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

/* The test file is included directly into the same translation unit as the
   coreutils cat implementation, so we can access its internal static symbols:
   - infile
   - input_desc
   - newlines2
   - pending_cr
   - line_buf, line_num_print, line_num_start, line_num_end
   - cat(...)
*/

static const char line_buf_init_template[] = {
  ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ',
  ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', '0',
  '\t', '\0'
};

/* Helper to reset global numbering buffer and pointers to their initial state. */
static void reset_line_numbering_state(void) {
  /* line_buf has size LINE_COUNTER_BUF_LEN in the program. */
  memcpy(line_buf, line_buf_init_template, sizeof(line_buf_init_template));
  line_num_print = line_buf + LINE_COUNTER_BUF_LEN - 8;
  line_num_start = line_buf + LINE_COUNTER_BUF_LEN - 3;
  line_num_end = line_buf + LINE_COUNTER_BUF_LEN - 3;
}

/* Helper: run cat() with given input and flags, capturing stdout into a malloc'd buffer.
   Returns output buffer (NUL-terminated for convenience) and sets *out_len.
   On error, returns NULL and sets *out_len = 0.
   This helper ensures stdout is restored before returning (to satisfy Unity rules). */
static char* run_cat_and_capture(const unsigned char *input, size_t input_len,
                                 idx_t insize, idx_t outsize,
                                 bool show_nonprinting, bool show_tabs,
                                 bool number, bool number_nonblank,
                                 bool show_ends, bool squeeze_blank,
                                 size_t *out_len)
{
  *out_len = 0;
  int inpipe[2];
  if (pipe(inpipe) != 0) {
    return NULL;
  }

  /* Write input and close writer to signal EOF. */
  ssize_t wr = write(inpipe[1], input, input_len);
  if (wr < 0 || (size_t)wr != input_len) {
    close(inpipe[0]);
    close(inpipe[1]);
    return NULL;
  }
  close(inpipe[1]);

  /* Redirect stdout to capture output. */
  int outpipe[2];
  if (pipe(outpipe) != 0) {
    close(inpipe[0]);
    return NULL;
  }

  int saved_stdout = dup(STDOUT_FILENO);
  if (saved_stdout < 0) {
    close(inpipe[0]);
    close(outpipe[0]);
    close(outpipe[1]);
    return NULL;
  }
  if (dup2(outpipe[1], STDOUT_FILENO) < 0) {
    close(inpipe[0]);
    close(outpipe[0]);
    close(outpipe[1]);
    close(saved_stdout);
    return NULL;
  }
  close(outpipe[1]); /* stdout now refers to this writer; close the extra fd */

  /* Set globals required by cat(). */
  infile = "test-input";
  input_desc = inpipe[0];

  /* Prepare buffers: inbuf needs +1 for sentinel; outbuf big enough (we use outsize*4 + 1024) */
  idx_t inbuf_len = insize + 1;
  if (inbuf_len < 2) inbuf_len = 2; /* ensure minimal space for sentinel */
  char *inbuf = (char *)malloc((size_t)inbuf_len);
  if (!inbuf) {
    /* Restore stdout before returning. */
    dup2(saved_stdout, STDOUT_FILENO);
    close(saved_stdout);
    close(inpipe[0]);
    close(outpipe[0]);
    return NULL;
  }

  idx_t outbuf_len = outsize * 4 + 1024;
  if (outbuf_len < outsize + 16) outbuf_len = outsize + 16;
  char *outbuf = (char *)malloc((size_t)outbuf_len);
  if (!outbuf) {
    dup2(saved_stdout, STDOUT_FILENO);
    close(saved_stdout);
    close(inpipe[0]);
    close(outpipe[0]);
    free(inbuf);
    return NULL;
  }

  /* Call the function under test. */
  bool ok = cat(inbuf, insize, outbuf, outsize,
                show_nonprinting, show_tabs, number, number_nonblank,
                show_ends, squeeze_blank);

  /* Close input read end now that cat returned. */
  close(inpipe[0]);

  /* Restore stdout before doing any assertions or reading result. */
  dup2(saved_stdout, STDOUT_FILENO);
  close(saved_stdout);

  /* Collect output. */
  char *result = NULL;
  size_t cap = 0;
  for (;;) {
    char buf[4096];
    ssize_t r = read(outpipe[0], buf, sizeof buf);
    if (r < 0) {
      free(inbuf);
      free(outbuf);
      close(outpipe[0]);
      free(result);
      return NULL;
    }
    if (r == 0) break;
    if (*out_len + (size_t)r + 1 > cap) {
      size_t new_cap = (*out_len + (size_t)r + 1) * 2;
      char *tmp = (char *)realloc(result, new_cap);
      if (!tmp) {
        free(inbuf);
        free(outbuf);
        close(outpipe[0]);
        free(result);
        return NULL;
      }
      result = tmp;
      cap = new_cap;
    }
    memcpy(result + *out_len, buf, (size_t)r);
    *out_len += (size_t)r;
  }
  close(outpipe[0]);

  /* NUL-terminate for convenience; the data is textual in our tests. */
  if (result) result[*out_len] = '\0';

  free(inbuf);
  free(outbuf);

  /* If the function indicated failure, treat as error (but we've already restored stdout). */
  if (!ok) {
    free(result);
    *out_len = 0;
    return NULL;
  }

  return result;
}

void setUp(void) {
  /* Reset persistent global state that cat() uses across invocations. */
  newlines2 = 0;
  pending_cr = false;
  reset_line_numbering_state();
  /* Provide a default infile name for error reporting, though errors not expected. */
  infile = "test-input";
}

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

/* Helper to format numbering prefix exactly like coreutils cat: width 6, then a tab. */
static void fmt_num_prefix(int n, char *dst, size_t dstlen) {
  /* Enough room for 6 digits + tab + NUL */
  snprintf(dst, dstlen, "%6d\t", n);
}

/* Test 1: Basic pass-through with no options. */
void test_cat_basic_passthrough(void) {
  const char *in = "Hello\tWorld\nSecond line\n";
  size_t out_len = 0;
  char *out = run_cat_and_capture((const unsigned char *)in, strlen(in),
                                  (idx_t)64, (idx_t)4096,
                                  false, false, false, false, false, false, &out_len);
  TEST_ASSERT_NOT_NULL(out);
  TEST_ASSERT_EQUAL_STRING(in, out);
  free(out);
}

/* Test 2: Show tabs (-T). */
void test_cat_show_tabs(void) {
  const char *in = "a\tb\n\t\n";
  const char *expected = "a^Ib\n^I\n";
  size_t out_len = 0;
  char *out = run_cat_and_capture((const unsigned char *)in, strlen(in),
                                  (idx_t)64, (idx_t)4096,
                                  false, true, false, false, false, false, &out_len);
  TEST_ASSERT_NOT_NULL(out);
  TEST_ASSERT_EQUAL_STRING(expected, out);
  free(out);
}

/* Test 3: Show ends (-E) basic. */
void test_cat_show_ends_basic(void) {
  const char *in = "line1\n\nline2\n";
  const char *expected = "line1$\n$\nline2$\n";
  size_t out_len = 0;
  char *out = run_cat_and_capture((const unsigned char *)in, strlen(in),
                                  (idx_t)64, (idx_t)4096,
                                  false, false, false, false, true, false, &out_len);
  TEST_ASSERT_NOT_NULL(out);
  TEST_ASSERT_EQUAL_STRING(expected, out);
  free(out);
}

/* Test 4: Show ends with CRLF where CR and LF are in the same input buffer. */
void test_cat_show_ends_crlf_in_buffer(void) {
  const unsigned char in[] = { 'A', '\r', '\n', 'B', '\n' };
  const char *expected = "A^M$\nB$\n";
  size_t out_len = 0;
  /* insize large enough to read all at once so CR and LF are in the same buffer */
  char *out = run_cat_and_capture(in, sizeof(in),
                                  (idx_t)64, (idx_t)4096,
                                  false, false, false, false, true, false, &out_len);
  TEST_ASSERT_NOT_NULL(out);
  TEST_ASSERT_EQUAL_STRING(expected, out);
  free(out);
}

/* Test 5: Show ends with CRLF split across input buffers (pending_cr path). */
void test_cat_show_ends_crlf_across_boundary(void) {
  const unsigned char in[] = { 'A', '\r', '\n' };
  const char *expected = "A^M$\n";
  size_t out_len = 0;
  /* Small insize ensures first read sees 'A\r' and sentinel, then next read sees '\n'. */
  char *out = run_cat_and_capture(in, sizeof(in),
                                  (idx_t)2, (idx_t)4096,
                                  false, false, false, false, true, false, &out_len);
  TEST_ASSERT_NOT_NULL(out);
  TEST_ASSERT_EQUAL_STRING(expected, out);
  free(out);
}

/* Test 6: Number all lines (-n). */
void test_cat_number_all_lines(void) {
  const char *in = "a\n\nb\n";
  char expected[256];
  char p1[16], p2[16], p3[16];
  fmt_num_prefix(1, p1, sizeof p1);
  fmt_num_prefix(2, p2, sizeof p2);
  fmt_num_prefix(3, p3, sizeof p3);
  snprintf(expected, sizeof expected, "%s%s\n%s\n%s%s\n", p1, "a", p2, p3, "b");
  size_t out_len = 0;
  char *out = run_cat_and_capture((const unsigned char *)in, strlen(in),
                                  (idx_t)64, (idx_t)4096,
                                  false, false, true, false, false, false, &out_len);
  TEST_ASSERT_NOT_NULL(out);
  TEST_ASSERT_EQUAL_STRING(expected, out);
  free(out);
}

/* Test 7: Number nonblank (-b) with -n present: only non-empty lines numbered. */
void test_cat_number_nonblank(void) {
  const char *in = "a\n\n\nb\n\n";
  char expected[256];
  char p1[16], p2[16];
  fmt_num_prefix(1, p1, sizeof p1);
  fmt_num_prefix(2, p2, sizeof p2);
  /* Expect:
     <p1>a\n
     \n
     \n
     <p2>b\n
     \n
  */
  snprintf(expected, sizeof expected, "%s%s\n\n\n%s%s\n\n", p1, "a", p2, "b");
  size_t out_len = 0;
  char *out = run_cat_and_capture((const unsigned char *)in, strlen(in),
                                  (idx_t)64, (idx_t)4096,
                                  false, false, true, true, false, false, &out_len);
  TEST_ASSERT_NOT_NULL(out);
  TEST_ASSERT_EQUAL_STRING(expected, out);
  free(out);
}

/* Test 8: Squeeze blank (-s) collapses multiple empty lines into one. */
void test_cat_squeeze_blank(void) {
  const char *in = "a\n\n\n\nb\n\n";
  const char *expected = "a\n\nb\n\n";
  size_t out_len = 0;
  char *out = run_cat_and_capture((const unsigned char *)in, strlen(in),
                                  (idx_t)64, (idx_t)4096,
                                  false, false, false, false, false, true, &out_len);
  TEST_ASSERT_NOT_NULL(out);
  TEST_ASSERT_EQUAL_STRING(expected, out);
  free(out);
}

/* Test 9: Show nonprinting (-v) for control, DEL, and high-bit chars; tabs preserved when -T not set. */
void test_cat_show_nonprinting_basic(void) {
  unsigned char in[] = { 0x01, 0x09, 0x7F, 0xC8, '\n' }; /* SOH, TAB, DEL, 200, NL */
  const char *expected = "^A\t^?M-H\n";
  size_t out_len = 0;
  char *out = run_cat_and_capture(in, sizeof(in),
                                  (idx_t)64, (idx_t)4096,
                                  true, false, false, false, false, false, &out_len);
  TEST_ASSERT_NOT_NULL(out);
  TEST_ASSERT_EQUAL_STRING(expected, out);
  free(out);
}

/* Test 10: Show nonprinting (-v) with show tabs (-T): tabs rendered as ^I. */
void test_cat_show_nonprinting_with_tabs(void) {
  const char *in = "\t\n";
  const char *expected = "^I\n";
  size_t out_len = 0;
  char *out = run_cat_and_capture((const unsigned char *)in, strlen(in),
                                  (idx_t)64, (idx_t)4096,
                                  true, true, false, false, false, false, &out_len);
  TEST_ASSERT_NOT_NULL(out);
  TEST_ASSERT_EQUAL_STRING(expected, out);
  free(out);
}

int main(void) {
  UNITY_BEGIN();
  RUN_TEST(test_cat_basic_passthrough);
  RUN_TEST(test_cat_show_tabs);
  RUN_TEST(test_cat_show_ends_basic);
  RUN_TEST(test_cat_show_ends_crlf_in_buffer);
  RUN_TEST(test_cat_show_ends_crlf_across_boundary);
  RUN_TEST(test_cat_number_all_lines);
  RUN_TEST(test_cat_number_nonblank);
  RUN_TEST(test_cat_squeeze_blank);
  RUN_TEST(test_cat_show_nonprinting_basic);
  RUN_TEST(test_cat_show_nonprinting_with_tabs);
  return UNITY_END();
}