function isGeoAvailable() {
  "use strict";
  return navigator.geolocation;
}

function setMessage(message) {
  "use strict";
  var geo = document.getElementById("geo");
  if (geo) {
    geo.innerHTML = message;
  }
  else {
    console.log("setMessage()", message);
  }
}

function getPositionMessage(position) {
  "use strict";

  var coords = position.coords;

  var date = new Date(position.timestamp);

  var message = "<p>Position: </p>\n" +
    "<ul>\n" +
    "  <li>Timestamp: " + position.timestamp + " = " + date.toLocaleString() + "</li>\n" +
    "  <li>Accuracy: " + coords.accuracy + " meters</li>\n" +
    "  <li>Latitude: " + coords.latitude + "</li>" +
    "  <li>Longitude: " + coords.longitude + "</li>" +
    "  <li>Altitude: " + (coords.altitude ? coords.altitude : "unknown") + "</li>" +
    "  <li>Altitude Accuracy: " + (coords.altitudeAccuracy ? coords.altitudeAccuracy : 0) + "</li>" +
    "  <li>Heading: " + (coords.heading ? coords.heading : "unknown") + "</li>\n" +
    "  <li>Speed: " + (coords.speed ? coords.speed : "unknown") + "</li>\n"
    "  </ul>\n";

  return message;
}

function showPositionMessage(position) {
  "use strict";
  setMessage("showPositionMessage()", getPositionMessage(position));
}

function showPositionError(error) {
  "use strict";
  var reason;
  switch (error.code) {
    case error.POSITION_UNAVAILABLE:
      reason = "Position unavailable";
      break;
    case error.PERMISSION_DENIED:
      reason = "Permission denied";
      break;
    case error.TIMEOUT:
      reason = "Timeout"
      break;
    default:
      reason = "Unknown position error (" + error.code + ")";
      break;
  }
  setMessage(reason + ": " + error.message);
}

if (isGeoAvailable()) {
  navigator.geolocation.getCurrentPosition(showPositionMessage, showPositionError);
}
else {
  setMessage('Geolocation API is not available.');
}