// object to store the listeners grouped by actionTypes
const listenersMap = {};

/**
 * The middleware
 * example usage: createStore(rootReducer, applyMiddleware(thunk, reduxActionListener, reduxLogger))
 */
export const reduxActionListener = store => next => action => {
    // store the prev state to keep it for the listener
    const prevState = store.getState();
    // make sure the original action runs first, so errors won't prevent from running
    const result = next(action);
    // notify all listeners that attached to the type
    const listeners = listenersMap[action.type];
    if (listeners) {
        // eslint-disable-next-line no-console
        console.log(`[ActionListener] Notifying ${listeners.length} listener(s) of action: ${action.type}`);
        const params = { action, state: store.getState(), prevState, store };
        for (const listener of listeners) {
            listener(params);
        }
    }
    // important: return the original result
    return result;
};

/**
 * Adds an action listener callback on the specified action type
 * @param {string} actionType
 * @param {listenerFn} function
 * @return the remove function
 */
export const addActionListener = (actionType, listenerFn) => {
    const listeners = listenersMap[actionType] || (listenersMap[actionType] = []);
    listeners.push(listenerFn);
    return () => {
        const index = listeners.indexOf(listenerFn);
        if (index > -1) {
            listeners.splice(index, 1);
        }
    };
};