feat: voucher purchase flow

assets/controllers/field_validity_controller.js

@@ -0,0 +1,22 @@
+import {Controller} from '@hotwired/stimulus'
+
+/*
+ * Keeps buttons disabled until the given fields pass the browser's constraint validation
+ * (required, min, max, step, …), which the form types render from the same rules the server
+ * validates. A text field holding only whitespace counts as empty, as NotBlank does.
+ *
+ * Works on forms with novalidate too: that only stops the browser from blocking the submit.
+ */
+export default class extends Controller {
+    static targets = ['field', 'button']
+
+    connect() {
+        this.update()
+    }
+
+    update() {
+        const invalid = this.fieldTargets.some(field => !field.checkValidity()
+            || ('radio' !== field.type && 'checkbox' !== field.type && '' === field.value.trim()))
+        this.buttonTargets.forEach(button => button.disabled = invalid)
+    }
+}