How to bound the draggable div within the container

Question

I am using react with typescript and I implemented the w3school drag div example in my react app. Now, I am trying to bound this draggable div within the boundary. Currently, my box is moving outside the container. please help how to achieve this without using any third-party library.

Here is my sandbox demo

my code:

import "./styles.css";
import React, { useRef } from "react";

export default function App() {
  const dragRef = useRef<HTMLDivElement>(null);
  let pos1 = 0,
    pos2 = 0,
    pos3 = 0,
    pos4 = 0;

  const drag = (event: any) => {
    const boundingBox = dragRef.current;

    if (boundingBox) {
      event = event || window.event;
      event.preventDefault();
      pos1 = pos3 - event.clientX;
      pos2 = pos4 - event.clientY;
      pos3 = event.clientX;
      pos4 = event.clientY;
      boundingBox.style.top = boundingBox.offsetTop - pos2 + "px";
      boundingBox.style.left = boundingBox.offsetLeft - pos1 + "px";
    }
  };

  const stop = () => {
    const boundingBox = dragRef.current;
    if (boundingBox) {
      boundingBox.onmouseup = null;
      boundingBox.onmousemove = null;
    }
  };

  const start = (event: any) => {
    const box = dragRef.current;
    if (box) {
      event = event || window.event;
      event.preventDefault();
      pos3 = event.clientX;
      pos4 = event.clientY;
      box.onmouseup = stop;
      box.onmousemove = drag;
    }
  };

  return (
    <div className="App">
      <div
        ref={dragRef}
        className="draggableDiv"
        onMouseDown={start}
        onMouseMove={drag}
        onMouseUp={stop}
      ></div>
    </div>
  );
}

and the external CSS file:

.App {
  font-family: sans-serif;
  height: 350px;
  width: 400px;
  background-color: rgb(132, 190, 241);
  position: relative;
}

.draggableDiv {
  position: absolute;
  height: 40px;
  width: 40px;
  background-color: red;
  cursor: grab;
}