//================================================================
//    chatd.cc
//    Web browserをクライアントとするチャットデーモン
//    Copyright (C) Naoki Watanabe. 1999-2000. All rights reserved.
//================================================================

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>


// Port number of this chat server.
const int CHAT_PORT   = 1080;

// Maximum number of clients at the same time.
const int MAX_CLIENTS = 16;

// Size of data buffer.
const int BUF_SIZE    = 1024;

//---- Definition of class Socket.
class Socket
{
  int         sc;       // socket descriptor.
  sockaddr_in addr;     // address of the socket.

public:
  //-- default constructor.
  Socket( void ) : sc(0) {
  }

  //-- constructor for the base socket.
  Socket( const u_short port ){
    sc = socket( AF_INET, SOCK_STREAM, 0 );

    addr.sin_family      = AF_INET;
    addr.sin_addr.s_addr = INADDR_ANY;
    addr.sin_port        = htons(port);

    if( bind( sc, (sockaddr*)&addr, sizeof(sockaddr_in)) < 0 ){
      perror("bind");
      exit(1);
    }
  
    listen( sc, MAX_CLIENTS+1 );
  }

  //-- destructor
  ~Socket(){
    Close();
  }

  //-- accept a new socket from the base socket.
  void Accept( const Socket& base ){
#if defined(_XOPEN_SOURCE_EXTENDED)
    size_t len = sizeof(sockaddr_in);
#else
    int len = sizeof(sockaddr_in);
#endif

    sc = accept( base.sc, (sockaddr*)&addr, &len );
  }

  //-- receive a messege.
  void Recv( char buf[BUF_SIZE] ){
    int len = read( sc, buf, BUF_SIZE );
    buf[len] = '\0';
  }

  //-- send a messege.
  void Send( char* buf ){
    // An error means the disconnection of the socket by the client
    // if SIGPIPE signal does not stop this process.
    if( write( sc, buf, strlen(buf) ) < 0 ) Close();
  }

  //-- close this socket.
  void Close( void ){
    close(sc);
    sc = 0;
  }

  //-- check if the socket is connecting.
  int IsActive( void ){
    return sc!=0;
  }

  //-- return the remote address of this connection.
  struct in_addr RemoteAddr( void ){
    // return the IP in network order.
    return addr.sin_addr;
  }

  //-- return the remote port of this connection.
  u_short RemotePort( void ){
    // return the Port in localhost order.
    return ntohs(addr.sin_port);
  }
};



int main( void )
{
  Socket base(CHAT_PORT);   // socket for listening.
  Socket from;              // socket for accepting.
  Socket to[MAX_CLIENTS];   // socket for sending.
  char   buf[BUF_SIZE];     // data buffer.
  char   msg[BUF_SIZE];     // data buffer.

  signal( SIGPIPE, SIG_IGN );  // to escape from the broken pipe error.

  while(1){
    from.Accept(base);
    from.Recv(buf); // may receive the GET request line.

    if( 1 == sscanf( buf, "GET /submit?messege=%s", msg ) ){
      //---- block for the submittion.

      // send a noresponse header to the submit frame.
      from.Send( "HTTP/1.0 204 No Response\n\n" );
      from.Close();

      // send the messege to the content frames of all browsers.
      snprintf( buf, sizeof(buf), "%s.%d: %s<BR>\n",
		inet_ntoa(from.RemoteAddr()), from.RemotePort(), msg );
      for( int i=0; i<MAX_CLIENTS; i++ ){
	if( to[i].IsActive() ) to[i].Send(buf);
      }

    }else if( !strncmp( buf, "GET / ", 6 ) ){
      //---- block for the frameset.

      from.Send( "HTTP/1.0 200 OK\n"
                 "Content-type: text/html\n\n"
                 "<FRAMESET ROWS=\"84,*\">\n"
		 "<FRAME SRC=/input>\n"
		 "<FRAME SRC=/content>\n"
		 "</FRAMESET>\n" );
      from.Close();

    }else if( !strncmp( buf, "GET /input", 10 ) ){
      //---- block for the input frame.

      from.Send( "HTTP/1.0 200 OK\n"
                 "Content-type: text/html\n\n"
                 "<FORM METHOD=GET ACTION=/submit>"
		 "<INPUT TYPE=TEXT   NAME=messege>"
		 "<INPUT TYPE=RESET  VALUE=Reset >"
		 "<INPUT TYPE=SUBMIT VALUE=Submit>"
		 "</FORM>\n" );
      from.Close();

    }else if( !strncmp( buf, "GET /content", 10 ) ){
      //---- block for the content frame.

      int i; // search an unoccupied socket.
      for( i=0; i<MAX_CLIENTS && to[i].IsActive(); i++ );

      if( i==MAX_CLIENTS ){
        // in case all sockets are occupied, reject the connection.
	from.Send( "HTTP/1.0 200 OK\n"
                   "Content-type: text/html\n\n"
	           "<H1>Sorry, now this chat is too crowded.</H1>\n" );
	from.Close();
      }else{
        // entry the socket, make a greeting.
	to[i] = from;
	to[i].Send( "HTTP/1.0 200 OK\n"
                    "Content-type: text/html\n"
		    "\n"
		    "<BODY>\n"
		    "<SCRIPT LANGUAGE=JavaScript>\n"
		    "<!--\n"
		    "function toBottom(){\n"
		    "  scroll(0,100000);\n"
		    "  setTimeout('toBottom()',1000);\n"
		    "}\n"
		    "toBottom();\n"
		    "// -->\n"
		    "</SCRIPT>\n"
		    "\n"
		    "<PRE>\n"
		    "=========================================\n"
	            "   Web-independent smart chat server.    \n"
		    "Originally designed by Naoki Watanabe.   \n"
		    "Last modified on Mar 12th, 2000 by Naoki.\n"
		    "=========================================\n"
		    "</PRE>\n"
		    );
      }
    }else{
      //---- block for an illegal call.
      from.Send( "HTTP/1.0 200 OK\n"
                 "Content-type: text/html\n\n"
		 "<H1>Illegal access.</H1>\n" );
      from.Close();
    }
  }

  return 0;
}