/**
 * Application state storage
 */
export default class Storage {

    /**
     * Create a state storage with an initial state
     * @param  {[type]} inistate [description]
     * @return {[type]}          [description]
     */
    constructor(inistate) {
        this.state = inistate || {};
        this.listeners = [];
        if (__DEV__) {
            /* eslint no-console: "off" */
            console.log('storage', inistate);
        }
    }

    /**
     * Add a listener to the state storage
     * @param  {[type]} listener function listener to receive notification about storage changes
     * @return {[type]}          [description]
     */
    addListener(listener) {
        if (this.listeners.indexOf(listener) === -1) {
            this.listeners.push(listener);
        }
    }

    /**
     * Remove a listener from the storage
     * @param  {[type]} listener Listener function previously registered
     * @return {[type]}          [description]
     */
    removeListener(listener) {
        if (__DEV__) {
            // simple check to avoid memory leak
            if (!listener) {
                throw new Error('Invalid listener to remove from app: ' + listener);
            }

            if (this.listeners.indexOf(listener) === -1) {
                throw new Error('Listener not found: ' + listener);
            }
        }
        var index = this.listeners.indexOf(listener);
        if (index >= 0) {
            this.listeners.splice(index, 1);
        }
    }

    /**
     * Set application state, mixing the current state with the new given one
     * @param {String} action The action that originated the state change
     * @param {[type]} obj    THe state to be incorporated to the current state
     */
    dispatch(action, obj) {
        // call listeners
        const states = [];
        const lst = this.listeners;
        lst.forEach(listener => {
            const res = listener(action, obj);
            if (res) {
                states.push(res);
            }
        });

        // update state, if any
        states.forEach(st => {
            for (var p in st) {
                const val = st[p];
                if (val === undefined || val === null) {
                    delete this.state[p];
                } else {
                    this.state[p] = obj[p];
                }
            }
        });
    }

    getState() {
        return this.state;
    }

    /**
     * Merge the given state with the actual state
     */
    setState(st) {
        for (var k in st) {
            const val = st[k];
            this.state[k] = val;
        }
    }
}