feat(config): add configuration window (#70)

src/settings/settings-control-dom.ts

@@ -0,0 +1,34 @@
+import type { ConfigSettingsSnapshotValue } from '../types/settings';
+
+export function createElement<K extends keyof HTMLElementTagNameMap>(
+  tagName: K,
+  className?: string,
+): HTMLElementTagNameMap[K] {
+  const element = document.createElement(tagName);
+  if (className) {
+    element.className = className;
+  }
+  return element;
+}
+
+export function addOption(select: HTMLSelectElement, value: string, label = value): void {
+  const option = createElement('option') as HTMLOptionElement;
+  option.value = value;
+  option.textContent = label;
+  select.append(option);
+}
+
+export function uniqueSorted(values: Iterable<string>): string[] {
+  return [...new Set([...values].filter(Boolean))].sort((a, b) => a.localeCompare(b));
+}
+
+export function isSecretSnapshotValue(
+  value: ConfigSettingsSnapshotValue,
+): value is { configured: boolean } {
+  return Boolean(
+    value &&
+    typeof value === 'object' &&
+    'configured' in value &&
+    typeof (value as { configured?: unknown }).configured === 'boolean',
+  );
+}