/*!
 * The reveal.js markdown plugin. Handles parsing of
 * markdown inside of presentations as well as loading
 * of external markdown documents.
 */

import { marked } from "marked";

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

const SCRIPT_END_PLACEHOLDER = "__SCRIPT_END__";

const CODE_LINE_NUMBER_REGEX = /\[([\s\d,|-]*)\]/;

const HTML_ESCAPE_MAP = {
  "&": "&",
  "<": "&lt;",
  ">": "&gt;",
  '"': "&quot;",
  "'": "&#39;",
};

const Plugin = () => {
  // The reveal.js instance this plugin is attached to
  let deck;

  /**
   * 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"),
        function (m, p1) {
          return "\n" + p1;
        }
      );
    } else if (leadingWs > 1) {
      text = text.replace(
        new RegExp("\\n? {" + leadingWs + "}(.*)", "g"),
        function (m, p1) {
          return "\n" + p1;
        }
      );
    }

    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))) {
      var 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(scope) {
    return new Promise(function (resolve) {
      var externalPromises = [];

      [].slice
        .call(
          scope.querySelectorAll(
            "section[data-markdown]:not([data-markdown-parsed])"
          )
        )
        .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 {
            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),
            });
          }
        });

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

  function loadExternalMarkdown(section) {
    return new Promise(function (resolve, reject) {
      var xhr = new XMLHttpRequest(),
        url = section.getAttribute("data-markdown");

      var 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) {
        console.warn(
          "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(
      '([^"= ]+?)="([^"]+?)"|(data-[^"= ]+?)(?=[" ])',
      "mg"
    );
    var nodeValue = node.nodeValue;
    var matches, matchesClass;
    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))) {
        if (matchesClass[2]) {
          elementTarget.setAttribute(matchesClass[1], matchesClass[2]);
        } else {
          elementTarget.setAttribute(matchesClass[3], "");
        }
      }
      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
    ) {
      var previousParentElement = element;
      for (var i = 0; i < element.childNodes.length; i++) {
        var childElement = element.childNodes[i];
        if (i > 0) {
          var j = i - 1;
          while (j >= 0) {
            var aPreviousChildElement = element.childNodes[j];
            if (
              typeof aPreviousChildElement.setAttribute == "function" &&
              aPreviousChildElement.tagName != "BR"
            ) {
              previousParentElement = aPreviousChildElement;
              break;
            }
            j = j - 1;
          }
        }
        var 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 = deck
      .getRevealElement()
      .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();
  }

  function escapeForHTML(input) {
    return input.replace(/([&<>'"])/g, (char) => HTML_ESCAPE_MAP[char]);
  }

  return {
    id: "markdown",

    /**
     * Starts processing and converting Markdown within the
     * current reveal.js deck.
     */
    init: function (reveal) {
      deck = reveal;

      let { renderer, animateLists, ...markedOptions } =
        deck.getConfig().markdown || {};

      if (!renderer) {
        renderer = new marked.Renderer();

        renderer.code = (code, language) => {
          // Off by default
          let lineNumbers = "";

          // Users can opt in to show line numbers and highlight
          // specific lines.
          // ```javascript []        show line numbers
          // ```javascript [1,4-8]   highlights lines 1 and 4-8
          if (CODE_LINE_NUMBER_REGEX.test(language)) {
            lineNumbers = language.match(CODE_LINE_NUMBER_REGEX)[1].trim();
            lineNumbers = `data-line-numbers="${lineNumbers}"`;
            language = language.replace(CODE_LINE_NUMBER_REGEX, "").trim();
          }

          // Escape before this gets injected into the DOM to
          // avoid having the HTML parser alter our code before
          // highlight.js is able to read it
          code = escapeForHTML(code);

          return `<pre><code ${lineNumbers} class="${language}">${code}</code></pre>`;
        };
      }

      if (animateLists === true) {
        renderer.listitem = (text) => `<li class="fragment">${text}</li>`;
      }

      marked.setOptions({
        renderer,
        ...markedOptions,
      });

      return processSlides(deck.getRevealElement()).then(convertSlides);
    },

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

export default Plugin;