notifier';
 
 /** @template T @typedef {import('@endo/eventual-send').EOnly<T>} EOnly */
 
+/**
+ *
+ * @param {Brand<'set'>} quoteBrand
+ * @param {Amount<'nat'>} amountIn
+ * @param {Amount<'nat'>} amountOut
+ * @param {ERef<import('@agoric/time/src/types').TimerService>} timer
+ * @param {import('@agoric/time').Timestamp} timestamp
+ * @param {ERef<Mint<'set'>>} quoteMint
+ * @returns {Promise<PriceQuote>}
+ */
+export const mintQuote = async (
+  quoteBrand,
+  amountIn,
+  amountOut,
+  timer,
+  timestamp,
+  quoteMint,
+) => {
+  const quoteAmount = {
+    brand: quoteBrand,
+    value: [{ amountIn, amountOut, timer, timestamp }],
+  };
+  const quotePayment = await E(quoteMint).mintPayment({
+    brand: quoteBrand,
+    value: [quoteAmount],
+  });
+  return harden({ quoteAmount, quotePayment });
+};
+
 /**
  * @param {object} opts
  * @param {ERef<Mint<'set'>>} [opts.quoteMint]
@@ -84,15 +113,14 @@ export const makePriceAuthorityTransform = async ({
     const amountIn = transformSourceAmountIn(sourceAmountIn);
     const amountOut = transformSourceAmountOut(sourceAmountOut);
 
-    const quoteAmount = {
-      brand: quoteBrand,
-      value: [{ amountIn, amountOut, timer, timestamp }],
-    };
-    const quotePayment = await E(quoteMint).mintPayment({
-      brand: quoteBrand,
-      value: [quoteAmount],
-    });
-    return harden({ quoteAmount, quotePayment });
+    return mintQuote(
+      quoteBrand,
+      amountIn,
+      amountOut,
+      timer,
+      timestamp,
+      quoteMint,
+    );
   };
 
   /**