/**
 * Create a control to show or hide values
 * 
 * Possible options are:
 * 
 *  - froms: an Element, an Array of Element, or a NodeList. A
 *    listener will be attached to **all** input of those elements
 *    and will trigger the check on changes
 *  - test: a function which will test the element and will return true 
 *    if the content must be shown, false if it must be hidden.
 *    The function will receive the `froms` as first argument, and the 
 *    event as second argument.
 *  - container: an Element, an Array of Element, or a Node List. The 
 *    child nodes will be hidden / shown inside this container
 *  - event_name: the name of the event to listen to. `'change'` by default.
 * 
 * @param object options
 */
var ShowHide = function(options) {
    var
        froms =  typeof options.froms[Symbol.iterator] === "function" ? options.froms : [ options.froms ], //options.froms;
        test = options.test,
        container = typeof options.container[Symbol.iterator] === "function" ? options.container : [ options.container ],
        is_shown = true,
        event_name = 'event_name' in options ? options.event_name : 'change',
        container_content = [];

    window.addEventListener('load', function(event) {
        // keep the content in memory
        for (let c of container.values()) {
            let contents = [];
            for (let el of c.childNodes.values()) {
                contents.push(el);
            }
            container_content.push(contents);
        }

        // attach the listener on each input
        for (let f of froms.values()) {
            let inputs = f.querySelectorAll('input');
            for (let input of inputs.values()) {
                input.addEventListener(event_name, function(e) {
                    onChange(e);
                });
            }
        }

        // first launch of the show/hide
        onChange(event);
    });

    
    var onChange = function (event) {
        var result = test(froms, event);

        if (result === true) {
            if (is_shown === false) {
                for (let i of container_content.keys()) {
                    var contents = container_content[i];
                    for (let el of contents.values()) {
                        container[i].appendChild(el);
                    }
                }
                is_shown = true;
            }
        } else if (result === false) {
            if (is_shown) {
                for (let contents of container_content.values()) {
                    for (let el of contents.values()) {
                        el.remove();
                    }
                }
                is_shown = false;
            }
        } else {
            throw "the result of test is not a boolean";
        }
        
    };
};

export {ShowHide};