1 files changed, 78 insertions, 0 deletions
diff --git a/packages/frontend/src/scripts/focus-trap.ts b/packages/frontend/src/scripts/focus-trap.ts
new file mode 100644
index 0000000000..a5df36f520
--- /dev/null
+++ b/packages/frontend/src/scripts/focus-trap.ts
@@ -0,0 +1,78 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import { getHTMLElementOrNull } from '@/scripts/get-dom-node-or-null.js';
+
+const focusTrapElements = new Set<HTMLElement>();
+const ignoreElements = [
+	'script',
+	'style',
+];
+
+function containsFocusTrappedElements(el: HTMLElement): boolean {
+	return Array.from(focusTrapElements).some((focusTrapElement) => {
+		return el.contains(focusTrapElement);
+	});
+}
+
+function releaseFocusTrap(el: HTMLElement): void {
+	focusTrapElements.delete(el);
+	if (el.inert === true) {
+		el.inert = false;
+	}
+	if (el.parentElement != null && el !== document.body) {
+		el.parentElement.childNodes.forEach((siblingNode) => {
+			const siblingEl = getHTMLElementOrNull(siblingNode);
+			if (!siblingEl) return;
+			if (siblingEl !== el && (focusTrapElements.has(siblingEl) || containsFocusTrappedElements(siblingEl) || focusTrapElements.size === 0)) {
+				siblingEl.inert = false;
+			} else if (
+				focusTrapElements.size > 0 &&
+				!containsFocusTrappedElements(siblingEl) &&
+				!focusTrapElements.has(siblingEl) &&
+				!ignoreElements.includes(siblingEl.tagName.toLowerCase())
+			) {
+				siblingEl.inert = true;
+			} else {
+				siblingEl.inert = false;
+			}
+		});
+		releaseFocusTrap(el.parentElement);
+	}
+}
+
+export function focusTrap(el: HTMLElement, hasInteractionWithOtherFocusTrappedEls: boolean, parent: true): void;
+export function focusTrap(el: HTMLElement, hasInteractionWithOtherFocusTrappedEls?: boolean, parent?: false): { release: () => void; };
+export function focusTrap(el: HTMLElement, hasInteractionWithOtherFocusTrappedEls = false, parent = false): { release: () => void; } | void {
+	if (el.inert === true) {
+		el.inert = false;
+	}
+	if (el.parentElement != null && el !== document.body) {
+		el.parentElement.childNodes.forEach((siblingNode) => {
+			const siblingEl = getHTMLElementOrNull(siblingNode);
+			if (!siblingEl) return;
+			if (
+				siblingEl !== el &&
+				(
+					hasInteractionWithOtherFocusTrappedEls === false ||
+					(!focusTrapElements.has(siblingEl) && !containsFocusTrappedElements(siblingEl))
+				) &&
+				!ignoreElements.includes(siblingEl.tagName.toLowerCase())
+			) {
+				siblingEl.inert = true;
+			}
+		});
+		focusTrap(el.parentElement, hasInteractionWithOtherFocusTrappedEls, true);
+	}
+
+	if (!parent) {
+		focusTrapElements.add(el);
+
+		return {
+			release: () => {
+				releaseFocusTrap(el);
+			},
+		};
+	}
+}