core.js

var maxFeedItems = 15;
var req;
var buildPopupAfterResponse = false;
var OnFeedSuccess = null;
var OnFeedFail = null;
var retryMilliseconds = 120000;

function SetInitialOption(key, value) {
  if (localStorage[key] == null) {
    localStorage[key] = value;
  }
}

function UpdateIfReady(force) {
  var lastRefresh = parseFloat(localStorage["HN.LastRefresh"]);
  var interval = parseFloat(localStorage["HN.RequestInterval"]);
  var nextRefresh = lastRefresh + interval;
  var curTime = parseFloat((new Date()).getTime());
  var isReady = (curTime > nextRefresh);
  var isNull = (localStorage["HN.LastRefresh"] == null);
  if ((force == true) || (localStorage["HN.LastRefresh"] == null)) {
    UpdateFeed();
  }
  else {
    if (isReady) {
      UpdateFeed();
    }
  }
}

function UpdateFeed() {
  var xhr = new XMLHttpRequest();
  xhr.open('GET', 'https://news.ycombinator.com/rss');
  xhr.onload = function() {
    if (xhr.status === 200) {
      onRssSuccess(xhr.responseText);
    }
    else {
      onRssError();
    }
  };
  xhr.send();
}

function onRssSuccess(doc) {
  console.log('doc', doc);
  if (!doc) {
    handleFeedParsingFailed("Not a valid feed.");
    return;
  }
  links = parseHNLinks(doc);
  SaveLinksToLocalStorage(links);
  if (buildPopupAfterResponse == true) {
    buildPopup(links);
    buildPopupAfterResponse = false;
  }
  localStorage["HN.LastRefresh"] = (new Date()).getTime();
}

function updateLastRefreshTime() {
  localStorage["HN.LastRefresh"] = (new Date()).getTime();
}

function onRssError(xhr, type, error) {
  handleFeedParsingFailed('Failed to fetch RSS feed.');
}

function handleFeedParsingFailed(error) {
  //var feed = document.getElementById("feed");
  //feed.className = "error"
  //feed.innerText = "Error: " + error;
  localStorage["HN.LastRefresh"] = localStorage["HN.LastRefresh"] + retryMilliseconds;
}

function parseXml(xml) {
  var xmlDoc;
  try {
    xmlDoc = new ActiveXObject('Microsoft.XMLDOM');
    xmlDoc.async = false;
    xmlDoc.loadXML(xml);
  } 
  catch (e) {
    xmlDoc = (new DOMParser).parseFromString(xml, 'text/xml');
  }

  return xmlDoc;
}

function parseHNLinks(rawXmlStr) {
  var parser = new DOMParser();
  var doc = parser.parseFromString(rawXmlStr, "text/xml");
  var entries = doc.getElementsByTagName('entry');
  if (entries.length == 0) {
    entries = doc.getElementsByTagName('item');
  }
  var count = Math.min(entries.length, maxFeedItems);
  var links = new Array();
  for (var i=0; i< count; i++) {
    item = entries.item(i);
    var hnLink = new Object();
    //Grab the title
    var itemTitle = item.getElementsByTagName('title')[0];
    if (itemTitle) {
      hnLink.Title = itemTitle.textContent;
    } else {
      hnLink.Title = "Unknown Title";
    }
    
    //Grab the Link
    var itemLink = item.getElementsByTagName('link')[0];
    if (!itemLink) {
      itemLink = item.getElementsByTagName('comments')[0];
    }
    if (itemLink) {
      hnLink.Link = itemLink.textContent;
    } else {
      hnLink.Link = '';
    }

    //Grab the comments link
    var commentsLink = item.getElementsByTagName('comments')[0];
    if (commentsLink) {
      hnLink.CommentsLink = commentsLink.textContent;
    } else {
      hnLink.CommentsLink = '';
    }
    
    links.push(hnLink);
  }
  return links;
}

function SaveLinksToLocalStorage(links) {
  localStorage["HN.NumLinks"] = links.length;
  for (var i=0; i<links.length; i++) {
    localStorage["HN.Link" + i] = JSON.stringify(links[i]);
  }
}

function RetrieveLinksFromLocalStorage() {
  var numLinks = localStorage["HN.NumLinks"];
  if (numLinks == null) {
    return null;
  }
  else {
    var links = new Array();
    for (var i=0; i<numLinks; i++) {
      links.push(JSON.parse(localStorage["HN.Link" + i]))
    }
    return links;
  }
}

function openOptions() {
  var optionsUrl = chrome.extension.getURL('options.html');
  chrome.tabs.create({url: optionsUrl});
}

function openLink(e) {
  e.preventDefault();
  openUrl(this.href, (localStorage['HN.BackgroundTabs'] == 'false'));
}

function openLinkFront(e) {
  e.preventDefault();
  openUrl(this.href, true);
}

function printTime(d) {
  var hour   = d.getHours();
  var minute = d.getMinutes();
  var ap = "AM";
  if (hour   > 11) { ap = "PM";             }
  if (hour   > 12) { hour = hour - 12;      }
  if (hour   == 0) { hour = 12;             }
  if (minute < 10) { minute = "0" + minute; }
  var timeString = hour +
          ':' +
          minute +
          " " +
          ap;
  return timeString;
}

// Show |url| in a new tab.
function openUrl(url, take_focus) {
  // Only allow http and https URLs.
  if (url.indexOf("http:") != 0 && url.indexOf("https:") != 0) {
    return;
  }
  chrome.tabs.create({url: url, selected: take_focus});
}
  
function hideElement(id) {
  var e = document.getElementById(id);
  e.style.display = 'none';
}

function showElement(id) {
  var e = document.getElementById(id);
  e.style.display = 'block';
}

function toggle(id) {
  var e = document.getElementById(id);
  if(e.style.display == 'block')
    e.style.display = 'none';
  else
    e.style.display = 'block';
}