#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <errno.h>

int main(int argc, char *argv[])
{

    errno = 0;

    enum
    {
        UDP = 17,
        SIZE = 1024,
        ERROR = -1,
        SUCCESS = 0
    };

    struct
    {
        int exchange_socket;
        int port;
        char *server_name;
        struct hostent *server_ip;
        // internet format
        struct sockaddr_in server_addr;
        socklen_t server_addrlen;
    } info;

    info.server_addrlen = sizeof(info.server_addr);

    putchar('\n');

    puts("[ Host name to connect: ]");
    fflush(stdin);
    char buffer[SIZE];
    fscanf(stdin, "%512s[^\n]", buffer);
    // string allocating
    if (NULL == (info.server_name = strndup(buffer, strlen(buffer))))
    {
        perror("strndup");
        exit(1);
    }

    memset(buffer, 0, SIZE);

    puts("[ Host port to connect: ]");
    fflush(stdin);
    while (1)
    {
        int flag = scanf("%d", &info.port);
        if ('\r' == getchar())
            break;
        if (flag > 0)
            break;
    }

    errno = 0;
    if (ERROR == (info.exchange_socket = socket(AF_INET, SOCK_DGRAM, UDP)))
    {
        perror("socket");
        exit(1);
    }
    perror("socket");

    if (NULL == (info.server_ip = gethostbyname(info.server_name)))
    {
        herror("gethostbyname");
        shutdown(info.exchange_socket, SHUT_RDWR);
        close(info.exchange_socket);
        exit(1);
    }
    herror("gethostbyname");

    memset(&info.server_addr, 0, sizeof(info.server_addr));
    info.server_addr.sin_family = AF_INET;
    info.server_addr.sin_port = htons(info.port);
    memcpy(&info.server_addr.sin_addr.s_addr, info.server_ip->h_addr, info.server_ip->h_length);

    while (1)
    {
        sendto(info.exchange_socket, "Ping\r\n", strlen("Ping\r\n"), 0, (struct sockaddr *) &info.server_addr,  info.server_addrlen);
        memset(buffer, 0, SIZE);
        recvfrom(info.exchange_socket, buffer, SIZE-1, 0, (struct sockaddr *) &info.server_addr, &info.server_addrlen);

        if (strstr(buffer, "Pong\r\n"))
        {
            memset(buffer, 0, SIZE);
            break;
        }
        else
            memset(buffer, 0, SIZE);
    }

    puts("Path to save file:");
    fflush(stdin);
    fscanf(stdin, "%512s[^\n]", buffer);

    FILE *file = 0;
    if (file = fopen(buffer, "w"))
        perror("fopen");
    else
    {
        perror("fopen");
        shutdown(info.exchange_socket, SHUT_RDWR);
        close(info.exchange_socket);
        exit(1);
    }

    if (ERROR == chmod(buffer, S_IRUSR|S_IWUSR|S_IXUSR))
    {
        perror("chmod");
        fclose(file);
        shutdown(info.exchange_socket, SHUT_RDWR);
        close(info.exchange_socket);
        exit(1);
    }
    perror("chmod");
    memset(buffer, 0, SIZE);

 /*   if (setvbuf(file, buffer, _IONBF, SIZE) != SUCCESS)
    {
        perror("setvbuf");
        fclose(file);
        shutdown(info.exchange_socket, SHUT_RDWR);
        close(info.exchange_socket);
        exit(1);
    }
    perror("setvbuf");
*/
    while (1)
    {
        sendto(info.exchange_socket, "Ping\r\n", strlen("Ping\r\n"), 0, (struct sockaddr *) &info.server_addr,  info.server_addrlen);
        memset(buffer, 0, SIZE);
        recvfrom(info.exchange_socket, buffer, SIZE-1, 0, (struct sockaddr *) &info.server_addr, &info.server_addrlen);

        if (strstr(buffer, "Pong\r\n"))
        {
            memset(buffer, 0, SIZE);
            break;
        }
        else
            memset(buffer, 0, SIZE);
    }

    puts("\n--- File receiving ---");

    ssize_t current_size = 0;
    ssize_t received_bytes = 0;

    while ((received_bytes = recvfrom(info.exchange_socket, buffer, SIZE-1, 0, (struct sockaddr *) &info.server_addr, &info.server_addrlen)) > 0)
    {
        fwrite(buffer, sizeof(buffer[0]), received_bytes, file);
        current_size += received_bytes;

        fprintf(stderr, "[%d] %s", current_size, buffer);

        memset(buffer, 0, SIZE);
    }

    printf("Received bytes: %d", current_size);
    puts("\n--- EOF ---\n");

    fclose(file);

    shutdown(info.exchange_socket, SHUT_RDWR);
    close(info.exchange_socket);

    putchar('\n');

    return 0;
}