#include "../../unity/unity.h"
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <errno.h>
#include <locale.h>
#include <stdio.h>
#include <signal.h>

/* program_name is declared by coreutils headers included before this test */
extern char const *program_name;

/* Helper: read all data from fd into a dynamically-allocated buffer.
   Returns 0 on success, -1 on error. On success, *buf points to malloc'd
   memory (NUL-terminated for convenience) and *len to its length. */
static int read_all_fd(int fd, char **buf, size_t *len)
{
  size_t cap = 1024;
  size_t used = 0;
  char *out = (char *)malloc(cap);
  if (!out) return -1;

  for (;;)
  {
    if (used == cap)
    {
      size_t ncap = cap * 2;
      char *tmp = (char *)realloc(out, ncap);
      if (!tmp) { free(out); return -1; }
      out = tmp;
      cap = ncap;
    }
    ssize_t n = read(fd, out + used, cap - used);
    if (n > 0)
    {
      used += (size_t)n;
      continue;
    }
    if (n == 0)
      break;
    if (errno == EINTR)
      continue;
    free(out);
    return -1;
  }
  /* NUL-terminate for strstr convenience */
  if (used == cap)
  {
    char *tmp = (char *)realloc(out, cap + 1);
    if (!tmp) { free(out); return -1; }
    out = tmp;
  }
  out[used] = '\0';
  *buf = out;
  *len = used;
  return 0;
}

/* Helper: create a pipe with CLOEXEC if available, else set it manually. */
static int make_pipe_cloexec(int p[2])
{
#ifdef O_CLOEXEC
  if (pipe2(p, O_CLOEXEC) == 0)
    return 0;
  if (errno != ENOSYS && errno != EINVAL)
    return -1;
#endif
  if (pipe(p) != 0)
    return -1;
  /* set CLOEXEC on both ends */
  for (int i = 0; i < 2; i++)
  {
    int flags = fcntl(p[i], F_GETFD);
    if (flags >= 0)
      fcntl(p[i], F_SETFD, flags | FD_CLOEXEC);
  }
  return 0;
}

/* Run usage(status) in a child, capturing its stdout and stderr.
   On success returns 0 and populates outputs (caller must free *out and *err).
   On failure returns -1. */
static int run_usage_and_capture(int status,
                                 char **out, size_t *out_len,
                                 char **err, size_t *err_len,
                                 int *exit_code)
{
  int out_p[2] = {-1,-1};
  int err_p[2] = {-1,-1};
  if (make_pipe_cloexec(out_p) != 0) return -1;
  if (make_pipe_cloexec(err_p) != 0)
  {
    close(out_p[0]); close(out_p[1]);
    return -1;
  }

  fflush(stdout);
    fflush(stderr);
    pid_t pid = fork();
  if (pid < 0)
  {
    close(out_p[0]); close(out_p[1]);
    close(err_p[0]); close(err_p[1]);
    return -1;
  }

  if (pid == 0)
  {
    /* Child: redirect stdout/stderr to pipes */
    /* Avoid stdio buffering issues by setting line buffering or unbuffered */
    /* But since we dup the fds, exit() will flush appropriately */
    if (dup2(out_p[1], STDOUT_FILENO) < 0) _exit(127);
    if (dup2(err_p[1], STDERR_FILENO) < 0) _exit(127);
    close(out_p[0]); close(out_p[1]);
    close(err_p[0]); close(err_p[1]);

    /* Ensure program_name has a value */
    if (!program_name || program_name[0] == '\0')
      program_name = "mknod";

    /* Call the function under test; it should not return. */
    usage(status);

    /* If it returns, exit with sentinel code. */
    _exit(123);
  }

  /* Parent */
  close(out_p[1]);
  close(err_p[1]);

  char *out_buf = NULL, *err_buf = NULL;
  size_t out_sz = 0, err_sz = 0;

  int r1 = read_all_fd(out_p[0], &out_buf, &out_sz);
  int r2 = read_all_fd(err_p[0], &err_buf, &err_sz);

  close(out_p[0]);
  close(err_p[0]);

  int wstatus = 0;
  pid_t w = -1;
  do {
    w = waitpid(pid, &wstatus, 0);
  } while (w < 0 && errno == EINTR);

  if (r1 != 0 || r2 != 0 || w < 0)
  {
    free(out_buf);
    free(err_buf);
    return -1;
  }

  int code = -1;
  if (WIFEXITED(wstatus))
    code = WEXITSTATUS(wstatus);
  else if (WIFSIGNALED(wstatus))
    code = 128 + WTERMSIG(wstatus);

  *out = out_buf; *out_len = out_sz;
  *err = err_buf; *err_len = err_sz;
  *exit_code = code;
  return 0;
}

/* Helper: check if buffer contains substring (ASCII) */
static int buf_contains(const char *buf, const char *needle)
{
  if (!buf || !needle) return 0;
  return strstr(buf, needle) != NULL;
}

void setUp(void) {
  /* Force C locale for deterministic messages */
  setenv("LC_ALL", "C", 1);
  setlocale(LC_ALL, "C");

  /* Ensure program_name is set consistently for messages */
  if (!program_name || program_name[0] == '\0')
    program_name = "mknod";
  else
    program_name = "mknod";
}

void tearDown(void) {
  /* Nothing to cleanup */
}

static void free_captured(char *out, char *err)
{
  free(out);
  free(err);
}

void test_usage_success_outputs_usage_and_exits_zero(void)
{
  char *out = NULL, *err = NULL;
  size_t out_len = 0, err_len = 0;
  int code = -1;

  int rc = run_usage_and_capture(EXIT_SUCCESS, &out, &out_len, &err, &err_len, &code);
  TEST_ASSERT_EQUAL_INT_MESSAGE(0, rc, "run_usage_and_capture failed");

  /* Check exit code */
  TEST_ASSERT_EQUAL_INT(EXIT_SUCCESS, code);

  /* stderr should be empty for success usage */
  TEST_ASSERT_TRUE_MESSAGE(err_len == 0 || (err && err[0] == '\0'),
                           "Expected no stderr output for successful usage()");

  /* stdout should contain usage header and key content */
  TEST_ASSERT_TRUE_MESSAGE(buf_contains(out, "Usage: mknod"),
                           "stdout should contain 'Usage: mknod'");
  TEST_ASSERT_TRUE_MESSAGE(buf_contains(out, "TYPE may be"),
                           "stdout should mention 'TYPE may be'");
  TEST_ASSERT_TRUE_MESSAGE(buf_contains(out, "block (buffered) special file"),
                           "stdout should describe block special file");

  free_captured(out, err);
}

void test_usage_nonzero_status_emits_try_help_and_exits_status(void)
{
  char *out = NULL, *err = NULL;
  size_t out_len = 0, err_len = 0;
  int code = -1;

  int wanted = 2;
  int rc = run_usage_and_capture(wanted, &out, &out_len, &err, &err_len, &code);
  TEST_ASSERT_EQUAL_INT_MESSAGE(0, rc, "run_usage_and_capture failed");

  /* Expect the exact exit status */
  TEST_ASSERT_EQUAL_INT(wanted, code);

  /* stdout should be empty in the error path */
  TEST_ASSERT_TRUE_MESSAGE(out_len == 0 || (out && out[0] == '\0'),
                           "Expected no stdout output when status != EXIT_SUCCESS");

  /* stderr should contain a try-help message mentioning '--help' and program name */
  TEST_ASSERT_TRUE_MESSAGE(buf_contains(err, "--help"),
                           "stderr should contain '--help' hint");
  TEST_ASSERT_TRUE_MESSAGE(buf_contains(err, "mknod"),
                           "stderr should mention program name 'mknod'");
  TEST_ASSERT_TRUE_MESSAGE(buf_contains(err, "Try"),
                           "stderr should start with a 'Try' hint");

  free_captured(out, err);
}

void test_usage_success_includes_mode_option_line(void)
{
  char *out = NULL, *err = NULL;
  size_t out_len = 0, err_len = 0;
  int code = -1;

  int rc = run_usage_and_capture(EXIT_SUCCESS, &out, &out_len, &err, &err_len, &code);
  TEST_ASSERT_EQUAL_INT_MESSAGE(0, rc, "run_usage_and_capture failed");

  TEST_ASSERT_EQUAL_INT(EXIT_SUCCESS, code);
  TEST_ASSERT_TRUE_MESSAGE(buf_contains(out, "-m, --mode"),
                           "stdout should document the -m, --mode option");

  /* Ensure no unexpected stderr output */
  TEST_ASSERT_TRUE_MESSAGE(err_len == 0 || (err && err[0] == '\0'),
                           "Expected no stderr output for successful usage()");

  free_captured(out, err);
}

int main(void)
{
  UNITY_BEGIN();
  RUN_TEST(test_usage_success_outputs_usage_and_exits_zero);
  RUN_TEST(test_usage_nonzero_status_emits_try_help_and_exits_status);
  RUN_TEST(test_usage_success_includes_mode_option_line);
  return UNITY_END();
}