package stdx;

import java.io.Closeable;
import java.util.ArrayList;

public abstract class ResPool{
 public static interface Resource extends Closeable{
 public void setPool(ResPool pool);
 }

 class Data{
 private int num = 0;
 private long utime = 0;
 private Boolean idle = true;
 private Resource conn = null;

 void close(){
 if (conn == null) return;
 conn.setPool(null);
 Utils.Close(conn);
 conn = null;
 }
 void release(){
 if (checkSuccess(conn)){
 idle = true;
 }
 else{
 close();
 }
 }
 Closeable get() throws Exception{
 if (conn == null){
 num = 0;
 conn = create();
 conn.setPool(ResPool.this);
 }

 utime = System.currentTimeMillis();
 idle = false;
 ++num;

 return conn;
 }
 }

 int maxlen = 8;
 int timeout = 60;
 ArrayList<Data> vec = new ArrayList<Data>();

 public abstract Resource create() throws Exception;
 public abstract boolean checkSuccess(Closeable conn);

 public void destroy(){
 synchronized(vec){
 for (Data item : vec){
 if (item.idle) item.close();
 item.utime = 0;
 }
 }
 }
 public void setLength(int maxlen){
 this.maxlen = maxlen;
 }
 public void setTimeout(int timeout){
 this.timeout = timeout;
 }
 public void release(Closeable conn){
 synchronized(vec){
 for (Data item : vec){
 if (conn == item.conn){
 item.release();
 return;
 }
 }
 }

 Utils.Close(conn);
 }
 public Closeable get() throws Exception{
 long start = System.currentTimeMillis();

 while (true){
 long now = System.currentTimeMillis();

 synchronized(vec){
 Data res = null;

 for (Data item : vec){
 if (item.idle || item.conn == null){
 if (item.num < 100 && item.utime + timeout * 1000 > now) return item.get();
 item.close();
 res = item;
 }
 }

 if (res == null){
 if (vec.size() >= maxlen){
 if (start + 1000 < System.currentTimeMillis()) throw new Exception("resource busy");
 Thread.sleep(10);
 continue;
 }

 vec.add(res = new Data());
 }

 return res.get();
 }
 }
 }
}