From a17c4462b4e6a96ad47d36ade22b321423ca859a Mon Sep 17 00:00:00 2001
From: Daniel <80175477+dan437@users.noreply.github.com>
Date: Thu, 22 Jul 2021 19:29:31 +0200
Subject: [PATCH] Add token decimals validation in Swaps (#11587)

* Add token decimals validation in Swaps
* Use camelCase
---
 app/_locales/en/messages.json             |  4 +++
 ui/pages/swaps/build-quote/build-quote.js | 37 ++++++++++++++++-------
 ui/pages/swaps/build-quote/index.scss     |  5 +++
 ui/pages/swaps/index.js                   | 18 ++++++++---
 ui/pages/swaps/swaps.util.js              |  9 ++++++
 ui/pages/swaps/swaps.util.test.js         | 23 ++++++++++++++
 6 files changed, 81 insertions(+), 15 deletions(-)

diff --git a/app/_locales/en/messages.json b/app/_locales/en/messages.json
index 73f8d3f1b..94df54cd8 100644
--- a/app/_locales/en/messages.json
+++ b/app/_locales/en/messages.json
@@ -2302,6 +2302,10 @@
     "message": "Verified on $1 sources.",
     "description": "Indicates the number of token information sources that recognize the symbol + address. $1 is a decimal number."
   },
+  "swapTooManyDecimalsError": {
+    "message": "$1 allows up to $2 decimals",
+    "description": "$1 is a token symbol and $2 is the max. number of decimals allowed for the token"
+  },
   "swapTransactionComplete": {
     "message": "Transaction complete"
   },
diff --git a/ui/pages/swaps/build-quote/build-quote.js b/ui/pages/swaps/build-quote/build-quote.js
index 4985a8f6d..5b26ba4cb 100644
--- a/ui/pages/swaps/build-quote/build-quote.js
+++ b/ui/pages/swaps/build-quote/build-quote.js
@@ -74,6 +74,7 @@ export default function BuildQuote({
   maxSlippage,
   selectedAccountAddress,
   isFeatureFlagLoaded,
+  tokenFromError,
 }) {
   const t = useContext(I18nContext);
   const dispatch = useDispatch();
@@ -367,6 +368,11 @@ export default function BuildQuote({
     }
   }
 
+  const swapYourTokenBalance = t('swapYourTokenBalance', [
+    fromTokenString || '0',
+    fromTokenSymbol,
+  ]);
+
   return (
     <div className="build-quote">
       <div className="build-quote__content">
@@ -406,28 +412,35 @@ export default function BuildQuote({
         />
         <div
           className={classnames('build-quote__balance-message', {
-            'build-quote__balance-message--error': balanceError,
+            'build-quote__balance-message--error':
+              balanceError || tokenFromError,
           })}
         >
-          {!balanceError &&
+          {!tokenFromError &&
+            !balanceError &&
             fromTokenSymbol &&
-            t('swapYourTokenBalance', [
-              fromTokenString || '0',
-              fromTokenSymbol,
-            ])}
-          {balanceError && fromTokenSymbol && (
+            swapYourTokenBalance}
+          {!tokenFromError && balanceError && fromTokenSymbol && (
             <div className="build-quite__insufficient-funds">
               <div className="build-quite__insufficient-funds-first">
                 {t('swapsNotEnoughForTx', [fromTokenSymbol])}
               </div>
               <div className="build-quite__insufficient-funds-second">
-                {t('swapYourTokenBalance', [
-                  fromTokenString || '0',
-                  fromTokenSymbol,
-                ])}
+                {swapYourTokenBalance}
               </div>
             </div>
           )}
+          {tokenFromError && (
+            <>
+              <div className="build-quote__form-error">
+                {t('swapTooManyDecimalsError', [
+                  fromTokenSymbol,
+                  fromTokenDecimals,
+                ])}
+              </div>
+              <div>{swapYourTokenBalance}</div>
+            </>
+          )}
         </div>
         <div className="build-quote__swap-arrows-row">
           <button
@@ -560,6 +573,7 @@ export default function BuildQuote({
         }}
         submitText={t('swapReviewSwap')}
         disabled={
+          tokenFromError ||
           !isFeatureFlagLoaded ||
           !Number(inputValue) ||
           !selectedToToken?.address ||
@@ -582,4 +596,5 @@ BuildQuote.propTypes = {
   setMaxSlippage: PropTypes.func,
   selectedAccountAddress: PropTypes.string,
   isFeatureFlagLoaded: PropTypes.bool.isRequired,
+  tokenFromError: PropTypes.string,
 };
diff --git a/ui/pages/swaps/build-quote/index.scss b/ui/pages/swaps/build-quote/index.scss
index 1ebf6cab6..fbdff0def 100644
--- a/ui/pages/swaps/build-quote/index.scss
+++ b/ui/pages/swaps/build-quote/index.scss
@@ -87,6 +87,11 @@
         color: $Black-100;
       }
 
+      .build-quote__form-error:first-of-type {
+        font-weight: bold;
+        color: $Red-500;
+      }
+
       div:last-of-type {
         font-weight: normal;
         color: $Grey-500;
diff --git a/ui/pages/swaps/index.js b/ui/pages/swaps/index.js
index d2a30b904..8c7c7a6cf 100644
--- a/ui/pages/swaps/index.js
+++ b/ui/pages/swaps/index.js
@@ -34,6 +34,7 @@ import {
   fetchAndSetSwapsGasPriceInfo,
   fetchSwapsLiveness,
   getUseNewSwapsApi,
+  getFromToken,
 } from '../../ducks/swaps/swaps';
 import {
   AWAITING_SIGNATURES_ROUTE,
@@ -70,6 +71,7 @@ import {
   fetchTopAssets,
   getSwapsTokensReceivedFromTxMeta,
   fetchAggregatorMetadata,
+  countDecimals,
 } from './swaps.util';
 import AwaitingSignatures from './awaiting-signatures';
 import AwaitingSwap from './awaiting-swap';
@@ -94,6 +96,7 @@ export default function Swap() {
   const [inputValue, setInputValue] = useState(fetchParams?.value || '');
   const [maxSlippage, setMaxSlippage] = useState(fetchParams?.slippage || 3);
   const [isFeatureFlagLoaded, setIsFeatureFlagLoaded] = useState(false);
+  const [tokenFromError, setTokenFromError] = useState(null);
 
   const routeState = useSelector(getBackgroundSwapRouteState);
   const selectedAccount = useSelector(getSelectedAccount);
@@ -108,6 +111,7 @@ export default function Swap() {
   const chainId = useSelector(getCurrentChainId);
   const isSwapsChain = useSelector(getIsSwapsChain);
   const useNewSwapsApi = useSelector(getUseNewSwapsApi);
+  const fromToken = useSelector(getFromToken);
 
   const {
     balance: ethBalance,
@@ -288,10 +292,15 @@ export default function Swap() {
 
                 const onInputChange = (newInputValue, balance) => {
                   setInputValue(newInputValue);
-                  dispatch(
-                    setBalanceError(
-                      new BigNumber(newInputValue || 0).gt(balance || 0),
-                    ),
+                  const balanceError = new BigNumber(newInputValue || 0).gt(
+                    balance || 0,
+                  );
+                  // "setBalanceError" is just a warning, a user can still click on the "Review Swap" button.
+                  dispatch(setBalanceError(balanceError));
+                  setTokenFromError(
+                    countDecimals(newInputValue) > fromToken.decimals
+                      ? 'tooManyDecimals'
+                      : null,
                   );
                 };
 
@@ -304,6 +313,7 @@ export default function Swap() {
                     selectedAccountAddress={selectedAccountAddress}
                     maxSlippage={maxSlippage}
                     isFeatureFlagLoaded={isFeatureFlagLoaded}
+                    tokenFromError={tokenFromError}
                   />
                 );
               }}
diff --git a/ui/pages/swaps/swaps.util.js b/ui/pages/swaps/swaps.util.js
index 2e0a9b1dc..701409a4a 100644
--- a/ui/pages/swaps/swaps.util.js
+++ b/ui/pages/swaps/swaps.util.js
@@ -826,3 +826,12 @@ export const getSwapsLivenessForNetwork = (swapsFeatureFlags = {}, chainId) => {
     useNewSwapsApi: false,
   };
 };
+
+/**
+ * @param {number} value
+ * @returns number
+ */
+export const countDecimals = (value) => {
+  if (!value || Math.floor(value) === value) return 0;
+  return value.toString().split('.')[1]?.length || 0;
+};
diff --git a/ui/pages/swaps/swaps.util.test.js b/ui/pages/swaps/swaps.util.test.js
index 81220cbd4..f4a2fdfbe 100644
--- a/ui/pages/swaps/swaps.util.test.js
+++ b/ui/pages/swaps/swaps.util.test.js
@@ -31,6 +31,7 @@ import {
   isContractAddressValid,
   getNetworkNameByChainId,
   getSwapsLivenessForNetwork,
+  countDecimals,
 } from './swaps.util';
 
 jest.mock('../../helpers/utils/storage-helpers.js', () => ({
@@ -450,4 +451,26 @@ describe('Swaps Util', () => {
       ).toMatchObject(expectedSwapsLiveness);
     });
   });
+
+  describe('countDecimals', () => {
+    it('returns 0 decimals for an undefined value', () => {
+      expect(countDecimals()).toBe(0);
+    });
+
+    it('returns 0 decimals for number: 1', () => {
+      expect(countDecimals(1)).toBe(0);
+    });
+
+    it('returns 1 decimals for number: 1.1', () => {
+      expect(countDecimals(1.1)).toBe(1);
+    });
+
+    it('returns 3 decimals for number: 1.123', () => {
+      expect(countDecimals(1.123)).toBe(3);
+    });
+
+    it('returns 9 decimals for number: 1.123456789', () => {
+      expect(countDecimals(1.123456789)).toBe(9);
+    });
+  });
 });