/*
  Copyright (C) 2014  Brazil
  Copyright (C) 2018-2022  Sutou Kouhei <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 as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  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
*/

#ifdef GRN_EMBEDDED
#  define GRN_PLUGIN_FUNCTION_TAG token_filters_stem
#endif

#include <grn_str.h>

#include <groonga.h>
#include <groonga/token_filter.h>

#include <ctype.h>
#include <string.h>

#include <libstemmer.h>

typedef struct {
  grn_obj algorithm;
  bool keep_original;
} grn_stem_token_filter_options;

typedef struct {
  grn_stem_token_filter_options *options;
  grn_tokenize_mode mode;
  bool is_enabled;
  struct sb_stemmer *stemmer;
  grn_tokenizer_token token;
  grn_obj buffer;
} grn_stem_token_filter;

static void
stem_options_init(grn_ctx *ctx, grn_stem_token_filter_options *options)
{
  GRN_TEXT_INIT(&(options->algorithm), 0);
  GRN_TEXT_SETS(ctx, &(options->algorithm), "english");
  GRN_TEXT_PUTC(ctx, &(options->algorithm), '\0');
  options->keep_original = false;
}

static void *
stem_open_options(grn_ctx *ctx,
                  grn_obj *token_filter,
                  grn_obj *raw_options,
                  void *user_data)
{
  grn_stem_token_filter_options *options;

  options = GRN_PLUGIN_MALLOC(ctx, sizeof(grn_stem_token_filter_options));
  if (!options) {
    GRN_PLUGIN_ERROR(ctx,
                     GRN_NO_MEMORY_AVAILABLE,
                     "[token-filter][stem] "
                     "failed to allocate memory for options");
    return NULL;
  }

  stem_options_init(ctx, options);

  GRN_OPTION_VALUES_EACH_BEGIN(ctx, raw_options, i, name, name_length) {
    grn_raw_string name_raw;
    name_raw.value = name;
    name_raw.length = name_length;

    if (GRN_RAW_STRING_EQUAL_CSTRING(name_raw, "algorithm")) {
      const char *algorithm;
      unsigned int length;
      length = grn_vector_get_element(ctx,
                                      raw_options,
                                      i,
                                      &algorithm,
                                      NULL,
                                      NULL);
      GRN_TEXT_SET(ctx, &(options->algorithm), algorithm, length);
      GRN_TEXT_PUTC(ctx, &(options->algorithm), '\0');
    } else if (GRN_RAW_STRING_EQUAL_CSTRING(name_raw, "keep_original")) {
      options->keep_original =
        grn_vector_get_element_bool(ctx,
                                    raw_options,
                                    i,
                                    options->keep_original);
    }
  } GRN_OPTION_VALUES_EACH_END();

  return options;
}

static void
stem_close_options(grn_ctx *ctx, void *data)
{
  grn_stem_token_filter_options *options = data;
  GRN_OBJ_FIN(ctx, &(options->algorithm));
  GRN_PLUGIN_FREE(ctx, options);
}

static void *
stem_init(grn_ctx *ctx, grn_tokenizer_query *query)
{
  grn_obj *lexicon;
  unsigned int i;
  grn_stem_token_filter_options *options;
  grn_stem_token_filter *token_filter;

  lexicon = grn_tokenizer_query_get_lexicon(ctx, query);
  i = grn_tokenizer_query_get_token_filter_index(ctx, query);
  options = grn_table_cache_token_filters_options(ctx,
                                                  lexicon,
                                                  i,
                                                  stem_open_options,
                                                  stem_close_options,
                                                  NULL);
  if (ctx->rc != GRN_SUCCESS) {
    return NULL;
  }

  token_filter = GRN_PLUGIN_MALLOC(ctx, sizeof(grn_stem_token_filter));
  if (!token_filter) {
    GRN_PLUGIN_ERROR(ctx, GRN_NO_MEMORY_AVAILABLE,
                     "[token-filter][stem] "
                     "failed to allocate grn_stem_token_filter");
    return NULL;
  }
  token_filter->options = options;
  token_filter->mode = grn_tokenizer_query_get_mode(ctx, query);
  token_filter->is_enabled = true;
  grn_obj *query_options = grn_tokenizer_query_get_options(ctx, query);
  if (query_options) {
    grn_proc_prefixed_options_parse(ctx,
                                    query_options,
                                    "TokenFilterStem.",
                                    "[token-filter][stem]",
                                    "enable",
                                    GRN_PROC_OPTION_VALUE_BOOL,
                                    &(token_filter->is_enabled),
                                    NULL);
    if (ctx->rc != GRN_SUCCESS) {
      GRN_PLUGIN_FREE(ctx, token_filter);
      return NULL;
    }
  }

  {
    const char *algorithm = GRN_TEXT_VALUE(&(token_filter->options->algorithm));
    /* TODO: Support other encoding. */
    const char *encoding = "UTF_8";
    token_filter->stemmer = sb_stemmer_new(algorithm, encoding);
    if (!token_filter->stemmer) {
      GRN_PLUGIN_FREE(ctx, token_filter);
      GRN_PLUGIN_ERROR(ctx, GRN_INVALID_ARGUMENT,
                       "[token-filter][stem] "
                       "failed to create stemmer: "
                       "algorithm=<%s>, encoding=<%s>",
                       algorithm, encoding);
      return NULL;
    }
  }
  grn_tokenizer_token_init(ctx, &(token_filter->token));
  GRN_TEXT_INIT(&(token_filter->buffer), 0);

  return token_filter;
}

static bool
is_stemmable(grn_obj *data, bool *is_all_upper)
{
  const char *current, *end;
  bool have_lower = false;
  bool have_upper = false;

  *is_all_upper = false;

  switch (data->header.domain) {
  case GRN_DB_SHORT_TEXT :
  case GRN_DB_TEXT :
  case GRN_DB_LONG_TEXT :
    break;
  default :
    return false;
  }

  current = GRN_TEXT_VALUE(data);
  end = current + GRN_TEXT_LEN(data);

  for (; current < end; current++) {
    if (islower((unsigned char)*current)) {
      have_lower = true;
      continue;
    }
    if (isupper((unsigned char)*current)) {
      have_upper = true;
      continue;
    }
    if (isdigit((unsigned char)*current)) {
      continue;
    }
    switch (*current) {
    case '-' :
    case '\'' :
      break;
    default :
      return false;
    }
  }

  if (!have_lower && have_upper) {
    *is_all_upper = true;
  }

  return true;
}

static void
normalize(grn_ctx *ctx,
          const char *string, unsigned int length,
          grn_obj *normalized)
{
  const char *current, *end;
  const char *unwritten;

  current = unwritten = string;
  end = current + length;

  for (; current < end; current++) {
    if (isupper((unsigned char)*current)) {
      if (current > unwritten) {
        GRN_TEXT_PUT(ctx, normalized, unwritten, current - unwritten);
      }
      GRN_TEXT_PUTC(ctx, normalized, (char)tolower((unsigned char)*current));
      unwritten = current + 1;
    }
  }

  if (current != unwritten) {
    GRN_TEXT_PUT(ctx, normalized, unwritten, current - unwritten);
  }
}

static void
unnormalize(grn_ctx *ctx,
            const char *string, unsigned int length,
            grn_obj *normalized)
{
  const char *current, *end;
  const char *unwritten;

  current = unwritten = string;
  end = current + length;

  for (; current < end; current++) {
    if (islower((unsigned char)*current)) {
      if (current > unwritten) {
        GRN_TEXT_PUT(ctx, normalized, unwritten, current - unwritten);
      }
      GRN_TEXT_PUTC(ctx, normalized, (char)toupper((unsigned char)*current));
      unwritten = current + 1;
    }
  }

  if (current != unwritten) {
    GRN_TEXT_PUT(ctx, normalized, unwritten, current - unwritten);
  }
}

static void
stem_filter(grn_ctx *ctx,
            grn_token *current_token,
            grn_token *next_token,
            void *user_data)
{
  grn_stem_token_filter *token_filter = user_data;
  grn_obj *data;
  bool is_all_upper = false;

  if (!token_filter->is_enabled) {
    return;
  }

  if (GRN_CTX_GET_ENCODING(ctx) != GRN_ENC_UTF8) {
    return;
  }

  data = grn_token_get_data(ctx, current_token);
  if (!is_stemmable(data, &is_all_upper)) {
    return;
  }

  {
    const sb_symbol *stemmed;

    if (is_all_upper) {
      grn_obj *buffer;
      buffer = &(token_filter->buffer);
      GRN_BULK_REWIND(buffer);
      normalize(ctx,
                GRN_TEXT_VALUE(data),
                (unsigned int)GRN_TEXT_LEN(data),
                buffer);
      stemmed = sb_stemmer_stem(token_filter->stemmer,
                                GRN_TEXT_VALUE(buffer),
                                (int)GRN_TEXT_LEN(buffer));
      if (!stemmed) {
        GRN_PLUGIN_ERROR(ctx, GRN_NO_MEMORY_AVAILABLE,
                         "[token-filter][stem] "
                         "failed to allocate memory for stemmed word: <%.*s> "
                         "(normalized: <%.*s>)",
                         (int)GRN_TEXT_LEN(data), GRN_TEXT_VALUE(data),
                         (int)GRN_TEXT_LEN(buffer), GRN_TEXT_VALUE(buffer));
        return;
      }
      GRN_BULK_REWIND(buffer);
      unnormalize(ctx,
                  stemmed,
                  (unsigned int)sb_stemmer_length(token_filter->stemmer),
                  buffer);
      grn_token_set_data(ctx,
                         next_token,
                         GRN_TEXT_VALUE(buffer),
                         (int)GRN_TEXT_LEN(buffer));
    } else {
      stemmed = sb_stemmer_stem(token_filter->stemmer,
                                GRN_TEXT_VALUE(data),
                                (int)GRN_TEXT_LEN(data));
      if (!stemmed) {
        GRN_PLUGIN_ERROR(ctx, GRN_NO_MEMORY_AVAILABLE,
                         "[token-filter][stem] "
                         "failed to allocate memory for stemmed word: <%.*s>",
                         (int)GRN_TEXT_LEN(data), GRN_TEXT_VALUE(data));
        return;
      }
      grn_token_set_data(ctx, next_token,
                         stemmed,
                         sb_stemmer_length(token_filter->stemmer));
    }
  }

  if (token_filter->mode == GRN_TOKENIZE_ADD &&
      token_filter->options->keep_original) {
    grn_token_add_status(ctx, next_token, GRN_TOKEN_KEEP_ORIGINAL);
  }
}

static void
stem_fin(grn_ctx *ctx, void *user_data)
{
  grn_stem_token_filter *token_filter = user_data;
  if (!token_filter) {
    return;
  }

  grn_tokenizer_token_fin(ctx, &(token_filter->token));
  if (token_filter->stemmer) {
    sb_stemmer_delete(token_filter->stemmer);
  }
  GRN_OBJ_FIN(ctx, &(token_filter->buffer));
  GRN_PLUGIN_FREE(ctx, token_filter);
}

grn_rc
GRN_PLUGIN_INIT(grn_ctx *ctx)
{
  return ctx->rc;
}

grn_rc
GRN_PLUGIN_REGISTER(grn_ctx *ctx)
{
  grn_obj *token_filter;

  token_filter = grn_token_filter_create(ctx, "TokenFilterStem", -1);
  grn_token_filter_set_init_func(ctx, token_filter, stem_init);
  grn_token_filter_set_filter_func(ctx, token_filter, stem_filter);
  grn_token_filter_set_fin_func(ctx, token_filter, stem_fin);

  return ctx->rc;
}

grn_rc
GRN_PLUGIN_FIN(grn_ctx *ctx)
{
  return GRN_SUCCESS;
}
