source: node_modules/prismjs/plugins/toolbar/prism-toolbar.js

(function () {

        if (typeof Prism === 'undefined' || typeof document === 'undefined') {
                return;
        }

        var callbacks = [];
        var map = {};
        var noop = function () {};

        Prism.plugins.toolbar = {};

        /**
         * @typedef ButtonOptions
         * @property {string} text The text displayed.
         * @property {string} [url] The URL of the link which will be created.
         * @property {Function} [onClick] The event listener for the `click` event of the created button.
         * @property {string} [className] The class attribute to include with element.
         */

        /**
         * Register a button callback with the toolbar.
         *
         * @param {string} key
         * @param {ButtonOptions|Function} opts
         */
        var registerButton = Prism.plugins.toolbar.registerButton = function (key, opts) {
                var callback;

                if (typeof opts === 'function') {
                        callback = opts;
                } else {
                        callback = function (env) {
                                var element;

                                if (typeof opts.onClick === 'function') {
                                        element = document.createElement('button');
                                        element.type = 'button';
                                        element.addEventListener('click', function () {
                                                opts.onClick.call(this, env);
                                        });
                                } else if (typeof opts.url === 'string') {
                                        element = document.createElement('a');
                                        element.href = opts.url;
                                } else {
                                        element = document.createElement('span');
                                }

                                if (opts.className) {
                                        element.classList.add(opts.className);
                                }

                                element.textContent = opts.text;

                                return element;
                        };
                }

                if (key in map) {
                        console.warn('There is a button with the key "' + key + '" registered already.');
                        return;
                }

                callbacks.push(map[key] = callback);
        };

        /**
         * Returns the callback order of the given element.
         *
         * @param {HTMLElement} element
         * @returns {string[] | undefined}
         */
        function getOrder(element) {
                while (element) {
                        var order = element.getAttribute('data-toolbar-order');
                        if (order != null) {
                                order = order.trim();
                                if (order.length) {
                                        return order.split(/\s*,\s*/g);
                                } else {
                                        return [];
                                }
                        }
                        element = element.parentElement;
                }
        }

        /**
         * Post-highlight Prism hook callback.
         *
         * @param env
         */
        var hook = Prism.plugins.toolbar.hook = function (env) {
                // Check if inline or actual code block (credit to line-numbers plugin)
                var pre = env.element.parentNode;
                if (!pre || !/pre/i.test(pre.nodeName)) {
                        return;
                }

                // Autoloader rehighlights, so only do this once.
                if (pre.parentNode.classList.contains('code-toolbar')) {
                        return;
                }

                // Create wrapper for <pre> to prevent scrolling toolbar with content
                var wrapper = document.createElement('div');
                wrapper.classList.add('code-toolbar');
                pre.parentNode.insertBefore(wrapper, pre);
                wrapper.appendChild(pre);

                // Setup the toolbar
                var toolbar = document.createElement('div');
                toolbar.classList.add('toolbar');

                // order callbacks
                var elementCallbacks = callbacks;
                var order = getOrder(env.element);
                if (order) {
                        elementCallbacks = order.map(function (key) {
                                return map[key] || noop;
                        });
                }

                elementCallbacks.forEach(function (callback) {
                        var element = callback(env);

                        if (!element) {
                                return;
                        }

                        var item = document.createElement('div');
                        item.classList.add('toolbar-item');

                        item.appendChild(element);
                        toolbar.appendChild(item);
                });

                // Add our toolbar to the currently created wrapper of <pre> tag
                wrapper.appendChild(toolbar);
        };

        registerButton('label', function (env) {
                var pre = env.element.parentNode;
                if (!pre || !/pre/i.test(pre.nodeName)) {
                        return;
                }

                if (!pre.hasAttribute('data-label')) {
                        return;
                }

                var element; var template;
                var text = pre.getAttribute('data-label');
                try {
                        // Any normal text will blow up this selector.
                        template = document.querySelector('template#' + text);
                } catch (e) { /* noop */ }

                if (template) {
                        element = template.content;
                } else {
                        if (pre.hasAttribute('data-url')) {
                                element = document.createElement('a');
                                element.href = pre.getAttribute('data-url');
                        } else {
                                element = document.createElement('span');
                        }

                        element.textContent = text;
                }

                return element;
        });

        /**
         * Register the toolbar with Prism.
         */
        Prism.hooks.add('complete', hook);
}());