/**
 * The reveal.js markdown plugin. Handles parsing of
 * markdown inside of presentations as well as loading
 * of external markdown documents.
 */
(function (root, factory) {
    if (typeof define === 'function' && define.amd) {
        root.marked = require('./marked');
        root.RevealMarkdown = factory(root.marked);
    } else if (typeof exports === 'object') {
        module.exports = factory(require('./marked'));
    } else {
        // Browser globals (root is window)
        root.RevealMarkdown = factory(root.marked);
    }
}(this, function (marked) {

    var DEFAULT_SLIDE_SEPARATOR = '^\r?\n---\r?\n$',
        DEFAULT_NOTES_SEPARATOR = 'notes?:',
        DEFAULT_ELEMENT_ATTRIBUTES_SEPARATOR = '\\\.element\\\s*?(.+?)$',
        DEFAULT_SLIDE_ATTRIBUTES_SEPARATOR = '\\\.slide:\\\s*?(\\\S.+?)$';

    var SCRIPT_END_PLACEHOLDER = '__SCRIPT_END__';


    /**
     * Retrieves the markdown contents of a slide section
     * element. Normalizes leading tabs/whitespace.
     */
    function getMarkdownFromSlide(section) {

        // look for a <script> or <textarea data-template> wrapper
        var template = section.querySelector('[data-template]') || section.querySelector('script');

        // strip leading whitespace so it isn't evaluated as code
        var text = (template || section).textContent;

        // restore script end tags
        text = text.replace(new RegExp(SCRIPT_END_PLACEHOLDER, 'g'), '</script>');

        var leadingWs = text.match(/^\n?(\s*)/)[1].length,
            leadingTabs = text.match(/^\n?(\t*)/)[1].length;

        if (leadingTabs > 0) {
            text = text.replace(new RegExp('\\n?\\t{' + leadingTabs + '}', 'g'), '\n');
        } else if (leadingWs > 1) {
            text = text.replace(new RegExp('\\n? {' + leadingWs + '}', 'g'), '\n');
        }

        return text;

    }

    /**
     * Given a markdown slide section element, this will
     * return all arguments that aren't related to markdown
     * parsing. Used to forward any other user-defined arguments
     * to the output markdown slide.
     */
    function getForwardedAttributes(section) {

        var attributes = section.attributes;
        var result = [];

        for (var i = 0, len = attributes.length; i < len; i++) {
            var name = attributes[i].name,
                value = attributes[i].value;

            // disregard attributes that are used for markdown loading/parsing
            if (/data\-(markdown|separator|vertical|notes)/gi.test(name)) continue;

            if (value) {
                result.push(name + '="' + value + '"');
            } else {
                result.push(name);
            }
        }

        return result.join(' ');

    }

    /**
     * Inspects the given options and fills out default
     * values for what's not defined.
     */
    function getSlidifyOptions(options) {

        options = options || {};
        options.separator = options.separator || DEFAULT_SLIDE_SEPARATOR;
        options.notesSeparator = options.notesSeparator || DEFAULT_NOTES_SEPARATOR;
        options.attributes = options.attributes || '';

        return options;

    }

    /**
     * Helper function for constructing a markdown slide.
     */
    function createMarkdownSlide(content, options) {

        options = getSlidifyOptions(options);

        var notesMatch = content.split(new RegExp(options.notesSeparator, 'mgi'));

        if (notesMatch.length === 2) {
            content = notesMatch[0] + '<aside class="notes">' + marked(notesMatch[1].trim()) + '</aside>';
        }

        // prevent script end tags in the content from interfering
        // with parsing
        content = content.replace(/<\/script>/g, SCRIPT_END_PLACEHOLDER);

        return '<script type="text/template">' + content + '</script>';

    }

    /**
     * Parses a data string into multiple slides based
     * on the passed in separator arguments.
     */
    function slidify(markdown, options) {

        options = getSlidifyOptions(options);

        var separatorRegex = new RegExp(options.separator + (options.verticalSeparator ? '|' + options.verticalSeparator : ''), 'mg'),
            horizontalSeparatorRegex = new RegExp(options.separator);

        var matches,
            lastIndex = 0,
            isHorizontal,
            wasHorizontal = true,
            content,
            sectionStack = [];

        // iterate until all blocks between separators are stacked up
        while (matches = separatorRegex.exec(markdown)) {
            notes = null;

            // determine direction (horizontal by default)
            isHorizontal = horizontalSeparatorRegex.test(matches[0]);

            if (!isHorizontal && wasHorizontal) {
                // create vertical stack
                sectionStack.push([]);
            }

            // pluck slide content from markdown input
            content = markdown.substring(lastIndex, matches.index);

            if (isHorizontal && wasHorizontal) {
                // add to horizontal stack
                sectionStack.push(content);
            } else {
                // add to vertical stack
                sectionStack[sectionStack.length - 1].push(content);
            }

            lastIndex = separatorRegex.lastIndex;
            wasHorizontal = isHorizontal;
        }

        // add the remaining slide
        (wasHorizontal ? sectionStack : sectionStack[sectionStack.length - 1]).push(markdown.substring(lastIndex));

        var markdownSections = '';

        // flatten the hierarchical stack, and insert <section data-markdown> tags
        for (var i = 0, len = sectionStack.length; i < len; i++) {
            // vertical
            if (sectionStack[i] instanceof Array) {
                markdownSections += '<section ' + options.attributes + '>';

                sectionStack[i].forEach(function (child) {
                    markdownSections += '<section data-markdown>' + createMarkdownSlide(child, options) + '</section>';
                });

                markdownSections += '</section>';
            } else {
                markdownSections += '<section ' + options.attributes + ' data-markdown>' + createMarkdownSlide(sectionStack[i], options) + '</section>';
            }
        }

        return markdownSections;

    }

    /**
     * Parses any current data-markdown slides, splits
     * multi-slide markdown into separate sections and
     * handles loading of external markdown.
     */
    function processSlides() {

        return new Promise(function (resolve) {

            var externalPromises = [];

            [].slice.call(document.querySelectorAll('[data-markdown]')).forEach(function (section, i) {

                if (section.getAttribute('data-markdown').length) {

                    externalPromises.push(loadExternalMarkdown(section).then(
                        // Finished loading external file
                        function (xhr, url) {
                            section.outerHTML = slidify(xhr.responseText, {
                                separator: section.getAttribute('data-separator'),
                                verticalSeparator: section.getAttribute('data-separator-vertical'),
                                notesSeparator: section.getAttribute('data-separator-notes'),
                                attributes: getForwardedAttributes(section)
                            });
                        },

                        // Failed to load markdown
                        function (xhr, url) {
                            section.outerHTML = '<section data-state="alert">' +
                                'ERROR: The attempt to fetch ' + url + ' failed with HTTP status ' + xhr.status + '.' +
                                'Check your browser\'s JavaScript console for more details.' +
                                '<p>Remember that you need to serve the presentation HTML from a HTTP server.</p>' +
                                '</section>';
                        }
                    ));

                } else if (section.getAttribute('data-separator') || section.getAttribute('data-separator-vertical') || section.getAttribute('data-separator-notes')) {

                    section.outerHTML = slidify(getMarkdownFromSlide(section), {
                        separator: section.getAttribute('data-separator'),
                        verticalSeparator: section.getAttribute('data-separator-vertical'),
                        notesSeparator: section.getAttribute('data-separator-notes'),
                        attributes: getForwardedAttributes(section)
                    });

                } else {
                    section.innerHTML = createMarkdownSlide(getMarkdownFromSlide(section));
                }

            });

            Promise.all(externalPromises).then(resolve);

        });

    }

    function loadExternalMarkdown(section) {

        return new Promise(function (resolve, reject) {

            var xhr = new XMLHttpRequest(),
                url = section.getAttribute('data-markdown');

            datacharset = section.getAttribute('data-charset');

            // see https://developer.mozilla.org/en-US/docs/Web/API/element.getAttribute#Notes
            if (datacharset != null && datacharset != '') {
                xhr.overrideMimeType('text/html; charset=' + datacharset);
            }

            xhr.onreadystatechange = function (section, xhr) {
                if (xhr.readyState === 4) {
                    // file protocol yields status code 0 (useful for local debug, mobile applications etc.)
                    if ((xhr.status >= 200 && xhr.status < 300) || xhr.status === 0) {

                        resolve(xhr, url);

                    } else {

                        reject(xhr, url);

                    }
                }
            }.bind(this, section, xhr);

            xhr.open('GET', url, true);

            try {
                xhr.send();
            } catch (e) {
                alert('Failed to get the Markdown file ' + url + '. Make sure that the presentation and the file are served by a HTTP server and the file can be found there. ' + e);
                resolve(xhr, url);
            }

        });

    }

    /**
     * Check if a node value has the attributes pattern.
     * If yes, extract it and add that value as one or several attributes
     * to the target element.
     *
     * You need Cache Killer on Chrome to see the effect on any FOM transformation
     * directly on refresh (F5)
     * http://stackoverflow.com/questions/5690269/disabling-chrome-cache-for-website-development/7000899#answer-11786277
     */
    function addAttributeInElement(node, elementTarget, separator) {

        var mardownClassesInElementsRegex = new RegExp(separator, 'mg');
        var mardownClassRegex = new RegExp("([^\"= ]+?)=\"([^\"=]+?)\"", 'mg');
        var nodeValue = node.nodeValue;
        if (matches = mardownClassesInElementsRegex.exec(nodeValue)) {

            var classes = matches[1];
            nodeValue = nodeValue.substring(0, matches.index) + nodeValue.substring(mardownClassesInElementsRegex.lastIndex);
            node.nodeValue = nodeValue;
            while (matchesClass = mardownClassRegex.exec(classes)) {
                elementTarget.setAttribute(matchesClass[1], matchesClass[2]);
            }
            return true;
        }
        return false;
    }

    /**
     * Add attributes to the parent element of a text node,
     * or the element of an attribute node.
     */
    function addAttributes(section, element, previousElement, separatorElementAttributes, separatorSectionAttributes) {

        if (element != null && element.childNodes != undefined && element.childNodes.length > 0) {
            previousParentElement = element;
            for (var i = 0; i < element.childNodes.length; i++) {
                childElement = element.childNodes[i];
                if (i > 0) {
                    j = i - 1;
                    while (j >= 0) {
                        aPreviousChildElement = element.childNodes[j];
                        if (typeof aPreviousChildElement.setAttribute == 'function' && aPreviousChildElement.tagName != "BR") {
                            previousParentElement = aPreviousChildElement;
                            break;
                        }
                        j = j - 1;
                    }
                }
                parentSection = section;
                if (childElement.nodeName == "section") {
                    parentSection = childElement;
                    previousParentElement = childElement;
                }
                if (typeof childElement.setAttribute == 'function' || childElement.nodeType == Node.COMMENT_NODE) {
                    addAttributes(parentSection, childElement, previousParentElement, separatorElementAttributes, separatorSectionAttributes);
                }
            }
        }

        if (element.nodeType == Node.COMMENT_NODE) {
            if (addAttributeInElement(element, previousElement, separatorElementAttributes) == false) {
                addAttributeInElement(element, section, separatorSectionAttributes);
            }
        }
    }

    /**
     * Converts any current data-markdown slides in the
     * DOM to HTML.
     */
    function convertSlides() {

        var sections = document.querySelectorAll('[data-markdown]:not([data-markdown-parsed])');

        [].slice.call(sections).forEach(function (section) {

            section.setAttribute('data-markdown-parsed', true);

            var notes = section.querySelector('aside.notes');
            var markdown = getMarkdownFromSlide(section);

            section.innerHTML = marked(markdown);
            addAttributes(section, section, null, section.getAttribute('data-element-attributes') ||
                section.parentNode.getAttribute('data-element-attributes') ||
                DEFAULT_ELEMENT_ATTRIBUTES_SEPARATOR,
                section.getAttribute('data-attributes') ||
                section.parentNode.getAttribute('data-attributes') ||
                DEFAULT_SLIDE_ATTRIBUTES_SEPARATOR);

            // If there were notes, we need to re-add them after
            // having overwritten the section's HTML
            if (notes) {
                section.appendChild(notes);
            }

        });

        return Promise.resolve();

    }

    // API
    var RevealMarkdown = {

        /**
         * Starts processing and converting Markdown within the
         * current reveal.js deck.
         *
         * @param {function} callback function to invoke once
         * we've finished loading and parsing Markdown
         */
        init: function (callback) {

            if (typeof marked === 'undefined') {
                throw 'The reveal.js Markdown plugin requires marked to be loaded';
            }

            if (typeof hljs !== 'undefined') {
                marked.setOptions({
                    highlight: function (code, lang) {
                        return hljs.highlightAuto(code, [lang]).value;
                    }
                });
            }

            // marked can be configured via reveal.js config options
            var options = Reveal.getConfig().markdown;
            if (options) {
                marked.setOptions(options);
            }

            return processSlides().then(convertSlides);

        },

        // TODO: Do these belong in the API?
        processSlides: processSlides,
        convertSlides: convertSlides,
        slidify: slidify

    };

    // Register our plugin so that reveal.js will call our
    // plugin 'init' method as part of the initialization
    Reveal.registerPlugin('markdown', RevealMarkdown);

    return RevealMarkdown;

}));