/**
  Keep track of when the browser is in focus.
**/
export default {
  name: "focus-event",

  initialize: function() {
    var hidden = "hidden";

    // Default to true
    Discourse.set("hasFocus", true);

    var gotFocus = function() {
      if (!Discourse.get("hasFocus")) {
        Discourse.setProperties({ hasFocus: true, notify: false });
      }
    };

    var lostFocus = function() {
      if (Discourse.get("hasFocus")) {
        Discourse.set("hasFocus", false);
      }
    };

    var onchange = function(evt) {
      var v = "visible",
        h = "hidden",
        evtMap = {
          focus: v,
          focusin: v,
          pageshow: v,
          blur: h,
          focusout: h,
          pagehide: h
        };

      evt = evt || window.event;
      if (evt.type in evtMap) {
        if (evtMap[evt.type] === "hidden") {
          lostFocus();
        } else {
          gotFocus();
        }
      } else {
        if (this[hidden]) {
          lostFocus();
        } else {
          gotFocus();
        }
      }
    };

    // from StackOverflow http://stackoverflow.com/a/1060034/17174
    if (hidden in document) {
      document.addEventListener("visibilitychange", onchange);
    } else if ((hidden = "mozHidden") in document) {
      document.addEventListener("mozvisibilitychange", onchange);
    } else if ((hidden = "webkitHidden") in document) {
      document.addEventListener("webkitvisibilitychange", onchange);
    } else if ((hidden = "msHidden") in document) {
      document.addEventListener("msvisibilitychange", onchange);
    }
    // All others (including iPad which is a bit weird and gives onpageshow / hide
    else {
      window.onpageshow = window.onpagehide = window.onfocus = window.onblur = onchange;
    }
  }
};