#include <arpa/inet.h>
#include <fcntl.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <unistd.h>

#include "eblapp.h"

#define PORT 1069
#define MAX_PACKET_SIZE 1024
#define TIMEOUT 5

void error(const char *msg) {
  perror(msg);
  exit(1);
}

int main(int argc, char *argv[]) {
  if (argc < 3) {
    fprintf(stderr, "Usage: %s hostname filename\n", argv[0]);
    exit(1);
  }

  char buffer[MAX_PACKET_SIZE];
  uint32_t current_offset = 0;
  int sockfd;
  struct sockaddr_in serv_addr;
  struct hostent *server;

  sockfd = socket(AF_INET, SOCK_DGRAM, 0);
  if (sockfd < 0)
    error("ERROR opening socket");

  server = gethostbyname(argv[1]);
  if (server == NULL) {
    fprintf(stderr, "ERROR, no such host\n");
    exit(1);
  }

  memset((char *)&serv_addr, 0, sizeof(serv_addr));
  serv_addr.sin_family = AF_INET;
  memcpy((char *)&serv_addr.sin_addr.s_addr, (char *)server->h_addr,
         server->h_length);
  serv_addr.sin_port = htons(PORT);

  struct Eblapp_request *request = (struct Eblapp_request *)buffer;
  request->opcode = EBLAPP_REQUEST_FILE;
  request->filename_size = strlen(argv[2]);
  memcpy(request + 1, argv[2], request->filename_size);

  int packet_len = strlen(argv[2]) + sizeof(*request);

  if (sendto(sockfd, buffer, packet_len, 0, (struct sockaddr *)&serv_addr,
             sizeof(serv_addr)) < 0) {
    error("ERROR sending RRQ");
  }

  printf("Requesting file: %s\n", argv[2]);

  // Open output file
  int fd = open(argv[3], O_WRONLY | O_CREAT | O_TRUNC, 0644);
  if (fd < 0) {
    error("ERROR creating file");
  }

  int wtf = 0;
  while (1) {
    fd_set readfds;
    struct timeval tv;
    struct Eblapp_transfer_data *data = (struct Eblapp_transfer_data *)buffer;

    FD_ZERO(&readfds);
    FD_SET(sockfd, &readfds);
    tv.tv_sec = TIMEOUT;
    tv.tv_usec = 0;

    int rv = select(sockfd + 1, &readfds, NULL, NULL, &tv);
    if (rv > 0) {
      socklen_t serv_len = sizeof(serv_addr);
      int n = recvfrom(sockfd, buffer, MAX_PACKET_SIZE, 0,
                       (struct sockaddr *)&serv_addr, &serv_len);
      if (n < 4)
        continue;

      printf("opcode %d\n", data->opcode);
      if (data->opcode == EBLAPP_TRANSFER_DATA) { // DATA
        struct Eblapp_ack ack = {0};
        if (data->block_start != current_offset) {
          if (!wtf) {
            printf("Invalid order (%d/%d)\n", data->block_start,
                   current_offset);
            ack.opcode = EBLAPP_WTF;
            ack.ack_byte = current_offset;
            if (sendto(sockfd, &ack, sizeof(ack), 0,
                       (struct sockaddr *)&serv_addr, serv_len) < 0) {
              error("ERROR sending ACK");
            }
            wtf = 1;
          }
        } else {
          wtf = 0;
          printf("got %d\n", current_offset);
          current_offset += (n - 8);
          ack.opcode = EBLAPP_ACK;
          ack.ack_byte = current_offset;
          if (sendto(sockfd, &ack, sizeof(ack), 0,
                     (struct sockaddr *)&serv_addr, serv_len) < 0) {
            error("ERROR sending ACK");
          }
          write(fd, buffer + 8, (n - 8));
        }
      } else if (data->opcode == EBLAPP_TRANSFER_END) {
        printf("got transfer end\n");
        break;
      }
    }
  }

  close(sockfd);
  close(fd);
  return 0;
}