/**
 * Resplendent RPCs
 * CS 241 - Spring 2019
 */
#include <arpa/inet.h>
#include <errno.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <unistd.h>
#include <netdb.h>

#include "common.h"
#include "common.h"
#include "dns_query.h"
#include "dns_query_svc_impl.h"

#define CACHE_FILE "cache_files/rpc_server_cache"

char *contact_nameserver(query *argp, char *host, int port) {
  // Your code here
  // Look in the header file for a few more comments

  struct sockaddr_in a;
  memset(&a, 0, sizeof(struct sockaddr_in));
  a.sin_family = AF_INET;
  a.sin_port = htons((uint16_t)port);

  inet_pton(AF_INET, host, &(a.sin_addr));

  int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
  ssize_t r;
  do {
    r = sendto(sockfd, argp->host, strlen(argp->host), 0, (struct sockaddr*)&(a), sizeof(a));
  } while (r == -1 && errno == EINTR);

  char *buffer = calloc(16, 1);
  struct sockaddr_storage addr;
  socklen_t size = sizeof(addr);
  do {
    r = recvfrom(sockfd, buffer, 15, 0, (struct sockaddr*)&(addr), &size);
  } while (r == -1 && errno == EAGAIN);

  if (strcmp(buffer, "-1.-1.-1.-1") == 0){ return NULL;}

  return buffer;
}

void create_response(query *argp, char *ipv4_address, response *res) {
  // Your code here
  // As before there are comments in the header file
  if (!ipv4_address){
    //set result fields
    res->success = 0;
    struct host_address *a = calloc(sizeof(struct host_address), 1);
    //set host_address fields
    a->host = calloc(strlen(argp->host)+1, 1);
    strcpy(a->host, argp->host);
    a->host_ipv4_address = calloc(sizeof(char*), 1);
    //set res address
    res->address = a;
    return;
  }

  res->success = 1;
  struct host_address *a = malloc(sizeof(struct host_address));
  //set host_address fields
  a->host = calloc(strlen(argp->host)+1, 1);
  strcpy(a->host, argp->host);

  a->host_ipv4_address = calloc(strlen(ipv4_address)+1, 1);
  strcpy(a->host_ipv4_address, ipv4_address);

  //set res address
  res->address = a;
  return;

}

// Stub code

response *dns_query_1_svc(query *argp, struct svc_req *rqstp) {
  printf("Resolving query...\n");
  // check its cache, 'rpc_server_cache'
  // if it's in cache, return with response object with the ip address
  char *ipv4_address = check_cache_for_address(argp->host, CACHE_FILE);
  if (ipv4_address == NULL) {
    // not in the cache. contact authoritative servers like a recursive dns
    // server
    printf("Domain not found in server's cache. Contacting authoritative "
        "servers...\n");
    char *host = getenv("NAMESERVER_HOST");
    int port = strtol(getenv("NAMESERVER_PORT"), NULL, 10);
    ipv4_address = contact_nameserver(argp, host, port);
  } else {
    // it is in the server's cache; no need to ask the authoritative
    // servers.
    printf("Domain found in server's cache!\n");
  }

  static response res;
  xdr_free(xdr_response, &res); // Frees old memory in the response struct
  create_response(argp, ipv4_address, &res);

  free(ipv4_address);

  return &res;
}