package com.dy.pipIrrWebFile.fm;

import java.util.Calendar;

public class FileNameIdUtil {

	private static int add = 0 ;
	private static int chengShu = 1000 ;
	private static int maxAdd = 999 ;
	private static long last = 0 ;
	
	//后缀
	private static String suffix = "0" ;

	static {
		last = current() ;
	}
    
	/**
	 * 为自实现程序提供的ID生成器
	 * 15长度ID，年度取两位，如果是17位长度ID，年度取四位，那17位数字超出了javascript的表数范围 
	 */
    public  String generate(){
    	return doGenerate() ;	
    }
    
    /**
     * 设置后缀，不同子系统设置不同的后缀
     * @param suffix
     */
    public static void setSuffix(String suffix)throws Exception{
    	if(suffix == null || suffix.trim().equals("")){
    		throw new Exception("后缀不能为空") ;
    	}
    	FileNameIdUtil.suffix = suffix.trim() ;
    }
    
    /**
     * 执行生成
     * @return
     */
    private synchronized String doGenerate(){
    	Long id = null ;
    	long now = current() ;
    	if(now != last){
    		//上次生成ID 与本次生成ID 不在同一秒内
    		last = now ;
    		add = 0 ;
    		id = last * chengShu + add ++;
    	}else{
    		//上次生成ID 与本次生成ID 在同一秒内
    		if(add == maxAdd){
    			//附加量已经用尽
    			waitNextSecond(last) ;//等到下一秒
    			id = last * chengShu + add ++ ;//返回上一秒生成的ID
				add = 0 ;//附加量归零，为下一秒准备
    		}else{
    			//附加量未用尽
    			id = last * chengShu + add ++ ;
    		}
    	}
    	return id + suffix ;	
    }
    /**
     * 等待下一秒到来
     * @param last
     */
    private void waitNextSecond(Long last){
    	try {
			Thread.sleep(10);
		} catch (InterruptedException e) {
		}finally{
			long now = current() ;
			if(now == last){
				waitNextSecond(last) ;
			}
		}
    }

   
	
    /**
     * 格式为 150516010203
     * @return
     */
	private static long current(){
		Calendar cal = Calendar.getInstance();
		long d = (cal.get(Calendar.YEAR) % 100) * 10000000000L 
		+ (cal.get(Calendar.MONTH) + 1) * 100000000L 
		+ cal.get(Calendar.DAY_OF_MONTH) * 1000000L 
		+ cal.get(Calendar.HOUR_OF_DAY) * 10000L 
		+ cal.get(Calendar.MINUTE) * 100L 
		+ cal.get(Calendar.SECOND)  ;
		
		return d ;
	}

	public static void main(String args[]){
		FileNameIdUtil o = new FileNameIdUtil() ;
		int total = 800 ;
		long start = System.currentTimeMillis() ;
		for(int i = 0 ; i < total ; i++){
			System.out.println((String)(o.generate())) ;
		}
		long end = System.currentTimeMillis() ;
		System.out.println("产生" + total + "ID用时" + (end - start) + "毫秒");
	}
	
}