Input validation (#598)

* chore: another one

components/AssetInput/WhaleInput.tsx

@@ -126,7 +126,10 @@ ref) => {
               onChange={({ target }) => {
                 onChange({
                   ...token,
-                  amount: amountInputValidation(target.value),
+                  amount: amountInputValidation(
+                    target.value,
+                    tokenInfo?.decimals
+                  ),
                 });
               }}
             />

util/amountInputValidation.ts

@@ -2,20 +2,26 @@
  * General use validation function for when the user supplies a positive decimal value.
  * For example it is used with token and slippage amounts.
  * @param input The user supplied value
+ * @param decimals Optional number of decimals to respect
  * @returns Validated string that has invalid patterns removed
  */
-export const amountInputValidation = (input: string): string => {
-  const amount = input.
-    // Limiting the number of characters to be 32
+export const amountInputValidation = (input: string, decimals?: number): string => {
+  let amount = input.
     slice(0, 32).
-    // Disallowing leading decimal place and multiple zeros before decimal place
     replace(/^(?:\.|0{2,}\.)/u, '0.').
-    // Eliminating multiple leading zeros before the numbers between 1-9
-    replace(/^0+(?=[0-9])/u, '').
-    // Remove excess zeros after decimal point
-    replace(/\.(\d+?)0{2,}$/u, '.$10')
-  // Ensuring multiple decimal points can't be used
-  return input.indexOf('.') !== amount.lastIndexOf('.') ?
-    amount.slice(0, amount.indexOf('.') + 1) + amount.slice(amount.indexOf('.')).replaceAll('.', '')
-    : amount;
+    replace(/^0+(?=[0-9])/u, '')
+
+  // Handle multiple decimal points
+  if (input.indexOf('.') !== amount.lastIndexOf('.')) {
+    amount = amount.slice(0, amount.indexOf('.') + 1) +
+      amount.slice(amount.indexOf('.')).replaceAll('.', '')
+  }
+
+  // If decimals is specified, just limit decimal places without padding
+  if (decimals !== undefined && amount.includes('.')) {
+    const [whole, fraction] = amount.split('.')
+    amount = `${whole}.${fraction.slice(0, decimals)}`
+  }
+
+  return amount
 }