Create redux reducer to change state nested object value - reactjs

Question

I am new to React-Redux and i am struggling with a proof-of-concept project (list of movies) in order to learn the basics of redux. I am quite good at React, but Redux is another deal...
So, in my repo and specifically in Smart Component MoviesList.jsx (https://bitbucket.org/vforvaios/react-movie-app/src/05a6241eff3a1896eca91bb1800e8e017f8b569a/src/MoviesList.jsx?at=feature%2Fadd_redux&fileviewer=file-view-default) i am wondering how to dispatch the correct action to change the rating (increment, decrement) in each SingleMovieItem (https://bitbucket.org/vforvaios/react-movie-app/src/05a6241eff3a1896eca91bb1800e8e017f8b569a/src/SingleMovieItem.jsx?at=feature%2Fadd_redux&fileviewer=file-view-default) and what would be the correct reducer to achieve that. Could anyone help me with this?
In other words, to show a real example of what i mean...
Lets say that there is a main App and we make use of the
<Provider store={store}>
<App />
</Provider>
And then the App contains the following:
import React, { Component } from 'react';
import MoviesList from './MoviesList'
class App extends Component {
render() {
return (
<div>
<MoviesList />
</div>
)
}
}
export default App;
And then, the MovieList.jsd contains the following:
import React, { Component } from 'react';
import { addRating } from './actions';
import SingleMovieItem from './SingleMovieItem';
import { connect } from "react-redux";
const mapStateToProps = state => {
return {
allMovies: state
};
};
const mapDispatchToProps = (dispatch) => {
return {
onIncrement: (id) => dispatch(addRating(id))
};
};
class MovieList extends Component {
constructor(props) {
super(props);
}
handleIncrement = id => {
}
render() {
return (
<div>
<ul className="moviesList">
{this.props.allMovies.movies.map(movie => {
return (
<SingleMovieItem
key={movie.id}
movie={movie}
onIncrement={this.handleIncrement(movie.id)} />
);
})}
</ul>
</div>
)
}
}
export default connect(mapStateToProps, mapDispatchToProps)(MovieList);
What would be the reducer to increment rating of each singlemovie
if initialState is
const initialState = {
movies: [
{
id: "1",
title: "Harry Potter 1",
url: "harry-1.jpg",
rating: "2"
},
{
id: "2",
title: "Harry Potter 2",
url: "harry-2.jpg",
rating: "3"
}
]
};
Thanks in advance.