"use strict";

/**
 * @callback wmarkdown_ajax_callback
 * @param {?string} response
 * @param {!number} status
 * @param {!number} state
 * @param {!boolean} ok
 * @param {!string} message
 * @return {void}
 */

/**
 * @callback wmarkdown_preload_callback
 * @param {?HTMLElement} element 
 * @param {!boolean} asynchronous 
 * @param {!integer} error 
 * @returns {void}
 */

/**
 * @callback wmarkdown_element_event_callback
 * @param {!HTMLElement} element 
 * @param {!Event} event 
 * @returns {void}
 */

/**
 * @class
 * @constructor
 * @param {?string|Object.<string, any|null>} [inputs]
 * @returns {void}
 * @access public
 */
export const WMarkDown = (function(){
    
    /**
     * @constructs WMarkDown
     * @param {?string|Object.<string, any|null>} [inputs] 
     * @returns {void}
     * @access private
     */
    const WMarkDown = function(inputs){

        /** @type {WMarkDown} */
        const self = this,
            /** @type {Array.<string>} */
            dictionary_done = [],
            /** @type {Array.<Object.<string, Array.<RegExp, string>|Array.<String>>>} */
            dictionary = [],
            /** @type {Array.<HTMLElement>} */
            root_boxes = [],
            /** @type {string} */
            hash_alphabet = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz",
            /** @type {number} */
            hash_length = 11,
            /** @type {Array.<string>} */
            hashes = [],
            /** @type {Array.<Array.<string>>} */
            type_dictionary = [
                ["JavaScript/ECMAScript", "js", "javascript", "ecma", "ecmascript", "node", "nodejs", "typescript", "ts"],
                ["Python", "python", "py"]
            ];
        /** @type {number|null} */
        let thread_inteval = null,
            /** @type {boolean} */
            dictionary_loaded = false,
            /** @type {Array.<string, string, RegExp} */
            dictionary_item_mark = ["###@==_", "_==@###", /\#{3}\@\={2}_([0-9]+)_\={2}\@\#{3}/g],
            /** @type {number} */
            dictionary_z = 500,
            /** @type {Array.<string>} */
            dictionary_boxes = [], 
            /** @type {boolean|null} */
            check_gui_controls = null;

        /**
         * @returns {void}
         * @access private
         */
        const constructor = () => {

            if(typeof inputs == "string")
                inputs = {dictionary : inputs};

            thread_inteval = setInterval(thread_method, 250);

            if(inputs.dictionary){

                /** @type {number} */
                let loaded = 0;
                /** @type {Array.<string>} */
                const dictionaries = inputs.dictionary instanceof Array ? inputs.dictionary : [inputs.dictionary],
                    /**
                     * @returns {void}
                     */
                    end = () => ++ loaded == dictionaries.length && (dictionary_loaded = true);

                dictionaries.forEach(url => WMarkDown.get(url, data => {
                    try{
                        self.add_to_dictionary(JSON.parse(data));
                    }catch(exception){
                        console.error(exception);
                    };
                    end();
                }));

            };

        };

        /**
         * @param {!Array.<Array.<string, string>, Array.<string>, Array.<string>>} data
         * @returns {void}
         * @access public
         */
        this.add_to_dictionary = data => data.forEach(([patterns, definition, links]) => {

            /** @type {number|null} */
            let i = null;

            patterns[0] instanceof Array || (patterns = [patterns]);

            patterns.forEach(([pattern, text]) => {
                if(!dictionary_done.includes(text)){
                    if(i === null)
                        dictionary[i = dictionary.length] = {
                            patterns : [[WMarkDown.format_pattern(pattern), text]],
                            definition : typeof definition == "string" ? definition : definition.join(""),
                            links : links
                        };
                    else
                        dictionary[i].patterns.push([WMarkDown.format_pattern(pattern), text]);
                };
            });

        });

        /**
         * @returns {string}
         * @access public
         */
        this.get_hash = () => {

            /** @type {string} */
            let hash;
            /** @type {number} */
            const l = hash_alphabet.length;

            do{
                hash = "";
                while((hash += hash_alphabet[Math.random() * l >> 0]).length < hash_length);
            }while(
                hashes.includes(hash) ||
                /^[0-9]/.test(hash) ||
                document.querySelector("." + hash + ",#" + hash + ",[name=" + hash + "]")
            );
            hashes.push(hash);

            return hash;
        };

        /**
         * @param {!NodeList} block
         * @returns {void}
         * @access public
         */
        this.format_dictionary = block => block.childNodes.forEach((item, i) => {

            /** @type {Array.<Array.<number, HTMLSpanElement>>} */
            const blocks = [];

            if(item.nodeName == "#text"){
                if(item.textContent.trim()){

                    /** @type {string} */
                    let html = item.textContent;
                    /** @type {Array.<number, RegExpMatchArray, string>} */
                    const items = [];

                    dictionary.forEach((item, k) => {
                        item.patterns.forEach(([pattern, text]) => {
                            html = html.replace(pattern, (...matches) => {

                                /** @type {number} */
                                const j = items.length;

                                items.push([k, matches, text.replace(/\$([0-9])/g, (all, match_i) => {
                                    return matches[match_i] !== null && matches[match_i] !== undefined ? matches[match_i] : "";
                                })]);

                                return dictionary_item_mark[0] + j + dictionary_item_mark[1];
                            });
                        });
                    });

                    if(html != item.textContent){

                        /** @type {HTMLSpanElement} */
                        const element = document.createElement("span");

                        blocks.push([i, element]);

                        element.innerHTML = html.replace(dictionary_item_mark[2], (_, j) => {

                            /** @type {Array.<number, RegExpMatchArray, string>} */
                            const [k, matches, text] = items[Number(j)];

                            return `<span class="wmd-dictionary-item" data-role="link" data-i="` + k + `" data-hash="` + self.get_hash() + `" data-preload="` + self.preload_hash(span => {
                                span.addEventListener("click", self.dictionary_over);
                            }) + `">` + text + `</span>`;
                        });

                    };

                };
            }else if(
                !["img", "a", "audio", "canvas", "picture"].includes((item.tagName || item.nodeName).toLowerCase()) &&
                !["wmd-excluded", "wmd-code-block", "wmd-code-doc"].some(class_name => item.classList && item.classList.contains(class_name))
            ){
                self.format_dictionary(item);
                addEventListener("click", self.dictionary_out);
            };

            blocks.forEach(([i, element]) => {
                block.insertBefore(element, block.childNodes[i]);
                block.childNodes[i + 1].remove();
            });

        });

        /**
         * @param {!HTMLElement} item
         * @returns {HTMLElement|null}
         * @access public
         */
        this.get_root_box = item => {

            /** @type {HTMLElement|null} */
            let box = null;

            while(item && item.classList && (item = item.parentNode))
                item.classList && item.classList.contains("wmarkdown") && (box = item);

            return box;
        };

        /**
         * @param {!HTMLUListElement} data_box
         * @param {!String} i18n
         * @param {!String} text
         * @param {!String} action
         * @returns {HTMLLIElement}
         * @access private
         */
        const add_button_data = (data_box, i18n, text, action) => {

            /** @type {HTMLLIElement} */
            const button = data_box.appendChild(document.createElement("li"));

            button.setAttribute("data-i18n", i18n);
            button.setAttribute("data-i18n-without", true);
            button.setAttribute("title", text);
            button.addEventListener("click", action);
            button.innerHTML = (`
                <span data-icon="` + i18n + `"></span>
                <span data-i18n="` + i18n + `">` + text + `</span>
                <span class="value">` + text + `</span>
            `);

            return button;
        };

        /**
         * @param {!HTMLElement} box
         * @param {!String} name
         * @param {!Array.<String, String, String>} [buttons]
         * @returns {void}
         * @access private
         */
        const set_special_type = (box, name, buttons) => {

            while(!box.classList.contains("wmd-code-block") && (box = box.parentNode));

            /** @type {HTMLUListElement} */
            const data = box.querySelector(".data");

            box.querySelector("li[data-i18n=type]>.value").innerHTML = name;
            add_button_data(data, "view_switch", "View switch", event => WMarkDown.view_switch(event.target, event));

            buttons && buttons.forEach(([i18n, text, action]) => add_button_data(data, i18n, text, action));

        };

        /**
         * @param {!HTMLElement} content 
         * @param {!String} language 
         * @returns {HTMLDivElement}
         * @access private
         */
        const build_special_type = (content, language) => {
            content.parentNode.childNodes.forEach(item => item.tagName && item.setAttribute("data-visible", false));

            /** @type {HTMLDivElement} */
            const box = content.parentNode.appendChild(document.createElement("div"));

            box.setAttribute("class", "view");
            box.setAttribute("data-visible", true);
            set_special_type(content, language);

            return box;
        };

        /**
         * @param {HTMLElement} item 
         * @returns {HTMLElement|null}
         * @access public
         */
        this.get_anp = item => {

            while(!item.classList.contains("anp") && (item = item.parentNode))
                if(!item.classList){
                    item = null;
                    break;
                };

            return item;
        };

        const code_block_format = () => {

            document.querySelectorAll(".wmd-code-block[data-processed=false]").forEach(block => {

                /** @type {string} */
                const language = block.getAttribute("data-type").toLowerCase(),
                    /** @type {HTMLElement} */
                    content = block.querySelector(".content"), 
                    /** @type {String} */
                    type = block.getAttribute("data-type").toLowerCase(), 
                    /** @type {HTMLElement|null} */
                    anp_item = self.get_anp(block), 
                    /** @type {Boolean} */
                    dark_mode = (
                        anp_item ? (anp_item.getAttribute("data-gui-mode") == "dark" || (anp_item.getAttribute("data-gui-mode") == "default" && anp_item.getAttribute("data-dark-mode") == "true")) : 
                    window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches);

                block.setAttribute("data-processed", true);

                mermaid.initialize({
                    theme : dark_mode ? "dark" : "default", 
                    themeVariables : {fontSize : "16px"}
                });

                if(["math", "maths", "mathjax"].includes(language)){
                    build_special_type(content, "MathJax").innerHTML = MathJax.tex2chtml(content.innerText).outerHTML;
                    MathJax.startup.document.clear();
                    MathJax.startup.document.updateDocument();
                }else if(["mermaid", "mermaidjs", "mermaid_js"].includes(language)){

                    /** @type {HTMLDivElement} */
                    const box = build_special_type(content, "Mermaid JS");

                    mermaid.render(self.get_hash(), content.innerText).then(graph => box.innerHTML = graph.svg);

                }else
                    try{
                        content.innerHTML = hljs.highlight(content.innerText, {language : (
                            ["wmd-examples", "wmd", "wmarkdown"].includes(language) ? "markdown" :
                        language)}).value;
                        type_dictionary.some(alternatives => {
                            if(alternatives.includes(type)){
                                block.querySelector("[data-i18n=type]>.value").innerText = alternatives[0];
                                return true;
                            };
                            return false;
                        });
                    }catch(exception){};

            });

        };

        const build_dictionary_items = () => {

            if(dictionary_loaded){

                /** @type {HTMLElement} */
                const block = document.querySelector("[data-dictionary-processed=false]");

                if(block && [...block.childNodes].slice(-3).some(item => (
                    item.classList &&
                    item.classList.contains("wmd-process-and-loaded")
                ))){

                    block.querySelectorAll(".wmd-process-and-loaded").forEach(item => {
                        item.parentNode.hasAttribute("data-dictionary-processed") &&
                        item.parentNode.setAttribute("data-dictionary-processed", true);
                        item.remove();
                    });

                    self.format_dictionary(block);

                };

            };

        };

        const process_lists = () => document.querySelectorAll("[data-list-unprocessed=true]").forEach(list => {

            /** @type {HTMLSpanElement} */
            const deployer = list.parentNode.insertBefore(document.createElement("span"), list.parentNode.childNodes[0]);

            deployer.addEventListener("click", WMarkDown.deploy);
            deployer.setAttribute("data-deployed", list.getAttribute("data-deployed"));
            deployer.innerHTML = (`
                <span data-icon="deploy"></span>
                <span data-i18n="deploy">Deploy</span>
            `);

            list.setAttribute("data-list-unprocessed", false);

        });

        const autoload_media = body => document.querySelectorAll(".wmd-media[data-status=unloaded]").forEach((item, i) => {

            /** @type {DOMRect} */
            const bounds = item.getBoundingClientRect();

            if(
                (bounds.y + bounds.height > -100 && bounds.y < body.offsetHeight + 100) &&
                (bounds.x + bounds.width > -100 && bounds.x < body.offsetWidth + 100)
            ){

                /** @type {HTMLElement} */
                const main_item = item.querySelector("noscript+*");

                item.setAttribute("data-status", "loading");

                if(main_item.tagName.toLowerCase() == "img"){
                    main_item.addEventListener("load", event => WMarkDown.image_loaded(event.target, event));
                    main_item.addEventListener("error", event => WMarkDown.image_loaded(event.target, event));
                    item.setAttribute("data-status", "loading");
                    WMarkDown.image_load(main_item);
                };

            };

        });

        /**
         * @returns {void}
         * @access private
         */
        const thread_method = () => {

            /** @type {HTMLBodyElement} */
            const body = document.querySelector("body");

            code_block_format();

            build_dictionary_items();

            process_lists();

            document.querySelectorAll(".wmd-media[data-status=unprocessed]").forEach(item => item.setAttribute("data-status", "unloaded"));

            if(body){

                autoload_media(body);

                document.querySelectorAll(".wmarkdown[data-menu-processed=false]").forEach(block => {
                    if(block.getAttribute("data-menu-processed") == "true")
                        return;

                    /** @type {HTMLUListElement|null} */
                    let menu = document.querySelector(".wmd-main-menu>ul");
                    /** @type {Array.<HTMLHeadingElement>} */
                    const items = block.querySelectorAll("h1,h2,h3,h4,h5,h6");

                    if(items.length){

                        /** @type {number} */
                        let current_level = 0;

                        if(!menu){

                            /** @type {HTMLDivElement} */
                            const button = document.querySelector("header").appendChild(document.createElement("div"));

                            (menu = (
                                document.querySelector("[data-cells]") || document.querySelector("body")
                            ).appendChild(document.createElement("nav"))).appendChild(document.createElement("ul"));
                            menu.setAttribute("class", "wmd-main-menu");
                            menu.setAttribute("data-visible", false);
                            menu = menu.childNodes[0];

                            addEventListener("click", WMarkDown.hide_menu);

                            button.innerHTML += (`
                                <span data-i18n="menu" data-i18n-without="true" title="Menu" data-preload="` + self.preload_hash(span => {
                                span.addEventListener("click", event => WMarkDown.show_menu(event.target, event));
                            }) + `">
                                    <span data-icon="menu"></span>
                                    <span data-i18n="menu">Menu</span>
                                </span>
                            `);
                            button.setAttribute("class", "wmd-main-menu-button");
                            button.setAttribute("data-role", "link");

                        };

                        current_level = [...items].reduce((lower, item) => {

                            const level = Number(item.tagName[1]);

                            return level < lower ? level : lower
                        }, 6);
                        items.forEach(item => {

                            const level = Number(item.tagName[1]),
                                menu_item = document.createElement("li"),
                                anchor = menu_item.appendChild(document.createElement("a"));

                            menu_item.setAttribute("data-level", level);
                            anchor.innerText = item.innerText;
                            anchor.setAttribute("href", "#" + item.getAttribute("id"));
                            anchor.setAttribute("target", "_self");
                            anchor.setAttribute("title", item.innerText);

                            if(current_level < level){

                                const subblock = menu.childNodes[menu.childNodes.length - 1];

                                if(!(menu = subblock.childNodes[menu.childNodes.length - 1]) || menu.tagName.toLowerCase() != "ul"){

                                    const button_deployer = subblock.insertBefore(document.createElement("span"), subblock.childNodes[0]);

                                    menu = subblock.appendChild(document.createElement("ul"));

                                    button_deployer.setAttribute("data-deployed", false);
                                    button_deployer.addEventListener("click", WMarkDown.deploy);
                                    button_deployer.innerHTML = (`
                                        <span data-icon="deploy"></span>
                                        <span data-i18n="deploy">Deploy</span>
                                    `);
                                    button_deployer.setAttribute("data-role", "link");

                                };

                                current_level ++;

                            }else
                                while(current_level > level && menu.parentNode.parentNode.tagName.toLowerCase() == "ul"){
                                    current_level --;
                                    menu = menu.parentNode.parentNode;
                                };

                            menu.appendChild(menu_item);

                        });

                    };

                    block.setAttribute("data-menu-processed", true);
                    block.querySelectorAll(".wmarkdown[data-menu-processed=false]").forEach(subblock => subblock.setAttribute("data-menu-processed", true));
                    
                    window.location.hash && (window.location.href = window.location.hash);

                });

            };

        };

        /**
         * @param {!HTMLElement} box 
         * @returns {number}
         * @access public
         */
        this.get_next_z = box => {

            /** @type {number} */
            let z = 10;

            box.childNodes.forEach(node => {
                if(node && node.style){
                    
                    /** @type {number} */
                    const item_z = Number(node.style.zIndex) || 0;
                    
                    item_z >= z && (z = item_z + 1);

                };
            });

            return z;
        };

        /**
         * @param {!MouseEvent} event
         * @returns {void}
         * @access public
         */
        this.dictionary_over = event => setTimeout(() => {

            /** @type {string|null} */
            const hash = event.target.getAttribute("data-hash");

            if(!hash || dictionary_boxes.includes(hash))
                return;

            /** @type {HTMLBodyElement} */
            const body = document.querySelector("body"),
                  /** @type {HTMLDivElement} */
                  box = document.querySelector("body").appendChild(document.createElement("div")),
                  /** @type {DOMRect} */
                  bounds = event.target.getBoundingClientRect(),
                  /** @type {number} */
                  x = bounds.x + (bounds.width / 2),
                  /** @type {number} */
                  y = bounds.y + (bounds.height / 2),
                  /** @type {number} */
                  i = Number(event.target.getAttribute("data-i")), 
                  /** @type {string} */
                  own_keys = [];

            box.setAttribute("class", "wmd-dictionary-box");
            box.setAttribute("data-dictionary-box", hash);

            dictionary_boxes.push(hash);

            box.innerHTML = (`
                <div class="definition">` + dictionary[i].patterns.reduce((definition, [pattern, text]) => (
                    definition.replace(pattern, () => {
                        own_keys.push(text.replace(/\$[0-9]/g, ""));
                        return dictionary_item_mark[0] + (own_keys.length - 1) + dictionary_item_mark[1];
                    })
                ), dictionary[i].definition).replace(dictionary_item_mark[2], (all, i) => `<b class="wmd-excluded">` + own_keys[i] + `</b>`) + `</div>
                <nav class="links">` + dictionary[i].links.map(link => `<a href="` + link + `" target="_blank" title="` + link + `" data-type="` + (
                    link.toLowerCase().match(/^(http|ftp|ws)s?\:\/{2}(w+[a-z0-9]\.)?([^\/]+)/i)[3].replace(/[^a-z0-9]+/g, "_")
                ) + `" style="background-image:url('` + link.match(/^[^\:]+\:\/{2}[^\/]+/)[0] + `/favicon.ico');"></a>`).join("") + `</nav>
            `);

            // box.style.zIndex = dictionary_z ++;
            box.style.zIndex = self.get_next_z(box.parentNode);
            if(x > body.offsetWidth / 2)
                box.style.right = (body.offsetWidth - x) + "px";
            else
                box.style.left = x + "px";
            if(y > body.offsetHeight / 2)
                box.style.bottom = (body.offsetHeight - y) + "px";
            else
                box.style.top = y + "px";

            setTimeout(() => self.format_dictionary(box.querySelector(".definition")), 100);

        }, 100);

        /**
         * @param {!MouseEvent} event
         * @returns {void}
         * @access public
         * @static
         */
        this.dictionary_out = event => {

            /** @type {string|null} */
            let hash = null,
                /** @type {HTMLElement} */
                item = event.target,
                /** @type {string|null} */
                box_hash = null,
                /** @type {string|null} */
                item_hash = null;

            while(item.classList){
                if(item.classList.contains("wmd-dictionary-box")){
                    box_hash = hash = item.getAttribute("data-dictionary-box");
                    break;
                }else if(item.classList.contains("wmd-dictionary-item"))
                    item_hash = hash = item.getAttribute("data-hash");
                item = item.parentNode;
            };

            if(hash){

                /** @type {number} */
                let i = dictionary_boxes.indexOf(hash);

                if(++ i){

                    /** @type {number} */
                    let j,
                        /** @type {number} */
                        k;

                    if(box_hash)
                        [j, k] = (
                            !dictionary_boxes.includes(item_hash) ? [i, dictionary_boxes.length] :
                        [i = dictionary_boxes.indexOf(item_hash) + 1, dictionary_boxes.length]);
                    else{
                        [j, k] = [0, dictionary_boxes.length];
                        i = 0;
                    };

                    dictionary_boxes.slice(j, k).forEach(hash => {
                        document.querySelector(".wmd-dictionary-box[data-dictionary-box=" + hash + "]").remove();
                        dictionary_boxes.splice(i, 1);
                    });

                    return;
                };

            };

            document.querySelectorAll(".wmd-dictionary-box").forEach(box => box.remove());
            dictionary_boxes = [];

        };

        /**
         * @param {!wmarkdown_preload_callback} callback 
         * @returns {string}
         * @access public
         */
        this.preload_hash = callback => {

            /** @type {string} */
            const hash = self.get_hash();

            WMarkDown.preload("[data-preload=" + hash + "]", item => {
                item && item.removeAttribute("data-preload");
                hashes.splice(hashes.indexOf(hash), 1);
                callback(item);
            });

            return hash;
        };

        constructor();

    };

    /**
     * @param {!string} pattern
     * @returns {RegExp}
     * @access public
     * @static
     */
    WMarkDown.format_pattern = pattern => {

        /** @type {RegExpMatchArray} */
        const matches = pattern.match(/^\/(.+)\/([a-z]*)$/);

        matches || console.log([pattern, matches]);

        return new RegExp(matches[1], matches[2]);
    };

    /**
     * @param {!string} url
     * @param {!wmarkdown_ajax_callback} callback
     * @returns {XMLHttpRequest}
     * @access public
     * @static
     */
    WMarkDown.get = (url, callback) => {

        /** @type {boolean} */
        let ended = false;
        /** @type {XMLHttpRequest} */
        const ajax = new XMLHttpRequest(),
                /** @type {number} */
                time = Date.now(),
                /**
                 * @param {!string} message
                 * @returns {void}
                 */
                end = message => !ended && (ended = true) && typeof callback == "function" && callback(
                    ajax.responseText,
                    ajax.status,
                    ajax.readyState,
                    message == "OK",
                    message
                );

        ajax.open("get", url, true);
        ajax.timeout = 2000;
        ajax.onreadystatechange = () => {
            if(ended)
                return;
            if(ajax.readyState == 4)
                end((ajax.status >= 200 && ajax.status < 300) || [301, 302, 304].includes(ajax.status) ? "OK" : "HTTP_ERROR");
            else if(Date.now() - time > 2000)
                end("FORCED_TIMEOUT");
        };
        ajax.send(null);

        ajax.onerror = () => end("ERROR");
        ajax.onabort = () => end("ABORTED");
        ajax.ontimeout = () => end("TIMEOUT");

        return ajax;
    };

    /**
     * @param {!MouseEvent} event
     * @returns {void}
     * @access public
     * @static
     */
    WMarkDown.deploy = event => {
        
        const item = event.target.hasAttribute("data-deployed") ? event.target : event.target.parentNode;

        item.setAttribute("data-deployed", item.getAttribute("data-deployed") == "false");
        
    };

    /**
     * @param {!HTMLImageElement} item
     * @param {!ErrorEvent} [event]
     * @returns {void}
     * @access public
     * @static
     */
    WMarkDown.image_load = (item, event) => {

        /** @type {Array.<string>} */
        const images = JSON.parse(atob(item.getAttribute("data-sources"))),
            /** @type {number} */
            i = Number(item.getAttribute("data-i"));

        if(i >= images.length){
            item.parentNode.setAttribute("data-status", "error");
            return;
        };

        item.setAttribute("src", images[i]);
        item.setAttribute("data-i", i + 1);

    };

    /**
     * @param {!HTMLImageElement} item
     * @param {!EventTarget} [event]
     * @returns {void}
     * @access public
     * @static
     */
    WMarkDown.image_loaded = (item, event) => {

        /** @type {HTMLSpanElement|Null} */
        const span_image = item.parentNode.querySelector(".image");

        item.parentNode.setAttribute("data-status", "success");

        span_image && (span_image.style.backgroundImage = "url('" + item.src + "')");

    };

    /**
     * @param {!EventTarget} [event]
     * @returns {void}
     * @access public
     * @static
     */
    WMarkDown.show_menu = event => document.querySelector(".wmd-main-menu").setAttribute("data-visible", true);

    /**
     * @param {!EventTarget} event
     * @returns {void}
     * @access public
     * @static
     */
    WMarkDown.hide_menu = event => {
        if(
            event.target.parentNode.parentNode.classList &&
            event.target.parentNode.parentNode.classList.contains("wmd-main-menu-button")
        )
            return;

        /** @type {HTMLElement|null} */
        const main_menu = document.querySelector(".wmd-main-menu");

        if(!main_menu || main_menu.getAttribute("data-visible") == "false")
            return;

        /** @type {HTMLElement} */
        let item = event.target;

        while(item.tagName.toLowerCase() != "body" && item != main_menu)
            item = item.parentNode;

        item != main_menu && main_menu.setAttribute("data-visible", false);

    };

    /**
     * @param {!HTMLElement} item
     * @param {!MouseEvent} [event]
     * @returns {void}
     * @access public
     * @static
     */
    WMarkDown.view_switch = (item, event) => {

        /** @type {HTMLDivElement} */
        const box = item.parentNode.parentNode.querySelector(".code");

        if(!box)
            return;

        /** @type {HTMLDivElement} */
        const view = box.querySelector(".view"),
            /** @type {Boolean} */
            visible = view.getAttribute("data-visible") != "true";

        view.setAttribute("data-visible", visible);
        ["lines", "content"].forEach(key => box.querySelector("." + key).setAttribute("data-visible", !visible));

    };

    /**
     * @param {!(string|HTMLElement)} selector 
     * @param {!wmarkdown_preload_callback} callback 
     * @returns {void}
     * @access public
     * @static
     */
    WMarkDown.preload = (selector, callback) => {
        if(typeof callback == "function"){
            if(!selector)
                callback(null, false, 1 << 1);
            else if(selector.tagName || selector.nodeName)
                callback(selector, false, 0);
            else if(typeof selector == "string"){
                
                /** @type {HTMLElement|null} */
                let item = null;

                try{
                    if(item = document.querySelector(selector)){
                        callback(item, false, 0);
                        return;
                    };
                }catch(exception){
                    callback(null, false, 1 << 0);
                    return;
                };

                /** @type {number} */
                const date = Date.now(), 
                    /** @type {number} */
                    interval = setInterval(() => {
                        if(item = document.querySelector(selector)){
                            clearInterval(interval);
                            callback(item, true, 0);
                        }else if(Date.now() - date > 2000){
                            clearInterval(interval);
                            callback(null, false, 1 << 2);
                        };
                    }, 250);

            }else 
                callback(null, false, 1 << 3);
        };
    };

    return WMarkDown;
})();