function intersect(a, b) {
  if (b.length > a.length) { [a, b] = [b, a]; } // loop over shorter array
  return a.filter(item => (b.indexOf(item) !== -1));
}

function insertAfter(newNode, referenceNode) {
    referenceNode.parentNode.insertBefore(newNode, referenceNode.nextSibling);
}

function moveAll(fromNode, toNode) {
  for (let c; c = fromNode.firstChild; ) { toNode.appendChild(c); }
}

function removeAllFrom(fromNode) {
  for (let c; c = fromNode.lastChild; ) { fromNode.removeChild(c); }
}

function makeIframe(src, w, h, scrolling='no') {
  let iframe = document.createElement('iframe');
  iframe.style.width = w;
  iframe.style.height = h;
  iframe.frameBorder = 0;
  iframe.scrolling = scrolling;
  iframe.setAttribute('allowFullScreen', '');
  iframe.src = src;
  return iframe;
}

function wrapIntoTag(node, tagName, className) {
  let tag = document.createElement(tagName);
  if (className !== undefined) { tag.className = className; }
  tag.appendChild(node);
  return tag;
}

function makeResizableToRatio(element, ratio) {
  element.dataset['ratio'] = ratio;
  makeResizable(element, w => w * element.dataset['ratio']);
}

// calcHeight :: Number -> Number -- calculate element height for a given width
function makeResizable(element, calcHeight) {
  const resizeToRatio = el => { el.style.height = (calcHeight(el.offsetWidth)).toFixed(2) + 'px'; };
  window.addEventListener('resize', () => resizeToRatio(element));
  resizeToRatio(element);
}

function getEmbeddableLinkTypes() {
  return [
    {
      name: 'Jpeg and png images',
      id: 'embed_jpeg_and_png_images',
      ctsDefault: false,
      re: /\.(jpeg|jpg|png|svg)(:[a-zA-Z]+)?(?:\?[\w&;\?=]*)?$/i,
      makeNode: function(aNode) {
        let aNode2 = document.createElement('a');
        let imgNode = document.createElement('img');
        imgNode.src = aNode.href;
        aNode2.href = aNode.href;
        aNode2.appendChild(imgNode);
        return wrapIntoTag(aNode2, 'div', 'picture compact');
      }
    },
    {
      name: 'Gif images',
      id: 'embed_gif_images',
      ctsDefault: true,
      re: /\.gif(:[a-zA-Z]+)?(?:\?[\w&;\?=]*)?$/i,
      makeNode: function(aNode) {
        let aNode2 = document.createElement('a');
        let imgNode = document.createElement('img');
        imgNode.src = aNode.href;
        aNode2.href = aNode.href;
        aNode2.appendChild(imgNode);
        return wrapIntoTag(aNode2, 'div', 'picture compact');
      }
    },
    {
      name: 'Video (webm, mp4, ogv)',
      id: 'embed_webm_and_mp4_videos',
      ctsDefault: false,
      re: /\.(webm|mp4|m4v|ogv)(?:\?[\w&;\?=]*)?$/i,
      makeNode: function(aNode) {
        let video = document.createElement('video');
        video.src = aNode.href;
        video.title = aNode.href;
        video.setAttribute('controls', '');
        return wrapIntoTag(video, 'div', 'video compact');
      }
    },
    {
      name: 'Audio (mp3, ogg, weba, opus, m4a, oga, wav)',
      id: 'embed_sound_files',
      ctsDefault: false,
      re: /\.(mp3|ogg|weba|opus|m4a|oga|wav)(?:\?[\w&;\?=]*)?$/i,
      makeNode: function(aNode) {
        let audio = document.createElement('audio');
        audio.src = aNode.href;
        audio.title = aNode.href;
        audio.setAttribute('controls', '');
        return wrapIntoTag(audio, 'div', 'audio');
      }
    },
    {
      name: 'YouTube videos (and playlists)',
      id: 'embed_youtube_videos',
      onByDefault: false,
      ctsDefault: false,
      re: /^(?:https?:)?\/\/(?:www\.|m\.)?(?:youtu(?:(?:\.be\/|be\.com\/(?:v|embed)\/)([-\w]+)|be\.com\/watch)((?:(?:\?|&(?:amp;)?)(?:\w+=[-\.\w]*[-\w]))*)|youtube\.com\/playlist\?list=([-\w]*)(&(amp;)?[-\w\?=]*)?)/i,
      makeNode: function(aNode, reResult) {
        let [url, v, args, plist] = reResult;
        let iframeUrl;
        if (plist !== undefined) {
          iframeUrl = '//www.youtube-nocookie.com/embed/videoseries?list=' + plist;
        } else {
          args = args.replace(/^\?/, '');
          let arr = args.split('&').map(s => s.split('='));
          let pp = {}; arr.forEach(z => pp[z[0]] = z[1]);
          let embedArgs = { rel: '0' };
          if (pp.t != undefined) {
            const tre = /^(?:(\d+)|(?:(\d+)h)?(?:(\d+)m)?(\d+)s|(?:(\d+)h)?(\d+)m|(\d+)h)$/i;
            let [, t, h, m, s, h1, m1, h2] = tre.exec(pp.t);
            embedArgs['start'] = (+t) || ((+(h || h1 || h2 || 0))*60*60 + (+(m || m1 || 0))*60 + (+(s || 0)));
          }
          if (pp.list !== undefined) {
            embedArgs['list'] = pp.list;
          }
          v = v || pp.v;
          iframeUrl = '//www.youtube-nocookie.com/embed/' + v + '?' + Object.keys(embedArgs).map(k => `${k}=${embedArgs[k]}`).join('&');
        }
        let iframe = makeIframe(iframeUrl, '100%', '360px');
        setTimeout(() => makeResizableToRatio(iframe, 9.0/16.0), 10);
        return wrapIntoTag(iframe, 'div', 'youtube resizableV');
      }
    },
    {
      name: 'Vimeo videos',
      id: 'embed_vimeo_videos',
      onByDefault: false,
      ctsDefault: false,
      //re: /^(?:https?:)?\/\/(?:www\.)?(?:player\.)?vimeo\.com\/(?:(?:video\/|album\/[\d]+\/video\/)?([\d]+)|([\w-]+)\/(?!videos)([\w-]+))/i,
      re: /^(?:https?:)?\/\/(?:www\.)?(?:player\.)?vimeo\.com\/(?:video\/|album\/[\d]+\/video\/)?([\d]+)/i,
      makeNode: function(aNode, reResult) {
        let iframe = makeIframe('//player.vimeo.com/video/' + reResult[1], '100%', '360px');
        setTimeout(() => makeResizableToRatio(iframe, 9.0/16.0), 10);
        return wrapIntoTag(iframe, 'div', 'vimeo resizableV');
      }
    }
  ];
}

function embedLink(aNode, linkTypes, container, alwaysCts, afterNode) {
  let anyEmbed = false;
  let linkId = (aNode.href.replace(/^https?:/i, '').replace(/\'/i,''));
  let sameEmbed = container.querySelector(`*[data-linkid='${linkId}']`); // do not embed the same thing twice
  if (sameEmbed === null) {
    anyEmbed = [].some.call(linkTypes, function(linkType) {
        let reResult = linkType.re.exec(aNode.href);
        if (reResult !== null) {
          if ((linkType.match !== undefined) && (linkType.match(aNode, reResult) === false)) { return false; }
          let newNode = linkType.makeNode(aNode, reResult);
          if (!newNode) { return false; }
          newNode.setAttribute('data-linkid', linkId);
          if (afterNode !== undefined) {
            insertAfter(newNode, afterNode);
          } else {
            container.appendChild(newNode);
          }
          aNode.classList.add('embedLink');
          return true;
        }
    });
  }
  return anyEmbed;
}

function embedLinks(aNodes, container, alwaysCts, afterNode) {
  let anyEmbed = false;
  let embeddableLinkTypes = getEmbeddableLinkTypes();
  Array.from(aNodes).forEach(aNode => {
    let isEmbedded = embedLink(aNode, embeddableLinkTypes, container, alwaysCts, afterNode);
    anyEmbed = anyEmbed || isEmbedded;
  });
  return anyEmbed;
}

function articleInfo(article) {
  let tagNodes = article.querySelectorAll('.msg-tags > *');
  let tags = Array.from(tagNodes).map(d => d.textContent.toLowerCase());
  return { tags: tags };
}

function embedLinksToX(x, beforeNodeSelector, allLinksSelector, ctsUsers, ctsTags) {
  let isCtsPost = false;
  let allLinks = x.querySelectorAll(allLinksSelector);

  let existingContainer = x.querySelector('div.embedContainer');
  if (existingContainer !== null) {
    embedLinks(allLinks, existingContainer, isCtsPost);
  } else {
    let embedContainer = document.createElement('div');
    embedContainer.className = 'embedContainer';

    let anyEmbed = embedLinks(allLinks, embedContainer, isCtsPost);
    if (anyEmbed) {
      let beforeNode = x.querySelector(beforeNodeSelector);
      x.insertBefore(embedContainer, beforeNode);
    }
  }
}

function embedLinksToArticles() {
  let ctsUsers = [], ctsTags = []; // TODO click-to-show users and tags
  let beforeNodeSelector = 'nav.l';
  let allLinksSelector = 'p:not(.ir) a, pre a';
  Array.from(document.querySelectorAll('#content > article')).forEach(article => {
    embedLinksToX(article, beforeNodeSelector, allLinksSelector, ctsUsers, ctsTags);
  });
}

function embedLinksToPost() {
  let ctsUsers = [], ctsTags = []; // TODO click-to-show users and tags
  let beforeNodeSelector = '.msg-txt + *';
  let allLinksSelector = '.msg-txt a';
  Array.from(document.querySelectorAll('#content .msg-cont')).forEach(msg => {
    embedLinksToX(msg, beforeNodeSelector, allLinksSelector, ctsUsers, ctsTags);
  });
}

exports.embed = function() {
  if (document.querySelectorAll('#content > article').length) {
    embedLinksToArticles();
  } else {
    embedLinksToPost();
  }
};