// ----------------------------------------------------------------------------
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ----------------------------------------------------------------------------

#pragma warning disable 0618

using System;
using System.Diagnostics;
using System.Net;
using System.Net.IP;
using System.Net.Sockets;
using System.Collections;

using Microsoft.SingSharp;
using Microsoft.Singularity;
using Microsoft.Singularity.Channels;
using Microsoft.Singularity.Directory;
using NetStack.Contracts;
using NetStack.Channels.Public;

namespace Smb.Shared
{
	class NetUtil
	{
		public static TcpContract.Imp:ReadyState! BindTcp()
		{
			TcpContract.Imp! tcp_imp;
			TcpContract.Exp! tcp_exp;
			TcpContract.NewChannel(out tcp_imp, out tcp_exp);
			try {
				DirectoryUtil.BindService(TcpContract.ModuleName, tcp_exp);
				tcp_imp.RecvReady();
				return tcp_imp;
			}
			catch (Exception ex) {
				delete tcp_imp;
				throw ex;
			}
		}
		
        public static TcpConnectionContract.Imp:ReadyState! CreateTcpConnection()
        {
            TcpContract.Imp! tcp = BindTcp();
            
            TcpConnectionContract.Imp! connection_imp;
            TcpConnectionContract.Exp! connection_exp;
            TcpConnectionContract.NewChannel(out connection_imp, out connection_exp);

            tcp.SendCreateTcpSession(connection_exp);
            
            switch receive {
				case tcp.Ack():
					delete tcp;
					connection_imp.RecvReady();
					// DebugStub.WriteLine("Successfully created TCP connection.");
					return connection_imp;
				
				case tcp.ChannelClosed():
					delete tcp;
					throw new Exception("A TCP connection could not be created.  The TCP module closed its channel.");
					
				case unsatisfiable:
					delete tcp;
					throw new Exception("A TCP connection could not be created.  Unsatisfiable select.");
            }
        }
        
        public static TcpConnectionContract.Imp:Connected! ConnectAny(string! hostname, int port)
        {
			try {
				IPv4 ip_address;
				
				if (IPv4.Parse(hostname, out ip_address)) {
					// A single address.
					return Connect((uint)ip_address, port);
				}
				IPHostEntry hostentry = Dns.GetHostByName(hostname);
				
				if (hostentry == null)
					throw new Exception("DNS resolution failed.");

				IPAddress[] addresses = hostentry.AddressList;
				if (addresses == null)
					throw new Exception("Host entry did not return addresses.");
				
				if (addresses.Length == 0)
					throw new Exception("This hostname does not have any addresses.");
					
				if (addresses.Length == 1) {
					return Connect((uint)((!)addresses[0]).Address, port);
				}
				
				foreach (IPAddress addr in addresses) {	
					IPAddress address = (!)addr;
					
					TcpConnectionContract.Imp:ReadyState! conn = CreateTcpConnection();
					conn.SendConnect((uint)address.Address, (ushort)port);
					
					switch receive {
						case conn.OK():
							return conn;
						
						case unsatisfiable:
							delete conn;
							throw new Exception("Unsatisfiable read");
							
						case conn.CouldNotConnect(error):
							delete conn;
							continue;
					}
				}
				
				throw new Exception(String.Format("All attempts to connect to the host failed.  {0} addresses were attempted.", addresses.Length));
	        
			}
			catch (Exception ex) {
				throw new Exception(String.Format("Failed to connect to hostname '{0}'.", hostname), ex);
			}
        }
        
        public static TcpConnectionContract.Imp:Connected! Connect(uint ipv4_address, int port)
        {
			TcpConnectionContract.Imp:ReadyState! conn = CreateTcpConnection();
			
			// The TCP/IP stack currently does not properly handle dynamic client endpoints.
			// It will will reuse a local TCP port before it ought to.  So if you are attempting
			// to connect to the same remote address:port as a previous connection, you'll wind 
			// up with the exact same TCP tuple.  The remote endpoint will either reset the
			// connection, or will simply not respond.  So, for now, we just pick a random local
			// port, in the dynamic range.  The right thing to do is to fix the Singularity
			// TCP/IP service; this is just a temporary work-around.
			
			// conn.SendBindLocalEndPoint(0, 0);
			
			Random rand = new Random();
			int localPort = rand.Next(30000) + 1024;
			conn.SendBindLocalEndPoint(0, (ushort)localPort);
			
			
			switch receive {
				case conn.OK():
					// DebugStub.WriteLine("Socket bound");
					break;
					
				case conn.InvalidEndPoint():
					DebugStub.WriteLine("bind: InvalidEndPoint");
					throw new Exception("The TCP/IP driver refused the bind request.");
					
				case conn.ChannelClosed():
					throw new Exception("TCP/IP driver closed channel during bind!");
			}
			
			conn.SendConnect(ipv4_address, (ushort)port);
			
			IPv4 addr = new IPv4(ipv4_address);
			
			switch receive {
				case conn.OK():
					return conn;
				
				case unsatisfiable:
					delete conn;
					throw new Exception(String.Format("Could not connect to TCP destination '{0}'.  Unsatisfiable read.", addr.ToString()));
					
				case conn.CouldNotConnect(error):
					delete conn;
					throw new Exception(String.Format("Could not connect to TCP destination '{0}:{1}': {2}", addr.ToString(), port.ToString(), TcpException.GetMessageForTcpError(error)));
			}
        }
        
        
	}
}