refactor(pages): refine Project pages

* refactor ProjectOverview component to let consumers handle the value
* extract project overview depending on Github to avoid fetching
Github API if the project is not on Github
* wrap dynamic import in a useMemo hook to avoid infinite rerender
* fix table of contents by adding a useMutationObserver hook to refresh
headings tree (without it useHeadingsTree is not retriggered once the
dynamic import is done)
* add Cypress tests

3 files changed, 78 insertions, 0 deletions

diff --git a/src/utils/hooks/use-mutation-observer/index.ts b/src/utils/hooks/use-mutation-observer/index.ts
new file mode 100644
index 0000000..16780fe
--- /dev/null
+++ b/src/utils/hooks/use-mutation-observer/index.ts
@@ -0,0 +1 @@
+export * from './use-mutation-observer';
diff --git a/src/utils/hooks/use-mutation-observer/use-mutation-observer.test.ts b/src/utils/hooks/use-mutation-observer/use-mutation-observer.test.ts
new file mode 100644
index 0000000..62ed559
--- /dev/null
+++ b/src/utils/hooks/use-mutation-observer/use-mutation-observer.test.ts
@@ -0,0 +1,42 @@
+import { beforeEach, describe, expect, it, jest } from '@jest/globals';
+import { renderHook } from '@testing-library/react';
+import { useMutationObserver } from './use-mutation-observer';
+
+describe('useMutationObserver', () => {
+  beforeEach(() => {
+    jest.restoreAllMocks();
+  });
+
+  it('can create a new observer', () => {
+    const callback = jest.fn();
+    const observerSpy = jest.spyOn(MutationObserver.prototype, 'observe');
+    const wrapper = document.createElement('div');
+    const options: MutationObserverInit = { childList: true };
+
+    renderHook(() =>
+      useMutationObserver({
+        callback,
+        options,
+        ref: { current: wrapper },
+      })
+    );
+
+    expect(observerSpy).toHaveBeenCalledTimes(1);
+    expect(observerSpy).toHaveBeenCalledWith(wrapper, options);
+  });
+
+  it('does not create a new observer when ref is null', () => {
+    const callback = jest.fn();
+    const observerSpy = jest.spyOn(MutationObserver.prototype, 'observe');
+
+    renderHook(() =>
+      useMutationObserver({
+        callback,
+        options: { childList: true },
+        ref: { current: null },
+      })
+    );
+
+    expect(observerSpy).not.toHaveBeenCalled();
+  });
+});
diff --git a/src/utils/hooks/use-mutation-observer/use-mutation-observer.ts b/src/utils/hooks/use-mutation-observer/use-mutation-observer.ts
new file mode 100644
index 0000000..6043055
--- /dev/null
+++ b/src/utils/hooks/use-mutation-observer/use-mutation-observer.ts
@@ -0,0 +1,35 @@
+import { type RefObject, useEffect } from 'react';
+import type { Nullable } from '../../../types';
+
+type UseMutationObserverProps<T extends Nullable<HTMLElement>> = {
+  /**
+   * A callback to execute when mutations are observed.
+   */
+  callback: MutationCallback;
+  /**
+   * The options passed to mutation observer.
+   */
+  options: MutationObserverInit;
+  /**
+   * A reference to the DOM node to observe.
+   */
+  ref: RefObject<T>;
+};
+
+export const useMutationObserver = <T extends Nullable<HTMLElement>>({
+  callback,
+  options,
+  ref,
+}: UseMutationObserverProps<T>) => {
+  useEffect(() => {
+    if (!ref.current) return undefined;
+
+    const observer = new MutationObserver(callback);
+
+    observer.observe(ref.current, options);
+
+    return () => {
+      observer.disconnect();
+    };
+  }, [callback, options, ref]);
+};