package de.pixart.messenger.utils;

import android.annotation.TargetApi;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.LinkProperties;
import android.net.Network;
import android.net.RouteInfo;
import android.os.Build;
import android.os.Bundle;
import android.os.Parcelable;
import android.util.Log;

import java.io.IOException;
import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.SocketTimeoutException;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Random;
import java.util.TreeMap;
import java.util.regex.Pattern;

import de.measite.minidns.Client;
import de.measite.minidns.DNSMessage;
import de.measite.minidns.Record;
import de.measite.minidns.Record.CLASS;
import de.measite.minidns.Record.TYPE;
import de.measite.minidns.record.A;
import de.measite.minidns.record.AAAA;
import de.measite.minidns.record.Data;
import de.measite.minidns.record.SRV;
import de.measite.minidns.util.NameUtil;
import de.pixart.messenger.Config;
import de.pixart.messenger.xmpp.jid.Jid;

public class DNSHelper {

    public static final Pattern PATTERN_IPV4 = Pattern.compile("\\A(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)(\\.(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)){3}\\z");
    public static final Pattern PATTERN_IPV6_HEX4DECCOMPRESSED = Pattern.compile("\\A((?:[0-9A-Fa-f]{1,4}(?::[0-9A-Fa-f]{1,4})*)?) ::((?:[0-9A-Fa-f]{1,4}:)*)(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)(\\.(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)){3}\\z");
    public static final Pattern PATTERN_IPV6_6HEX4DEC = Pattern.compile("\\A((?:[0-9A-Fa-f]{1,4}:){6,6})(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)(\\.(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)){3}\\z");
    public static final Pattern PATTERN_IPV6_HEXCOMPRESSED = Pattern.compile("\\A((?:[0-9A-Fa-f]{1,4}(?::[0-9A-Fa-f]{1,4})*)?)::((?:[0-9A-Fa-f]{1,4}(?::[0-9A-Fa-f]{1,4})*)?)\\z");
    public static final Pattern PATTERN_IPV6 = Pattern.compile("\\A(?:[0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}\\z");

    protected static Client client = new Client();

    protected static Context context;

    public static Bundle getSRVRecord(final Jid jid, Context context) throws IOException {
        DNSHelper.context = context;
        final String host = jid.getDomainpart();
        final List<InetAddress> servers = Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP ? getDnsServers(context) : getDnsServersPreLollipop();
        Bundle b = new Bundle();
        boolean interrupted = false;
        for (InetAddress server : servers) {
            if (Thread.currentThread().isInterrupted()) {
                interrupted = true;
                break;
            }
            b = queryDNS(host, server);
            if (b.containsKey("values")) {
                return b;
            }
        }
        if (!b.containsKey("values")) {
            Log.d(Config.LOGTAG, (interrupted ? "Thread interrupted during DNS query" : "all dns queries failed") + ". provide fallback A record");
            ArrayList<Parcelable> values = new ArrayList<>();
            values.add(createNamePortBundle(host, 5222, false));
            b.putParcelableArrayList("values", values);
        }
        return b;
    }

    @TargetApi(21)
    private static List<InetAddress> getDnsServers(Context context) {
        List<InetAddress> servers = new ArrayList<>();
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        Network[] networks = connectivityManager == null ? null : connectivityManager.getAllNetworks();
        if (networks == null) {
            return getDnsServersPreLollipop();
        }
        for (int i = 0; i < networks.length; ++i) {
            LinkProperties linkProperties = connectivityManager.getLinkProperties(networks[i]);
            if (linkProperties != null) {
                if (hasDefaultRoute(linkProperties)) {
                    servers.addAll(0, getIPv4First(linkProperties.getDnsServers()));
                } else {
                    servers.addAll(getIPv4First(linkProperties.getDnsServers()));
                }
            }
        }
        if (servers.size() > 0) {
            Log.d(Config.LOGTAG, "used lollipop variant to discover dns servers in " + networks.length + " networks");
        }
        return servers.size() > 0 ? servers : getDnsServersPreLollipop();
    }

    private static List<InetAddress> getIPv4First(List<InetAddress> in) {
        List<InetAddress> out = new ArrayList<>();
        for (InetAddress addr : in) {
            if (addr instanceof Inet4Address) {
                out.add(0, addr);
            } else {
                out.add(addr);
            }
        }
        return out;
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    private static boolean hasDefaultRoute(LinkProperties linkProperties) {
        for (RouteInfo route : linkProperties.getRoutes()) {
            if (route.isDefaultRoute()) {
                return true;
            }
        }
        return false;
    }

    private static List<InetAddress> getDnsServersPreLollipop() {
        List<InetAddress> servers = new ArrayList<>();
        String[] dns = client.findDNS();
        for (int i = 0; i < dns.length; ++i) {
            try {
                servers.add(InetAddress.getByName(dns[i]));
            } catch (UnknownHostException e) {
                //ignore
            }
        }
        return servers;
    }

    private static class TlsSrv {
        private final SRV srv;
        private final boolean tls;

        public TlsSrv(SRV srv, boolean tls) {
            this.srv = srv;
            this.tls = tls;
        }
    }

    private static void fillSrvMaps(final String qname, final InetAddress dnsServer, final Map<Integer, List<TlsSrv>> priorities, final Map<String, List<String>> ips4, final Map<String, List<String>> ips6, final boolean tls) throws IOException {
        final DNSMessage message = client.query(qname, TYPE.SRV, CLASS.IN, dnsServer.getHostAddress());
        for (Record[] rrset : new Record[][]{message.getAnswers(), message.getAdditionalResourceRecords()}) {
            for (Record rr : rrset) {
                Data d = rr.getPayload();
                final String name = rr.getName() != null ? rr.getName().toLowerCase(Locale.US) : null;
                if (d instanceof SRV && NameUtil.idnEquals(qname, name)) {
                    SRV srv = (SRV) d;
                    if (!priorities.containsKey(srv.getPriority())) {
                        priorities.put(srv.getPriority(), new ArrayList<TlsSrv>());
                    }
                    priorities.get(srv.getPriority()).add(new TlsSrv(srv, tls));
                } else if (d instanceof SRV) {
                    Log.d(Config.LOGTAG, "found unrecognized SRV record with name: " + name);
                }
                if (d instanceof A) {
                    A a = (A) d;
                    if (!ips4.containsKey(name)) {
                        ips4.put(name, new ArrayList<String>());
                    }
                    ips4.get(name).add(a.toString());
                }
                if (d instanceof AAAA) {
                    AAAA aaaa = (AAAA) d;
                    if (!ips6.containsKey(name)) {
                        ips6.put(name, new ArrayList<String>());
                    }
                    ips6.get(name).add("[" + aaaa.toString() + "]");
                }
            }
        }
    }

    public static Bundle queryDNS(String host, InetAddress dnsServer) {
        Bundle bundle = new Bundle();
        try {
            client.setTimeout(Config.SOCKET_TIMEOUT * 1000);
            final String qname = "_xmpp-client._tcp." + host.toLowerCase(Locale.US);
            final String tlsQname = "_xmpps-client._tcp." + host.toLowerCase(Locale.US);
            Log.d(Config.LOGTAG, "using dns server: " + dnsServer.getHostAddress() + " to look up " + host);

            final Map<Integer, List<TlsSrv>> priorities = new TreeMap<>();
            final Map<String, List<String>> ips4 = new TreeMap<>();
            final Map<String, List<String>> ips6 = new TreeMap<>();

            fillSrvMaps(qname, dnsServer, priorities, ips4, ips6, false);
            fillSrvMaps(tlsQname, dnsServer, priorities, ips4, ips6, true);

            final List<TlsSrv> result = new ArrayList<>();
            for (final List<TlsSrv> s : priorities.values()) {
                result.addAll(s);
            }

            final ArrayList<Bundle> values = new ArrayList<>();
            if (result.size() == 0) {
                DNSMessage response;
                try {
                    response = client.query(host, TYPE.A, CLASS.IN, dnsServer.getHostAddress());
                    for (int i = 0; i < response.getAnswers().length; ++i) {
                        values.add(createNamePortBundle(host, 5222, response.getAnswers()[i].getPayload(), false));
                    }
                } catch (SocketTimeoutException e) {
                    Log.d(Config.LOGTAG, "ignoring timeout exception when querying A record on " + dnsServer.getHostAddress());
                }
                try {
                    response = client.query(host, TYPE.AAAA, CLASS.IN, dnsServer.getHostAddress());
                    for (int i = 0; i < response.getAnswers().length; ++i) {
                        values.add(createNamePortBundle(host, 5222, response.getAnswers()[i].getPayload(), false));
                    }
                } catch (SocketTimeoutException e) {
                    Log.d(Config.LOGTAG, "ignoring timeout exception when querying AAAA record on " + dnsServer.getHostAddress());
                }
                values.add(createNamePortBundle(host, 5222, false));
                bundle.putParcelableArrayList("values", values);
                return bundle;
            }
            for (final TlsSrv tlsSrv : result) {
                final SRV srv = tlsSrv.srv;
                final String name = srv.getName() != null ? srv.getName().toLowerCase(Locale.US) : null;
                if (ips6.containsKey(name)) {
                    values.add(createNamePortBundle(name, srv.getPort(), ips6, tlsSrv.tls));
                } else {
                    try {
                        DNSMessage response = client.query(name, TYPE.AAAA, CLASS.IN, dnsServer.getHostAddress());
                        for (int i = 0; i < response.getAnswers().length; ++i) {
                            values.add(createNamePortBundle(name, srv.getPort(), response.getAnswers()[i].getPayload(), tlsSrv.tls));
                        }
                    } catch (SocketTimeoutException e) {
                        Log.d(Config.LOGTAG, "ignoring timeout exception when querying AAAA record on " + dnsServer.getHostAddress());
                    }
                }
                if (ips4.containsKey(name)) {
                    values.add(createNamePortBundle(name, srv.getPort(), ips4, tlsSrv.tls));
                } else {
                    DNSMessage response = client.query(name, TYPE.A, CLASS.IN, dnsServer.getHostAddress());
                    for (int i = 0; i < response.getAnswers().length; ++i) {
                        values.add(createNamePortBundle(name, srv.getPort(), response.getAnswers()[i].getPayload(), tlsSrv.tls));
                    }
                }
                values.add(createNamePortBundle(name, srv.getPort(), tlsSrv.tls));
            }
            bundle.putParcelableArrayList("values", values);
        } catch (SocketTimeoutException e) {
            bundle.putString("error", "timeout");
        } catch (Exception e) {
            bundle.putString("error", "unhandled");
        }
        return bundle;
    }

    private static Bundle createNamePortBundle(String name, int port, final boolean tls) {
        Bundle namePort = new Bundle();
        namePort.putString("name", name);
        namePort.putBoolean("tls", tls);
        namePort.putInt("port", port);
        return namePort;
    }

    private static Bundle createNamePortBundle(String name, int port, Map<String, List<String>> ips, final boolean tls) {
        Bundle namePort = new Bundle();
        namePort.putString("name", name);
        namePort.putBoolean("tls", tls);
        namePort.putInt("port", port);
        if (ips != null) {
            List<String> ip = ips.get(name);
            Collections.shuffle(ip, new Random());
            namePort.putString("ip", ip.get(0));
        }
        return namePort;
    }

    private static Bundle createNamePortBundle(String name, int port, Data data, final boolean tls) {
        Bundle namePort = new Bundle();
        namePort.putString("name", name);
        namePort.putBoolean("tls", tls);
        namePort.putInt("port", port);
        if (data instanceof A) {
            namePort.putString("ip", data.toString());
        } else if (data instanceof AAAA) {
            namePort.putString("ip", "[" + data.toString() + "]");
        }
        return namePort;
    }

    public static boolean isIp(final String server) {
        return server != null && (
                PATTERN_IPV4.matcher(server).matches()
                        || PATTERN_IPV6.matcher(server).matches()
                        || PATTERN_IPV6_6HEX4DEC.matcher(server).matches()
                        || PATTERN_IPV6_HEX4DECCOMPRESSED.matcher(server).matches()
                        || PATTERN_IPV6_HEXCOMPRESSED.matcher(server).matches());
    }
}