Create common error handler and input field validator

radicale/web/internal_data/js/utils/error.js

@@ -0,0 +1,74 @@
+/**
+ * This file is part of Radicale Server - Calendar Server
+ * Copyright © 2026-2026 Max Berger <max@berger.name>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/**
+ * ErrorHandler manages error messages for a HTMLElement.
+ */
+export class ErrorHandler {
+    /**
+     * @param {HTMLElement} element
+     */
+    constructor(element) {
+        /** @type {HTMLElement} */ this._element = element;
+        /** @type {string} */ this._lastHTML = "anything_but_blank";
+        this.clearError();
+    }
+
+    /**
+     * Sets an error message for a given key.
+     * @param {string} errorMessage
+     */
+    setError(errorMessage) {
+        this._update([errorMessage]);
+    }
+
+    /**
+     * Sets multiple error messages.
+     * @param {string[]} errorMessages
+     */
+    setErrors(errorMessages) {
+        this._update(errorMessages);
+    }
+
+    clearError() {
+        this._update([]);
+    }
+
+
+    /**
+     * Updates the element visibility and text content.
+     * @param {string[]} errorMessages
+     * @private
+     */
+    _update(errorMessages) {
+        let html = "";
+        if (errorMessages.length > 0) {
+            html = errorMessages.join("<br>");
+        }
+
+        if (html !== this._lastHTML) {
+            this._element.innerHTML = html;
+            if (html) {
+                this._element.classList.remove("hidden");
+            } else {
+                this._element.classList.add("hidden");
+            }
+            this._lastHTML = html;
+        }
+    }
+}