#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";

/* Reverse input_file.  Dump the result in a temporary file.  Return the temp
 * file's name.  The caller must free the filename. */
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");
  FILE* f = fdopen(fd, "w");
  if (f == NULL) err(EX_IOERR, "Couldn't open temporary file");
  reverse_file(input_file, f);
  if (fclose(f) == EOF) err(EX_IOERR, "Couldn't close temporary file");
  return temp_filename;
}

/* Compare the contents of two files.  Terminate with a diagnostic if they
 * differ. */
void compare(const char* filename1, const char* filename2) {
  FILE* f1 = fopen(filename1, "r");
  if (f1 == NULL) err(EX_IOERR, "Couldn't open file %s", filename1);
  FILE* f2 = fopen(filename2, "r");
  if (f2 == NULL) err(EX_IOERR, "Couldn't open file %s", filename2);

  for (int pos = 0; ; pos++) {
    int c1 = fgetc(f1);
    int c2 = fgetc(f2);
    if (c1 == EOF && ferror(f1)) err(EX_IOERR, "Error reading file %s", filename1);
    if (c2 == EOF && ferror(f2)) err(EX_IOERR, "Error reading file %s", filename2);
    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 file %s", filename1);
  if (fclose(f2) != 0) err(EX_IOERR, "Couldn't close file %s", filename2);
}

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

  compare(test_file, back_to_normal);

  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);
}

void test_reverse_from_file_then_from_stream_is_the_same() {
  int pipefd[2];
  if (pipe(pipefd) == -1) err(EX_OSERR, "Couldn't create pipe");

  pid_t pid = fork();
  if (pid == -1) err(EX_OSERR, "Couldn't fork");
  if (pid == 0) {
    if (close(pipefd[0]) == -1) err(EX_OSERR, "Couldn't close unneeded pipe descriptor");
    FILE* to_second = fdopen(pipefd[1], "w");
    if (to_second == NULL) err(EX_IOERR, "Couldn't open pipe for writing");
    reverse_file(test_file, to_second);
    exit(0);
  }
  if (close(pipefd[1]) == -1) err(EX_OSERR, "Couldn't close unneeded pipe descriptor");
  FILE* from_first = fdopen(pipefd[0], "r");
  if (from_first == NULL) err(EX_IOERR, "Couldn't open pipe for reading");
  char* out_temp_filename = strdup("/tmp/reverse_test.XXXXXX");
  int out_fd = mkstemp(out_temp_filename);
  if (out_fd == -1) err(EX_IOERR, "Couldn't make a temporary file");
  FILE* out_file = fdopen(out_fd, "w");
  if (out_file == NULL) err(EX_IOERR, "Couldn't open temporary file");
  reverse_stream(from_first, out_file);
  if (fclose(out_file) == EOF) err(EX_IOERR, "Couldn't close temporary file");

  compare(test_file, out_temp_filename);

  if (unlink(out_temp_filename) == -1) err(EX_IOERR, "Couldn't remove temp output file");
  free(out_temp_filename);
}

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