feat: Auto re-calculate the items rate once changing the invoice exchange rate.

packages/webapp/src/containers/Sales/Invoices/InvoiceForm/utils.tsx

@@ -5,7 +5,7 @@ import intl from 'react-intl-universal';
 import moment from 'moment';
 import * as R from 'ramda';
 import { Intent } from '@blueprintjs/core';
-import { omit, first, sumBy } from 'lodash';
+import { omit, first, sumBy, round } from 'lodash';
 import {
   compose,
   transformToForm,
@@ -57,7 +57,7 @@ export const defaultInvoice = {
   reference_no: '',
   invoice_message: '',
   terms_conditions: '',
-  exchange_rate: 1,
+  exchange_rate: '1',
   currency_code: '',
   branch_id: '',
   warehouse_id: '',
@@ -398,3 +398,85 @@ export const useIsInvoiceTaxExclusive = () => {
 
   return values.inclusive_exclusive_tax === TaxType.Exclusive;
 };
+
+/**
+ * Convert the given rate to the local currency.
+ * @param {number} rate
+ * @param {number} exchangeRate
+ * @returns {number}
+ */
+export const convertToForeignCurrency = (
+  rate: number,
+  exchangeRate: number,
+) => {
+  return rate * exchangeRate;
+};
+
+/**
+ * Converts the given rate to the base currency.
+ * @param {number} rate
+ * @param {number} exchangeRate
+ * @returns {number}
+ */
+export const covertToBaseCurrency = (rate: number, exchangeRate: number) => {
+  return rate / exchangeRate;
+};
+
+/**
+ * Reverts the given rate from the old exchange rate and covert it to the new
+ * currency based on the given new exchange rate.
+ * @param {number} rate -
+ * @param {number} oldExchangeRate - Old exchange rate.
+ * @param {number} newExchangeRate - New exchange rate.
+ * @returns {number}
+ */
+const revertAndConvertExchangeRate = (
+  rate: number,
+  oldExchangeRate: number,
+  newExchangeRate: number,
+) => {
+  const oldValue = convertToForeignCurrency(rate, oldExchangeRate);
+  const newValue = covertToBaseCurrency(oldValue, newExchangeRate);
+
+  return round(newValue, 3);
+};
+
+/**
+ * Assign the new item entry rate after converting to the new exchange rate.
+ * @params {number} oldExchangeRate -
+ * @params {number} newExchangeRate -
+ * @params {IItemEntry} entries -
+ */
+const assignRateRevertAndCovertExchangeRate = R.curry(
+  (oldExchangeRate: number, newExchangeRate: number, entries: IItemEntry[]) => {
+    return entries.map((entry) => ({
+      ...entry,
+      rate: revertAndConvertExchangeRate(
+        entry.rate,
+        oldExchangeRate,
+        newExchangeRate,
+      ),
+    }));
+  },
+);
+
+/**
+ * Compose invoice entries on exchange rate change.
+ * @returns {(oldExchangeRate: number, newExchangeRate: number) => IItemEntry[]}
+ */
+export const useInvoiceEntriesOnExchangeRateChange = () => {
+  const {
+    values: { entries },
+  } = useFormikContext();
+
+  return React.useMemo(() => {
+    return R.curry((oldExchangeRate: number, newExchangeRate: number) => {
+      return R.compose(
+        // Updates entries total.
+        updateItemsEntriesTotal,
+        // Assign a new rate of the given new exchange rate from the old exchange rate.
+        assignRateRevertAndCovertExchangeRate(oldExchangeRate, newExchangeRate),
+      )(entries);
+    });
+  }, [entries]);
+};