/*!
 * \file server.c
 * \author Peter C. Chapin, Nathan S. Brown
 * \brief Trivial FTP client
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <arpa/inet.h>
#include <netdb.h>
#include <sys/socket.h>
#ifndef S_SPLIT_S     // Workaround for splint.
#include <unistd.h>
#endif

#include "server.h"
#define BUFFER_SIZE 128

// ============
// Main Program
// ============

void SIGCHLD_handler(int signal_number)
{
    int status;
    while (waitpid(-1, &status, WNOHANG) > 0) ;
}

int main(int argc, char **argv)
{
    int                 listen_handle;       // Handle of accepting socket.
    unsigned short      port = 69;           // Default TFTP port.
    struct sockaddr_in6 server_address;      // Defines listening address.
    struct sockaddr_in6 client_address;      // Defines struct to hold the client address.
    int                 file_handle;         // Handle of the file.
    int                 buffer[BUFFER_SIZE]; // Multipurpose buffer.
    socklen_t           cli_add_len;         // Holds the return value for the client address.
    pid_t               child_id;            // Process ID number of a child process.

    cli_add_len = sizeof(client_address);

    // Do I have an explicit port number?
    if (argc == 2)
    {
        port = atoi(argv[1]);
    }

    // Creates the server socket as an IPv4 UDP socket.
    if ((listen_handle = socket(PF_INET6, SOCK_DGRAM, 0)) < 0)
    {
        perror("Unable to create socket");
        return 1;
    }

    // Creates the structure for the server socket address
    memset(&server_address, 0, sizeof(server_address));
    server_address.sin6_family      = PF_INET6;
    server_address.sin6_addr = in6addr_any;
    server_address.sin6_port        = htons(port);

    if (bind(listen_handle, (struct sockaddr *) &server_address, sizeof(server_address)) < 0)
    {
        perror("Unable to bind socket");
        close(listen_handle);
        return 1;
    }

    while (1)
    {
        // Call recvfrom() to get a request datagram from the client.
        // This also gives you the client address.
        if ( recvfrom(listen_handle, buffer, BUFFER_SIZE, 0, (struct sockaddr *) &client_address, &cli_add_len) == -1 )
        {
            perror("Request was problematic");
        }
        else
        {
            // Create a child process to handle this client
            if (child_id = 0)
            {
                // Close the socket used to receive client requests.
                close(listen_handle);
                // Create a new socket for communication with this client.
                if ((listen_handle = socket(PF_INET6, SOCK_DGRAM, 0)) < 0)
                {
                    perror("Unable to create socket");
                    return 1;
                }
                // ?? I know that I'm supposed to not use the default port of 69 anymore,
                // correct? How do I create a new auto assigned port for the child?

                // Extract the file name from the request and open the file.

                // ?? Not sure what to do here...I know I have to somehow extract the file
                // name from the 3rd byte of the RRQ up to the first null character, I just
                // am not sure how to go about that.
                if ( (file_handle = open( file_name, O_RDONLY)) == -1 )
                {
                    // File failed to open.
                    perror("File failed to open.");
                }
                else
                {
                    send_file(file_handle);
                    // ?? I'm currently building the server.c, and then moving on to the
                    // implementation of the send_file.c. I have to be honest and say that
                    // I'm fairly uncomfortable and unknowing of what I'm supposed to do there.
                    // When I get to that point I'll try and get as far as I can, but just a
                    // heads up that I might need some help there too. Thanks Peter!
                }
                exit;
            }
        }
    }

    printf("Hello world!\n");
    return EXIT_SUCCESS;
}