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

/* The test file is included within dd.c, so we can access its internal
   symbols and helper functions/state directly (e.g., cache_round, globals). */

/* Helper: get system page size into the program's global page_size. */
static void tests_set_pagesize(void)
{
  if (page_size == 0)
    {
#if defined(_SC_PAGESIZE)
      long ps = sysconf(_SC_PAGESIZE);
      if (ps <= 0)
        ps = 4096;
      page_size = (idx_t) ps;
#else
      page_size = 4096;
#endif
    }
}

/* Helper: reset cache_round pending for a given fd to 0 without invoking
   invalidate_cache (so no syscalls or output_offset changes). */
static void tests_reset_pending(int fd)
{
  off_t rem = cache_round(fd, 0);
  if (rem != 0)
    {
      /* Bring the accumulated length up to the next IO_BUFSIZE multiple. */
      off_t need = (off_t)IO_BUFSIZE - rem;
      (void) cache_round(fd, need);
    }
}

/* Helper: create an anonymous temporary file, sized to multiple pages. */
static int tests_make_temp_file(off_t size)
{
  char tmpl[] = "/tmp/dd_invalidate_cache_testXXXXXX";
  int fd = mkstemp(tmpl);
  if (fd >= 0)
    {
      /* Unlink so it is removed when closed. */
      unlink(tmpl);
      if (size > 0)
        {
          if (ftruncate(fd, size) != 0)
            {
              /* Best effort; ignore error. */
            }
        }
    }
  return fd;
}

/* Helper: redirect stdout to fd; returns saved original stdout fd via *saved. */
static int tests_redirect_stdout(int new_fd, int *saved)
{
  int s = dup(STDOUT_FILENO);
  if (s < 0)
    return -1;
  if (dup2(new_fd, STDOUT_FILENO) < 0)
    {
      close(s);
      return -1;
    }
  *saved = s;
  return 0;
}

/* Helper: restore stdout from saved fd. */
static void tests_restore_stdout(int saved)
{
  if (saved >= 0)
    {
      (void) dup2(saved, STDOUT_FILENO);
      close(saved);
    }
}

void setUp(void)
{
  tests_set_pagesize();
  /* Provide sane defaults for globals used by invalidate_cache */
  i_nocache_eof = false;
  o_nocache_eof = false;
  input_seekable = true;
  input_offset = 0;
  /* Reset rounding state for both stdin and stdout. */
  tests_reset_pending(STDIN_FILENO);
  tests_reset_pending(STDOUT_FILENO);
}

void tearDown(void)
{
  /* Nothing persistent to clean. */
}

/* 1) Small len on stdin should early-return true (no advisory), and
      advance internal pending by len. */
void test_invalidate_cache_stdin_small_len_no_advise(void)
{
  tests_reset_pending(STDIN_FILENO);
  input_seekable = true;
  input_offset = 12345; /* Arbitrary non-negative; shouldn't be used here. */

  off_t before = cache_round(STDIN_FILENO, 0);
  TEST_ASSERT_EQUAL_INT64(0, (long long)before);

  bool ret = invalidate_cache(STDIN_FILENO, (off_t)1);
  TEST_ASSERT_TRUE(ret);

  off_t after = cache_round(STDIN_FILENO, 0);
  TEST_ASSERT_EQUAL_INT64(1, (long long)after);
}

/* 2) len==0, no pending, and nocache_eof==false => early return true. */
void test_invalidate_cache_stdout_noop_eof_when_nocache_eof_false(void)
{
  tests_reset_pending(STDOUT_FILENO);
  o_nocache_eof = false;

  bool ret = invalidate_cache(STDOUT_FILENO, (off_t)0);
  TEST_ASSERT_TRUE(ret);
}

/* 3) On stdout backed by a regular file:
      - accumulate a non-zero pending via a small len (no advisory expected),
      - with o_nocache_eof=true and len==0, we expect an advisory attempt,
        returning true if posix_fadvise is available, else false/ENOTSUP,
      - then perform a full-chunk advisory with len==IO_BUFSIZE. */
void test_invalidate_cache_stdout_eof_pending_and_full_chunk(void)
{
  int tmpfd = tests_make_temp_file((off_t)(page_size * 4));
  TEST_ASSERT_MESSAGE(tmpfd >= 0, "Failed to create temporary file");

  int saved_out = -1;
  int redir = tests_redirect_stdout(tmpfd, &saved_out);
  TEST_ASSERT_MESSAGE(redir == 0, "Failed to redirect stdout");

  /* Do not use Unity asserts while stdout is redirected beyond this point. */
  bool err = false;
  const char *err_msg = NULL;

  /* Ensure pending==0 for stdout. */
  tests_reset_pending(STDOUT_FILENO);
  if (cache_round(STDOUT_FILENO, 0) != 0)
    { err = true; err_msg = "Pending not reset to 0"; }

  /* Small len: should early-return true and set pending to IO_BUFSIZE-1. */
  bool r_small = invalidate_cache(STDOUT_FILENO, (off_t)(IO_BUFSIZE - 1));
  off_t pend1 = cache_round(STDOUT_FILENO, 0);
  if (!r_small || pend1 != (off_t)(IO_BUFSIZE - 1))
    { err = true; err_msg = "Small len did not set pending as expected"; }

  /* EOF advisory with nocache_eof=true and non-zero pending. */
  o_nocache_eof = true;
  errno = 0;
  bool r_eof = invalidate_cache(STDOUT_FILENO, (off_t)0);
  int e_eof = errno;

  /* Clear pending back to 0 via direct rounding (no advisory). */
  (void) cache_round(STDOUT_FILENO, (off_t)1);
  if (cache_round(STDOUT_FILENO, 0) != 0)
    { err = true; err_msg = "Failed to clear pending to 0"; }

  /* Full-chunk advisory. */
  errno = 0;
  bool r_full = invalidate_cache(STDOUT_FILENO, (off_t)IO_BUFSIZE);
  int e_full = errno;

  /* Restore stdout before any Unity asserts. */
  tests_restore_stdout(saved_out);
  close(tmpfd);

  if (err)
    TEST_FAIL_MESSAGE(err_msg);

#if HAVE_POSIX_FADVISE
  TEST_ASSERT_TRUE_MESSAGE(r_eof, "EOF nocache advisory should succeed (posix_fadvise)");
  TEST_ASSERT_TRUE_MESSAGE(r_full, "Full-chunk advisory should succeed (posix_fadvise)");
  /* On success, coreutils sets errno to adv_ret (0). */
  TEST_ASSERT_EQUAL_INT_MESSAGE(0, e_eof, "errno not 0 after EOF advisory");
  TEST_ASSERT_EQUAL_INT_MESSAGE(0, e_full, "errno not 0 after full advisory");
#else
  TEST_ASSERT_FALSE_MESSAGE(r_eof, "EOF nocache advisory should fail without posix_fadvise");
  TEST_ASSERT_FALSE_MESSAGE(r_full, "Full-chunk advisory should fail without posix_fadvise");
  TEST_ASSERT_EQUAL_INT_MESSAGE(ENOTSUP, e_eof, "errno should be ENOTSUP without posix_fadvise (EOF)");
  TEST_ASSERT_EQUAL_INT_MESSAGE(ENOTSUP, e_full, "errno should be ENOTSUP without posix_fadvise (full)");
#endif
}

/* 4) stdin not seekable: expect false and errno=ESPIPE when len yields clen>0. */
void test_invalidate_cache_stdin_not_seekable(void)
{
  tests_reset_pending(STDIN_FILENO);
  input_seekable = false;
  errno = 0;
  bool ret = invalidate_cache(STDIN_FILENO, (off_t)IO_BUFSIZE);
  int e = errno;
  TEST_ASSERT_FALSE(ret);
  TEST_ASSERT_EQUAL_INT(ESPIPE, e);
}

int main(void)
{
  UNITY_BEGIN();
  RUN_TEST(test_invalidate_cache_stdin_small_len_no_advise);
  RUN_TEST(test_invalidate_cache_stdout_noop_eof_when_nocache_eof_false);
  RUN_TEST(test_invalidate_cache_stdout_eof_pending_and_full_chunk);
  RUN_TEST(test_invalidate_cache_stdin_not_seekable);
  return UNITY_END();
}