package org.ibex.mail;
import java.io.*;
import java.util.*;
import java.net.*;
import org.ibex.util.*;
import org.ibex.net.*;
import org.xbill.DNS.*;
import org.xbill.DNS.Message;
import javax.naming.*;
import javax.naming.directory.*;


// FEATURE: use DNSJava for reverse lookups?
// FEATURE: investigate other cool stuff in DNSJava we can use
public class DNSUtil {

    public static String reverseLookup(InetAddress ip) throws IOException {
        Resolver res = new ExtendedResolver();
        Message response =
            res.send(Message.newQuery(Record.newRecord(ReverseMap.fromAddress(ip), Type.PTR, DClass.IN)));
        Record[] answers = response.getSectionArray(Section.ANSWER);
        return answers.length==0 ? null : answers[0].rdataToString();
    }

    public static InetAddress[] getMailExchangerIPs(String hostName) {
        InetAddress[] ret;
        try {
            Hashtable env = new Hashtable();
            env.put("java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory");
            DirContext ictx = new InitialDirContext(env);
            Attributes attrs = ictx.getAttributes(hostName, new String[] { "MX" });
            Attribute attr = attrs.get("MX");
            if (attr == null) {
                ret = new InetAddress[1];
                try {
                    ret[0] = InetAddress.getByName(hostName);
                    if (ret[0].equals(IP.getIP(127,0,0,1)) || ret[0].isLoopbackAddress()) throw new UnknownHostException();
                    return ret;
                } catch (UnknownHostException uhe) {
                    Log.warn(DNSUtil.class, "no MX hosts or A record for " + hostName);
                    return new InetAddress[0];
                }
            } else {
                ret = new InetAddress[attr.size()];
                NamingEnumeration ne = attr.getAll();
                for(int i=0; ne.hasMore();) {
                    String mx = (String)ne.next();
                    // FIXME we should be sorting here
                    mx = mx.substring(mx.indexOf(" ") + 1);
                    if (mx.charAt(mx.length() - 1) == '.') mx = mx.substring(0, mx.length() - 1);
                    try {
                        InetAddress ia = InetAddress.getByName(mx);
                        if (ia.equals(IP.getIP(127,0,0,1)) || ia.isLoopbackAddress()) continue;
                        ret[i++] = ia;
                    } catch (Exception e) {
                        Log.info("safe to ignore", e);
                    }
                }
            }
        } catch (Exception e) {
            Log.warn(DNSUtil.class, "couldn't find MX host for " + hostName + " due to");
            Log.warn(DNSUtil.class, e);
            return new InetAddress[0];
        }
        return ret;
    }

}