/****************************************************************************
 * server.c                                                                 *
 *                                                                          *
 * LocalGate Local Filesystem -> WWW Gateway                                *
 *                                                                          *
 * LocalGate allows a user to access HTML files on the local filesystem     *
 * as if they had a web server to access the files.                         *
 *                                                                          *
 * server.c: server core for LocalGate.                                     *
 *                                                                          *
 * Copyright (C) 1997  Michael Chu                                          *
 * This file is part of the LocalGate local filesystem -> WWW gateway.      *
 *                                                                          *
 * This program is free software; you can redistribute it and/or modify     *
 * it under the terms of the GNU General Public License as published by     *
 * the Free Software Foundation; either version 2 of the License, or        *
 * (at your option) any later version.                                      *
 *                                                                          *
 * This program is distributed in the hope that it will be useful,          *
 * but WITHOUT ANY WARRANTY; without even the implied warranty of           *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the            *
 * GNU General Public License for more details.                             *
 *                                                                          *
 * You should have received a copy of the GNU General Public License        *
 * along with this program; if not, write to the Free Software              *
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.                *
 *                                                                          *
 * Contact information:      Michael Chu                                    *
 *                           mmchu@pobox.com                                *
 ****************************************************************************/


/*********************************** INCLUDES *******************************/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <netinet/in.h>
#include <signal.h>
#include <errno.h>
#include "netutils.h"
#include "miscutils.h"
#include "server.h"


/********************************** FUNCTIONS *******************************/

/****************************************************************************
 * main:                                                                    *
 *                                                                          *
 * Summary: Main function that is the body of the server.                   *
 *                                                                          *
 * Input:   argc: number of command-line arguments.                         *
 *          argv: list of command-line arguments.                           *
 *                                                                          *
 * Returns: Error code: 0 (zero) if execution ended okay.                   *
 *                      Non-zero if execution ended incorrectly.            *
 *                                                                          *
 * Global State Affected:                                                   *
 *          Server is started.                                              *
 ****************************************************************************/
int main(int argc, char *argv[]) {
  int serverPort = 0;                 /* server port to connect to. */
  int mainSocketId = 0;               /* main server socket id. */
  int newSocketId = 0;                /* new connection socket id. */
  int childPID = 0;                   /* child process id. */
  char *localFileRequest = NULL;      /* stores local filename requested. */

  /* set default server TCP port. */
  serverPort = DEFAULT_SERVER_TCP_PORT;

  /* check arguments. */
  if (argc > 2) {
    /* show usage. */
    fprintf(stderr, "USAGE: %s [TCP_PORT_TO_USE]\n", argv[0]);

    /* return error. */
    return(1);
  } else if (argc == 2) {
    /* if the second argument is not an unsigned integer, then error. */
    if (!(isUnsignedInteger(argv[1]))) {
      /* show error. */
      fprintf(stderr, "TCP port MUST BE NON-NEGATIVE!\n");

      /* exit with error. */
      exit(1);
    }

    /* get the server port from the command-line argument. */
    serverPort = atoi(argv[1]);

    /* make sure that port is greater than reserved boundary. */
    if (serverPort <= IPPORT_USERRESERVED) {
      /* show error. */
      fprintf(stderr, "TCP port MUST BE GREATER THAN %d!\n", 
	      IPPORT_USERRESERVED);

      /* exit with error. */
      exit(1);
    }
  }

  /* let system know we do not care about exit status of our children
     to prevent zombie processes from forming. */
  signal(SIGCLD, SIG_IGN);

  /* initialize the socket. */
  mainSocketId = socketInit(serverPort);

  /* make sure socket was setup correctly. */
  if (mainSocketId < 0) {
    /* exit with error. */
    exit(1);
  }

  /* continuously iterate to accept socket connections. */
  for (;;) {
    /* accept incoming connection. */
    newSocketId = getIncomingConnection(mainSocketId);

    /* make sure socket was connected correctly. */
    if (newSocketId >= 0) {
      /* fork off another child to handle this connection. */
      childPID = fork();

      /* if this the PID returned is negative, then we have an error. */
      /* if it is zero, then we are the child. */
      if (childPID < 0) {
	/* show error. */
	fprintf(stderr, "Error forking off child! (errno = %d)\n", errno);
      } else if (childPID == 0) {
	/* get local file request. */
	localFileRequest = getLocalFileRequest(newSocketId);

	/* if we got back an actual valid filename, then try to send the
	   file through the socket. */
	if (localFileRequest != NULL) {
	  /* write file to socket. */
	  writeFileToSocket(newSocketId, localFileRequest);

	  /* free local file request name. */
	  free(localFileRequest);
	  localFileRequest = NULL;
	}

	/* close the new socket. */
	close(newSocketId);

	/* exit correctly. */
	exit(0);
      }

      /* close the new socket. */
      close(newSocketId);
    }
  }
}