define(["filters/nodefilter"], function (NodeFilter) {
  return function () {
    var targets = [];
    var filterObservers = [];
    var filters = [];
    var filteredData;
    var data;

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

    function add(d) {
      targets.push(d);

      if (filteredData !== undefined)
        d.setData(filteredData);
    }

    function setData(d) {
      data = d;
      refresh();
    }

    function refresh() {
      if (data === undefined)
        return;

      var filter = filters.reduce( function (a, f) {
        return function (d) {
          return a(d) && f.run(d);
        };
      }, function () { return true; });

      filteredData = new NodeFilter(filter)(data);

      targets.forEach( function (t) {
        t.setData(filteredData);
      });
    }

    function notifyObservers() {
      filterObservers.forEach( function (d) {
        d.filtersChanged(filters);
      });
    }

    function addFilter(d) {
      filters.push(d);
      notifyObservers();
      d.setRefresh(refresh);
      refresh();
    }

    function removeFilter(d) {
      filters = filters.filter( function (e) { return d !== e; } );
      notifyObservers();
      refresh();
    }

    function watchFilters(d) {
      filterObservers.push(d);

      d.filtersChanged(filters);

      return function () {
        filterObservers = filterObservers.filter( function (e) { return d !== e; });
      };
    }

    return { add: add,
             remove: remove,
             setData: setData,
             addFilter: addFilter,
             removeFilter: removeFilter,
             watchFilters: watchFilters,
             refresh: refresh
           };
  };
});