Update CBS Mobile App codebase

src/modules/payments/hooks/useTransferForm.ts

@@ -0,0 +1,69 @@
+import { useMemo, useState } from 'react';
+
+import { useAccountSelection } from '../../home/hooks/useAccounts';
+
+/**
+ * The half of a transfer form that is the same whichever way the money is
+ * addressed: which account it leaves, how much, and the note against it.
+ *
+ * The account list is read from `GET /accounts` on every mount — never from
+ * Redux, and never carried in from the previous screen.
+ *
+ * There is no balance check here, and that is not an omission. No endpoint in
+ * the CBS API returns a balance, so the app has nothing to compare an amount
+ * against; inventing a limit would be worse than having none, because a
+ * customer refused by the app has no way to find out they were refused
+ * wrongly. The bank rejects an overdrawn transfer on submission, and that
+ * refusal is the authoritative one.
+ */
+export const useTransferForm = () => {
+  const { accounts, selectedAccountNumber, setSelectedAccountNumber, selectedAccount, isLoading, refetch } =
+    useAccountSelection();
+
+  const [amount, setAmount] = useState('');
+  const [remarks, setRemarks] = useState('');
+
+  /** Grouping separators are allowed in, but never reach the parsed value. */
+  const parsedAmount = useMemo(() => Number.parseFloat(amount.replace(/,/g, '')), [amount]);
+
+  const amountError = useMemo(() => {
+    if (amount.length === 0) {
+      return undefined;
+    }
+
+    if (Number.isNaN(parsedAmount) || parsedAmount <= 0) {
+      return 'Enter a valid amount';
+    }
+
+    return undefined;
+  }, [amount, parsedAmount]);
+
+  const amountValid = !amountError && parsedAmount > 0;
+
+  const handleAmountChange = (value: string) => {
+    // One decimal point, digits either side, at most two paise. Filtering on
+    // the way in beats validating after the fact: the field cannot hold
+    // something the parser would then have to reject.
+    const cleaned = value.replace(/[^0-9.]/g, '');
+    const [rupees = '', ...rest] = cleaned.split('.');
+    const paise = rest.join('').slice(0, 2);
+
+    setAmount(rest.length ? `${rupees}.${paise}` : rupees);
+  };
+
+  return {
+    accounts,
+    selectedAccount,
+    sourceAccountNumber: selectedAccountNumber,
+    setSourceAccountNumber: setSelectedAccountNumber,
+    accountsLoading: isLoading,
+    refetchAccounts: refetch,
+    amount,
+    handleAmountChange,
+    parsedAmount,
+    amountError,
+    amountValid,
+    remarks,
+    setRemarks,
+  };
+};