(function() {
  /**
   * Check and set a global guard letiable.
   * If this content script is injected into the same page again,
   * it will do nothing next time.
   */
  if (window.hasRun) {
    console.log("already run");
    return;
  }

  window.hasRun = true;

  let xml_parser = new XMLSerializer();
  let html_parser = new DOMParser();

  function xhrdoc(url, type, cb) {

    let xhr = new XMLHttpRequest();
    xhr.open('GET', url, true);

    xhr.responseType = 'document';
    xhr.overrideMimeType('text/' + type);

    xhr.onload = () => {
      if (xhr.readyState === xhr.DONE) {
        if (xhr.status === 200) {
          let resp = (type=="xml") ? xhr.responseXML : xhr.response;
          cb(resp);
        }
      }
    };

    xhr.send(null);
  }

  function applyxsl(xmlin, xsl, node, doc=document) {
    let xsltProcessor = new XSLTProcessor();
    xsltProcessor.importStylesheet(xsl);

    let fragment = xsltProcessor.transformToFragment(xmlin, doc);
    node.appendChild(fragment);
  }

  function getlang() {
    if (navigator.languages && navigator.languages[0])
      return navigator.languages[0];
    else if (navigator.language)
      return navigator.language;
    else
      return null;
  }

  function formatsubtitle() {
    try {
      let feed_desc = document.getElementById("feedSubtitleRaw");

      let html_desc = html_parser.parseFromString('<h2 id="feedSubtitleText">'+feed_desc.innerText+'</h2>', "text/html");
      let xml_desc = xml_parser.serializeToString(html_desc.body.firstChild);

      feed_desc.insertAdjacentHTML('afterend', xml_desc);

      feed_desc.parentNode.removeChild(feed_desc);
    }
    catch (e) {
      console.error(e);
      console.log(feed_desc.innerText);
    }
  }

  function formatdescriptions(el=document) {
    // unescapes descriptions to html then to xml
    let tohtml = el.getElementsByClassName("feedRawContent");

    for (let i = 0; i<tohtml.length; i++) {
      // in case of xhtml the content is already parsed
      if (tohtml[i].getAttribute("desctype") != "xhtml") {
        try {
          let html_desc = html_parser.parseFromString('<div class="feedEntryContent">'+tohtml[i].innerText+'</div>', "text/html");
          let xml_desc = xml_parser.serializeToString(html_desc.body.firstChild);

          tohtml[i].insertAdjacentHTML('afterend', xml_desc);
          tohtml[i].setAttribute("todel", 1);
        }
        catch (e) {
          console.error(e);
          console.log(tohtml[i].innerHTML);
        }
      }
    }

    el.querySelectorAll('.feedRawContent').forEach((a) => {
      if (a.getAttribute("todel") == "1") {
        a.remove();
      }
      else if (a.getAttribute("desctype") == "xhtml") {
        a.classList.add("feedEntryContent");
        a.classList.remove("feedRawContent");
      }
    })
  }

  function removeemptyenclosures(el=document) {
    let encs = el.getElementsByClassName("enclosures");

    for (let i = 0; i < encs.length; i++)
      if (!encs[i].firstChild)
        encs[i].style.display = "none";
  }

  function formatfilenames(el=document) {
    let encfn = el.getElementsByClassName("enclosureFilename");

    for (let i = 0; i<encfn.length; i++) {
      let url = new URL(encfn[i].innerText);

      if (url) {
        let fn = url.pathname.split("/").pop();

        if (fn != "")
          encfn[i].innerText = fn;
      }
    }
  }

  function formatfilesizes(el=document) {
    function humanfilesize(size) {
      let i = 0;

      if (size && size != "" && size > 0)
        i = Math.floor( Math.log(size) / Math.log(1024) );

      return ( size / Math.pow(1024, i) ).toFixed(2) * 1 + ' ' + ['B', 'kB', 'MB', 'GB', 'TB'][i];
    };

    let encsz = el.getElementsByClassName("enclosureSize");
    for (let i = 0; i<encsz.length; i++) {
      let hsize = humanfilesize(encsz[i].innerText);

      if (hsize)
        encsz[i].innerText = hsize;
    }
  }

  function formattitles(el=document) {
    let et = el.getElementsByClassName("entrytitle");

    for (let i = 0; i<et.length; i++) {
      //basically removes html content if there is some
      //only do it if there's a tag to avoid doing it when text titles cointain a '&'
      //(which can be caught but still displays an error in console, which is annoying)
      if (et[i].innerText.indexOf('<') >= 0) {
        let tmp = document.createElement("span");
        try {
          tmp.innerHTML = et[i].innerText;
          et[i].innerText = tmp.textContent;
        }
        catch (e) {
          console.error(e);
          console.log(et[i].innerText);
        }
      }
    }
  }

  function formatdates(el=document) {
    let lang = getlang();
    if (!lang)
      return;

    let opts = { weekday: 'long', year: 'numeric', month: 'long', day: 'numeric' };

    let ed = el.getElementsByClassName("lastUpdated");
    for (let i = 0; i<ed.length; i++) {
      let d = new Date(ed[i].innerText);
      if (isNaN(d))
        continue;

      let dstr = d.toLocaleDateString(lang, opts) + ' ' + d.toLocaleTimeString(lang);

      ed[i].innerText = dstr;
    }
  }

  function extensionimages(el=document) {
    let extimgs = el.getElementsByClassName("extImg");

    for (let i = 0; i<extimgs.length; i++)
      extimgs[i].src = chrome.extension.getURL(extimgs[i].attributes['data-src'].nodeValue);
  }

  function makepreviewhtml() {
    let doc = document.implementation.createHTMLDocument("");

    let feedBody = doc.createElement("div");
    feedBody.id = "feedBody";
    doc.body.appendChild(feedBody);

    let css = doc.createElement('link');
    css.setAttribute('rel', 'stylesheet');
    css.setAttribute('href', chrome.extension.getURL("preview.css"));
    doc.head.appendChild(css);

    return doc;
  }


  function detect() {
    let rootNode = document.getRootNode().documentElement;

    // for chrome
    let d = document.getElementById("webkit-xml-viewer-source-xml");
    if (d && d.firstChild)
      rootNode = d.firstChild;

    const rootName = rootNode.nodeName.toLowerCase();

    let isRSS1 = false;

    if (rootName == "rdf" || rootName == "rdf:rdf")
      if (rootNode.attributes['xmlns'])
        isRSS1 = (rootNode.attributes['xmlns'].nodeValue.search('rss') > 0)

    if ( rootName == "rss" || rootName == "channel"  // rss2
      || rootName == "feed"  // atom
      || isRSS1 )
      return rootNode;

    return null;
  }

  function main(feedNode) {
    let feed_url = window.location.href;
    let preview = makepreviewhtml();

    xhrdoc(chrome.extension.getURL("rss.xsl"), "xml", (xsl_xml) => {
      applyxsl(feedNode, xsl_xml, preview.getElementById("feedBody"), preview);

      // replace the content with the preview document
      document.replaceChild(document.importNode(preview.documentElement, true), document.documentElement);

      let t0 = performance.now();

      formatsubtitle();

      formatdescriptions();
      removeemptyenclosures();
      formatfilenames();
      formatfilesizes();
      formattitles();
      formatdates();
      extensionimages();

      let t1 = performance.now();
      //console.log("exec in: " + (t1 - t0) + "ms");

      document.title = document.getElementById("feedTitleText").innerText;
    });
  }

  let feedRoot = detect();

  if (feedRoot)
    main(feedRoot);

})();