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	/*
	* Copyright (c) 1996, 2021, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package sun.net.www.http;

	import java.io.IOException;
	import java.io.NotSerializableException;
	import java.io.ObjectInputStream;
	import java.io.ObjectOutputStream;
	import java.net.URL;
	import java.security.AccessController;
	import java.security.PrivilegedAction;
	import java.util.ArrayDeque;
	import java.util.ArrayList;
	import java.util.HashMap;
	import java.util.List;
	import java.util.concurrent.locks.Lock;
	import java.util.concurrent.locks.ReentrantLock;

	import jdk.internal.misc.InnocuousThread;
	import sun.security.action.GetIntegerAction;

	/**
	* A class that implements a cache of idle Http connections for keep-alive
	*
	* @author Stephen R. Pietrowicz (NCSA)
	* @author Dave Brown
	*/
	public class KeepAliveCache
	extends HashMap<KeepAliveKey, ClientVector>
	implements Runnable {
	@java.io.Serial
	private static final long serialVersionUID = -2937172892064557949L;

	/* maximum # keep-alive connections to maintain at once
	* This should be 2 by the HTTP spec, but because we don't support pipe-lining
	* a larger value is more appropriate. So we now set a default of 5, and the value
	* refers to the number of idle connections per destination (in the cache) only.
	* It can be reset by setting system property "http.maxConnections".
	*/
	static final int MAX_CONNECTIONS = 5;
	static int result = -1;
	@SuppressWarnings("removal")
	static int getMaxConnections() {
	if (result == -1) {
	result = AccessController.doPrivileged(
	new GetIntegerAction("http.maxConnections", MAX_CONNECTIONS))
	.intValue();
	if (result <= 0) {
	result = MAX_CONNECTIONS;
	}
	}
	return result;
	}

	static final int LIFETIME = 5000;

	// This class is never serialized (see writeObject/readObject).
	private final ReentrantLock cacheLock = new ReentrantLock();
	private Thread keepAliveTimer = null;

	/**
	* Constructor
	*/
	public KeepAliveCache() {}

	/**
	* Register this URL and HttpClient (that supports keep-alive) with the cache
	* @param url The URL contains info about the host and port
	* @param http The HttpClient to be cached
	*/
	@SuppressWarnings("removal")
	public void put(final URL url, Object obj, HttpClient http) {
	cacheLock.lock();
	try {
	boolean startThread = (keepAliveTimer == null);
	if (!startThread) {
	if (!keepAliveTimer.isAlive()) {
	startThread = true;
	}
	}
	if (startThread) {
	clear();
	/* Unfortunately, we can't always believe the keep-alive timeout we got
	* back from the server. If I'm connected through a Netscape proxy
	* to a server that sent me a keep-alive
	* time of 15 sec, the proxy unilaterally terminates my connection
	* The robustness to get around this is in HttpClient.parseHTTP()
	*/
	final KeepAliveCache cache = this;
	AccessController.doPrivileged(new PrivilegedAction<>() {
	public Void run() {
	keepAliveTimer = InnocuousThread.newSystemThread("Keep-Alive-Timer", cache);
	keepAliveTimer.setDaemon(true);
	keepAliveTimer.setPriority(Thread.MAX_PRIORITY - 2);
	keepAliveTimer.start();
	return null;
	}
	});
	}

	KeepAliveKey key = new KeepAliveKey(url, obj);
	ClientVector v = super.get(key);

	if (v == null) {
	int keepAliveTimeout = http.getKeepAliveTimeout();
	v = new ClientVector(keepAliveTimeout > 0 ?
	keepAliveTimeout * 1000 : LIFETIME);
	v.put(http);
	super.put(key, v);
	} else {
	v.put(http);
	}
	} finally {
	cacheLock.unlock();
	}
	}

	/* remove an obsolete HttpClient from its VectorCache */
	public void remove(HttpClient h, Object obj) {
	cacheLock.lock();
	try {
	KeepAliveKey key = new KeepAliveKey(h.url, obj);
	ClientVector v = super.get(key);
	if (v != null) {
	v.remove(h);
	if (v.isEmpty()) {
	removeVector(key);
	}
	}
	} finally {
	cacheLock.unlock();
	}
	}

	/* called by a clientVector thread when all its connections have timed out
	* and that vector of connections should be removed.
	*/
	private void removeVector(KeepAliveKey k) {
	assert cacheLock.isHeldByCurrentThread();
	super.remove(k);
	}

	/**
	* Check to see if this URL has a cached HttpClient
	*/
	public HttpClient get(URL url, Object obj) {
	cacheLock.lock();
	try {
	KeepAliveKey key = new KeepAliveKey(url, obj);
	ClientVector v = super.get(key);
	if (v == null) { // nothing in cache yet
	return null;
	}
	return v.get();
	} finally {
	cacheLock.unlock();
	}
	}

	/* Sleeps for an alloted timeout, then checks for timed out connections.
	* Errs on the side of caution (leave connections idle for a relatively
	* short time).
	*/
	@Override
	public void run() {
	do {
	try {
	Thread.sleep(LIFETIME);
	} catch (InterruptedException e) {}

	// Remove all outdated HttpClients.
	cacheLock.lock();
	try {
	long currentTime = System.currentTimeMillis();
	List<KeepAliveKey> keysToRemove = new ArrayList<>();

	for (KeepAliveKey key : keySet()) {
	ClientVector v = get(key);
	v.lock();
	try {
	KeepAliveEntry e = v.peek();
	while (e != null) {
	if ((currentTime - e.idleStartTime) > v.nap) {
	v.poll();
	e.hc.closeServer();
	} else {
	break;
	}
	e = v.peek();
	}

	if (v.isEmpty()) {
	keysToRemove.add(key);
	}
	} finally {
	v.unlock();
	}
	}

	for (KeepAliveKey key : keysToRemove) {
	removeVector(key);
	}
	} finally {
	cacheLock.unlock();
	}
	} while (!isEmpty());
	}

	/*
	* Do not serialize this class!
	*/
	@java.io.Serial
	private void writeObject(ObjectOutputStream stream) throws IOException {
	throw new NotSerializableException();
	}

	@java.io.Serial
	private void readObject(ObjectInputStream stream)
	throws IOException, ClassNotFoundException
	{
	throw new NotSerializableException();
	}
	}

	/* FILO order for recycling HttpClients, should run in a thread
	* to time them out. If > maxConns are in use, block.
	*/
	class ClientVector extends ArrayDeque<KeepAliveEntry> {
	@java.io.Serial
	private static final long serialVersionUID = -8680532108106489459L;
	private final ReentrantLock lock = new ReentrantLock();

	// sleep time in milliseconds, before cache clear
	int nap;

	ClientVector(int nap) {
	this.nap = nap;
	}

	HttpClient get() {
	lock();
	try {
	if (isEmpty()) {
	return null;
	}

	// Loop until we find a connection that has not timed out
	HttpClient hc = null;
	long currentTime = System.currentTimeMillis();
	do {
	KeepAliveEntry e = pop();
	if ((currentTime - e.idleStartTime) > nap) {
	e.hc.closeServer();
	} else {
	hc = e.hc;
	}
	} while ((hc == null) && (!isEmpty()));
	return hc;
	} finally {
	unlock();
	}
	}

	/* return a still valid, unused HttpClient */
	void put(HttpClient h) {
	lock();
	try {
	if (size() >= KeepAliveCache.getMaxConnections()) {
	h.closeServer(); // otherwise the connection remains in limbo
	} else {
	push(new KeepAliveEntry(h, System.currentTimeMillis()));
	}
	} finally {
	unlock();
	}
	}

	/* remove an HttpClient */
	boolean remove(HttpClient h) {
	lock();
	try {
	for (KeepAliveEntry curr : this) {
	if (curr.hc == h) {
	return super.remove(curr);
	}
	}
	return false;
	} finally {
	unlock();
	}
	}

	final void lock() {
	lock.lock();
	}

	final void unlock() {
	lock.unlock();
	}

	/*
	* Do not serialize this class!
	*/
	@java.io.Serial
	private void writeObject(ObjectOutputStream stream) throws IOException {
	throw new NotSerializableException();
	}

	@java.io.Serial
	private void readObject(ObjectInputStream stream)
	throws IOException, ClassNotFoundException
	{
	throw new NotSerializableException();
	}
	}

	class KeepAliveKey {
	private String protocol = null;
	private String host = null;
	private int port = 0;
	private Object obj = null; // additional key, such as socketfactory

	/**
	* Constructor
	*
	* @param url the URL containing the protocol, host and port information
	*/
	public KeepAliveKey(URL url, Object obj) {
	this.protocol = url.getProtocol();
	this.host = url.getHost();
	this.port = url.getPort();
	this.obj = obj;
	}

	/**
	* Determine whether or not two objects of this type are equal
	*/
	@Override
	public boolean equals(Object obj) {
	if ((obj instanceof KeepAliveKey) == false)
	return false;
	KeepAliveKey kae = (KeepAliveKey)obj;
	return host.equals(kae.host)
	&& (port == kae.port)
	&& protocol.equals(kae.protocol)
	&& this.obj == kae.obj;
	}

	/**
	* The hashCode() for this object is the string hashCode() of
	* concatenation of the protocol, host name and port.
	*/
	@Override
	public int hashCode() {
	String str = protocol+host+port;
	return this.obj == null? str.hashCode() :
	str.hashCode() + this.obj.hashCode();
	}
	}

	class KeepAliveEntry {
	HttpClient hc;
	long idleStartTime;

	KeepAliveEntry(HttpClient hc, long idleStartTime) {
	this.hc = hc;
	this.idleStartTime = idleStartTime;
	}
	}

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