/*
 * Copyright 2004-2019 H2 Group. Multiple-Licensed under the MPL 2.0,
 * and the EPL 1.0 (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.util;

import java.io.IOException;
import java.net.BindException;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.concurrent.TimeUnit;

import org.h2.api.ErrorCode;
import org.h2.engine.SysProperties;
import org.h2.message.DbException;
import org.h2.security.CipherFactory;

This utility class contains socket helper functions.
/**
 * This utility class contains socket helper functions.
 */
public class NetUtils {

    private static final int CACHE_MILLIS = 1000;
    private static InetAddress cachedBindAddress;
    private static String cachedLocalAddress;
    private static long cachedLocalAddressTime;

    private NetUtils() {
        // utility class
    }

    
Create a loopback socket (a socket that is connected to localhost) on
this port.
Params:
port – the port
ssl – if SSL should be used
Returns:
the socket/**
     * Create a loopback socket (a socket that is connected to localhost) on
     * this port.
     *
     * @param port the port
     * @param ssl if SSL should be used
     * @return the socket
     */
    public static Socket createLoopbackSocket(int port, boolean ssl)
            throws IOException {
        String local = getLocalAddress();
        try {
            return createSocket(local, port, ssl);
        } catch (IOException e) {
            try {
                return createSocket("localhost", port, ssl);
            } catch (IOException e2) {
                // throw the original exception
                throw e;
            }
        }
    }

    
Create a client socket that is connected to the given address and port.
Params:
server – to connect to (including an optional port)
defaultPort – the default port (if not specified in the server
           address)
ssl – if SSL should be used
Returns:
the socket/**
     * Create a client socket that is connected to the given address and port.
     *
     * @param server to connect to (including an optional port)
     * @param defaultPort the default port (if not specified in the server
     *            address)
     * @param ssl if SSL should be used
     * @return the socket
     */
    public static Socket createSocket(String server, int defaultPort,
            boolean ssl) throws IOException {
        int port = defaultPort;
        // IPv6: RFC 2732 format is '[a:b:c:d:e:f:g:h]' or
        // '[a:b:c:d:e:f:g:h]:port'
        // RFC 2396 format is 'a.b.c.d' or 'a.b.c.d:port' or 'hostname' or
        // 'hostname:port'
        int startIndex = server.startsWith("[") ? server.indexOf(']') : 0;
        int idx = server.indexOf(':', startIndex);
        if (idx >= 0) {
            port = Integer.decode(server.substring(idx + 1));
            server = server.substring(0, idx);
        }
        InetAddress address = InetAddress.getByName(server);
        return createSocket(address, port, ssl);
    }

    
Create a client socket that is connected to the given address and port.
Params:
address – the address to connect to
port – the port
ssl – if SSL should be used
Returns:
the socket/**
     * Create a client socket that is connected to the given address and port.
     *
     * @param address the address to connect to
     * @param port the port
     * @param ssl if SSL should be used
     * @return the socket
     */
    public static Socket createSocket(InetAddress address, int port, boolean ssl)
            throws IOException {
        long start = System.nanoTime();
        for (int i = 0;; i++) {
            try {
                if (ssl) {
                    return CipherFactory.createSocket(address, port);
                }
                Socket socket = new Socket();
                socket.connect(new InetSocketAddress(address, port),
                        SysProperties.SOCKET_CONNECT_TIMEOUT);
                return socket;
            } catch (IOException e) {
                if (System.nanoTime() - start >=
                        TimeUnit.MILLISECONDS.toNanos(SysProperties.SOCKET_CONNECT_TIMEOUT)) {
                    // either it was a connect timeout,
                    // or list of different exceptions
                    throw e;
                }
                if (i >= SysProperties.SOCKET_CONNECT_RETRY) {
                    throw e;
                }
                // wait a bit and retry
                try {
                    // sleep at most 256 ms
                    long sleep = Math.min(256, i * i);
                    Thread.sleep(sleep);
                } catch (InterruptedException e2) {
                    // ignore
                }
            }
        }
    }

    
Create a server socket. The system property h2.bindAddress is used if
set. If SSL is used and h2.enableAnonymousTLS is true, an attempt is
made to modify the security property jdk.tls.legacyAlgorithms
(in newer JVMs) to allow anonymous TLS.

This system change is effectively permanent for the lifetime of the JVM.
Params:
port – the port to listen on
ssl – if SSL should be used
See Also:
removeAnonFromLegacyAlgorithms.removeAnonFromLegacyAlgorithms()
Returns:
the server socket/**
     * Create a server socket. The system property h2.bindAddress is used if
     * set. If SSL is used and h2.enableAnonymousTLS is true, an attempt is
     * made to modify the security property jdk.tls.legacyAlgorithms
     * (in newer JVMs) to allow anonymous TLS.
     * <p>
     * This system change is effectively permanent for the lifetime of the JVM.
     * @see CipherFactory#removeAnonFromLegacyAlgorithms()
     *
     * @param port the port to listen on
     * @param ssl if SSL should be used
     * @return the server socket
     */
    public static ServerSocket createServerSocket(int port, boolean ssl) {
        try {
            return createServerSocketTry(port, ssl);
        } catch (Exception e) {
            // try again
            return createServerSocketTry(port, ssl);
        }
    }

    
Get the bind address if the system property h2.bindAddress is set, or
null if not.
Returns:
the bind address/**
     * Get the bind address if the system property h2.bindAddress is set, or
     * null if not.
     *
     * @return the bind address
     */
    private static InetAddress getBindAddress() throws UnknownHostException {
        String host = SysProperties.BIND_ADDRESS;
        if (host == null || host.isEmpty()) {
            return null;
        }
        synchronized (NetUtils.class) {
            if (cachedBindAddress == null) {
                cachedBindAddress = InetAddress.getByName(host);
            }
        }
        return cachedBindAddress;
    }

    private static ServerSocket createServerSocketTry(int port, boolean ssl) {
        try {
            InetAddress bindAddress = getBindAddress();
            if (ssl) {
                return CipherFactory.createServerSocket(port, bindAddress);
            }
            if (bindAddress == null) {
                return new ServerSocket(port);
            }
            return new ServerSocket(port, 0, bindAddress);
        } catch (BindException be) {
            throw DbException.get(ErrorCode.EXCEPTION_OPENING_PORT_2,
                    be, Integer.toString(port), be.toString());
        } catch (IOException e) {
            throw DbException.convertIOException(e, "port: " + port + " ssl: " + ssl);
        }
    }

    
Check if a socket is connected to a local address.
Params:
socket – the socket
Returns:
true if it is/**
     * Check if a socket is connected to a local address.
     *
     * @param socket the socket
     * @return true if it is
     */
    public static boolean isLocalAddress(Socket socket)
            throws UnknownHostException {
        InetAddress test = socket.getInetAddress();
        if (test.isLoopbackAddress()) {
            return true;
        }
        InetAddress localhost = InetAddress.getLocalHost();
        // localhost.getCanonicalHostName() is very slow
        String host = localhost.getHostAddress();
        for (InetAddress addr : InetAddress.getAllByName(host)) {
            if (test.equals(addr)) {
                return true;
            }
        }
        return false;
    }

    
Close a server socket and ignore any exceptions.
Params:
socket – the socket
Returns:
null/**
     * Close a server socket and ignore any exceptions.
     *
     * @param socket the socket
     * @return null
     */
    public static ServerSocket closeSilently(ServerSocket socket) {
        if (socket != null) {
            try {
                socket.close();
            } catch (IOException e) {
                // ignore
            }
        }
        return null;
    }

    
Get the local host address as a string.
For performance, the result is cached for one second.
Returns:
the local host address/**
     * Get the local host address as a string.
     * For performance, the result is cached for one second.
     *
     * @return the local host address
     */
    public static synchronized String getLocalAddress() {
        long now = System.nanoTime();
        if (cachedLocalAddress != null) {
            if (cachedLocalAddressTime + TimeUnit.MILLISECONDS.toNanos(CACHE_MILLIS) > now) {
                return cachedLocalAddress;
            }
        }
        InetAddress bind = null;
        boolean useLocalhost = false;
        try {
            bind = getBindAddress();
            if (bind == null) {
                useLocalhost = true;
            }
        } catch (UnknownHostException e) {
            // ignore
        }
        if (useLocalhost) {
            try {
                bind = InetAddress.getLocalHost();
            } catch (UnknownHostException e) {
                throw DbException.convert(e);
            }
        }
        String address;
        if (bind == null) {
            address = "localhost";
        } else {
            address = bind.getHostAddress();
            if (bind instanceof Inet6Address) {
                if (address.indexOf('%') >= 0) {
                    address = "localhost";
                } else if (address.indexOf(':') >= 0 && !address.startsWith("[")) {
                    // adds'[' and ']' if required for
                    // Inet6Address that contain a ':'.
                    address = "[" + address + "]";
                }
            }
        }
        if (address.equals("127.0.0.1")) {
            address = "localhost";
        }
        cachedLocalAddress = address;
        cachedLocalAddressTime = now;
        return address;
    }

    
Get the host name of a local address, if available.
Params:
localAddress – the local address
Returns:
the host name, or another text if not available/**
     * Get the host name of a local address, if available.
     *
     * @param localAddress the local address
     * @return the host name, or another text if not available
     */
    public static String getHostName(String localAddress) {
        try {
            InetAddress addr = InetAddress.getByName(localAddress);
            return addr.getHostName();
        } catch (Exception e) {
            return "unknown";
        }
    }

}