function getCurrentTabUrl(callback) {
  // Query filter to be passed to chrome.tabs.query - see
  // https://developer.chrome.com/extensions/tabs#method-query
  var queryInfo = {
    active: true,
    currentWindow: true
  };

  chrome.tabs.query(queryInfo, function(tabs) {
    // chrome.tabs.query invokes the callback with a list of tabs that match the
    // query. When the popup is opened, there is certainly a window and at least
    // one tab, so we can safely assume that |tabs| is a non-empty array.
    // A window can only have one active tab at a time, so the array consists of
    // exactly one tab.
    var tab = tabs[0];

    // A tab is a plain object that provides information about the tab.
    // See https://developer.chrome.com/extensions/tabs#type-Tab
    var url = tab.url;

    // tab.url is only available if the "activeTab" permission is declared.
    // If you want to see the URL of other tabs (e.g. after removing active:true
    // from |queryInfo|), then the "tabs" permission is required to see their
    // "url" properties.
    console.assert(typeof url == 'string', 'tab.url should be a string');

    callback(tab);
  });
}

document.addEventListener('DOMContentLoaded', function() {
  getCurrentTabUrl(function(tab) {
  	if(tab.url.indexOf("http://cartaoponto.dbseller.com.br") > -1) {
  		var statusDiv           = document.getElementById("status");
  		    statusDiv.innerHTML = "Horários calculados";
      chrome.tabs.executeScript(tab.id, {file: 'inject/calcular_horas_trabalhadas.js', runAt: "document_end"});
  	}
	});
});

chrome.runtime.onMessage.addListener(
  function(request, sender, sendResponse) {
    console.log(sender.tab ?
                "from a content script:" + sender.tab.url :
                "from the extension");
    document.getElementById('month-time').innerHTML = request.iTempoTrabalhadoMes;
    document.getElementById('time-to-use').innerHTML = request.iTempoTrabalhadoSemana;
  });

