/*
 * Created on 1 Nov 2006
 * Created by Paul Gardner
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program 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 for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */


package com.biglybt.core.util;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.*;
import java.util.*;
import java.util.regex.Pattern;

import com.biglybt.core.security.SESecurityManager;
import com.biglybt.pifimpl.local.utils.UtilitiesImpl.runnableWithException;

public class
NetUtils
{
	private static final int MIN_NI_CHECK_MILLIS 	= 30*1000;
	private static final int INC1_NI_CHECK_MILLIS 	= 2*60*1000;
	private static final int INC2_NI_CHECK_MILLIS 	= 15*60*1000;

	private static int	current_check_millis = MIN_NI_CHECK_MILLIS;

	private static long	last_ni_check	= -1;

	private static volatile List<NetworkInterface>		current_interfaces = new ArrayList<>();

	private static boolean						first_check	= true;
	private static boolean						check_in_progress;

	static final AESemaphore					ni_sem = new AESemaphore( "NetUtils:ni" );

	private static final Map<Object,Object[]>			host_or_address_map 	= new HashMap<>();

	private static final Object	RESULT_NULL = new Object();

	public static List<NetworkInterface>
	getNetworkInterfaces()

		throws SocketException
	{
		long	now = SystemTime.getMonotonousTime();

		boolean	do_check 	= false;
		boolean	is_first	= false;

		synchronized( NetUtils.class ){

			if ( !check_in_progress ){

				if ( last_ni_check < 0 || now - last_ni_check > current_check_millis ){

					do_check 			= true;
					check_in_progress	= true;

					if ( first_check ){

						first_check = false;
						is_first	= true;
					}
				}
			}
		}

		if ( do_check ){

			final runnableWithException<SocketException> do_it =
				new runnableWithException<SocketException>()
				{
					@Override
					public void
					run()

						throws SocketException
					{
						List<NetworkInterface> result = new ArrayList<>();

						try{
								// got some major CPU issues on some machines with crap loads of NIs

							long	start 	= SystemTime.getHighPrecisionCounter();

							Enumeration<NetworkInterface> nis = NetworkInterface_getNetworkInterfaces();

							long	elapsed_millis = ( SystemTime.getHighPrecisionCounter() - start ) / 1000000;

							long	old_period = current_check_millis;

							if ( elapsed_millis > (Constants.isAndroid?5000:1000) ){

								current_check_millis = INC2_NI_CHECK_MILLIS;

							}else if ( elapsed_millis > (Constants.isAndroid?1000:250) ){

								current_check_millis = INC1_NI_CHECK_MILLIS;
								
							}else{
								
								current_check_millis = MIN_NI_CHECK_MILLIS;
							}

							if ( old_period != current_check_millis ){

								Debug.out( "Network interface enumeration took " + elapsed_millis + ": " + (old_period<current_check_millis?"increased":"decreased" ) + " refresh frequency to " + current_check_millis + "ms" );
							}

							if ( nis != null ){

								while( nis.hasMoreElements()){

									result.add( nis.nextElement());
								}
							}

							// System.out.println( "getNI: elapsed=" + elapsed_millis + ", result=" + result.size());

						}finally{

							synchronized( NetUtils.class ){

								boolean changed = result.size() != current_interfaces.size();
								
								if ( !changed ){
								
									for ( int i=0;i<result.size();i++){
										
										if ( !result.get(i).equals( current_interfaces.get(i))){
										
											changed= true;
											
											break;
										}
									}
								}
								
								check_in_progress	= false;
								current_interfaces 	= result;

								last_ni_check	= SystemTime.getMonotonousTime();
								
								SecurityManager sec = System.getSecurityManager();
								
								if ( sec instanceof SESecurityManager.MySecurityManager ){
									
									if (((SESecurityManager.MySecurityManager)sec).filterNetworkInterfaces( result )){
										
										changed = true;
									}
								}
								
								if ( changed ){
								
									host_or_address_map.clear();
								}
							}

							ni_sem.releaseForever();
						}
					}
				};

			if ( is_first ){

				final AESemaphore do_it_sem = new AESemaphore( "getNIs" );

				final SocketException[]	error = { null };

				new AEThread2( "getNIAsync" )
				{
					@Override
					public void
					run()
					{
						try{
							do_it.run();

						}catch( SocketException e ){

							error[0] = e;

						}finally{

							do_it_sem.release();
						}
					}
				}.start();

				if ( !do_it_sem.reserve( 15*1000 )){

					Debug.out( "Timeout obtaining network interfaces" );

					ni_sem.releaseForever();

				}else{

					if ( error[0] != null ){

						throw( error[0] );
					}
				}
			}else{

				do_it.run();
			}
		}

		ni_sem.reserve();

		return( current_interfaces );
	}

	public static InetAddress
	getLocalHost()

		throws UnknownHostException
	{
		try{
			return( InetAddress.getLocalHost());

		}catch( Throwable e ){

				// sometimes get this when changing host name
				// return first non-loopback one

			try{
				List<NetworkInterface> 	nis = getNetworkInterfaces();

				for ( NetworkInterface ni: nis ){

					Enumeration addresses = ni.getInetAddresses();

					while( addresses.hasMoreElements()){

						InetAddress address = (InetAddress)addresses.nextElement();

						if ( address.isLoopbackAddress() || address instanceof Inet6Address ){

							continue;
						}

						return( address );
					}
				}
			}catch( Throwable f ){
			}

			return( InetAddress.getByName( "127.0.0.1" ));
		}
	}

	public static NetworkInterface
	getByName(
		String name )

		throws SocketException
	{
		return( getBySupport( name ));
	}

	public static NetworkInterface
	getByInetAddress(
		InetAddress addr )

		throws SocketException
	{
		return( getBySupport( addr ));
	}

	private static NetworkInterface
	getBySupport(
		Object 	name_or_address )

		throws SocketException
	{
		Object[] entry;

		synchronized( NetUtils.class ){

			entry = host_or_address_map.get( name_or_address );

			if ( entry != null ){

				synchronized( entry ){

					long	now = SystemTime.getMonotonousTime();

					Object result_or_error = entry[0];

					if ( result_or_error != null ){

						if (((Long)entry[1]) > now ){

								// not expired

							if ( result_or_error == RESULT_NULL ){

								return( null );

							}else if ( result_or_error instanceof NetworkInterface ){

								return((NetworkInterface)result_or_error );

							}else{

								throw((SocketException)result_or_error );
							}
						}

						entry[0] = null;
					}
				}
			}else{

				entry = new Object[2];

				host_or_address_map.put( name_or_address, entry );
			}
		}

		synchronized( entry ){

				// if another thread has done a concurrent lookup then re-use result

			Object result_or_error = entry[0];

			if ( result_or_error != null ){

				if ( result_or_error == RESULT_NULL ){

					return( null );

				}else if ( result_or_error instanceof NetworkInterface ){

					return((NetworkInterface)result_or_error );

				}else{

					throw((SocketException)result_or_error );
				}
			}

			long	start 	= SystemTime.getHighPrecisionCounter();

			Object			 	result 	= null;
			SocketException		error	= null;

			try{
				if ( name_or_address instanceof String ){

					String name = (String)name_or_address;
					
					if ( name.startsWith( "(") && name.endsWith( ")")){
					
							// regexpr for display name matching
												
						String expr = name.substring( 1, name.length() - 1 );
						
						boolean failed = false;
						
						try{
							Pattern p = RegExUtil.getCachedPattern( "NetUtils:display", expr, Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE );
						
							List<NetworkInterface> ifs = current_interfaces;

							if ( ifs != null ){
								
								NetworkInterface 	best 			= null;
								boolean				best_has_ias 	= false;
								
								for ( NetworkInterface x: ifs ){
									
									String dn = x.getDisplayName();
									
									if ( dn != null ){
																						
										if ( p.matcher( dn ).find()){
											
											boolean has_ias = false;
											
											Enumeration<InetAddress> ias = x.getInetAddresses();

											while( ias.hasMoreElements()){
												InetAddress ia = ias.nextElement();
												if ( ia instanceof Inet4Address ){
													has_ias = true;
													break;
												}else{
													if ( AddressUtils.isGlobalAddressV6(ia)){
														has_ias = true;
														break;
													}
												}
											}
											
											if ( best == null ){
											
												best 			= x;
												best_has_ias	= has_ias;
												
											}else{
												
												if ( has_ias ){
																									
													if ( best_has_ias ){
												
														best = null;
														
														Debug.out( "Multiple network interface matches for regex " + expr );
														
														failed = true;
														
														break;
														
													}else{
													
														best 			= x;
														best_has_ias	= has_ias;
													}
												}
											}
										}
									}
								}
								
								result = best;
							}
						}catch( Throwable e ){
							
							Debug.out( "Invalid network interface pattern: " +expr, e );
							
							failed = true;
						}
						
						if ( result == null && !failed ){
							
						}
					}else{
					
						result = NetworkInterface.getByName( name  );
					}

				}else{

					result = NetworkInterface.getByInetAddress((InetAddress)name_or_address );

				}

				if ( result == null ){

					result = RESULT_NULL;
				}
			}catch( SocketException e ){

				error = e;
			}

			long elapsed = ( SystemTime.getHighPrecisionCounter() - start ) / 1000000;

			entry[0] = result==null?error:result;

			long delay = 250*elapsed;

			if ( delay > 5*60*1000 ){

				delay = 5*60*1000;
			}

			entry[1] = SystemTime.getMonotonousTime() + delay;

			if ( error != null ){

				throw( error );

			}else{

				if ( result == RESULT_NULL ){

					return( null );

				}else{

					return((NetworkInterface)result);
				}
			}
		}
	}


	/**
	 * Calls NetworkInterface.getNetworkInterface, tries to recover from
	 * SocketException on some Android devices
	 */
	private static Enumeration<NetworkInterface> NetworkInterface_getNetworkInterfaces()
			throws SocketException {
		SocketException se;
		try {
			return NetworkInterface.getNetworkInterfaces();
		} catch (SocketException e) {
			/*
			Found on Android API 22 (Sony Bravia Android TV):
			java.net.SocketException
			     at java.net.NetworkInterface.rethrowAsSocketException(NetworkInterface.java:248)
			     at java.net.NetworkInterface.readIntFile(NetworkInterface.java:243)
			     at java.net.NetworkInterface.getByNameInternal(NetworkInterface.java:121)
			     at java.net.NetworkInterface.getNetworkInterfacesList(NetworkInterface.java:309)
			     at java.net.NetworkInterface.getNetworkInterfaces(NetworkInterface.java:298)
			     at whatevercalled getNetworkInterfaces()
			 Caused by: java.io.FileNotFoundException: /sys/class/net/p2p1/ifindex: open failed: ENOENT (No such file or directory)
			     at libcore.io.IoBridge.open(IoBridge.java:456)
			     at libcore.io.IoUtils$FileReader.<init>(IoUtils.java:209)
			     at libcore.io.IoUtils.readFileAsString(IoUtils.java:116)
			     at java.net.NetworkInterface.readIntFile(NetworkInterface.java:236)
			 	... 18 more
			 Caused by: android.system.ErrnoException: open failed: ENOENT (No such file or directory)
			     at libcore.io.Posix.open(Native Method)
			     at libcore.io.BlockGuardOs.open(BlockGuardOs.java:186)
			     at libcore.io.IoBridge.open(IoBridge.java:442)
			 	... 21 more
			 	*/
			se = e;
		}

		// Java 7 has getByIndex
		try {
			Method mGetByIndex = NetworkInterface.class.getDeclaredMethod(
					"getByIndex", int.class);
			List<NetworkInterface> list = new ArrayList<>();
			int i = 0;
			do {
				//NetworkInterface nif = NetworkInterface.getByIndex(i);
				NetworkInterface nif = null;
				try {
					nif = (NetworkInterface) mGetByIndex.invoke(null, i);
				} catch (IllegalAccessException e) {
					break;
				} catch (InvocationTargetException ignore) {
					// getByIndex throws SocketException
				}
				if (nif != null) {
					list.add(nif);
				} else if (i > 0) {
					break;
				}
				i++;
			} while (true);
			if (list.size() > 0) {
				return Collections.enumeration(list);
			}
		} catch (NoSuchMethodException ignore) {
		}

		// Worst case, try some common interface names
		List<NetworkInterface> list = new ArrayList<>();
		final String[] commonNames = {
			"lo",
			"eth",
			"lan",
			"wlan",
			"en", // Some Android's Ethernet
			"p2p", // Android
			"net", // Windows, usually TAP
			"ppp" // Windows
		};
		for (String commonName : commonNames) {
			try {
				NetworkInterface nif = NetworkInterface.getByName(commonName);
				if (nif != null) {
					list.add(nif);
				}

				// Could interfaces skip numbers?  Oh well..
				int i = 0;
				while (true) {
					nif = NetworkInterface.getByName(commonName + i);
					if (nif != null) {
						list.add(nif);
					} else {
						break;
					}
					i++;
				}
			} catch (Throwable ignore) {
			}
		}
		if (list.size() > 0) {
			return Collections.enumeration(list);
		}

		throw se;
	}
}
