#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <unistd.h>

// Server starten: nc -lp1337
// Dann Client (dieses Programm) starten
int main() {
  struct addrinfo *res;
  struct addrinfo hints = {
    .ai_family = AF_UNSPEC,
    .ai_socktype = SOCK_STREAM,
    .ai_flags = AI_ADDRCONFIG
  };
  int status = getaddrinfo("localhost", "1337", &hints, &res);

  // Fehlerbehandlung
  if (status == EAI_SYSTEM) {
    perror("gai");
    exit(1);
  } else if (status != 0) {
    fprintf(stderr, "%s\n", gai_strerror(status));
    exit(1);
  }
  int sock;
  struct addrinfo* curr;
  for (curr = res; curr != NULL; curr = curr->ai_next) {
    sock = socket(curr->ai_family, curr->ai_socktype, curr->ai_protocol);
    if (sock < 0) {
      continue;
    }

    if (0 == connect(sock, curr->ai_addr, curr->ai_addrlen)) {
      break;
    }

    close(sock);
  }

  if (curr == NULL) {
    exit(1);
    // Fehlerbehandlung
  }

  FILE *rx = fdopen(sock, "r");
  // Fehlerbehandlung
  int copy = dup(sock);
  // Fehlerbehandlung
  FILE *tx = fdopen(copy, "w");
  // Fehlerbehandlung
  
  int upper = 2;
  int read;
  while ((read = fgetc(rx)) != EOF) {
    if (upper == 2) {
      if (read == 'u') {
        upper = 1;
      } else if (read == 'l') {
        upper = 0;
      } else {
        fprintf(tx, "Invalid char");
        exit(EXIT_FAILURE);
      }
      continue;
    }

    if (upper) {
      fputc(toupper(read), tx);
    } else {
      fputc(tolower(read), tx);
      // FB
    }

    fflush(tx);
    // Fehlerbehandlung aller IO-Funktion
  }

  // Ressourcen freigeben
  
}