feat: Initial clean release of CHM

packages/app-mobile/utils/hooks/useBackHandler.ts

@@ -0,0 +1,24 @@
+import { useEffect, useRef } from 'react';
+import BackButtonService from '../../services/BackButtonService';
+
+type OnBackPress = ()=> (void|boolean);
+
+const useBackHandler = (onBackPress: OnBackPress|null) => {
+	const onBackPressRef = useRef(onBackPress);
+	onBackPressRef.current = onBackPress ?? (() => {});
+	const hasHandler = !!onBackPress;
+
+	useEffect(() => {
+		if (!hasHandler) return () => {};
+
+		const handler = () => {
+			return !!(onBackPressRef.current() ?? true);
+		};
+		BackButtonService.addHandler(handler);
+		return () => {
+			BackButtonService.removeHandler(handler);
+		};
+	}, [hasHandler]);
+};
+
+export default useBackHandler;