From 46937e66ed683e3f08b17cc38a36deb5a000c971 Mon Sep 17 00:00:00 2001
From: Sebastian Scatularo <sebastian.scatularo@xlabs.xyz>
Date: Wed, 9 Aug 2023 10:49:23 -0300
Subject: [PATCH] Enforce minimum amount for evm token transfers

---
 src/components/Transfer/Source.tsx |  5 +++-
 src/hooks/useMinimumAmountGuard.ts | 43 ++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 1 deletion(-)
 create mode 100644 src/hooks/useMinimumAmountGuard.ts

diff --git a/src/components/Transfer/Source.tsx b/src/components/Transfer/Source.tsx
index e447d6402..033096af0 100644
--- a/src/components/Transfer/Source.tsx
+++ b/src/components/Transfer/Source.tsx
@@ -52,6 +52,7 @@ import { RootState } from "../../store";
 import useTransferControl from "../../hooks/useTransferControl";
 import transferRules from "../../config/transferRules";
 import useRoundTripTransfer from "../../hooks/useRoundTripTransfer";
+import useMinimumAmountGuard from "../../hooks/useMinimumAmountGuard";
 
 const useStyles = makeStyles((theme) => ({
   chainSelectWrapper: {
@@ -169,7 +170,7 @@ function Source() {
     isPandle
   );
   /* End pandle token check */
-
+  const isBelowMinimum = useMinimumAmountGuard();
   return (
     <>
       <StepDescription>
@@ -260,6 +261,8 @@ function Source() {
               value={amount}
               onChange={handleAmountChange}
               disabled={isTransferDisabled || shouldLockFields}
+              error={isBelowMinimum}
+              helperText={isBelowMinimum ? "Amount is below minimum" : ""}
               onMaxClick={
                 uiAmountString && !parsedTokenAccount.isNativeAsset
                   ? handleMaxClick
diff --git a/src/hooks/useMinimumAmountGuard.ts b/src/hooks/useMinimumAmountGuard.ts
new file mode 100644
index 000000000..5afbe0b1d
--- /dev/null
+++ b/src/hooks/useMinimumAmountGuard.ts
@@ -0,0 +1,43 @@
+import type { RootState } from "../store";
+import { useMemo } from "react";
+import { useSelector } from "react-redux";
+import { ChainId, isEVMChain } from "@certusone/wormhole-sdk";
+
+function checkIfIsBelowMinimum(amount: string, decimals: number) {
+  try {
+    const divider = Math.pow(10, decimals);
+    const floatAmount = parseFloat(amount);
+    const intAmount = floatAmount * divider;
+    return Math.trunc(intAmount) <= 0;
+  } catch (err: any) {
+    console.error(err);
+    return true;
+  }
+}
+
+function getAdjustedDecimals(
+  chainId: ChainId,
+  isNativeAsset: boolean,
+  decimals: number
+) {
+  return isEVMChain(chainId) && !isNativeAsset && decimals > 8
+    ? decimals - 8
+    : decimals;
+}
+
+export default function useMinimumAmountGuard() {
+  const {
+    amount,
+    sourceChain,
+    sourceParsedTokenAccount: { decimals = 0, isNativeAsset = false } = {},
+  } = useSelector((state: RootState) => state.transfer);
+  const isBelowMinimum = useMemo(
+    () =>
+      checkIfIsBelowMinimum(
+        amount,
+        getAdjustedDecimals(sourceChain, isNativeAsset, decimals)
+      ),
+    [amount, sourceChain, isNativeAsset, decimals]
+  );
+  return isBelowMinimum;
+}