/**
 * Abstract base class for widget based cell renderer.
 */
qx.Class.define("qx.ui.virtual.cell.AbstractWidget",
{
  extend : qx.core.Object,
  implement : [qx.ui.virtual.cell.IWidgetCell],


  construct : function()
  {
    this.base(arguments);

    this.__pool = [];
  },


  events :
  {
    /** Fired when a new <code>LayoutItem</code> is created. */
    "created" : "qx.event.type.Data"
  },


  members :
  {
    __pool : null,


    /**
     * Creates the widget instance.
     *
     * @abstract
     * @return {qx.ui.core.LayoutItem} The widget used to render a cell
     */
    _createWidget : function() {
      throw new Error("abstract method call");
    },


    // interface implementation
    updateData : function(widget, data) {
      throw new Error("abstract method call");
    },


    // interface implementation
    updateStates : function(widget, states)
    {
      var oldStates = widget.getUserData("cell.states");

      // remove old states
      if (oldStates)
      {
        var newStates = states || {};
        for (var state in oldStates)
        {
          if (!newStates[state]) {
            widget.removeState(state);
          }
        }
      }
      else
      {
        oldStates = {};
      }

      // apply new states
      if (states)
      {
        for (var state in states)
        {
          if (!oldStates.state) {
            widget.addState(state);
          }
        }
      }

      widget.setUserData("cell.states", states);
    },


    // interface implementation
    getCellWidget : function(data, states)
    {
      var widget = this.__getWidgetFromPool();
      this.updateStates(widget, states);
      this.updateData(widget, data);
      return widget;
    },


    // interface implementation
    pool : function(widget) {
      this.__pool.push(widget);
    },

    /**
     * Cleanup all <code>LayoutItem</code> and destroy them.
     */
    _cleanupPool : function() {
      var widget = this.__pool.pop();

      while(widget)
      {
        widget.destroy();
        widget = this.__pool.pop();
      }
    },

    /**
     * Returns a <code>LayoutItem</code> from the pool, when the pool is empty
     * a new <code>LayoutItem</code> is created.
     *
     * @return {qx.ui.core.LayoutItem} The cell widget
     */
    __getWidgetFromPool : function()
    {
      var widget = this.__pool.pop();

      if (widget == null)
      {
        widget = this._createWidget();
        this.fireDataEvent("created", widget);
      }

      return widget;
    }
  },

  /*
   *****************************************************************************
      DESTRUCT
   *****************************************************************************
   */

  destruct : function()
  {
    this._cleanupPool();
    this.__pool = null;
  }
})
