feat: calculate total amount of form entries.

client/src/containers/Purchases/Bill/BillFormHeader.js

@@ -1,5 +1,7 @@
-import React from 'react';
+import React, { useMemo } from 'react';
 import classNames from 'classnames';
+import { sumBy } from 'lodash';
+import { useFormikContext } from 'formik';
 
 import { CLASSES } from 'common/classes';
 
@@ -10,11 +12,21 @@ import { PageFormBigNumber } from 'components';
  * Fill form header.
  */
 export default function BillFormHeader({ onBillNumberChanged }) {
+  const { values } = useFormikContext();
+
+  // Calculate the total due amount of bill entries.
+  const totalDueAmount = useMemo(() => sumBy(values.entries, 'total'), [
+    values.entries,
+  ]);
+
   return (
     <div className={classNames(CLASSES.PAGE_FORM_HEADER)}>
       <BillFormHeaderFields onBillNumberChanged={onBillNumberChanged} />
-
-      <PageFormBigNumber label={'Due Amount'} amount={0} currencyCode={'LYD'} />
+      <PageFormBigNumber
+        label={'Due Amount'}
+        amount={totalDueAmount}
+        currencyCode={'LYD'}
+      />
     </div>
   );
 }