#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h> 
#include <errno.h>
#include <sys/socket.h>
#include <unistd.h>
#include "dnshdr.h"


int main() 
{
    int sockfd;
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);

    if (sockfd < 0) {
        perror("Couldn't open socket. Is port available ?");
    }

    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));

    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY;
    server_addr.sin_port = htons(5353);

    if (bind(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
        perror("Couldn't bind socket to ip/port.");
        close(sockfd);
        return 1;
    }


    unsigned char* buffer = calloc(512, sizeof(char*));
    struct sockaddr_in client_addr;
    socklen_t client_len = sizeof(client_addr); 
    
    while (1) {
        int buflen;
        buflen = recvfrom(sockfd, buffer, 512, 0, (struct sockaddr*)&client_addr, &client_len);

        if (buflen < 0) {
            perror("Unable to receive data");
            continue;
        }

        printf("===== New request! %d bytes. =====\n", buflen);

        printf("Hexdump: \n");
        for(int i = 0; i<buflen; i++) 
        {
            printf("%02x ", buffer[i]);
            if ((i + 1) % 8 == 0) printf("  ");
            if ((i + 1) % 32 == 0) printf("\n");
        }
        printf("\n");

        struct dnshdr *hdr = (struct dnshdr*) buffer;
        uint16_t flags = ntohs(hdr->flags);

        printf("Id       : %d\n", ntohs(hdr->id));
        printf("Flags    : QR=%d OPCODE=%d AA=%d TC=%d RD=%d RA=%d Z=%d AD=%d CD=%d RCODE=%d\n",
            (flags & 0x8000) >> 15, 
            (flags & 0x7800) >> 11,
            (flags & 0x0400) >> 10,
            (flags & 0x0200) >> 9,
            (flags & 0x0100) >> 8,
            (flags & 0x0080) >> 7,
            (flags & 0x0040) >> 6,
            (flags & 0x0020) >> 5,
            (flags & 0x0010) >> 4,
            (flags & 0X000F)
        );
        printf("Qdcount  : %d\n", ntohs(hdr->qdcount));
        printf("Ancount  : %d\n", ntohs(hdr->ancount));
        printf("Nscount  : %d\n", ntohs(hdr->nscount));
        printf("Arcount  : %d\n", ntohs(hdr->arcount));

        
        

    }

    free(buffer);
    close(sockfd);
    return 1;

}