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

/* usage(int) is provided by the program under test. */
/* program_name is declared in headers included by the program source before this file. */

static char *read_all_from_fd (int fd, size_t *out_len)
{
  size_t cap = 4096;
  size_t len = 0;
  char *buf = (char *) malloc (cap);
  if (!buf)
    return NULL;

  for (;;)
    {
      if (len == cap)
        {
          size_t ncap = cap * 2;
          char *nbuf = (char *) realloc (buf, ncap);
          if (!nbuf)
            {
              free (buf);
              return NULL;
            }
          buf = nbuf;
          cap = ncap;
        }

      ssize_t r = read (fd, buf + len, cap - len);
      if (r < 0)
        {
          if (errno == EINTR)
            continue;
          free (buf);
          return NULL;
        }
      if (r == 0)
        break;
      len += (size_t) r;
    }

  /* NUL-terminate to make strstr safe (though len is provided). */
  if (len == cap)
    {
      char *nbuf = (char *) realloc (buf, cap + 1);
      if (!nbuf)
        {
          free (buf);
          return NULL;
        }
      buf = nbuf;
    }
  buf[len] = '\0';
  if (out_len)
    *out_len = len;
  return buf;
}

static int run_usage_and_capture (int status_code,
                                  char **out_stdout, size_t *out_stdout_len,
                                  char **out_stderr, size_t *out_stderr_len,
                                  int *out_exit_status)
{
  int pout[2];
  int perr[2];

  if (pipe (pout) != 0)
    return -1;
  if (pipe (perr) != 0)
    {
      close (pout[0]); close (pout[1]);
      return -1;
    }

  pid_t pid = fork ();
  if (pid < 0)
    {
      close (pout[0]); close (pout[1]);
      close (perr[0]); close (perr[1]);
      return -1;
    }

  if (pid == 0)
    {
      /* Child: redirect stdout/stderr and invoke usage(status_code). */
      (void) setenv ("LC_ALL", "C", 1);

      if (dup2 (pout[1], STDOUT_FILENO) < 0) _exit (127);
      if (dup2 (perr[1], STDERR_FILENO) < 0) _exit (127);

      close (pout[0]); close (pout[1]);
      close (perr[0]); close (perr[1]);

      usage (status_code);

      /* Not reached. */
      _exit (200);
    }

  /* Parent: close write ends, read output, wait for child. */
  close (pout[1]);
  close (perr[1]);

  size_t out_len = 0, err_len = 0;
  char *out_buf = read_all_from_fd (pout[0], &out_len);
  char *err_buf = read_all_from_fd (perr[0], &err_len);

  close (pout[0]);
  close (perr[0]);

  int wstatus = 0;
  if (waitpid (pid, &wstatus, 0) < 0)
    {
      free (out_buf);
      free (err_buf);
      return -1;
    }

  int exit_status = -1;
  if (WIFEXITED (wstatus))
    exit_status = WEXITSTATUS (wstatus);
  else
    exit_status = -2; /* Abnormal termination. */

  if (out_stdout) *out_stdout = out_buf; else free (out_buf);
  if (out_stdout_len) *out_stdout_len = out_len;
  if (out_stderr) *out_stderr = err_buf; else free (err_buf);
  if (out_stderr_len) *out_stderr_len = err_len;
  if (out_exit_status) *out_exit_status = exit_status;

  return 0;
}

void setUp(void) {
  /* No global setup needed. */
}

void tearDown(void) {
  /* No global teardown needed. */
}

/* Tests */

void test_usage_exit_zero_prints_full_help(void)
{
  /* program_name is provided by the program. Set it so help includes our chosen value. */
  program_name = "mycomm";

  char *capt_out = NULL;
  char *capt_err = NULL;
  size_t out_len = 0, err_len = 0;
  int exit_st = -1;

  int rc = run_usage_and_capture (EXIT_SUCCESS, &capt_out, &out_len, &capt_err, &err_len, &exit_st);
  TEST_ASSERT_EQUAL_INT_MESSAGE (0, rc, "Failed to run usage() in child process");
  TEST_ASSERT_EQUAL_INT_MESSAGE (0, exit_st, "usage(EXIT_SUCCESS) should exit with status 0");
  TEST_ASSERT_NOT_NULL_MESSAGE (capt_out, "Expected captured stdout buffer");
  TEST_ASSERT_NOT_NULL_MESSAGE (capt_err, "Expected captured stderr buffer");

  /* Full help should be on stdout; stderr should be empty. */
  TEST_ASSERT_TRUE_MESSAGE (out_len > 0, "Expected non-empty stdout for full help");
  TEST_ASSERT_EQUAL_UINT_MESSAGE (0, err_len, "Expected empty stderr for full help");

  /* Check for key substrings in help text (locale forced to C in child). */
  TEST_ASSERT_NOT_NULL_MESSAGE (strstr (capt_out, "Usage: mycomm"), "Help must include 'Usage: mycomm'");
  TEST_ASSERT_NOT_NULL_MESSAGE (strstr (capt_out, "[OPTION]"), "Help must mention [OPTION]");
  TEST_ASSERT_NOT_NULL_MESSAGE (strstr (capt_out, "Compare sorted files"), "Help should describe comparison");
  TEST_ASSERT_NOT_NULL_MESSAGE (strstr (capt_out, "--check-order"), "Help should mention --check-order");
  TEST_ASSERT_NOT_NULL_MESSAGE (strstr (capt_out, "--nocheck-order"), "Help should mention --nocheck-order");
  TEST_ASSERT_NOT_NULL_MESSAGE (strstr (capt_out, "--output-delimiter"), "Help should mention --output-delimiter");
  TEST_ASSERT_NOT_NULL_MESSAGE (strstr (capt_out, "--total"), "Help should mention --total");
  TEST_ASSERT_NOT_NULL_MESSAGE (strstr (capt_out, "--zero-terminated"), "Help should mention --zero-terminated");
  TEST_ASSERT_NOT_NULL_MESSAGE (strstr (capt_out, "Examples:"), "Help should include Examples section");
  TEST_ASSERT_NOT_NULL_MESSAGE (strstr (capt_out, "mycomm -12 file1 file2"), "Examples should include 'mycomm -12 file1 file2'");
  TEST_ASSERT_NOT_NULL_MESSAGE (strstr (capt_out, "mycomm -3 file1 file2"), "Examples should include 'mycomm -3 file1 file2'");

  free (capt_out);
  free (capt_err);
}

void test_usage_nonzero_status_prints_try_help_to_stderr(void)
{
  program_name = "mycomm";

  char *capt_out = NULL;
  char *capt_err = NULL;
  size_t out_len = 0, err_len = 0;
  int exit_st = -1;

  int expected_status = 7; /* arbitrary non-zero */
  int rc = run_usage_and_capture (expected_status, &capt_out, &out_len, &capt_err, &err_len, &exit_st);
  TEST_ASSERT_EQUAL_INT_MESSAGE (0, rc, "Failed to run usage() in child process");
  TEST_ASSERT_EQUAL_INT_MESSAGE (expected_status, exit_st, "usage(nonzero) should exit with that status");
  TEST_ASSERT_NOT_NULL_MESSAGE (capt_out, "Expected captured stdout buffer");
  TEST_ASSERT_NOT_NULL_MESSAGE (capt_err, "Expected captured stderr buffer");

  /* Error synopsis should be on stderr; stdout should be empty. */
  TEST_ASSERT_EQUAL_UINT_MESSAGE (0, out_len, "Expected empty stdout when emitting try-help");
  TEST_ASSERT_TRUE_MESSAGE (err_len > 0, "Expected non-empty stderr when emitting try-help");

  /* Check the try-help message contains our program_name and '--help'. */
  TEST_ASSERT_NOT_NULL_MESSAGE (strstr (capt_err, "Try "), "try-help should contain 'Try '");
  TEST_ASSERT_NOT_NULL_MESSAGE (strstr (capt_err, "mycomm"), "try-help should include program_name");
  TEST_ASSERT_NOT_NULL_MESSAGE (strstr (capt_err, "--help"), "try-help should suggest --help");

  free (capt_out);
  free (capt_err);
}

int main(void)
{
  UNITY_BEGIN();
  RUN_TEST(test_usage_exit_zero_prints_full_help);
  RUN_TEST(test_usage_nonzero_status_prints_try_help_to_stderr);
  return UNITY_END();
}