import { NError } from "./error";
import { Util } from "./util";

/**
 * 调度器，用于每次空闲的待操作序列调度
 */
export class Scheduler{
	private static tasks:Array<any> = [];
	public static dispatch(){
		Scheduler.tasks.forEach((item)=>{
			if(Util.isFunction(item.func)){
				if(item.thiser){
					item.func.call(item.thiser);
				}else{
					item.func();
				}
			}
		});
	}

	/**
	 * 启动调度器
	 * @param scheduleTick 	渲染间隔
	 */
	public static start(scheduleTick?:number){
		Scheduler.dispatch();
		if(window.requestAnimationFrame){
			window.requestAnimationFrame(Scheduler.start);
		}else{
			window.setTimeout(Scheduler.start,scheduleTick||50);
		}		
	}

	/**
	 * 添加任务
	 * @param foo 		任务和this指向
	 * @param thiser 	this指向
	 */
	public static addTask(foo:Function,thiser?:any){
		if(!Util.isFunction(foo)){
			throw new NError("invoke","Scheduler.addTask","0","function");
		}
		
		Scheduler.tasks.push({func:foo,thiser:thiser});
	}

	/**
	 * 移除任务
	 * @param foo 	任务
	 */
	public static removeTask(foo){
		if(!Util.isFunction(foo)){
			throw new NError("invoke","Scheduler.removeTask","0","function");
		}
		let ind = -1;
		if((ind = Scheduler.tasks.indexOf(foo)) !== -1){
			Scheduler.tasks.splice(ind,1);
		}	
	}
}