Added a validation for a minimum suggested amount for Tips & Donations (#17653)

closes https://github.com/TryGhost/Product/issues/3695

- Stripe has minimum charge amounts per currency, see
https://stripe.com/docs/currencies#minimum-and-maximum-charge-amounts
- We double these limits in our validation, to take into account
currency conversions to the main currency used on the Stripe account. If
the publishers enters a suggested amount below the limit, they will see
an error in Admin
- 0 is permitted as default value and corresponds to "no suggested
amount"

ghost/admin/app/components/settings/tips-and-donations.hbs

@@ -73,7 +73,11 @@
                                 @class="gh-btn gh-btn-black gh-btn-icon" />
                         </div>
                     </GhFormGroup>
+
                 </div>
+                {{#if this.tipsAndDonationsError}}
+                    <p class="gh-setting-error"><span class="red">{{this.tipsAndDonationsError}}</span></p>
+                {{/if}}
             </GhFormGroup>
         </div>
         {{/liquid-if}}

ghost/admin/app/components/settings/tips-and-donations.js

@@ -2,10 +2,11 @@ import Component from '@glimmer/component';
 import copyTextToClipboard from 'ghost-admin/utils/copy-text-to-clipboard';
 import envConfig from 'ghost-admin/config/environment';
 import {action} from '@ember/object';
-import {currencies} from 'ghost-admin/utils/currency';
+import {currencies, getSymbol, minimumAmountForCurrency} from 'ghost-admin/utils/currency';
 import {inject} from 'ghost-admin/decorators/inject';
 import {inject as service} from '@ember/service';
 import {task, timeout} from 'ember-concurrency';
+import {tracked} from '@glimmer/tracking';
 
 const CURRENCIES = currencies.map((currency) => {
     return {
@@ -20,6 +21,7 @@ export default class TipsAndDonations extends Component {
     @service membersUtils;
 
     @inject config;
+    @tracked tipsAndDonationsError = '';
 
     get allCurrencies() {
         return CURRENCIES;
@@ -58,7 +60,16 @@ export default class TipsAndDonations extends Component {
     setDonationsSuggestedAmount(event) {
         const amount = Math.abs(event.target.value);
         const amountInCents = Math.round(amount * 100);
+        const currency = this.settings.donationsCurrency;
+        const symbol = getSymbol(currency);
+        const minimumAmount = minimumAmountForCurrency(currency);
 
+        if (amountInCents !== 0 && amountInCents < minimumAmount) {
+            this.tipsAndDonationsError = `The suggested amount cannot be less than ${symbol}${minimumAmount / 100}.`;
+            return;
+        }
+
+        this.tipsAndDonationsError = '';
         this.settings.donationsSuggestedAmount = amountInCents;
     }
 

ghost/admin/app/utils/currency.js

@@ -162,3 +162,45 @@ export function getCurrencyOptions() {
         }
     ];
 }
+
+/*
+* Returns the minimum charge amount for a given currency,
+* based on Stripe's requirements. Values here are double the Stripe limits, to take conversions to the settlement currency into account.
+* @see https://stripe.com/docs/currencies#minimum-and-maximum-charge-amounts
+* @param {String} currency — Currency in the 3-letter ISO format (e.g. "USD", "EUR")
+* @retuns {Number} — Minimum amount in cents (e.g. 100 for $1.00)
+*/
+export function minimumAmountForCurrency(currency) {
+    switch (currency) {
+    case 'AED':
+        return 400;
+    case 'BGN':
+        return 200;
+    case 'CZK':
+        return 3000;
+    case 'DKK':
+        return 500;
+    case 'HKD':
+        return 800;
+    case 'HUF':
+        return 25000;
+    case 'JPY':
+        return 10000;
+    case 'MXN':
+        return 2000;
+    case 'MYR':
+        return 400;
+    case 'NOK':
+        return 600;
+    case 'PLN':
+        return 400;
+    case 'RON':
+        return 400;
+    case 'SEK':
+        return 600;
+    case 'THB':
+        return 2000;
+    default:
+        return 100;
+    }
+}