define(function () {
  return function () {
    var self = this;
    var objects = { nodes: {}, links: {} };
    var targets = [];
    var views = {};
    var currentView;
    var currentObject;
    var running = false;

    function saveState() {
      var e = [];

      if (currentView)
        e.push("v:" + currentView);

      if (currentObject) {
        if ("node" in currentObject)
          e.push("n:" + encodeURIComponent(currentObject.node.nodeinfo.node_id));

        if ("link" in currentObject)
          e.push("l:" + encodeURIComponent(currentObject.link.id));
      }

      var s = "#!" + e.join(";");

      window.history.pushState(s, undefined, s);
    }

    function resetView(push) {
      push = trueDefault(push);

      targets.forEach( function (t) {
        t.resetView();
      });

      if (push) {
        currentObject = undefined;
        saveState();
      }
    }

    function gotoNode(d) {
      if (!d)
        return false;

      targets.forEach( function (t) {
        t.gotoNode(d);
      });

      return true;
    }

    function gotoLink(d) {
      if (!d)
        return false;

      targets.forEach( function (t) {
        t.gotoLink(d);
      });

      return true;
    }

    function gotoLocation(d) {
      if (!d)
        return false;

      targets.forEach( function (t) {
        if(!t.gotoLocation)console.warn("has no gotoLocation", t);
        t.gotoLocation(d);
      });

      return true;
    }

    function loadState(s) {
      if (!s)
        return false;

      s = decodeURIComponent(s);

      if (!s.startsWith("#!"))
        return false;

      var targetSet = false;

      s.slice(2).split(";").forEach(function (d) {
        var args = d.split(":");

        if (args[0] === "v" && args[1] in views) {
          currentView = args[1];
          views[args[1]]();
        }

        var id;

        if (args[0] === "n") {
          id = args[1];
          if (id in objects.nodes) {
            currentObject = { node: objects.nodes[id] };
            gotoNode(objects.nodes[id]);
            targetSet = true;
          }
        }

        if (args[0] === "l") {
          id = args[1];
          if (id in objects.links) {
            currentObject = { link: objects.links[id] };
            gotoLink(objects.links[id]);
            targetSet = true;
          }
        }
      });

      return targetSet;
    }

    self.start = function () {
      running = true;

      if (!loadState(window.location.hash))
        resetView(false);

      window.onpopstate = function (d) {
        if (!loadState(d.state))
          resetView(false);
      };
    };

    self.view = function (d) {
      if (d in views) {
        views[d]();

        if (!currentView || running)
          currentView = d;

        if (!running)
          return;

        saveState();

        if (!currentObject) {
          resetView(false);
          return;
        }

        if ("node" in currentObject)
          gotoNode(currentObject.node);

        if ("link" in currentObject)
          gotoLink(currentObject.link);
      }
    };

    self.node = function (d) {
      return function () {
        if (gotoNode(d)) {
          currentObject = { node: d };
          saveState();
        }

        return false;
      };
    };

    self.link = function (d) {
      return function () {
        if (gotoLink(d)) {
          currentObject = { link: d };
          saveState();
        }

        return false;
      };
    };

    self.gotoLocation = gotoLocation;

    self.reset = function () {
      resetView();
    };

    self.addTarget = function (d) {
      targets.push(d);
    };

    self.removeTarget = function (d) {
      targets = targets.filter( function (e) {
        return d !== e;
      });
    };

    self.addView = function (k, d) {
      views[k] = d;
    };

    self.setData = function (data) {
      objects.nodes = {};
      objects.links = {};

      data.nodes.all.forEach( function (d) {
        objects.nodes[d.nodeinfo.node_id] = d;
      });

      data.graph.links.forEach( function (d) {
        objects.links[d.id] = d;
      });
    };

    return self;
  };
});