var Expressions = (function () {
  var ob = {};
  ob.initExpressions = initExpressions;

  function initExpressions(animation) {
    var stackCount = 0;
    var registers = [];

    function pushExpression() {
      stackCount += 1;
    }

    function popExpression() {
      stackCount -= 1;
      if (stackCount === 0) {
        releaseInstances();
      }
    }

    function registerExpressionProperty(expression) {
      if (registers.indexOf(expression) === -1) {
        registers.push(expression);
      }
    }

    function releaseInstances() {
      var i, len = registers.length;
      for (i = 0; i < len; i += 1) {
        registers[i].release();
      }
      registers.length = 0;
    }

    animation.renderer.compInterface = CompExpressionInterface(animation.renderer);
    animation.renderer.globalData.projectInterface.registerComposition(animation.renderer);
    animation.renderer.globalData.pushExpression = pushExpression;
    animation.renderer.globalData.popExpression = popExpression;
    animation.renderer.globalData.registerExpressionProperty = registerExpressionProperty;
  }
  return ob;
}());

expressionsPlugin = Expressions;