/* Copyright (c) 2001, 2021, Oracle and/or its affiliates.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.

   This program is also distributed with certain software (including
   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have included with MySQL.

   This program 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 General Public License, version 2.0, for more details.

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

/* Written by Sergei A. Golubchik, who has a shared copyright to this code */

#define FT_CORE
#include <fcntl.h>
#include <sys/types.h>
#include <algorithm>

#include "my_compiler.h"
#include "my_dbug.h"
#include "my_inttypes.h"
#include "my_macros.h"
#include "storage/myisam/ftdefs.h"
#include "storage/myisam/myisamdef.h"
#include "template_utils.h"

/* search with natural language queries */

typedef struct ft_doc_rec {
  my_off_t dpos;
  double weight;
} FT_DOC;

struct st_ft_info_nlq : public FT_INFO {
  MI_INFO *info;
  int ndocs;
  int curdoc;
  FT_DOC doc[1];
};

struct ALL_IN_ONE {
  MI_INFO *info;
  uint keynr;
  const CHARSET_INFO *charset;
  uchar *keybuff;
  TREE dtree;
};

struct FT_SUPERDOC {
  FT_DOC doc;
  FT_WORD *word_ptr;
  double tmp_weight;
};

static int FT_SUPERDOC_cmp(const void *, const void *a, const void *b) {
  const FT_SUPERDOC *p1 = pointer_cast<const FT_SUPERDOC *>(a);
  const FT_SUPERDOC *p2 = pointer_cast<const FT_SUPERDOC *>(b);
  if (p1->doc.dpos < p2->doc.dpos) return -1;
  if (p1->doc.dpos == p2->doc.dpos) return 0;
  return 1;
}

static int walk_and_match(void *v_word, uint32 count, void *v_aio) {
  FT_WORD *word = static_cast<FT_WORD *>(v_word);
  ALL_IN_ONE *aio = static_cast<ALL_IN_ONE *>(v_aio);
  int subkeys = 0, r;
  uint keylen, doc_cnt;
  FT_SUPERDOC sdoc, *sptr;
  TREE_ELEMENT *selem;
  double gweight = 1;
  MI_INFO *info = aio->info;
  MYISAM_SHARE *share = info->s;
  uchar *keybuff = aio->keybuff;
  MI_KEYDEF *keyinfo = info->s->keyinfo + aio->keynr;
  my_off_t key_root;
  uint extra = HA_FT_WLEN + info->s->rec_reflength;
  float tmp_weight;

  DBUG_TRACE;

  word->weight = LWS_FOR_QUERY;

  keylen = _ft_make_key(info, aio->keynr, keybuff, word, 0);
  keylen -= HA_FT_WLEN;
  doc_cnt = 0;

  if (share->concurrent_insert)
    mysql_rwlock_rdlock(&share->key_root_lock[aio->keynr]);

  key_root = share->state.key_root[aio->keynr];

  /* Skip rows inserted by current inserted */
  for (r = _mi_search(info, keyinfo, keybuff, keylen, SEARCH_FIND, key_root);
       !r &&
       (subkeys = ft_sintXkorr(info->lastkey + info->lastkey_length - extra)) >
           0 &&
       info->lastpos >= info->state->data_file_length;
       r = _mi_search_next(info, keyinfo, info->lastkey, info->lastkey_length,
                           SEARCH_BIGGER, key_root))
    ;

  if (share->concurrent_insert)
    mysql_rwlock_unlock(&share->key_root_lock[aio->keynr]);

  info->update |= HA_STATE_AKTIV; /* for _mi_test_if_changed() */

  /* The following should be safe, even if we compare doubles */
  while (!r && gweight) {
    if (keylen && ha_compare_text(aio->charset, info->lastkey + 1,
                                  info->lastkey_length - extra - 1, keybuff + 1,
                                  keylen - 1, false))
      break;

    if (subkeys < 0) {
      if (doc_cnt) return 1; /* index is corrupted */
      /*
        TODO here: unsafe optimization, should this word
        be skipped (based on subkeys) ?
      */
      keybuff += keylen;
      keyinfo = &info->s->ft2_keyinfo;
      key_root = info->lastpos;
      keylen = 0;
      if (share->concurrent_insert)
        mysql_rwlock_rdlock(&share->key_root_lock[aio->keynr]);
      r = _mi_search_first(info, keyinfo, key_root);
      goto do_skip;
    }
    tmp_weight = ft_floatXget(info->lastkey + info->lastkey_length - extra);
    /* The following should be safe, even if we compare doubles */
    if (tmp_weight == 0) return doc_cnt; /* stopword, doc_cnt should be 0 */

    sdoc.doc.dpos = info->lastpos;

    /* saving document matched into dtree */
    if (!(selem = tree_insert(&aio->dtree, &sdoc, 0, aio->dtree.custom_arg)))
      return 1;

    sptr = (FT_SUPERDOC *)ELEMENT_KEY((&aio->dtree), selem);

    if (selem->count == 1) /* document's first match */
      sptr->doc.weight = 0;
    else
      sptr->doc.weight += sptr->tmp_weight * sptr->word_ptr->weight;

    sptr->word_ptr = word;
    sptr->tmp_weight = tmp_weight;

    doc_cnt++;

    gweight = word->weight * GWS_IN_USE;
    if (gweight < 0 || doc_cnt > 2000000) gweight = 0;

    if (share->concurrent_insert)
      mysql_rwlock_rdlock(&share->key_root_lock[aio->keynr]);

    if (_mi_test_if_changed(info) == 0)
      r = _mi_search_next(info, keyinfo, info->lastkey, info->lastkey_length,
                          SEARCH_BIGGER, key_root);
    else
      r = _mi_search(info, keyinfo, info->lastkey, info->lastkey_length,
                     SEARCH_BIGGER, key_root);
  do_skip:
    while ((subkeys = ft_sintXkorr(info->lastkey + info->lastkey_length -
                                   extra)) > 0 &&
           !r && info->lastpos >= info->state->data_file_length)
      r = _mi_search_next(info, keyinfo, info->lastkey, info->lastkey_length,
                          SEARCH_BIGGER, key_root);

    if (share->concurrent_insert)
      mysql_rwlock_unlock(&share->key_root_lock[aio->keynr]);
  }
  word->weight = gweight;

  return 0;
}

static int walk_and_copy(void *v_from, uint32, void *v_to) {
  FT_SUPERDOC *from = static_cast<FT_SUPERDOC *>(v_from);
  FT_DOC **to = static_cast<FT_DOC **>(v_to);
  DBUG_TRACE;
  from->doc.weight += from->tmp_weight * from->word_ptr->weight;
  (*to)->dpos = from->doc.dpos;
  (*to)->weight = from->doc.weight;
  (*to)++;
  return 0;
}

static int walk_and_push(void *v_from, uint32, void *v_best) {
  FT_SUPERDOC *from = static_cast<FT_SUPERDOC *>(v_from);
  QUEUE *best = static_cast<QUEUE *>(v_best);
  DBUG_TRACE;
  from->doc.weight += from->tmp_weight * from->word_ptr->weight;
  best->elements = std::min(best->elements, uint(ft_query_expansion_limit - 1));
  queue_insert(best, (uchar *)&from->doc);
  return 0;
}

static int FT_DOC_cmp(void *, uchar *a_arg, uchar *b_arg) {
  FT_DOC *a = (FT_DOC *)a_arg;
  FT_DOC *b = (FT_DOC *)b_arg;
  double c = b->weight - a->weight;
  return ((c < 0) ? -1 : (c > 0) ? 1 : 0);
}

FT_INFO *ft_init_nlq_search(MI_INFO *info, uint keynr, uchar *query,
                            uint query_len, uint flags, uchar *record) {
  TREE wtree;
  ALL_IN_ONE aio;
  FT_DOC *dptr;
  st_ft_info_nlq *dlist = nullptr;
  my_off_t saved_lastpos = info->lastpos;
  struct st_mysql_ftparser *parser;
  MYSQL_FTPARSER_PARAM *ftparser_param;
  DBUG_TRACE;

  /* black magic ON */
  if ((int)(keynr = _mi_check_index(info, keynr)) < 0) return nullptr;
  if (_mi_readinfo(info, F_RDLCK, 1)) return nullptr;
  /* black magic OFF */

  aio.info = info;
  aio.keynr = keynr;
  aio.charset = info->s->keyinfo[keynr].seg->charset;
  aio.keybuff = info->lastkey + info->s->base.max_key_length;
  parser = info->s->keyinfo[keynr].parser;
  if (!(ftparser_param = ftparser_call_initializer(info, keynr, 0))) goto err;

  memset(&wtree, 0, sizeof(wtree));

  init_tree(&aio.dtree, 0, sizeof(FT_SUPERDOC), &FT_SUPERDOC_cmp, false,
            nullptr, nullptr);

  ft_parse_init(&wtree, aio.charset);
  ftparser_param->flags = 0;
  if (ft_parse(&wtree, query, query_len, parser, ftparser_param,
               &wtree.mem_root))
    goto err;

  if (tree_walk(&wtree, &walk_and_match, &aio, left_root_right)) goto err;

  if (flags & FT_EXPAND && ft_query_expansion_limit) {
    QUEUE best;
    init_queue(&best, key_memory_QUEUE, ft_query_expansion_limit, 0, false,
               &FT_DOC_cmp, nullptr);
    tree_walk(&aio.dtree, &walk_and_push, &best, left_root_right);
    while (best.elements) {
      my_off_t docid = ((FT_DOC *)queue_remove(&best, 0))->dpos;
      if (!(*info->read_record)(info, docid, record)) {
        info->update |= HA_STATE_AKTIV;
        ftparser_param->flags = MYSQL_FTFLAGS_NEED_COPY;
        if (unlikely(_mi_ft_parse(&wtree, info, keynr, record, ftparser_param,
                                  &wtree.mem_root))) {
          delete_queue(&best);
          goto err;
        }
      }
    }
    delete_queue(&best);
    reset_tree(&aio.dtree);
    if (tree_walk(&wtree, &walk_and_match, &aio, left_root_right)) goto err;
  }

  /*
    If ndocs == 0, this will not allocate RAM for FT_INFO.doc[],
    so if ndocs == 0, FT_INFO.doc[] must not be accessed.
   */
  dlist = (st_ft_info_nlq *)my_malloc(
      mi_key_memory_FT_INFO,
      sizeof(st_ft_info_nlq) +
          sizeof(FT_DOC) * (int)(aio.dtree.elements_in_tree - 1),
      MYF(0));
  if (!dlist) goto err;

  dlist->please = const_cast<struct _ft_vft *>(&_ft_vft_nlq);
  dlist->ndocs = aio.dtree.elements_in_tree;
  dlist->curdoc = -1;
  dlist->info = aio.info;
  dptr = dlist->doc;

  tree_walk(&aio.dtree, &walk_and_copy, &dptr, left_root_right);

  if (flags & FT_SORTED)
    std::sort(
        dlist->doc, dlist->doc + dlist->ndocs,
        [](const FT_DOC &a, const FT_DOC &b) { return b.weight < a.weight; });

err:
  delete_tree(&aio.dtree);
  delete_tree(&wtree);
  info->lastpos = saved_lastpos;
  return (FT_INFO *)dlist;
}

int ft_nlq_read_next(FT_INFO *handler_base, char *record) {
  st_ft_info_nlq *handler = (st_ft_info_nlq *)handler_base;
  MI_INFO *info = (MI_INFO *)handler->info;

  // Move to the next document that has a non-zero score.
  while (++handler->curdoc < handler->ndocs &&
         ft_nlq_get_relevance(handler) == 0.0) {
  }

  if (handler->curdoc >= handler->ndocs) {
    return HA_ERR_END_OF_FILE;
  }

  info->update &= (HA_STATE_CHANGED | HA_STATE_ROW_CHANGED);

  info->lastpos = handler->doc[handler->curdoc].dpos;
  if (!(*info->read_record)(info, info->lastpos, (uchar *)record)) {
    info->update |= HA_STATE_AKTIV; /* Record is read */
    return 0;
  }
  return my_errno();
}

float ft_nlq_find_relevance(FT_INFO *handler_base,
                            uchar *record [[maybe_unused]],
                            uint length [[maybe_unused]]) {
  st_ft_info_nlq *handler = (st_ft_info_nlq *)handler_base;
  int a, b, c;
  FT_DOC *docs = handler->doc;
  my_off_t docid = handler->info->lastpos;

  if (docid == HA_POS_ERROR) return -5.0;

  /* Assuming docs[] is sorted by dpos... */

  for (a = 0, b = handler->ndocs, c = (a + b) / 2; b - a > 1; c = (a + b) / 2) {
    if (docs[c].dpos > docid)
      b = c;
    else
      a = c;
  }
  /* bounds check to avoid accessing unallocated handler->doc  */
  if (a < handler->ndocs && docs[a].dpos == docid)
    return (float)docs[a].weight;
  else
    return 0.0;
}

void ft_nlq_close_search(FT_INFO *handler) { my_free(handler); }

float ft_nlq_get_relevance(FT_INFO *handler_base) {
  st_ft_info_nlq *handler = (st_ft_info_nlq *)handler_base;
  return (float)handler->doc[handler->curdoc].weight;
}

void ft_nlq_reinit_search(FT_INFO *handler_base) {
  st_ft_info_nlq *handler = (st_ft_info_nlq *)handler_base;
  handler->curdoc = -1;
}
