chore: import upstream snapshot with attribution

packages/emcn/src/components/modal/auto-focus.ts

@@ -0,0 +1,58 @@
+/**
+ * Default `onOpenAutoFocus` handler for emcn modals.
+ *
+ * Radix's native behavior focuses the first focusable descendant — usually the close
+ * button in `ModalHeader`. We instead focus the first visible text-entry control
+ * (input/textarea/contenteditable) inside the dialog, with the caret at the end.
+ *
+ * If no such control exists, we let Radix's default behavior run by not calling
+ * `preventDefault()`.
+ */
+
+const TEXT_INPUT_SELECTOR = [
+  'input:not([type="hidden"]):not([type="checkbox"]):not([type="radio"])' +
+    ':not([type="button"]):not([type="submit"]):not([type="reset"])' +
+    ':not([disabled]):not([readonly]):not([tabindex="-1"])',
+  'textarea:not([disabled]):not([readonly]):not([tabindex="-1"])',
+  '[contenteditable="true"]:not([tabindex="-1"])',
+  '[contenteditable=""]:not([tabindex="-1"])',
+].join(',')
+
+function isVisible(el: HTMLElement): boolean {
+  return el.offsetParent !== null || el.getClientRects().length > 0
+}
+
+/**
+ * Focus the first visible text-entry input within `root`, placing caret at end.
+ * Returns true if an element was focused.
+ */
+export function focusFirstTextInputIn(root: HTMLElement | null): boolean {
+  if (!root) return false
+  const target = Array.from(root.querySelectorAll<HTMLElement>(TEXT_INPUT_SELECTOR)).find(isVisible)
+  if (!target) return false
+
+  target.focus({ preventScroll: false })
+
+  if (target instanceof HTMLInputElement || target instanceof HTMLTextAreaElement) {
+    const end = target.value.length
+    try {
+      target.setSelectionRange(end, end)
+    } catch {
+      // Some input types (number, email, etc.) reject setSelectionRange — ignore.
+    }
+  } else if (target.isContentEditable) {
+    const range = document.createRange()
+    range.selectNodeContents(target)
+    range.collapse(false)
+    const sel = window.getSelection()
+    sel?.removeAllRanges()
+    sel?.addRange(range)
+  }
+  return true
+}
+
+export function focusFirstTextInput(event: Event): void {
+  if (focusFirstTextInputIn(event.currentTarget as HTMLElement | null)) {
+    event.preventDefault()
+  }
+}