// IN THE CONTAINER THIS FUNCTION IS PASSED A BOOK
export function selectBook(book){
    return {
        type: 'BOOK_SELECTED', // DESCRIBES THE TYPE OF EVENT/ACTION
        payload: book // DATA
    };
}

// DEFAULT STATE TO NULL TO PREVENT RETURNING AN UNDEFINED VALUE
export default function(state = null, action){
    switch (action.type) {
        case 'BOOK_SELECTED':
            return action.payload;
    }
    // IF WE DON'T CARE ABOUT THE ACTION, JUST RETURN STATE
    return state;
}

import { combineReducers } from 'redux';

// IMPORT REDUCERS
import BooksReducer from './reducer_books';
import ActiveBookReducer from './reducer_active_book';

// APPLICATION STATE CENTRALIZED INTO ONE OBJECT THAT GETS CALLED BY OUR CONTAINERS
const rootReducer = combineReducers({
  books: BooksReducer,
  activeBook: ActiveBookReducer
});

export default rootReducer;

// glue between React and Redux
import { connect } from 'react-redux';

// use this to make sure the action generated by the Action Creator flows through the reducers
import { bindActionCreators } from 'redux';

// takes our application state as an argument
// this function is the glue between React and Redux
// whenever our application state changes, this container will instantly re-render
function mapStateToProps(state) {
    // whatever gets returned will show up as props inside of the container
    return {
        // to reference this object we use "this.props.books", because "books" is the key we assigned
        // "state.books" is a reference to the global state object formed by combineReducers()
        books: state.books
    };
}

// anything returned from this function will end up as props to the container
// now we can call this.props.selectBook for our (onClick example)
function mapDispatchToProps(dispatch){
    // Whenever selectBook is called the result will be passed to all reducers
    // dispatch is a function, the 2nd parameter that makes sure the result is received and sent to all the reducers
    // selectBook is a function that returns an object
    // the purpose of bindActionCreators and dispatch is to specifically take what gets returned from selectBook and make sure it flows through all reducers
    return bindActionCreators({ selectBook }, dispatch);
}

// connect takes a function and a component and produces a container
// whenever the application state changes the object in mapStateToProps will be assigned as props to the component
export default connect(mapStateToProps, mapDispatchToProps)(BookList);