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;