#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "util/versie.h"


static void usage(FILE *f) {
  fprintf(f,
      "Gebruik: omd [-hV] <bestand...>\n"
      "\n"
      "Draai alle regels om\n"
      "\n"
      "  -h    Toon deze hulptekst\n"
      "  -V    Toon versienummer\n");
}

// Returns pointer to argument array containing the file names
static char** parse_options(int argc, char **argv) {
  int opt;
  while ((opt = getopt(argc, argv, "hV")) != -1) {
    switch (opt) {
      case 'h':
        usage(stdout);
        exit(0);

      case 'V':
        drukkedoos_print_versie(stdout);
        exit(0);

      case '?':
        fprintf(stderr, "omd: Ongeldige optie: -%c\n", optopt);
        usage(stderr);
        exit(1);
    }
  }

  return argv + optind;
}

static void reverse_in_place(char *buf, size_t len) {
  // TODO: kijk of dit sneller kan met SIMD
  for (size_t i = 0, j = len - 1; i < len / 2; i++, j--) {
    char c = buf[i];
    buf[i] = buf[j];
    buf[j] = c;
  }
}

static void process(const char *fname, FILE *f) {
  char *line = NULL;
  size_t linen = 0;

  ssize_t nread = 0;
  while ((errno = 0, nread = getline(&line, &linen, f)) != -1) {
    if (line[nread - 1] == '\n') nread--;
    reverse_in_place(line, nread);
    printf("%s", line);
  }

  free(line);

  if (errno != 0) {
    printf("omd: fout bij lezen uit bestand '%s'\n", fname);
    exit(1);
  }
}

int entry_omd(int argc, char **argv) {
  char **args = parse_options(argc, argv);
  if (*args == NULL) {
    process(NULL, stdin);
  } else {
    while (*args != NULL) {
      FILE *f = fopen(*args, "r");
      if (!f) {
        fprintf(stderr, "omd: Kon bestand '%s' niet openen\n", *args);
        return 1;
      }
      process(*args, f);
      fclose(f);
      args++;
    }
  }
  return 0;
}