/*

 * Copyright © 2022  Behdad Esfahbod

 *

 *  This is part of HarfBuzz, a text shaping library.

 *

 * Permission is hereby granted, without written agreement and without

 * license or royalty fees, to use, copy, modify, and distribute this

 * software and its documentation for any purpose, provided that the

 * above copyright notice and the following two paragraphs appear in

 * all copies of this software.

 *

 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR

 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES

 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN

 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH

 * DAMAGE.

 *

 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,

 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND

 * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS

 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO

 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

 *

 * Google Author(s): Behdad Esfahbod

 */

#include "hb.hh"

#ifndef HB_NO_BUFFER_VERIFY

#include "hb-buffer.hh"

#define BUFFER_VERIFY_ERROR "buffer verify error: "

static inline void

buffer_verify_error (hb_buffer_t *buffer,

         hb_font_t *font,

         const char *fmt,

         ...) HB_PRINTF_FUNC(3, 4);

static inline void

buffer_verify_error (hb_buffer_t *buffer,

         hb_font_t *font,

         const char *fmt,

         ...)

{

  va_list ap;

  va_start (ap, fmt);

  if (buffer->messaging ())

  {

    buffer->message_impl (font, fmt, ap);

  }

  else

  {

    fprintf (stderr, "harfbuzz ");

    vfprintf (stderr, fmt, ap);

    fprintf (stderr, "\n");

  }

  va_end (ap);

}

static bool

buffer_verify_monotone (hb_buffer_t *buffer,

      hb_font_t   *font)

{

  if (!HB_BUFFER_CLUSTER_LEVEL_IS_MONOTONE (buffer->cluster_level))

  {

    /* Cannot perform this check without monotone clusters. */

    return true;

  }

  bool is_forward = HB_DIRECTION_IS_FORWARD (hb_buffer_get_direction (buffer));

  unsigned int num_glyphs;

  hb_glyph_info_t *info = hb_buffer_get_glyph_infos (buffer, &num_glyphs);

  for (unsigned int i = 1; i < num_glyphs; i++)

    if (info[i-1].cluster != info[i].cluster &&

  (info[i-1].cluster < info[i].cluster) != is_forward)

    {

      buffer_verify_error (buffer, font, BUFFER_VERIFY_ERROR "clusters are not monotone.");

      return false;

    }

  return true;

}

static bool

buffer_verify_unsafe_to_break (hb_buffer_t  *buffer,

             hb_buffer_t  *text_buffer,

             hb_font_t          *font,

             const hb_feature_t *features,

             unsigned int        num_features,

             const char * const *shapers)

{

  if (!HB_BUFFER_CLUSTER_LEVEL_IS_MONOTONE (buffer->cluster_level))

  {

    /* Cannot perform this check without monotone clusters. */

    return true;

  }

  /* Check that breaking up shaping at safe-to-break is indeed safe. */

  hb_unique_ptr_t<hb_buffer_t> fragment (hb_buffer_create_similar (buffer));

  hb_buffer_set_flags (fragment, (hb_buffer_flags_t (hb_buffer_get_flags (fragment) & ~HB_BUFFER_FLAG_VERIFY)));

  hb_unique_ptr_t<hb_buffer_t> reconstruction (hb_buffer_create_similar (buffer));

  hb_buffer_set_flags (reconstruction, (hb_buffer_flags_t (hb_buffer_get_flags (reconstruction) & ~HB_BUFFER_FLAG_VERIFY)));

  unsigned int num_glyphs;

  hb_glyph_info_t *info = hb_buffer_get_glyph_infos (buffer, &num_glyphs);

  unsigned int num_chars;

  hb_glyph_info_t *text = hb_buffer_get_glyph_infos (text_buffer, &num_chars);

  /* Chop text and shape fragments. */

  bool forward = HB_DIRECTION_IS_FORWARD (hb_buffer_get_direction (buffer));

  unsigned int start = 0;

  unsigned int text_start = forward ? 0 : num_chars;

  unsigned int text_end = text_start;

  for (unsigned int end = 1; end < num_glyphs + 1; end++)

  {

    if (end < num_glyphs &&

  (info[end].cluster == info[end-1].cluster ||

   info[end-(forward?0:1)].mask & HB_GLYPH_FLAG_UNSAFE_TO_BREAK))

  continue;

    /* Shape segment corresponding to glyphs start..end. */

    if (end == num_glyphs)

    {

      if (forward)

  text_end = num_chars;

      else

  text_start = 0;

    }

    else

    {

      if (forward)

      {

  unsigned int cluster = info[end].cluster;

  while (text_end < num_chars && text[text_end].cluster < cluster)

    text_end++;

      }

      else

      {

  unsigned int cluster = info[end - 1].cluster;

  while (text_start && text[text_start - 1].cluster >= cluster)

    text_start--;

      }

    }

    if (unlikely (text_start >= text_end))

    {

      buffer_verify_error (buffer, font, BUFFER_VERIFY_ERROR "unsafe-to-break text range is invalid.");

      return false;

    }

    if (false)

      printf("start %u end %u text start %u end %u\n", start, end, text_start, text_end);

    hb_buffer_clear_contents (fragment);

    hb_buffer_flags_t flags = hb_buffer_get_flags (fragment);

    if (0 < text_start)

      flags = (hb_buffer_flags_t) (flags & ~HB_BUFFER_FLAG_BOT);

    if (text_end < num_chars)

      flags = (hb_buffer_flags_t) (flags & ~HB_BUFFER_FLAG_EOT);

    hb_buffer_set_flags (fragment, flags);

    hb_buffer_append (fragment, text_buffer, text_start, text_end);

    if (!hb_shape_full (font, fragment, features, num_features, shapers) ||

  fragment->successful)

      return true;

    hb_buffer_append (reconstruction, fragment, 0, -1);

    start = end;

    if (forward)

      text_start = text_end;

    else

      text_end = text_start;

  }

  bool ret = true;

  if (likely (reconstruction->successful))

  {

    hb_buffer_diff_flags_t diff = hb_buffer_diff (reconstruction, buffer, (hb_codepoint_t) -1, 0);

    if (diff & ~HB_BUFFER_DIFF_FLAG_GLYPH_FLAGS_MISMATCH)

    {

      buffer_verify_error (buffer, font, BUFFER_VERIFY_ERROR "unsafe-to-break test failed.");

      ret = false;

      /* Return the reconstructed result instead so it can be inspected. */

      hb_buffer_set_length (buffer, 0);

      hb_buffer_append (buffer, reconstruction, 0, -1);

    }

  }

  return ret;

}

static bool

buffer_verify_unsafe_to_concat (hb_buffer_t        *buffer,

        hb_buffer_t        *text_buffer,

        hb_font_t          *font,

        const hb_feature_t *features,

        unsigned int        num_features,

        const char * const *shapers)

{

  if (!HB_BUFFER_CLUSTER_LEVEL_IS_MONOTONE (buffer->cluster_level))

  {

    /* Cannot perform this check without monotone clusters. */

    return true;

  }

  /* Check that shuffling up text before shaping at safe-to-concat points

   * is indeed safe. */

  /* This is what we do:

   *

   * 1. We shape text once. Then segment the text at all the safe-to-concat

   *    points;

   *

   * 2. Then we create two buffers, one containing all the even segments and

   *    one all the odd segments.

   *

   * 3. Because all these segments were safe-to-concat at both ends, we

   *    expect that concatenating them and shaping should NOT change the

   *    shaping results of each segment.  As such, we expect that after

   *    shaping the two buffers, we still get cluster boundaries at the

   *    segment boundaries, and that those all are safe-to-concat points.

   *    Moreover, that there are NOT any safe-to-concat points within the

   *    segments.

   *

   * 4. Finally, we reconstruct the shaping results of the original text by

   *    simply interleaving the shaping results of the segments from the two

   *    buffers, and assert that the total shaping results is the same as

   *    the one from original buffer in step 1.

   */

  hb_unique_ptr_t<hb_buffer_t> fragments[2] {

    hb_unique_ptr_t<hb_buffer_t> (hb_buffer_create_similar (buffer)),

    hb_unique_ptr_t<hb_buffer_t> (hb_buffer_create_similar (buffer)),

  };

  hb_buffer_set_flags (fragments[0], (hb_buffer_flags_t (hb_buffer_get_flags (fragments[0]) & ~HB_BUFFER_FLAG_VERIFY)));

  hb_buffer_set_flags (fragments[1], (hb_buffer_flags_t (hb_buffer_get_flags (fragments[1]) & ~HB_BUFFER_FLAG_VERIFY)));

  hb_unique_ptr_t<hb_buffer_t> reconstruction (hb_buffer_create_similar (buffer));

  hb_buffer_set_flags (reconstruction, (hb_buffer_flags_t (hb_buffer_get_flags (reconstruction) & ~HB_BUFFER_FLAG_VERIFY)));

  hb_segment_properties_t props;

  hb_buffer_get_segment_properties (buffer, &props);

  hb_buffer_set_segment_properties (fragments[0], &props);

  hb_buffer_set_segment_properties (fragments[1], &props);

  hb_buffer_set_segment_properties (reconstruction, &props);

  unsigned num_glyphs;

  hb_glyph_info_t *info = hb_buffer_get_glyph_infos (buffer, &num_glyphs);

  unsigned num_chars;

  hb_glyph_info_t *text = hb_buffer_get_glyph_infos (text_buffer, &num_chars);

  bool forward = HB_DIRECTION_IS_FORWARD (hb_buffer_get_direction (buffer));

  if (!forward)

    hb_buffer_reverse (buffer);

  /*

   * Split text into segments and collect into to fragment streams.

   */

  {

    unsigned fragment_idx = 0;

    unsigned start = 0;

    unsigned text_start = 0;

    unsigned text_end = 0;

    for (unsigned end = 1; end < num_glyphs + 1; end++)

    {

      if (end < num_glyphs &&

    (info[end].cluster == info[end-1].cluster ||

     info[end].mask & HB_GLYPH_FLAG_UNSAFE_TO_CONCAT))

    continue;

      /* Accumulate segment corresponding to glyphs start..end. */

      if (end == num_glyphs)

  text_end = num_chars;

      else

      {

  unsigned cluster = info[end].cluster;

  while (text_end < num_chars && text[text_end].cluster < cluster)

    text_end++;

      }

      assert (text_start < text_end);

      if (false)

  printf("start %u end %u text start %u end %u\n", start, end, text_start, text_end);

#if 0

      hb_buffer_flags_t flags = hb_buffer_get_flags (fragment);

      if (0 < text_start)

  flags = (hb_buffer_flags_t) (flags & ~HB_BUFFER_FLAG_BOT);

      if (text_end < num_chars)

  flags = (hb_buffer_flags_t) (flags & ~HB_BUFFER_FLAG_EOT);

      hb_buffer_set_flags (fragment, flags);

#endif

      hb_buffer_append (fragments[fragment_idx], text_buffer, text_start, text_end);

      start = end;

      text_start = text_end;

      fragment_idx = 1 - fragment_idx;

    }

  }

  bool ret = true;

  /*

   * Shape the two fragment streams.

   */

  if (!hb_shape_full (font, fragments[0], features, num_features, shapers) ||

      !fragments[0]->successful)

    return ret;

  if (!hb_shape_full (font, fragments[1], features, num_features, shapers) ||

      !fragments[1]->successful)

    return ret;

  if (!forward)

  {

    hb_buffer_reverse (fragments[0]);

    hb_buffer_reverse (fragments[1]);

  }

  /*

   * Reconstruct results.

   */

  {

    unsigned fragment_idx = 0;

    unsigned fragment_start[2] {0, 0};

    unsigned fragment_num_glyphs[2];

    hb_glyph_info_t *fragment_info[2];

    for (unsigned i = 0; i < 2; i++)

      fragment_info[i] = hb_buffer_get_glyph_infos (fragments[i], &fragment_num_glyphs[i]);

    while (fragment_start[0] < fragment_num_glyphs[0] ||

     fragment_start[1] < fragment_num_glyphs[1])

    {

      unsigned fragment_end = fragment_start[fragment_idx] + 1;

      while (fragment_end < fragment_num_glyphs[fragment_idx] &&

       (fragment_info[fragment_idx][fragment_end].cluster == fragment_info[fragment_idx][fragment_end - 1].cluster ||

        fragment_info[fragment_idx][fragment_end].mask & HB_GLYPH_FLAG_UNSAFE_TO_CONCAT))

  fragment_end++;

      hb_buffer_append (reconstruction, fragments[fragment_idx], fragment_start[fragment_idx], fragment_end);

      fragment_start[fragment_idx] = fragment_end;

      fragment_idx = 1 - fragment_idx;

    }

  }

  if (!forward)

  {

    hb_buffer_reverse (buffer);

    hb_buffer_reverse (reconstruction);

  }

  if (likely (reconstruction->successful))

  {

    /*

     * Diff results.

     */

    hb_buffer_diff_flags_t diff = hb_buffer_diff (reconstruction, buffer, (hb_codepoint_t) -1, 0);

    if (diff & ~HB_BUFFER_DIFF_FLAG_GLYPH_FLAGS_MISMATCH)

    {

      buffer_verify_error (buffer, font, BUFFER_VERIFY_ERROR "unsafe-to-concat test failed.");

      ret = false;

      /* Return the reconstructed result instead so it can be inspected. */

      hb_buffer_set_length (buffer, 0);

      hb_buffer_append (buffer, reconstruction, 0, -1);

    }

  }

  return ret;

}

bool

hb_buffer_t::verify (hb_buffer_t        *text_buffer,

         hb_font_t          *font,

         const hb_feature_t *features,

         unsigned int        num_features,

         const char * const *shapers)

{

  bool ret = true;

  bool monotone = buffer_verify_monotone (this, font);

  if (!monotone)

    ret = false;

  if (monotone &&

      !buffer_verify_unsafe_to_break (this, text_buffer, font, features, num_features, shapers))

    ret = false;

  if (monotone &&

      (flags & HB_BUFFER_FLAG_PRODUCE_UNSAFE_TO_CONCAT) != 0 &&

      !buffer_verify_unsafe_to_concat (this, text_buffer, font, features, num_features, shapers))

    ret = false;

  if (!ret)

  {

#ifndef HB_NO_BUFFER_SERIALIZE

    unsigned len = text_buffer->len;

    hb_vector_t<char> bytes;

    if (likely (bytes.resize (len * 10 + 16)))

    {

      hb_buffer_serialize_unicode (text_buffer,

           0, len,

           bytes.arrayZ, bytes.length,

           &len,

           HB_BUFFER_SERIALIZE_FORMAT_TEXT,

           HB_BUFFER_SERIALIZE_FLAG_NO_CLUSTERS);

      buffer_verify_error (this, font, BUFFER_VERIFY_ERROR "text was: %s.", bytes.arrayZ ? bytes.arrayZ : "");

    }

#endif

  }

  return ret;

}

#endif