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    /*
 * Copyright (c) 2011-2013 The original author or authors
 * ------------------------------------------------------
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Apache License v2.0 which accompanies this distribution.
 *
 *     The Eclipse Public License is available at
 *     http://www.eclipse.org/legal/epl-v10.html
 *
 *     The Apache License v2.0 is available at
 *     http://www.opensource.org/licenses/apache2.0.php
 *
 * You may elect to redistribute this code under either of these licenses.
 */
package io.jsync.dns.impl;

import io.jsync.AsyncResult;
import io.jsync.Handler;
import io.jsync.dns.*;
import io.jsync.dns.DnsResponseCode;
import io.jsync.dns.impl.netty.*;
import io.jsync.dns.impl.netty.decoder.RecordDecoderFactory;
import io.jsync.dns.impl.netty.decoder.record.MailExchangerRecord;
import io.jsync.dns.impl.netty.decoder.record.ServiceRecord;
import io.jsync.impl.AsyncInternal;
import io.jsync.impl.DefaultContext;
import io.jsync.impl.DefaultFutureResult;
import io.jsync.net.impl.PartialPooledByteBufAllocator;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.socket.DatagramChannel;
import io.netty.channel.socket.nio.NioDatagramChannel;

import java.net.*;
import java.util.*;
import java.util.concurrent.ThreadLocalRandom;

/**
 * @author Norman Maurer
 */
public final class DefaultDnsClient implements DnsClient {

    private static final char[] HEX_TABLE = "0123456789abcdef".toCharArray();
    private final Bootstrap bootstrap;
    private final List dnsServers;
    private final DefaultContext actualCtx;
    private final AsyncInternal async;

    public DefaultDnsClient(AsyncInternal async, InetSocketAddress... dnsServers) {
        if (dnsServers == null || dnsServers.length == 0) {
            throw new IllegalArgumentException("Need at least one default DNS Server");
        }

        // use LinkedList as we will traverse it all the time
        this.dnsServers = new LinkedList<>(Arrays.asList(dnsServers));
        actualCtx = async.getOrCreateContext();
        this.async = async;
        bootstrap = new Bootstrap();
        bootstrap.group(actualCtx.getEventLoop());
        bootstrap.channel(NioDatagramChannel.class);
        bootstrap.option(ChannelOption.ALLOCATOR, PartialPooledByteBufAllocator.INSTANCE);
        bootstrap.handler(new ChannelInitializer() {
            @Override
            protected void initChannel(DatagramChannel ch) throws Exception {
                ChannelPipeline pipeline = ch.pipeline();
                pipeline.addLast(new DnsQueryEncoder());
                pipeline.addLast(new DnsResponseDecoder());
            }
        });
    }

    @Override
    public DnsClient lookup4(String name, final Handler> handler) {
        lookup(name, new HandlerAdapter(handler), DnsEntry.TYPE_A);
        return this;
    }

    @Override
    public DnsClient lookup6(String name, final Handler> handler) {
        lookup(name, new HandlerAdapter(handler), DnsEntry.TYPE_AAAA);
        return this;
    }

    @Override
    public DnsClient lookup(String name, final Handler> handler) {
        lookup(name, new HandlerAdapter(handler), DnsEntry.TYPE_A, DnsEntry.TYPE_AAAA);
        return this;
    }

    @Override
    public DnsClient resolveA(String name, final Handler>> handler) {
        lookup(name, handler, DnsEntry.TYPE_A);
        return this;
    }

    @Override
    public DnsClient resolveCNAME(String name, Handler>> handler) {
        lookup(name, handler, DnsEntry.TYPE_CNAME);
        return this;
    }

    @Override
    public DnsClient resolveMX(String name, final Handler>> handler) {
        lookup(name, new ConvertingHandler(handler, DefaultMxRecordComparator.INSTANCE) {
            @Override
            protected MxRecord convert(MailExchangerRecord entry) {
                return new DefaultMxRecord(entry);
            }
        }, DnsEntry.TYPE_MX);
        return this;
    }

    @Override
    public DnsClient resolveTXT(String name, final Handler>> handler) {
        lookup(name, new Handler() {
            @SuppressWarnings("unchecked")
            @Override
            public void handle(AsyncResult event) {
                if (event.failed()) {
                    handler.handle(event);
                } else {
                    List txts = new ArrayList<>();
                    List> records = (List>) event.result();
                    for (List txt : records) {
                        txts.addAll(txt);
                    }
                    handler.handle(new DefaultFutureResult(txts));
                }
            }
        }, DnsEntry.TYPE_TXT);
        return this;
    }

    @Override
    public DnsClient resolvePTR(String name, final Handler> handler) {
        lookup(name, new HandlerAdapter(handler), DnsEntry.TYPE_PTR);
        return this;
    }

    @Override
    public DnsClient resolveAAAA(String name, Handler>> handler) {
        lookup(name, handler, DnsEntry.TYPE_AAAA);
        return this;
    }

    @Override
    public DnsClient resolveNS(String name, Handler>> handler) {
        lookup(name, handler, DnsEntry.TYPE_NS);
        return this;
    }

    @Override
    public DnsClient resolveSRV(String name, final Handler>> handler) {
        lookup(name, new ConvertingHandler(handler, DefaultSrvRecordComparator.INSTANCE) {
            @Override
            protected SrvRecord convert(ServiceRecord entry) {
                return new DefaultSrvRecord(entry);
            }
        }, DnsEntry.TYPE_SRV);
        return this;
    }

    @Override
    public DnsClient reverseLookup(String address, final Handler> handler) {
        // TODO:  Check if the given address is a valid ip address before pass it to InetAddres.getByName(..)
        //        This is need as otherwise it may try to perform a DNS lookup.
        //        An other option would be to change address to be of type InetAddress.
        try {
            final InetAddress inetAddress = InetAddress.getByName(address);
            byte[] addr = inetAddress.getAddress();

            StringBuilder reverseName = new StringBuilder(64);
            if (inetAddress instanceof Inet4Address) {
                // reverse ipv4 address
                reverseName.append(addr[3] & 0xff).append(".")
                        .append(addr[2] & 0xff).append(".")
                        .append(addr[1] & 0xff).append(".")
                        .append(addr[0] & 0xff);
            } else {
                // It is an ipv 6 address time to reverse it
                for (int i = 0; i < 16; i++) {
                    reverseName.append(HEX_TABLE[(addr[15 - i] & 0xf)]);
                    reverseName.append(".");
                    reverseName.append(HEX_TABLE[(addr[15 - i] >> 4) & 0xf]);
                    if (i != 15) {
                        reverseName.append(".");
                    }
                }
            }
            reverseName.append(".in-addr.arpa");

            return resolvePTR(reverseName.toString(), new Handler>() {
                @Override
                public void handle(AsyncResult event) {
                    if (event.failed()) {
                        handler.handle(event);
                    } else {
                        String result = (String) event.result();
                        try {
                            handler.handle(new DefaultFutureResult<>(InetAddress.getByAddress(result, inetAddress.getAddress())));
                        } catch (UnknownHostException e) {
                            // Should never happen
                            handler.handle(new DefaultFutureResult(e));
                        }
                    }
                }
            });
        } catch (final UnknownHostException e) {
            // Should never happen as we work with ip addresses as input
            // anyway just in case notify the handler
            actualCtx.execute(new Runnable() {
                public void run() {
                    handler.handle(new DefaultFutureResult(e));

                }
            });
        }
        return this;
    }

    @SuppressWarnings("unchecked")
    private void lookup(final String name, final Handler handler, final int... types) {
        final DefaultFutureResult result = new DefaultFutureResult<>();
        result.setHandler(handler);
        lookup(dnsServers.iterator(), name, result, types);
    }

    @SuppressWarnings("unchecked")
    private void lookup(final Iterator dns, final String name, final DefaultFutureResult result, final int... types) {
        bootstrap.connect(dns.next()).addListener(new RetryChannelFutureListener(dns, name, result, types) {
            @Override
            public void onSuccess(ChannelFuture future) throws Exception {
                DnsQuery query = new DnsQuery(ThreadLocalRandom.current().nextInt());
                for (int type : types) {
                    query.addQuestion(new DnsQuestion(name, type));
                }
                future.channel().writeAndFlush(query).addListener(new RetryChannelFutureListener(dns, name, result, types) {
                    @Override
                    public void onSuccess(ChannelFuture future) throws Exception {
                        future.channel().pipeline().addLast(new SimpleChannelInboundHandler() {
                            @Override
                            protected void channelRead0(ChannelHandlerContext ctx, DnsResponse msg) throws Exception {
                                DnsResponseCode code = DnsResponseCode.valueOf(msg.getHeader().getResponseCode());

                                if (code == DnsResponseCode.NOERROR) {
                                    List resources = msg.getAnswers();
                                    List records = new ArrayList<>(resources.size());
                                    for (DnsResource resource : msg.getAnswers()) {
                                        Object record = RecordDecoderFactory.getFactory().decode(resource.type(), msg, resource);
                                        records.add(record);
                                    }

                                    setResult(result, ctx.channel().eventLoop(), records);
                                } else {
                                    setResult(result, ctx.channel().eventLoop(), new DnsException(code));
                                }
                                ctx.close();
                            }

                            @Override
                            public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
                                setResult(result, ctx.channel().eventLoop(), cause);
                                ctx.close();
                            }
                        });
                    }
                });
            }
        });
    }

    @SuppressWarnings("unchecked")
    private void setResult(final DefaultFutureResult r, EventLoop loop, final Object result) {
        if (r.complete()) {
            return;
        }
        if (actualCtx.isOnCorrectWorker(loop)) {
            try {
                async.setContext(actualCtx);
                if (result instanceof Throwable) {
                    r.setFailure((Throwable) result);
                } else {
                    r.setResult(result);
                }
            } catch (Throwable t) {
                actualCtx.reportException(t);
            }
        } else {
            actualCtx.execute(new Runnable() {
                public void run() {
                    if (result instanceof Throwable) {
                        r.setFailure((Throwable) result);
                    } else {
                        r.setResult(result);
                    }
                }
            });
        }
    }

    private static final class HandlerAdapter implements Handler>> {
        private final Handler handler;

        HandlerAdapter(Handler handler) {
            this.handler = handler;
        }

        @SuppressWarnings("unchecked")
        @Override
        public void handle(AsyncResult> event) {
            if (event.failed()) {
                handler.handle(event);
            } else {
                List result = event.result();
                if (result.isEmpty()) {
                    handler.handle(new DefaultFutureResult<>((T) null));
                } else {
                    handler.handle(new DefaultFutureResult<>(result.get(0)));
                }
            }
        }
    }

    protected abstract class ConvertingHandler implements Handler>> {
        private final Handler handler;
        private final Comparator comparator;

        ConvertingHandler(Handler>> handler, Comparator comparator) {
            this.handler = handler;
            this.comparator = comparator;
        }

        @SuppressWarnings("unchecked")
        @Override
        public void handle(AsyncResult> event) {
            if (event.failed()) {
                handler.handle(event);
            } else {
                List records = (List) event.result();
                for (int i = 0; i < records.size(); i++) {
                    F record = (F) records.get(i);
                    records.set(i, convert(record));
                }

                Collections.sort(records, comparator);
                handler.handle(new DefaultFutureResult(records));
            }
        }

        protected abstract T convert(F entry);
    }

    private abstract class RetryChannelFutureListener implements ChannelFutureListener {
        private final Iterator dns;
        private final String name;
        private final DefaultFutureResult result;
        private final int[] types;

        RetryChannelFutureListener(final Iterator dns, final String name, final DefaultFutureResult result, final int... types) {
            this.dns = dns;
            this.name = name;
            this.result = result;
            this.types = types;
        }

        @Override
        public final void operationComplete(ChannelFuture future) throws Exception {
            if (!future.isSuccess()) {
                if (!result.complete()) {
                    if (dns.hasNext()) {
                        // try next dns server
                        lookup(dns, name, result, types);
                    } else {
                        // TODO: maybe use a special exception ?
                        result.setFailure(future.cause());
                    }
                }
            } else {
                onSuccess(future);
            }
        }

        protected abstract void onSuccess(ChannelFuture future) throws Exception;
    }


}
    
    
    
    

    




    
    
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