barbe.js

var host = "wurstify.me";
var pingInterval = 60000; // ms
var pingIntervalId = undefined;
var enabledSince = 0;

// source: http://stackoverflow.com/questions/736513/how-do-i-parse-a-url-into-hostname-and-path-in-javascript
var reURLInformation = new RegExp([
    '^(https?:)//', // protocol
    '(([^:/?#]*)(?::([0-9]+))?)', // host (hostname and port)
    '(/[^?#]*)', // pathname
    '(\\?[^#]*|)', // search
    '(#.*|)$' // hash
].join(''));

chrome.webRequest.onBeforeRequest.addListener(
  function(info) {
    if(localStorage.wurstifyEnabled == "true") {
    	if(info.method == "GET" && info.type == "image") {
        var match = info.url.match(reURLInformation);
        if(match && match[2] != host) {
          var proto = "https";
          if(match[1] == "http:") {
            proto = "http";
          }
          return {redirectUrl: proto + "://" + host + "/proxy?since=" + enabledSince + "&url=" + encodeURIComponent(info.url)};
        }
    	}
    }
  },
  // filters
  {
    urls: [
      "http://*/*",
      "https://*/*",
    ],
    types: ["image"]
  },
  // extraInfoSpec
  ["blocking"]);

var setEnabled = function(enabled) {
  if(enabled) {
    localStorage.wurstifyEnabled = "true";
    enabledSince = 0;
  }
  else {
    localStorage.wurstifyEnabled = "false";
  }

  updateIcon();
  updatePingInterval();
}

chrome.browserAction.onClicked.addListener(function(tab) {

  var currentlyEnabled = (localStorage.wurstifyEnabled == "true");
  setEnabled(!currentlyEnabled);

  chrome.tabs.reload(tab.id);
});

var updateIcon = function() {
  if(localStorage.wurstifyEnabled == "true") {
    chrome.browserAction.setIcon({
      path: "icon38.png"
    });
  }
  else {
    chrome.browserAction.setIcon({
      path: "icon38_disabled.png"
    });
  }
}

var ping = function() {
  enabledSince += pingInterval/1000;

  var xhr = new XMLHttpRequest();
  xhr.onreadystatechange = function() {
    if(xhr.readyState == 4 && xhr.status == 518) {
      setEnabled(false);
    }
  }
  xhr.open("HEAD", "https://" + host + "/ping?since=" + enabledSince + "&t=" + (new Date()).getTime(), true);
  xhr.send();
}

var updatePingInterval = function() {
  if(localStorage.wurstifyEnabled == "true") {
    if(pingIntervalId == undefined) {
      pingIntervalId = setInterval(ping, pingInterval);
    }
  }
  else {
    if(pingIntervalId != undefined) {
      clearInterval(pingIntervalId);
      pingIntervalId = undefined;
    }
  }
}

updateIcon();
updatePingInterval();