ERC20 to ERC20 calculateInput & calculateOutput (#39)

src/helpers/exchange-utils.js

@@ -2,6 +2,11 @@ import {BigNumber as BN} from "bignumber.js";
 
 export const calculateExchangeRateFromInput = async opts => {
   const { inputCurrency, outputCurrency } = opts;
+
+  if (!inputCurrency || !outputCurrency) {
+    return;
+  }
+
   if (inputCurrency === outputCurrency) {
     console.error(`Input and Output currency cannot be the same`);
     return;
@@ -14,10 +19,18 @@ export const calculateExchangeRateFromInput = async opts => {
   if (outputCurrency === 'ETH' && inputCurrency !== 'ETH') {
     return ERC20_TO_ETH.calculateOutput(opts);
   }
+
+  return ERC20_TO_ERC20.calculateOutput(opts);
+
 };
 
 export const calculateExchangeRateFromOutput = async opts => {
   const { inputCurrency, outputCurrency } = opts;
+
+  if (!inputCurrency || !outputCurrency) {
+    return;
+  }
+
   if (inputCurrency === outputCurrency) {
     console.error(`Input and Output currency cannot be the same`);
     return;
@@ -30,6 +43,8 @@ export const calculateExchangeRateFromOutput = async opts => {
   if (outputCurrency === 'ETH' && inputCurrency !== 'ETH') {
     return ERC20_TO_ETH.calculateInput(opts);
   }
+
+  return ERC20_TO_ERC20.calculateInput(opts);
 };
 
 const ETH_TO_ERC20 = {
@@ -202,7 +217,6 @@ const ERC20_TO_ETH = {
       contractStore,
     });
 
-    // const outputDecimals = await getDecimals({ address: inputCurrency, contractStore, drizzleCtx });
     const outputAmount = BN(output).multipliedBy(10 ** 18);
     const numerator = outputAmount .multipliedBy(BN(inputReserve).multipliedBy(1000));
     const denominator = BN(outputReserve).minus(outputAmount).multipliedBy(997);
@@ -217,6 +231,55 @@ const ERC20_TO_ETH = {
   },
 };
 
+const ERC20_TO_ERC20 = {
+  calculateOutput: async opts => {
+    const inputDecimals = await getDecimals({
+      address: opts.inputCurrency,
+      contractStore: opts.contractStore,
+      drizzleCtx: opts.drizzleCtx
+    });
+    const inputAmountA = BN(opts.input).multipliedBy(BN(10 ** inputDecimals));
+    const exchangeRateA = await ERC20_TO_ETH.calculateOutput({ ...opts, outputCurrency: 'ETH' });
+    const inputAmountB = inputAmountA.multipliedBy(exchangeRateA);
+    const exchangeRateB = await ETH_TO_ERC20.calculateOutput({
+      ...opts,
+      input: inputAmountB.dividedBy(BN(10 ** 18)),
+      inputCurrency: 'ETH',
+    });
+
+    if (!exchangeRateA || !exchangeRateB) {
+      return;
+    }
+
+    return exchangeRateA.multipliedBy(exchangeRateB);
+  },
+  calculateInput: async opts => {
+    const outputDecimals = await getDecimals({
+      address: opts.outputCurrency,
+      contractStore: opts.contractStore,
+      drizzleCtx: opts.drizzleCtx
+    });
+    const outputAmountA = BN(opts.output).multipliedBy(BN(10 ** outputDecimals))
+    const exchangeRateA = await ETH_TO_ERC20.calculateInput({ ...opts, inputCurrency: 'ETH' });
+    if (!exchangeRateA) {
+      return;
+    }
+
+    const inputAmountB = outputAmountA.dividedBy(exchangeRateA).dividedBy(10 ** 18);
+    const exchangeRateB = await ERC20_TO_ETH.calculateInput({
+      ...opts,
+      outputCurrency: 'ETH',
+      output: inputAmountB,
+    });
+
+    if (!exchangeRateB) {
+      return;
+    }
+
+    return exchangeRateA.multipliedBy(exchangeRateB);
+  },
+};
+
 
 
 function getDecimals({ address, drizzleCtx, contractStore }) {