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

/* program_name is defined in gnulib; referenced by usage(). */
extern char const *program_name;

/* Unity fixtures */
void setUp(void) {
  /* Setup code here, or leave empty */
}
void tearDown(void) {
  /* Cleanup code here, or leave empty */
}

/* Helper: read all data from fd into a malloc'd buffer.
   Returns 0 on success. On success, *out points to a NUL-terminated buffer and
   *out_len is the number of bytes read (not including the NUL). */
static int read_all_fd(int fd, char **out, size_t *out_len) {
  size_t cap = 4096;
  size_t len = 0;
  char *buf = (char *)malloc(cap);
  if (!buf) return -1;

  for (;;) {
    if (len == cap) {
      size_t ncap = cap * 2;
      char *nbuf = (char *)realloc(buf, ncap);
      if (!nbuf) {
        free(buf);
        return -1;
      }
      buf = nbuf;
      cap = ncap;
    }
    ssize_t n = read(fd, buf + len, cap - len);
    if (n < 0) {
      if (errno == EINTR) continue;
      free(buf);
      return -1;
    }
    if (n == 0) break;
    len += (size_t)n;
  }

  /* ensure NUL terminator */
  if (len == cap) {
    char *nbuf = (char *)realloc(buf, cap + 1);
    if (!nbuf) {
      free(buf);
      return -1;
    }
    buf = nbuf;
  }
  buf[len] = '\0';
  *out = buf;
  *out_len = len;
  return 0;
}

/* Helper: run usage(status) in a child process with program_name set to pname.
   Captures stdout/stderr into malloc'd buffers.
   Returns 0 on success, -1 on failure to set up/execute child.
   exit_code is set to the child's exit status if it exited normally,
   or -1 otherwise. */
static int run_usage_and_capture(const char *pname, int call_status,
                                 char **out_buf, size_t *out_len,
                                 char **err_buf, size_t *err_len,
                                 int *exit_code) {
  int pout[2] = {-1, -1};
  int perr[2] = {-1, -1};
  if (pipe(pout) < 0) return -1;
  if (pipe(perr) < 0) {
    close(pout[0]); close(pout[1]);
    return -1;
  }

  fflush(stdout);
    fflush(stderr);
    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, set program_name, then call usage(). */
    /* Ensure C locale for predictable output where applicable. */
    setenv("LC_ALL", "C", 1);

    /* Redirect stdout/stderr to pipes. */
    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]);

    /* Set program_name used by usage(). */
    program_name = pname;

    /* Call the target function; it will exit() the process. */
    usage(call_status);

    /* Should never reach here. */
    _exit(127);
  }

  /* Parent: close write ends, read from read ends. */
  close(pout[1]); close(perr[1]);

  int status;
  char *out_local = NULL, *err_local = NULL;
  size_t out_local_len = 0, err_local_len = 0;

  /* Read outputs before waiting to avoid potential deadlocks on full pipes. */
  int r1 = read_all_fd(pout[0], &out_local, &out_local_len);
  int r2 = read_all_fd(perr[0], &err_local, &err_local_len);

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

  if (r1 != 0 || r2 != 0) {
    if (out_local) free(out_local);
    if (err_local) free(err_local);
    /* Reap child to avoid zombies. */
    waitpid(pid, &status, 0);
    return -1;
  }

  if (waitpid(pid, &status, 0) < 0) {
    free(out_local);
    free(err_local);
    return -1;
  }

  if (WIFEXITED(status)) {
    *exit_code = WEXITSTATUS(status);
  } else {
    *exit_code = -1;
  }

  *out_buf = out_local;
  *out_len = out_local_len;
  *err_buf = err_local;
  *err_len = err_local_len;
  return 0;
}

/* Test: usage(EXIT_SUCCESS) prints help to stdout, stderr empty, exits 0. */
static void test_usage_success_outputs_help_to_stdout_and_exits_zero(void) {
  char *out = NULL, *err = NULL;
  size_t out_len = 0, err_len = 0;
  int ec = -2;

  int rc = run_usage_and_capture("cat", EXIT_SUCCESS, &out, &out_len, &err, &err_len, &ec);
  TEST_ASSERT_EQUAL_INT_MESSAGE(0, rc, "Failed to run usage() in child");
  TEST_ASSERT_EQUAL_INT_MESSAGE(EXIT_SUCCESS, ec, "usage(EXIT_SUCCESS) did not exit with 0");
  TEST_ASSERT_NOT_NULL_MESSAGE(out, "stdout buffer is NULL");
  TEST_ASSERT_TRUE_MESSAGE(out_len > 0, "stdout is empty for usage(EXIT_SUCCESS)");
  TEST_ASSERT_NOT_NULL_MESSAGE(err, "stderr buffer is NULL");
  TEST_ASSERT_EQUAL_UINT_MESSAGE(0, err_len, "stderr not empty for usage(EXIT_SUCCESS)");

  /* Check for stable option flag substrings in the help text. */
  TEST_ASSERT_NOT_NULL_MESSAGE(strstr(out, "-A, --show-all"), "Help missing '-A, --show-all'");
  TEST_ASSERT_NOT_NULL_MESSAGE(strstr(out, "-n, --number"), "Help missing '-n, --number'");
  TEST_ASSERT_NOT_NULL_MESSAGE(strstr(out, "-T, --show-tabs"), "Help missing '-T, --show-tabs'");

  free(out);
  free(err);
}

/* Test: usage(nonzero) prints 'try --help' to stderr, stdout empty, exits with status. */
static void test_usage_nonzero_status_outputs_try_help_to_stderr_and_exits_code(void) {
  char *out = NULL, *err = NULL;
  size_t out_len = 0, err_len = 0;
  int ec = -2;

  int rc = run_usage_and_capture("cat", 3, &out, &out_len, &err, &err_len, &ec);
  TEST_ASSERT_EQUAL_INT_MESSAGE(0, rc, "Failed to run usage() in child");
  TEST_ASSERT_EQUAL_INT_MESSAGE(3, ec, "usage(nonzero) did not exit with given status");
  TEST_ASSERT_NOT_NULL_MESSAGE(out, "stdout buffer is NULL");
  TEST_ASSERT_EQUAL_UINT_MESSAGE(0, out_len, "stdout should be empty for usage(nonzero)");
  TEST_ASSERT_NOT_NULL_MESSAGE(err, "stderr buffer is NULL");
  TEST_ASSERT_TRUE_MESSAGE(err_len > 0, "stderr is empty for usage(nonzero)");

  /* Look for stable markers: program name and '--help'. */
  TEST_ASSERT_NOT_NULL_MESSAGE(strstr(err, "cat"), "stderr missing program name");
  TEST_ASSERT_NOT_NULL_MESSAGE(strstr(err, "--help"), "stderr missing '--help' hint");

  free(out);
  free(err);
}

/* Test: program_name reflected in outputs for both success and failure cases. */
static void test_usage_reflects_program_name_in_outputs(void) {
  /* Success case: program_name should appear in full help (e.g., Usage line or Examples). */
  {
    char *out = NULL, *err = NULL;
    size_t out_len = 0, err_len = 0;
    int ec = -2;

    int rc = run_usage_and_capture("mycat", EXIT_SUCCESS, &out, &out_len, &err, &err_len, &ec);
    TEST_ASSERT_EQUAL_INT(0, rc);
    TEST_ASSERT_EQUAL_INT(EXIT_SUCCESS, ec);
    TEST_ASSERT_TRUE(out_len > 0);
    TEST_ASSERT_NOT_NULL(strstr(out, "mycat")); /* Should appear in Usage or Examples lines. */
    TEST_ASSERT_EQUAL_UINT(0, err_len);

    free(out);
    free(err);
  }

  /* Non-success case: program_name should appear in the 'try --help' diagnostic. */
  {
    char *out = NULL, *err = NULL;
    size_t out_len = 0, err_len = 0;
    int ec = -2;

    int rc = run_usage_and_capture("mycat", 2, &out, &out_len, &err, &err_len, &ec);
    TEST_ASSERT_EQUAL_INT(0, rc);
    TEST_ASSERT_EQUAL_INT(2, ec);
    TEST_ASSERT_EQUAL_UINT(0, out_len);
    TEST_ASSERT_TRUE(err_len > 0);
    TEST_ASSERT_NOT_NULL(strstr(err, "mycat"));
    TEST_ASSERT_NOT_NULL(strstr(err, "--help"));

    free(out);
    free(err);
  }
}

int main(void) {
  UNITY_BEGIN();
  RUN_TEST(test_usage_success_outputs_help_to_stdout_and_exits_zero);
  RUN_TEST(test_usage_nonzero_status_outputs_try_help_to_stderr_and_exits_code);
  RUN_TEST(test_usage_reflects_program_name_in_outputs);
  return UNITY_END();
}