'use strict';

/**
 * dom.js
 * A module that helps working with HTML elements in the DOM
 */

const boundaryRegex = /\s+/g;

/**
 * Add a wrapping of utility methods around a Node
 *
 * @param {Node} el Node to wrap
 * @return {Object} Utility-wrapped node
 */
const wrapNode = (el) => Object.freeze({
    node: el,

    // shortcuts
    get: selector => wrapNode(el.querySelector(selector)),
    all: selector => wrapEls(el.querySelectorAll(selector)),

    parent: () => wrapNode(el.parentNode),
    children: () => wrapEls(el.childNodes),

    add: subEl => el.appendChild(unwrapNode(subEl)),
    remove: () => el.parentNode.removeChild(el),

    getAttr: name => el.getAttribute(name),
    setAttr: (name, val) => el.setAttribute(name, val),

    /**
     * Add event listeners for all given events
     *
     * @param {string} events Whitespace-separated list of events
     * @param {function} listener Listener to add
     * @return {null}
     */
    on: (events, listener) => {
        events.trim().split(boundaryRegex).forEach(
            event => el.addEventListener(event, listener)
        );
    },

    /**
     * Remove event listeners for all given events
     *
     * @param {strings} events Whitespace-separated list of events
     * @param {function} listener Listener to remove
     * @return {null}
     */
    off: (events, listener) => {
        events.trim().split(boundaryRegex).forEach(
            event => el.removeEventListener(event, listener)
        );
    }
});

/**
 * Remove a wrapping around a Node
 *
 * @param {Object|Node} el A node, wrapped or not
 * @return {Node} Unwrapped node
 */
const unwrapNode = el => el instanceof Node ? el : el.node;

/**
 * Override the methods of an Array so that it
 * can easily manipulate Nodes it contains
 *
 * @param {Array} list A list to be wrapped
 * @return {Array} Expanded list
 */
const expandList = (list) => Object.assign(list, {
    // shortcuts
    on: function (events, listener) {
        this.forEach(node => node.on(events, listener));
    },

    off: function (events, listener) {
        this.forEach(node => node.off(events, listener));
    },

    /**
     * Check whether this list includes given node
     *
     * @param {Node|Object} el Element to check
     * @return {bool} True if this list contains `el`
     */
    includes: function (el) {
        const length = this.length;
        el = unwrapNode(el);

        for (let i = 0; i < length; i += 1) {
            if (el === unwrapNode(this[i])) {
                return true;
            }
        }

        return false;
    },

    /**
     * Filter nodes in the list, removing filtered out nodes
     *
     * @param {function} check A function that returns true to keep given el
     * @return {Array} New list of nodes after filtering
     */
    filter: function (check) {
        const length = this.length, newList = [];

        for (let i = 0; i < length; i += 1) {
            if (!check(this[i], i, this)) {
                this[i].remove();
            } else {
                newList.push(this[i]);
            }
        }

        return expandList(newList);
    }
});

/**
 * Turn a NodeList into a real Array of Nodes
 *
 * @param {NodeList} els List of nodes to wrap
 * @return {Array} An array of nodes
 */
const wrapList = (els) => {
    const result = [], length = els.length;

    for (let i = 0; i < length; i += 1) {
        result[i] = wrapNode(els[i]);
    }

    return expandList(result);
};

export const create = (name) => wrapNode(document.createElement(name));
export const html = wrapNode(document.documentElement);
export const head = wrapNode(document.head);
export const body = wrapNode(document.body);