Exhaustive Switch-Case Control Flow for Reducer State Transitions

import React, { useReducer } from 'react';
 
const initialState = { count: 0 };
 
function counterReducer(state, action) {
  switch (action.type) {
    case 'increment':
      return { ...state, count: state.count + action.payload };
    case 'decrement':
      return { ...state, count: Math.max(0, state.count - action.payload) };
    case 'reset':
      return initialState;
    default:
      throw new Error(`Unhandled action type: ${action.type}`);
  }
}
 
export function CounterWidget() {
  const [state, dispatch] = useReducer(counterReducer, initialState);
 
  return (
    <div>
      <p>Count: {state.count}</p>
      <button onClick={() => dispatch({ type: 'increment', payload: 1 })}>+1</button>
      <button onClick={() => dispatch({ type: 'decrement', payload: 1 })}>-1</button>
      <button onClick={() => dispatch({ type: 'reset' })}>Reset</button>
    </div>
  );
}