#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>
#include <locale.h>

/* Access the target function and globals from the program */
extern void usage (int status);
extern char const *program_name;

/* Helper: read all data from a file descriptor into a NUL-terminated buffer.
   Returns malloc'd buffer (caller must free). Sets *out_len to length (not including NUL).
   On error, returns NULL and *out_len = 0. */
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 + 1);
  if (!buf) {
    if (out_len) *out_len = 0;
    return NULL;
  }

  for (;;) {
    if (len == cap) {
      size_t ncap = cap * 2;
      char *nbuf = (char *)realloc(buf, ncap + 1);
      if (!nbuf) {
        free(buf);
        if (out_len) *out_len = 0;
        return NULL;
      }
      buf = nbuf;
      cap = ncap;
    }
    ssize_t n = read(fd, buf + len, cap - len);
    if (n > 0) {
      len += (size_t)n;
      continue;
    } else if (n == 0) {
      break; /* EOF */
    } else {
      if (errno == EINTR)
        continue;
      free(buf);
      if (out_len) *out_len = 0;
      return NULL;
    }
  }
  buf[len] = '\0';
  if (out_len) *out_len = len;
  return buf;
}

/* Helper: run usage(status) in a child, with program_name overridden, capture stdout/stderr and exit code.
   - progname_override: if non-NULL, set program_name = progname_override in the child before calling usage.
   - status: the status to pass to usage().

   Returns 0 on success (captures filled), -1 on failure to set up pipes/fork. */
static int spawn_usage_and_capture (const char *progname_override, int status,
                                    char **out_stdout, size_t *out_stdout_len,
                                    char **out_stderr, size_t *out_stderr_len,
                                    int *out_exit_code)
{
  int out_pipe[2] = {-1,-1};
  int err_pipe[2] = {-1,-1};

  if (pipe(out_pipe) < 0)
    return -1;
  if (pipe(err_pipe) < 0) {
    close(out_pipe[0]); close(out_pipe[1]);
    return -1;
  }

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

  if (pid == 0) {
    /* Child: redirect stdout/stderr and call usage(). No Unity assertions here. */
    /* Ensure predictable messages. */
    setenv("LC_ALL", "C", 1);
    setlocale(LC_ALL, "C");

    if (progname_override && *progname_override) {
      /* Assign the global program_name (pointer to const char). */
      program_name = progname_override;
    } else {
      /* Ensure default in case not already set. */
      program_name = "link";
    }

    /* Redirect stdout and stderr */
    close(out_pipe[0]);
    close(err_pipe[0]);

    if (dup2(out_pipe[1], STDOUT_FILENO) < 0) _exit(127);
    if (dup2(err_pipe[1], STDERR_FILENO) < 0) _exit(127);

    /* Close the extra fds after dup */
    close(out_pipe[1]);
    close(err_pipe[1]);

    /* Call the function (will exit). */
    usage(status);

    /* Should not reach here, but just in case, exit with sentinel. */
    _exit(255);
  }

  /* Parent: close write ends and read captured outputs. */
  close(out_pipe[1]);
  close(err_pipe[1]);

  char *cap_out = read_all_from_fd(out_pipe[0], out_stdout_len);
  char *cap_err = read_all_from_fd(err_pipe[0], out_stderr_len);

  close(out_pipe[0]);
  close(err_pipe[0]);

  int wstatus = 0;
  int rc;
  do {
    rc = waitpid(pid, &wstatus, 0);
  } while (rc < 0 && errno == EINTR);

  int exit_code = -1;
  if (rc >= 0) {
    if (WIFEXITED(wstatus)) {
      exit_code = WEXITSTATUS(wstatus);
    } else if (WIFSIGNALED(wstatus)) {
      exit_code = 128 + WTERMSIG(wstatus);
    } else {
      exit_code = -1;
    }
  }

  if (!cap_out) {
    /* Allocation/read failure: still provide empty buffers to avoid NULL deref in tests. */
    cap_out = (char *)malloc(1);
    if (cap_out) cap_out[0] = '\0';
    if (out_stdout_len) *out_stdout_len = 0;
  }
  if (!cap_err) {
    cap_err = (char *)malloc(1);
    if (cap_err) cap_err[0] = '\0';
    if (out_stderr_len) *out_stderr_len = 0;
  }

  if (out_stdout) *out_stdout = cap_out; else free(cap_out);
  if (out_stderr) *out_stderr = cap_err; else free(cap_err);
  if (out_exit_code) *out_exit_code = exit_code;

  return 0;
}

void setUp(void) {
  /* No global setup needed for these tests */
}

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

/* Test: Nonzero status EXIT_FAILURE path prints try-help to stderr, no stdout, exit code == EXIT_FAILURE */
void test_usage_failure_prints_try_help_and_exits_failure(void)
{
  char *out = NULL, *err = NULL;
  size_t out_len = 0, err_len = 0;
  int code = -1;

  int rc = spawn_usage_and_capture("link", EXIT_FAILURE, &out, &out_len, &err, &err_len, &code);
  TEST_ASSERT_EQUAL_INT_MESSAGE(0, rc, "Failed to spawn child for usage(EXIT_FAILURE)");

  TEST_ASSERT_EQUAL_INT(EXIT_FAILURE, code);
  TEST_ASSERT_NOT_NULL(out);
  TEST_ASSERT_NOT_NULL(err);
  TEST_ASSERT_EQUAL_UINT64_MESSAGE(0, (uint64_t)out_len, "Expected no stdout on failure");
  /* Expect: Try 'link --help' for more information. */
  TEST_ASSERT_TRUE_MESSAGE(strstr(err, "Try 'link --help' for more information.") != NULL,
                           "stderr should contain the try-help hint for link");

  free(out);
  free(err);
}

/* Test: Nonzero arbitrary status is propagated to exit code and prints try-help */
void test_usage_failure_with_arbitrary_status_propagated(void)
{
  const int arbitrary = 42;
  char *out = NULL, *err = NULL;
  size_t out_len = 0, err_len = 0;
  int code = -1;

  int rc = spawn_usage_and_capture("link", arbitrary, &out, &out_len, &err, &err_len, &code);
  TEST_ASSERT_EQUAL_INT_MESSAGE(0, rc, "Failed to spawn child for usage(42)");

  TEST_ASSERT_EQUAL_INT(arbitrary, code);
  TEST_ASSERT_EQUAL_UINT64_MESSAGE(0, (uint64_t)out_len, "Expected no stdout on failure");
  TEST_ASSERT_TRUE_MESSAGE(strstr(err, "Try 'link --help' for more information.") != NULL,
                           "stderr should contain the try-help hint for link");

  free(out);
  free(err);
}

/* Test: Success path prints usage/help to stdout, nothing to stderr, and exits with 0 */
void test_usage_success_prints_usage_and_exits_zero(void)
{
  char *out = NULL, *err = NULL;
  size_t out_len = 0, err_len = 0;
  int code = -1;

  int rc = spawn_usage_and_capture("link", EXIT_SUCCESS, &out, &out_len, &err, &err_len, &code);
  TEST_ASSERT_EQUAL_INT_MESSAGE(0, rc, "Failed to spawn child for usage(EXIT_SUCCESS)");

  TEST_ASSERT_EQUAL_INT(EXIT_SUCCESS, code);
  TEST_ASSERT_NOT_NULL(out);
  TEST_ASSERT_NOT_NULL(err);
  TEST_ASSERT_EQUAL_UINT64_MESSAGE(0, (uint64_t)err_len, "Expected no stderr on success");

  /* Check key substrings */
  TEST_ASSERT_TRUE_MESSAGE(strstr(out, "Usage: link FILE1 FILE2") != NULL,
                           "stdout should contain the main usage line with program name");
  TEST_ASSERT_TRUE_MESSAGE(strstr(out, "or:  link OPTION") != NULL,
                           "stdout should contain the alternative usage line");
  TEST_ASSERT_TRUE_MESSAGE(strstr(out, "Call the link function to create a link named FILE2") != NULL,
                           "stdout should contain the description line");
  /* Ensure help/version options are advertised (exact wording can vary by gettext/lib). */
  TEST_ASSERT_TRUE_MESSAGE(strstr(out, "--help") != NULL,
                           "stdout should mention the --help option");
  TEST_ASSERT_TRUE_MESSAGE(strstr(out, "--version") != NULL,
                           "stdout should mention the --version option");

  free(out);
  free(err);
}

/* Test: program_name variable is respected in the header lines */
void test_usage_respects_program_name_variable(void)
{
  const char *custom = "linky";
  char *out = NULL, *err = NULL;
  size_t out_len = 0, err_len = 0;
  int code = -1;

  int rc = spawn_usage_and_capture(custom, EXIT_SUCCESS, &out, &out_len, &err, &err_len, &code);
  TEST_ASSERT_EQUAL_INT_MESSAGE(0, rc, "Failed to spawn child for usage(EXIT_SUCCESS) with custom program_name");

  TEST_ASSERT_EQUAL_INT(EXIT_SUCCESS, code);
  TEST_ASSERT_EQUAL_UINT64_MESSAGE(0, (uint64_t)err_len, "Expected no stderr on success with custom name");

  TEST_ASSERT_TRUE_MESSAGE(strstr(out, "Usage: linky FILE1 FILE2") != NULL,
                           "stdout should use custom program_name in main usage line");
  TEST_ASSERT_TRUE_MESSAGE(strstr(out, "or:  linky OPTION") != NULL,
                           "stdout should use custom program_name in alternative usage line");

  free(out);
  free(err);
}

int main(void)
{
  UNITY_BEGIN();
  RUN_TEST(test_usage_failure_prints_try_help_and_exits_failure);
  RUN_TEST(test_usage_failure_with_arbitrary_status_propagated);
  RUN_TEST(test_usage_success_prints_usage_and_exits_zero);
  RUN_TEST(test_usage_respects_program_name_variable);
  return UNITY_END();
}