/* -*- c-basic-offset: 2 -*- */
/*
  Copyright(C) 2018 Brazil
  Copyright(C) 2018 Kouhei Sutou <kou@clear-code.com>

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License version 2.1 as published by the Free Software Foundation.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include "grn.h"
#include "grn_token_cursor.h"

#include "grn_pat.h"
#include "grn_str.h"

typedef struct {
  uint64_t offset;
  uint32_t length;
  grn_bool have_overlap;
  uint8_t first_character_length;
} grn_highlighter_location;

static int
grn_highlighter_location_compare(const void *data1, const void *data2)
{
  const grn_highlighter_location *location1 = data1;
  const grn_highlighter_location *location2 = data2;

  if (location1->offset == location2->offset) {
    return location1->length - location2->length;
  } else {
    return location1->offset - location2->offset;
  }
}

/*
 * TODO:
 *   * Support non HTML mode.
 *   * Support custom tag.
 */
struct _grn_highlighter {
  grn_obj_header header;

  grn_bool is_html_mode;
  grn_bool need_prepared;
  grn_obj raw_keywords;

  struct {
    const char *open;
    size_t open_length;
    const char *close;
    size_t close_length;
  } tag;

  /* For lexicon mode */
  struct {
    grn_obj *object;
    grn_encoding encoding;
    grn_obj lazy_keywords;
    grn_obj lazy_keyword_ids;
    grn_obj *token_id_chunks;
    grn_obj token_id_chunk_ids;
    grn_obj token_id_chunk;
    grn_obj token_ids;
    grn_obj token_locations;
    grn_obj candidates;
  } lexicon;

  /* For patricia trie mode */
  struct {
    grn_obj *keywords;
    grn_obj keyword_ids;
  } pat;
};

grn_highlighter *
grn_highlighter_open(grn_ctx *ctx)
{
  grn_highlighter *highlighter;

  GRN_API_ENTER;

  highlighter = GRN_MALLOCN(grn_highlighter, 1);
  if (!highlighter) {
    char errbuf[GRN_CTX_MSGSIZE];
    grn_strcpy(errbuf, GRN_CTX_MSGSIZE, ctx->errbuf);
    ERR(ctx->rc,
        "[highlighter][open] failed to allocate memory: %s",
        errbuf);
    GRN_API_RETURN(NULL);
  }

  highlighter->header.type = GRN_HIGHLIGHTER;
  highlighter->header.impl_flags = 0;
  highlighter->header.flags = 0;
  highlighter->header.domain = GRN_ID_NIL;

  highlighter->is_html_mode = GRN_TRUE;
  highlighter->need_prepared = GRN_TRUE;
  GRN_TEXT_INIT(&(highlighter->raw_keywords), GRN_OBJ_VECTOR);

  highlighter->tag.open = "<span class=\"keyword\">";
  highlighter->tag.open_length = strlen(highlighter->tag.open);
  highlighter->tag.close = "</span>";
  highlighter->tag.close_length = strlen(highlighter->tag.close);

  highlighter->lexicon.object = NULL;
  highlighter->lexicon.encoding = GRN_ENC_NONE;
  GRN_TEXT_INIT(&(highlighter->lexicon.lazy_keywords), GRN_OBJ_VECTOR);
  GRN_RECORD_INIT(&(highlighter->lexicon.lazy_keyword_ids),
                  GRN_OBJ_VECTOR,
                  GRN_ID_NIL);
  highlighter->lexicon.token_id_chunks = NULL;
  GRN_RECORD_INIT(&(highlighter->lexicon.token_id_chunk_ids),
                  GRN_OBJ_VECTOR,
                  GRN_ID_NIL);
  GRN_TEXT_INIT(&(highlighter->lexicon.token_id_chunk), 0);
  GRN_RECORD_INIT(&(highlighter->lexicon.token_ids), GRN_OBJ_VECTOR, GRN_ID_NIL);
  GRN_TEXT_INIT(&(highlighter->lexicon.token_locations), 0);
  GRN_TEXT_INIT(&(highlighter->lexicon.candidates), 0);

  highlighter->pat.keywords = NULL;
  GRN_RECORD_INIT(&(highlighter->pat.keyword_ids), GRN_OBJ_VECTOR, GRN_ID_NIL);

  GRN_API_RETURN(highlighter);
}

grn_rc
grn_highlighter_close(grn_ctx *ctx,
                      grn_highlighter *highlighter)
{
  GRN_API_ENTER;

  if (!highlighter) {
    GRN_API_RETURN(ctx->rc);
  }

  GRN_OBJ_FIN(ctx, &(highlighter->pat.keyword_ids));
  if (highlighter->pat.keywords) {
    grn_obj_close(ctx, highlighter->pat.keywords);
  }

  GRN_OBJ_FIN(ctx, &(highlighter->lexicon.lazy_keywords));
  GRN_OBJ_FIN(ctx, &(highlighter->lexicon.lazy_keyword_ids));
  if (highlighter->lexicon.token_id_chunks) {
    grn_obj_close(ctx, highlighter->lexicon.token_id_chunks);
  }
  GRN_OBJ_FIN(ctx, &(highlighter->lexicon.token_id_chunk_ids));
  GRN_OBJ_FIN(ctx, &(highlighter->lexicon.token_id_chunk));
  GRN_OBJ_FIN(ctx, &(highlighter->lexicon.candidates));
  GRN_OBJ_FIN(ctx, &(highlighter->lexicon.token_locations));
  GRN_OBJ_FIN(ctx, &(highlighter->lexicon.token_ids));

  GRN_OBJ_FIN(ctx, &(highlighter->raw_keywords));
  GRN_FREE(highlighter);

  GRN_API_RETURN(ctx->rc);
}

static void
grn_highlighter_remove_unused_ids(grn_ctx *ctx,
                                  grn_obj *table,
                                  grn_obj *added_ids,
                                  const char *tag)
{
  grn_table_cursor *cursor;
  size_t n;
  grn_id id;

  cursor = grn_table_cursor_open(ctx,
                                 table,
                                 NULL, 0,
                                 NULL, 0,
                                 0, -1, 0);
  if (!cursor) {
    grn_rc rc = ctx->rc;
    char errbuf[GRN_CTX_MSGSIZE];
    if (rc == GRN_SUCCESS) {
      rc = GRN_UNKNOWN_ERROR;
    }
    grn_strcpy(errbuf, GRN_CTX_MSGSIZE, ctx->errbuf);
    ERR(rc,
        "[highlighter][prepare]%s "
        "failed to create a cursor for internal patricia trie: %s",
        tag,
        errbuf);
    return;
  }

  n = GRN_BULK_VSIZE(added_ids) / sizeof(grn_id);
  while ((id = grn_table_cursor_next(ctx, cursor)) != GRN_ID_NIL) {
    size_t i;
    grn_bool using = GRN_FALSE;

    for (i = 0; i < n; i++) {
      if (id == GRN_RECORD_VALUE_AT(added_ids, i)) {
        using = GRN_TRUE;
        break;
      }
    }

    if (using) {
      continue;
    }

    grn_table_cursor_delete(ctx, cursor);
  }
  grn_table_cursor_close(ctx, cursor);
}

static void
grn_highlighter_prepare_lexicon(grn_ctx *ctx,
                                grn_highlighter *highlighter)
{
  grn_bool have_token_id_chunks = GRN_FALSE;
  grn_obj *lazy_keywords = &(highlighter->lexicon.lazy_keywords);
  grn_id lexicon_id;
  grn_obj *token_id_chunk_ids = &(highlighter->lexicon.token_id_chunk_ids);
  size_t i, n_keywords;
  grn_obj *token_id_chunk = &(highlighter->lexicon.token_id_chunk);

  GRN_BULK_REWIND(lazy_keywords);

  lexicon_id = grn_obj_id(ctx, highlighter->lexicon.object);
  highlighter->lexicon.lazy_keyword_ids.header.domain = lexicon_id;
  highlighter->lexicon.token_ids.header.domain = lexicon_id;

  grn_table_get_info(ctx,
                     highlighter->lexicon.object,
                     NULL,
                     &(highlighter->lexicon.encoding),
                     NULL,
                     NULL,
                     NULL);

  if (highlighter->lexicon.token_id_chunks) {
    /* TODO: It may be better that we remove all existing records here
     * for many keywords case. */
    have_token_id_chunks =
      grn_table_size(ctx, highlighter->lexicon.token_id_chunks) > 0;
  } else {
    highlighter->lexicon.token_id_chunks =
      grn_table_create(ctx,
                       NULL, 0,
                       NULL,
                       GRN_OBJ_TABLE_PAT_KEY,
                       grn_ctx_at(ctx, GRN_DB_SHORT_TEXT),
                       NULL);
    if (!highlighter->lexicon.token_id_chunks) {
      grn_rc rc = ctx->rc;
      char errbuf[GRN_CTX_MSGSIZE];
      if (rc == GRN_SUCCESS) {
        rc = GRN_UNKNOWN_ERROR;
      }
      grn_strcpy(errbuf, GRN_CTX_MSGSIZE, ctx->errbuf);
      ERR(rc,
          "[highlighter][prepare][lexicon] "
          "failed to create an internal patricia trie: %s",
          errbuf);
      return;
    }
    token_id_chunk_ids->header.domain =
      grn_obj_id(ctx, highlighter->lexicon.token_id_chunks);
  }

  GRN_BULK_REWIND(token_id_chunk_ids);

  n_keywords = grn_vector_size(ctx, &(highlighter->raw_keywords));
  for (i = 0; i < n_keywords; i++) {
    const char *keyword;
    unsigned int keyword_length;
    grn_token_cursor *cursor;
    grn_id token_id;

    keyword_length = grn_vector_get_element(ctx,
                                            &(highlighter->raw_keywords),
                                            i,
                                            &keyword,
                                            NULL,
                                            NULL);
    cursor = grn_token_cursor_open(ctx,
                                   highlighter->lexicon.object,
                                   keyword,
                                   keyword_length,
                                   GRN_TOKENIZE_ADD,
                                   0);
    if (!cursor) {
      continue;
    }
    while (grn_token_cursor_next(ctx, cursor) != GRN_ID_NIL) {
    }
    grn_token_cursor_close(ctx, cursor);

    cursor = grn_token_cursor_open(ctx,
                                   highlighter->lexicon.object,
                                   keyword,
                                   keyword_length,
                                   GRN_TOKENIZE_GET,
                                   0);
    if (!cursor) {
      continue;
    }
    GRN_BULK_REWIND(token_id_chunk);
    while ((token_id = grn_token_cursor_next(ctx, cursor)) != GRN_ID_NIL) {
      grn_token *token;
      GRN_TEXT_PUT(ctx, token_id_chunk, &token_id, sizeof(grn_id));
      token = grn_token_cursor_get_token(ctx, cursor);
      if (grn_token_get_force_prefix_search(ctx, token) &&
          highlighter->lexicon.object->header.type != GRN_TABLE_HASH_KEY) {
        const char *data;
        size_t data_length;

        data = grn_token_get_data_raw(ctx, token, &data_length);
        grn_vector_add_element(ctx,
                               lazy_keywords,
                               data,
                               data_length,
                               0,
                               GRN_DB_TEXT);
      }
    }
    grn_token_cursor_close(ctx, cursor);

    {
      grn_id token_id_chunk_id;

      {
        grn_encoding encoding = ctx->encoding;
        /* token_id_chunk is a binary data */
        ctx->encoding = GRN_ENC_NONE;
        token_id_chunk_id = grn_table_add(ctx,
                                          highlighter->lexicon.token_id_chunks,
                                          GRN_TEXT_VALUE(token_id_chunk),
                                          GRN_TEXT_LEN(token_id_chunk),
                                          NULL);
        ctx->encoding = encoding;
      }
      if (!have_token_id_chunks) {
        continue;
      }
      if (token_id_chunk_id == GRN_ID_NIL) {
        continue;
      }
      GRN_RECORD_PUT(ctx, token_id_chunk_ids, token_id_chunk_id);
    }
  }

  if (have_token_id_chunks) {
    grn_highlighter_remove_unused_ids(ctx,
                                      highlighter->lexicon.token_id_chunks,
                                      token_id_chunk_ids,
                                      "[prepare][lexicon]");
  }
}

static void
grn_highlighter_prepare_patricia_trie(grn_ctx *ctx,
                                      grn_highlighter *highlighter)
{
  grn_bool have_keywords = GRN_FALSE;
  grn_obj *keyword_ids = &(highlighter->pat.keyword_ids);

  if (highlighter->pat.keywords) {
    /* TODO: It may be better that we remove all existing records here
     * for many keywords case. */
    have_keywords = grn_table_size(ctx, highlighter->pat.keywords) > 0;
  } else {
    highlighter->pat.keywords =
      grn_table_create(ctx,
                       NULL, 0,
                       NULL,
                       GRN_OBJ_TABLE_PAT_KEY,
                       grn_ctx_at(ctx, GRN_DB_SHORT_TEXT),
                       NULL);
    if (!highlighter->pat.keywords) {
      grn_rc rc = ctx->rc;
      char errbuf[GRN_CTX_MSGSIZE];
      if (rc == GRN_SUCCESS) {
        rc = GRN_UNKNOWN_ERROR;
      }
      grn_strcpy(errbuf, GRN_CTX_MSGSIZE, ctx->errbuf);
      ERR(rc,
          "[highlighter][prepare][no-lexicon] "
          "failed to create an internal patricia trie: %s",
          errbuf);
      return;
    }
    keyword_ids->header.domain = grn_obj_id(ctx, highlighter->pat.keywords);
  }

  GRN_BULK_REWIND(keyword_ids);

  grn_obj_set_info(ctx,
                   highlighter->pat.keywords,
                   GRN_INFO_NORMALIZER,
                   grn_ctx_get(ctx, "NormalizerAuto", -1));

  {
    unsigned int i, n;

    n = grn_vector_size(ctx, &(highlighter->raw_keywords));
    for (i = 0; i < n; i++) {
      const char *keyword;
      unsigned int keyword_size;
      grn_id id;

      keyword_size = grn_vector_get_element(ctx,
                                            &(highlighter->raw_keywords),
                                            i,
                                            &keyword,
                                            NULL,
                                            NULL);
      id = grn_table_add(ctx,
                         highlighter->pat.keywords,
                         keyword,
                         keyword_size,
                         NULL);
      if (!have_keywords) {
        continue;
      }
      if (id == GRN_ID_NIL) {
        continue;
      }
      GRN_RECORD_PUT(ctx, keyword_ids, id);
    }
  }

  if (have_keywords) {
    grn_highlighter_remove_unused_ids(ctx,
                                      highlighter->pat.keywords,
                                      keyword_ids,
                                      "[prepare][no-lexicon]");
  }
}

static void
grn_highlighter_prepare(grn_ctx *ctx,
                        grn_highlighter *highlighter)
{
  if (highlighter->lexicon.object) {
    grn_highlighter_prepare_lexicon(ctx, highlighter);
  } else {
    grn_highlighter_prepare_patricia_trie(ctx, highlighter);
  }
  highlighter->need_prepared = GRN_FALSE;
}

static grn_bool
grn_ids_is_included(grn_id *ids, size_t n_ids, grn_id id)
{
  size_t i;

  for (i = 0; i < n_ids; i++) {
    if (ids[i] == ids[0]) {
      return GRN_TRUE;
    }
  }

  return GRN_FALSE;
}

static void
grn_highlighter_log_location(grn_ctx *ctx,
                             grn_log_level level,
                             const char *tag,
                             grn_highlighter_location *location,
                             const char *text,
                             size_t text_length)
{
  if (!grn_logger_pass(ctx, level)) {
    return;
  }

  GRN_LOG(ctx,
          level,
          "%s[location] "
          "[%" GRN_FMT_INT64U "...%" GRN_FMT_INT64U "](%u)[%s] <%.*s>",
          tag,
          location->offset,
          location->offset + location->length,
          location->first_character_length,
          location->have_overlap ? "overlapped" : "not-overlapped",
          (int)location->length,
          text + location->offset);
}

static uint64_t
grn_highlighter_highlight_lexicon_flush(grn_ctx *ctx,
                                        grn_log_level log_level,
                                        const char *tag,
                                        grn_highlighter *highlighter,
                                        const char *text,
                                        size_t text_length,
                                        grn_obj *output,
                                        grn_highlighter_location *location,
                                        uint64_t offset)
{
  grn_highlighter_log_location(ctx, log_level, tag, location, text, text_length);
  if (location->offset > offset) {
    grn_text_escape_xml(ctx,
                        output,
                        text + offset,
                        location->offset - offset);
  }
  GRN_TEXT_PUT(ctx,
               output,
               highlighter->tag.open,
               highlighter->tag.open_length);
  grn_text_escape_xml(ctx,
                      output,
                      text + location->offset,
                      location->length);
  GRN_TEXT_PUT(ctx,
               output,
               highlighter->tag.close,
               highlighter->tag.close_length);
  return location->offset + location->length;
}

static void
grn_highlighter_highlight_lexicon(grn_ctx *ctx,
                                  grn_highlighter *highlighter,
                                  const char *text,
                                  size_t text_length,
                                  grn_obj *output)
{
  const char *tag = "[highlighter][highlight][lexicon]";
  grn_log_level log_level = GRN_LOG_DEBUG;
  grn_token_cursor *cursor;
  grn_obj *lazy_keyword_ids = &(highlighter->lexicon.lazy_keyword_ids);
  grn_obj *token_ids = &(highlighter->lexicon.token_ids);
  grn_obj *token_locations = &(highlighter->lexicon.token_locations);
  grn_obj *candidates = &(highlighter->lexicon.candidates);

  GRN_BULK_REWIND(lazy_keyword_ids);
  GRN_BULK_REWIND(token_ids);
  GRN_BULK_REWIND(token_locations);
  cursor = grn_token_cursor_open(ctx,
                                 highlighter->lexicon.object,
                                 text,
                                 text_length,
                                 GRN_TOKENIZE_ADD,
                                 0);
  if (!cursor) {
    char errbuf[GRN_CTX_MSGSIZE];
    grn_strcpy(errbuf, GRN_CTX_MSGSIZE, ctx->errbuf);
    ERR(ctx->rc,
        "%s failed to start tokenizing: %s",
        tag,
        errbuf);
    return;
  }

  GRN_LOG(ctx, log_level, "%s[tokenize][start]", tag);
  while (cursor->status == GRN_TOKEN_CURSOR_DOING) {
    grn_id token_id = grn_token_cursor_next(ctx, cursor);
    grn_highlighter_location location;
    grn_token *token;

    if (token_id == GRN_ID_NIL) {
      continue;
    }
    token = grn_token_cursor_get_token(ctx, cursor);
    GRN_RECORD_PUT(ctx, token_ids, token_id);
    location.offset = grn_token_get_source_offset(ctx, token);
    location.length = grn_token_get_source_length(ctx, token);
    location.first_character_length =
      grn_token_get_source_first_character_length(ctx, token);
    location.have_overlap = grn_token_have_overlap(ctx, token);
    GRN_TEXT_PUT(ctx, token_locations, &location, sizeof(location));
    grn_highlighter_log_location(ctx,
                                 log_level,
                                 tag,
                                 &location,
                                 text,
                                 text_length);
  }
  grn_token_cursor_close(ctx, cursor);
  GRN_LOG(ctx, log_level, "%s[tokenize][end]", tag);

  {
    grn_obj *lexicon = highlighter->lexicon.object;
    grn_obj *chunks = highlighter->lexicon.token_id_chunks;
    grn_obj *lazy_keywords = &(highlighter->lexicon.lazy_keywords);
    size_t i;
    size_t n_keywords;

    n_keywords = grn_vector_size(ctx, lazy_keywords);
    for (i = 0; i < n_keywords; i++) {
      const char *keyword;
      unsigned int keyword_length;

      keyword_length = grn_vector_get_element(ctx,
                                              lazy_keywords,
                                              i,
                                              &keyword,
                                              NULL,
                                              NULL);
      GRN_LOG(ctx,
              log_level,
              "%s[prefix-search][start] %" GRN_FMT_SIZE ":<%.*s>",
              tag,
              i,
              (int)keyword_length,
              keyword);
      GRN_TABLE_EACH_BEGIN_MIN(ctx,
                               lexicon,
                               cursor,
                               id,
                               keyword, keyword_length,
                               GRN_CURSOR_PREFIX) {
        int added = 0;

        {
          grn_encoding encoding = ctx->encoding;
          ctx->encoding = GRN_ENC_NONE;
          grn_table_add(ctx, chunks, &id, sizeof(grn_id), &added);
          ctx->encoding = encoding;
        }
        if (grn_logger_pass(ctx, GRN_LOG_DEBUG)) {
          void *key;
          int key_size;
          key_size = grn_table_cursor_get_key(ctx, cursor, &key);
          GRN_LOG(ctx,
                  log_level,
                  "%s[prefix-search][%s] %" GRN_FMT_SIZE ":<%.*s>:<%.*s>",
                  tag,
                  added ? "added" : "not-added",
                  i,
                  (int)keyword_length,
                  keyword,
                  key_size,
                  (const char *)key);
        }
        if (added) {
          GRN_RECORD_PUT(ctx, lazy_keyword_ids, id);
        }
      } GRN_TABLE_EACH_END(ctx, cursor);
      GRN_LOG(ctx,
              log_level,
              "%s[prefix-search][end] %" GRN_FMT_SIZE ":<%.*s>",
              tag,
              i,
              (int)keyword_length,
              keyword);
    }
  }

  GRN_BULK_REWIND(candidates);
  {
    grn_obj *lazy_keyword_ids = &(highlighter->lexicon.lazy_keyword_ids);
    grn_id *raw_lazy_keyword_ids;
    size_t n_lazy_keyword_ids;
    grn_pat *chunks = (grn_pat *)(highlighter->lexicon.token_id_chunks);
    size_t i;
    size_t n_token_ids = GRN_BULK_VSIZE(token_ids) / sizeof(grn_id);
    grn_id *raw_token_ids = (grn_id *)GRN_BULK_HEAD(token_ids);
    grn_highlighter_location *raw_token_locations =
      (grn_highlighter_location *)GRN_BULK_HEAD(token_locations);

    raw_lazy_keyword_ids = (grn_id *)GRN_BULK_HEAD(lazy_keyword_ids);
    n_lazy_keyword_ids = GRN_BULK_VSIZE(lazy_keyword_ids) / sizeof(grn_id);

    for (i = 0; i < n_token_ids; i++) {
      grn_id chunk_id;

      GRN_LOG(ctx,
              log_level,
              "%s[lcp-search][start] %" GRN_FMT_SIZE,
              tag,
              i);
      {
        grn_encoding encoding = ctx->encoding;
        /* token_id_chunk is a binary data */
        ctx->encoding = GRN_ENC_NONE;
        chunk_id = grn_pat_lcp_search(ctx,
                                      chunks,
                                      raw_token_ids + i,
                                      (n_token_ids - i) * sizeof(grn_id));
        ctx->encoding = encoding;
      }
      if (chunk_id == GRN_ID_NIL) {
        GRN_LOG(ctx,
                log_level,
                "%s[lcp-search][end][nonexistent] %" GRN_FMT_SIZE,
                tag,
                i);
        continue;
      }

      {
        grn_id *ids;
        uint32_t key_size;
        size_t j;
        size_t n_ids;
        grn_highlighter_location candidate;
        grn_highlighter_location *first = raw_token_locations + i;

        candidate.have_overlap = GRN_FALSE;
        candidate.first_character_length = 0;

        {
          grn_encoding encoding = ctx->encoding;
          ctx->encoding = GRN_ENC_NONE;
          ids = (grn_id *)_grn_pat_key(ctx, chunks, chunk_id, &key_size);
          ctx->encoding = encoding;
        }
        n_ids = key_size / sizeof(grn_id);
        candidate.offset = first->offset;
        if (n_ids == 1 &&
            grn_ids_is_included(raw_lazy_keyword_ids,
                                n_lazy_keyword_ids,
                                ids[0])) {
          candidate.length = first->first_character_length;
        } else if (first->have_overlap && n_ids > 1) {
          candidate.length = first->first_character_length;
        } else {
          candidate.length = first->length;
        }
        for (j = 1; j < n_ids; j++) {
          grn_highlighter_location *current = raw_token_locations + i + j;
          grn_highlighter_location *previous = current - 1;
          uint32_t current_length;
          uint32_t previous_length;
          if (current->have_overlap && j + 1 < n_ids) {
            current_length = current->first_character_length;
          } else {
            current_length = current->length;
          }
          if (previous->have_overlap && j + 1 < n_ids) {
            previous_length = previous->first_character_length;
          } else {
            previous_length = previous->length;
          }
          if (current->offset == previous->offset) {
            if (current_length > previous_length) {
              candidate.length += current_length - previous_length;
            }
          } else {
            candidate.length += current_length;
          }
        }
        GRN_TEXT_PUT(ctx, candidates, &candidate, sizeof(candidate));
        grn_highlighter_log_location(ctx,
                                     log_level,
                                     tag,
                                     &candidate,
                                     text,
                                     text_length);
        GRN_LOG(ctx,
                log_level,
                "%s[lcp-search][end] %" GRN_FMT_SIZE,
                tag,
                i);
        i += n_ids - 1;
      }
    }
  }

  {
    grn_obj *chunks = highlighter->lexicon.token_id_chunks;
    size_t i, n_ids;

    n_ids = GRN_BULK_VSIZE(lazy_keyword_ids) / sizeof(grn_id);
    for (i = 0; i < n_ids; i++) {
      grn_id id = GRN_RECORD_VALUE_AT(lazy_keyword_ids, i);
      grn_encoding encoding = ctx->encoding;
      ctx->encoding = GRN_ENC_NONE;
      grn_table_delete(ctx, chunks, &id, sizeof(grn_id));
      ctx->encoding = encoding;
    }
  }

  {
    size_t i;
    size_t n_candidates =
      GRN_BULK_VSIZE(candidates) / sizeof(grn_highlighter_location);
    grn_highlighter_location *raw_candidates =
      (grn_highlighter_location *)GRN_BULK_HEAD(candidates);

    GRN_LOG(ctx,
            log_level,
            "%s[highlight][start] %" GRN_FMT_SIZE,
            tag,
            n_candidates);
    if (n_candidates == 0) {
      grn_text_escape_xml(ctx, output, text, text_length);
    } else {
      grn_highlighter_location *previous = NULL;
      uint64_t offset = 0;

      qsort(raw_candidates,
            n_candidates,
            sizeof(grn_highlighter_location),
            grn_highlighter_location_compare);
      previous = raw_candidates;
      for (i = 1; i < n_candidates; i++) {
        grn_highlighter_location *current = raw_candidates + i;
        if (previous->offset + previous->length >= current->offset) {
          if (previous->offset + previous->length >
              current->offset + current->length) {
            current->length = previous->length;
          } else {
            current->length += current->offset - previous->offset;
          }
          current->offset = previous->offset;
          previous = current;
          continue;
        }
        if (current->offset > previous->offset) {
          offset = grn_highlighter_highlight_lexicon_flush(ctx,
                                                           log_level,
                                                           tag,
                                                           highlighter,
                                                           text,
                                                           text_length,
                                                           output,
                                                           previous,
                                                           offset);
        }
        previous = current;
      }
      offset = grn_highlighter_highlight_lexicon_flush(ctx,
                                                       log_level,
                                                       tag,
                                                       highlighter,
                                                       text,
                                                       text_length,
                                                       output,
                                                       previous,
                                                       offset);
      if (offset < text_length) {
        grn_text_escape_xml(ctx,
                            output,
                            text + offset,
                            text_length - offset);
      }
    }
    GRN_LOG(ctx,
            log_level,
            "%s[highlight][end] %" GRN_FMT_SIZE,
            tag,
            n_candidates);
  }
}

static void
grn_highlighter_highlight_patricia_trie(grn_ctx *ctx,
                                        grn_highlighter *highlighter,
                                        const char *text,
                                        size_t text_length,
                                        grn_obj *output)
{
  const char *current = text;
  size_t current_length = text_length;

  while (current_length > 0) {
#define MAX_N_HITS 16
    grn_pat_scan_hit hits[MAX_N_HITS];
    const char *rest;
    int i, n_hits;
    size_t previous_length = 0;
    size_t chunk_length;

    n_hits = grn_pat_scan(ctx,
                          (grn_pat *)(highlighter->pat.keywords),
                          current, current_length,
                          hits, MAX_N_HITS,
                          &rest);
    for (i = 0; i < n_hits; i++) {
      if ((hits[i].offset - previous_length) > 0) {
        grn_text_escape_xml(ctx,
                            output,
                            current + previous_length,
                            hits[i].offset - previous_length);
      }
      GRN_TEXT_PUT(ctx,
                   output,
                   highlighter->tag.open,
                   highlighter->tag.open_length);
      grn_text_escape_xml(ctx,
                          output,
                          current + hits[i].offset,
                          hits[i].length);
      GRN_TEXT_PUT(ctx,
                   output,
                   highlighter->tag.close,
                   highlighter->tag.close_length);
      previous_length = hits[i].offset + hits[i].length;
    }

    chunk_length = rest - current;
    if ((chunk_length - previous_length) > 0) {
      grn_text_escape_xml(ctx,
                          output,
                          current + previous_length,
                          current_length - previous_length);
    }
    current_length -= chunk_length;
    current = rest;
#undef MAX_N_HITS
  }
}

grn_rc
grn_highlighter_highlight(grn_ctx *ctx,
                          grn_highlighter *highlighter,
                          const char *text,
                          int64_t text_length,
                          grn_obj *output)
{
  GRN_API_ENTER;

  if (text_length < 0) {
    text_length = strlen(text);
  }

  if (grn_vector_size(ctx, &(highlighter->raw_keywords)) == 0) {
    if (highlighter->is_html_mode) {
      grn_text_escape_xml(ctx,
                          output,
                          text,
                          text_length);
    } else {
      GRN_TEXT_PUT(ctx, output, text, text_length);
    }
    goto exit;
  }

  if (highlighter->need_prepared) {
    grn_highlighter_prepare(ctx, highlighter);
    if (ctx->rc != GRN_SUCCESS) {
      goto exit;
    }
  }

  if (highlighter->lexicon.object) {
    grn_highlighter_highlight_lexicon(ctx,
                                      highlighter,
                                      text,
                                      text_length,
                                      output);
  } else {
    grn_highlighter_highlight_patricia_trie(ctx,
                                            highlighter,
                                            text,
                                            text_length,
                                            output);
  }

exit :
  GRN_API_RETURN(ctx->rc);
}

grn_rc
grn_highlighter_set_lexicon(grn_ctx *ctx,
                            grn_highlighter *highlighter,
                            grn_obj *lexicon)
{
  GRN_API_ENTER;

  if (highlighter->lexicon.object != lexicon) {
    highlighter->need_prepared = GRN_TRUE;
    highlighter->lexicon.object = lexicon;
  }

  GRN_API_RETURN(ctx->rc);
}

grn_obj *
grn_highlighter_get_lexicon(grn_ctx *ctx,
                            grn_highlighter *highlighter)
{
  GRN_API_ENTER;

  GRN_API_RETURN(highlighter->lexicon.object);
}

grn_rc
grn_highlighter_add_keyword(grn_ctx *ctx,
                            grn_highlighter *highlighter,
                            const char *keyword,
                            int64_t keyword_length)
{
  unsigned int i, n_keywords;
  grn_obj *raw_keywords = &(highlighter->raw_keywords);

  GRN_API_ENTER;

  if (keyword_length < 0) {
    keyword_length = strlen(keyword);
  }

  if (keyword_length == 0) {
    goto exit;
  }

  n_keywords = grn_vector_size(ctx, raw_keywords);
  for (i = 0; i < n_keywords; i++) {
    const char *existing_keyword;
    unsigned int length;

    length = grn_vector_get_element(ctx,
                                    raw_keywords,
                                    i,
                                    &existing_keyword,
                                    NULL,
                                    NULL);
    if (length == keyword_length &&
        memcmp(keyword, existing_keyword, length) == 0) {
      goto exit;
    }
  }

  grn_vector_add_element(ctx,
                         raw_keywords,
                         keyword,
                         keyword_length,
                         0,
                         GRN_DB_TEXT);
  highlighter->need_prepared = GRN_TRUE;

exit :
  GRN_API_RETURN(ctx->rc);
}

grn_rc
grn_highlighter_clear_keywords(grn_ctx *ctx,
                               grn_highlighter *highlighter)
{
  grn_obj *raw_keywords = &(highlighter->raw_keywords);

  GRN_API_ENTER;

  GRN_BULK_REWIND(raw_keywords);
  highlighter->need_prepared = GRN_TRUE;

  GRN_API_RETURN(ctx->rc);
}
