Added stories for AdminX CurrencyField (#17882)

refs https://github.com/TryGhost/Product/issues/3745

---

This pull request adds a storybook file for the `CurrencyField`
component and changes its value prop to use cents instead of a string.
This improves the component's usability and consistency.

apps/admin-x-settings/src/admin-x-ds/global/form/CurrencyField.stories.tsx

@@ -0,0 +1,36 @@
+import {ReactNode} from 'react';
+import {useArgs} from '@storybook/preview-api';
+import type {Meta, StoryObj} from '@storybook/react';
+
+import CurrencyField from './CurrencyField';
+
+const meta = {
+    title: 'Global / Form / Currency field',
+    component: CurrencyField,
+    tags: ['autodocs'],
+    decorators: [(_story: () => ReactNode) => (<div style={{maxWidth: '400px'}}>{_story()}</div>)],
+    argTypes: {
+        hint: {
+            control: 'text'
+        },
+        rightPlaceholder: {
+            control: 'text'
+        }
+    }
+} satisfies Meta<typeof CurrencyField>;
+
+export default meta;
+type Story = StoryObj<typeof CurrencyField>;
+
+export const WithValue: Story = {
+    render: function Component(args) {
+        const [, updateArgs] = useArgs();
+
+        return <CurrencyField {...args} onChange={valueInCents => updateArgs({valueInCents})} />;
+    },
+    args: {
+        title: 'Amount',
+        hint: 'Notice how the value is the integer number of cents',
+        valueInCents: 500
+    }
+};

apps/admin-x-settings/src/admin-x-ds/global/form/CurrencyField.tsx

@@ -2,17 +2,25 @@ import React, {useState} from 'react';
 import TextField, {TextFieldProps} from './TextField';
 import {currencyFromDecimal, currencyToDecimal} from '../../../utils/currency';
 
-export type CurrencyFieldProps = Omit<TextFieldProps, 'type' | 'onChange'> & {
-    currency?: string
-    onChange?: (value: number) => void
+export type CurrencyFieldProps = Omit<TextFieldProps, 'type' | 'onChange' | 'value'> & {
+    valueInCents?: number;
+    currency?: string;
+    onChange?: (cents: number) => void;
 }
 
+/**
+ * A CurrencyField is a special type of [TextField](?path=/docs/global-form-textfield--docs) with
+ * some parsing to input currency values. While editing you can enter any number of decimals, but
+ * the value in `onChange` will be rounded and multiplied to get an integer number of cents.
+ *
+ * Available options are generally the same as TextField.
+ */
 const CurrencyField: React.FC<CurrencyFieldProps> = ({
-    value,
+    valueInCents,
     onChange,
     ...props
 }) => {
-    const [localValue, setLocalValue] = useState(currencyToDecimal(parseInt(value || '0')).toString());
+    const [localValue, setLocalValue] = useState(currencyToDecimal(valueInCents || 0).toString());
 
     // While the user is editing we allow more lenient input, e.g. "1.32.566" to make it easier to type and change
     const stripNonNumeric = (input: string) => input.replace(/[^\d.]+/g, '');

apps/admin-x-settings/src/components/settings/membership/TipsOrDonations.tsx

@@ -105,7 +105,7 @@ const TipsOrDonations: React.FC<{ keywords: string[] }> = ({keywords}) => {
                     />
                 )}
                 title='Suggested amount'
-                value={donationsSuggestedAmount}
+                valueInCents={parseInt(donationsSuggestedAmount)}
                 onBlur={validate}
                 onChange={cents => updateSetting('donations_suggested_amount', cents.toString())}
                 onKeyDown={() => clearError('donationsSuggestedAmount')}

apps/admin-x-settings/src/components/settings/membership/tiers/TierDetailModal.tsx

@@ -170,7 +170,7 @@ const TierDetailModal: React.FC<TierDetailModalProps> = ({tier}) => {
                                     placeholder='1'
                                     rightPlaceholder={`${formState.currency}/month`}
                                     title='Monthly price'
-                                    value={formState.monthly_price?.toString() || ''}
+                                    valueInCents={formState.monthly_price || 0}
                                     hideTitle
                                     onBlur={() => validators.monthly_price()}
                                     onChange={price => updateForm(state => ({...state, monthly_price: price}))}
@@ -181,7 +181,7 @@ const TierDetailModal: React.FC<TierDetailModalProps> = ({tier}) => {
                                     placeholder='10'
                                     rightPlaceholder={`${formState.currency}/year`}
                                     title='Yearly price'
-                                    value={formState.yearly_price?.toString() || ''}
+                                    valueInCents={formState.yearly_price || 0}
                                     hideTitle
                                     onBlur={() => validators.yearly_price()}
                                     onChange={price => updateForm(state => ({...state, yearly_price: price}))}