#include "reverse_lib.h"

#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>

static const char test_file[] = "reverse.c";

char* reverse_to_temp_file(const char* input_file) {
  char* temp_filename = strdup("/tmp/reverse_test.XXXXXX");
  int fd = mkstemp(temp_filename);
  if (fd == -1) err(EX_IOERR, "Couldn't make a temporary file");
  reverse_file(input_file, fd);
  if (close(fd) == -1) err(EX_IOERR, "Couldn't close temporary file");
  return temp_filename;
}

void test_reverse_twice_is_the_same() {
  char* intermediate = reverse_to_temp_file(test_file);
  char* back_to_normal = reverse_to_temp_file(intermediate);

  FILE* f1 = fopen(test_file, "r");
  if (f1 == NULL) err(EX_IOERR, "Couldn't open test file");
  FILE* f2 = fopen(back_to_normal, "r");
  if (f2 == NULL) err(EX_IOERR, "Couldn't open twice-reversed temp file");

  for (int pos = 0; ; pos++) {
    int c1 = fgetc(f1);
    int c2 = fgetc(f2);
    if (c1 == EOF && ferror(f1)) err(EX_IOERR, "Error reading test file");
    if (c2 == EOF && ferror(f2)) err(EX_IOERR, "Error reading twice-reversed temp file");
    if (c1 != c2) {
      errx(EX_SOFTWARE, "Unexpected difference found at offset %d after reversing twice.  "
                        "Expected %d but found %d", pos, c1, c2);
    }
    if (c1 == EOF) break;
  }

  if (fclose(f1) != 0) err(EX_IOERR, "Couldn't close test file");
  if (fclose(f2) != 0) err(EX_IOERR, "Couldn't close twice-reversed temp file");
  if (unlink(intermediate) == -1) err(EX_IOERR, "Couldn't remove intermediate temp file");
  if (unlink(back_to_normal) == -1) err(EX_IOERR, "Couldn't remove twice-reversed temp file");
  free(intermediate);
  free(back_to_normal);
}

int main() {
  test_reverse_twice_is_the_same();
  puts("PASS");
  return 0;
}