import java.io.IOException;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Random;

public class Main
{
	public static void main(String[] args) throws IOException
	{
		String userSearch = null;
		String userDNS = null;
		int userType = 0; 
		String search = "google.pl";
		//String DNS = "8.8.8.8"; // google [ograniczone dane, czesto puste wyniki]
		String DNS = "192.112.36.4"; // globalny DNS
		//String DNS = "62.233.233.233"; // DNS netii
		int type = 1;
		for(String arg : args)
		{
			if(arg.startsWith("-d="))
				userSearch = arg.substring(3);
			else if(arg.startsWith("-ns="))
				userDNS = arg.substring(4);
			else if(arg.startsWith("-t="))
				userType = Integer.parseInt(arg.substring(3));
		}

		if(userSearch == null)
		{
			System.out.println("Nie ustawiono poszukiwanej domeny. Zostanie uzyta domyslna wartosc: " + search);
		}
		else
		{
			search = userSearch;
			System.out.println("Ustawiono poszukiwana domene: " + search);
		}
		if(userDNS == null)
		{
			System.out.println("Nie ustawiono serwera DNS. Zostanie uzyta domyslna wartosc: " + DNS);	
		}
		else
		{
			DNS = userDNS;
			System.out.println("Ustawiono serwer DNS: " + search);
		}
		if(userType == 0)
		{
			System.out.println("Nie ustawiono typu zapytania. Zostanie uzyta domyslna wartosc: " + type);
		}
		else
		{
			type = userType;
			System.out.println("Ustawiono typ zapytania: " + type);
		}
		

		if(type < 1 || type >= DNS_Record.TYPES.length)
		{
			System.out.println("Nie znany typ zapytania. Dozwolone: 1 (A), 2 (NS), 5 (CNAME), 6 (SOA), 15 (MX), 16 (TXT)");
			System.exit(1);
		}

		DatagramSocket socket = new DatagramSocket(12345);
		socket.setSoTimeout(5000);
		DNS_Packet.socket = socket;

		Random random = new Random();
		while(true)
		{
			System.out.println("-------------------------------------------------------");
			DNS_Packet answer = get(search, DNS, type);
			System.out.println("OPCode: " + answer.OPCODE + ", Answers: " + answer.ANCount + ", Authority Records: " + answer.NSCount);
			boolean gotAnswer = false;

			if(answer.OPCODE != 0) // moze ta sama domena co wczesniej i petla musi sie przerwac, bo domena nie istnieje
			{
				System.out.println("Wystapil blad:");
				switch(answer.OPCODE)
				{
					case (byte) 1:
						System.out.println("Format Error");
						break;
					case (byte) 2:
						System.out.println("Server Failure");
						break;
					case (byte) 3:
						System.out.println("Name Error");
						break;
					case (byte) 4:
						System.out.println("Not Implemented");
						break;
					case (byte) 5:
						System.out.println("Refused");
						break;
					default:
						System.out.println("Nie obslugiwany. ID: " + answer.OPCODE);
						break;
				}
				break;
			}
			if(answer.ANCount > 0)
			{
				System.out.println("Odpowiedzi:");
				for(int i = 0; i < answer.ANCount; i++)
				{
					DNS_Record record = answer.ANList[i];
					answer.ptr = record.RData;
					if(record.QType == type)
					{
						gotAnswer = true;
					}
					switch(record.QType)
					{
						case (byte) 1: // A
							InetAddress address = InetAddress.getByAddress(new byte[]
                             { answer.response[answer.ptr++], answer.response[answer.ptr++], answer.response[answer.ptr++], answer.response[answer.ptr++] });
							System.out.println("Typ: A, Domena: " + record.domain + ", IP: " + address.getHostAddress());
							break;
						case (byte) 2: // NS
							System.out.println("Typ: NS, Domena: " + record.domain + ", Domena NS: " + answer.getStringFromPoint());
							break;
						case (byte) 5: // CNAME
							System.out.println("Typ: CNAME, Domena: " + record.domain + ", Rzeczywista domena: " + answer.getStringFromPoint());
							break;
						case (byte) 6: // SOA
							System.out.println("Typ: SOA, Domena: " + record.domain + ", Domena NS: " + answer.getStringFromPoint() + ", Email kontaktowy: " + answer.getStringFromPoint());
							break;
						case (byte) 15: // MX
							answer.ptr += 2;
							System.out.println("Typ: MX, Domena: " + record.domain + ", Adres: " + answer.getStringFromPoint());
							break;
						case (byte) 16: // TXT
							System.out.print("Typ: TXT, Domena: " + record.domain + ", Text: ");
							for(int tt = 0; tt < answer.response[answer.ptr]; tt++)
							{
								System.out.print((char) answer.response[answer.ptr + tt + 1]);
							}
							System.out.println();
							break;
						default:
							System.out.println("Otrzymano odpowiedz. Nie mozna pokazac danych. Nie obslugiwany typ pakietu Type ID: " + record.QType);
							break;
					
					}
				}
				if(gotAnswer)
				{
					break;
				}
			}
			if(!gotAnswer && answer.NSCount > 0)
			{

				System.out.println("Serwery NS:");
				ArrayList<String> dnsy = new ArrayList<String>();
				for(int i = 0; i < answer.NSCount; i++)
				{
					DNS_Record record = answer.NSList[i];
					if(record.QType == (byte) 2)
					{
						answer.ptr = record.RData;
						String otherDNS = answer.getStringFromPoint();
						if(!otherDNS.equals(DNS))
						{
							dnsy.add(otherDNS);	
						}
						System.out.println("Domena: " + record.domain + ", NS: " + otherDNS);
					}
					else if(record.QType == (byte) 6)
					{
						answer.ptr = record.RData;
						String otherDNS = answer.getStringFromPoint();
						if((type == 2 || type == 6) && search.endsWith(record.domain))
						{
							System.out.println("Typ: SOA, Domena: " + record.domain + ", Domena NS: " + otherDNS + ", Email kontaktowy: " + answer.getStringFromPoint());
							System.exit(1);
						}
						if(!otherDNS.equals(DNS))
						{
							dnsy.add(otherDNS);	
						}
						System.out.println("Domena: " + record.domain + ", SOA: " + otherDNS);
					}
					else
					{
						System.err.println("W 'Authority Record' otrzymano informacje o domenie: " + record.domain + ", typu: " + record.QType + ", obslugiwane jest tylko NS (2).");
					}
				}
				if(dnsy.size() == 0)
				{
					System.out.println("Nie uzyskano odpowiedzi podanego typu, ani adresow innych serwerow DNS.");
					break;
				}
				DNS = dnsy.get(random.nextInt(dnsy.size()));
				System.out.println("Wybrano nowy DNS: " + DNS);
			}
			else
			{
				System.out.println("Nie uzyskano odpowiedzi podanego typu, ani adresow innych serwerow DNS.");
				break;
			}
		}
		socket.close();
	}

	public static DNS_Packet get(String domain, String fromDNS, int type) throws UnknownHostException, IOException
	{
		DNS_Packet packet = new DNS_Packet(domain, type);
		boolean reponseReceived = false;
		for(int i = 0; i < 3; i++)
		{
			System.out.println("Wysylanie zapytania o " + domain + " do " + fromDNS + ", typ " + DNS_Record.TYPES[type] + ".");
			if(packet.query(InetAddress.getByName(fromDNS)))
			{
				reponseReceived = true;
				break;
			}
			else
			{
				System.out.println("Brak odpowiedzi przez 5 sekund.");
			}
		}
		if(reponseReceived)
		{
			packet.parseResponse();
		}
		else
		{
			System.out.println("Nie udalo sie uzyskac odpowiedzi od serwera DNS " + fromDNS);
			System.exit(1);
		}
		return packet;
	}
}