/* Copyright (c) 2016, 2024, 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 designed to work 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 either included with
   the program or referenced in the documentation.

   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 */

/**
  @file sql/histograms/singleton.cc
  Singleton histogram (implementation).
*/

#include "sql/histograms/singleton.h"

#include <algorithm>  // std::is_sorted
#include <iterator>
#include <new>

#include "field_types.h"  // enum_field_types
#include "my_base.h"      // ha_rows
#include "my_dbug.h"
#include "my_inttypes.h"
#include "mysql_time.h"
#include "sql-common/json_dom.h"               // Json_*
#include "sql/histograms/histogram_utility.h"  // DeepCopy
#include "sql/histograms/value_map.h"          // Value_map
#include "template_utils.h"

struct MEM_ROOT;

namespace histograms {

// Private constructor
template <class T>
Singleton<T>::Singleton(MEM_ROOT *mem_root, const std::string &db_name,
                        const std::string &tbl_name,
                        const std::string &col_name, Value_map_type data_type,
                        bool *error)
    : Histogram(mem_root, db_name, tbl_name, col_name,
                enum_histogram_type::SINGLETON, data_type, error),
      m_buckets(mem_root) {}

// Public factory method
template <class T>
Singleton<T> *Singleton<T>::create(MEM_ROOT *mem_root,
                                   const std::string &db_name,
                                   const std::string &tbl_name,
                                   const std::string &col_name,
                                   Value_map_type data_type) {
  bool error = false;
  Singleton<T> *singleton = new (mem_root)
      Singleton<T>(mem_root, db_name, tbl_name, col_name, data_type, &error);
  if (error) return nullptr;
  return singleton;
}

template <class T>
Singleton<T>::Singleton(MEM_ROOT *mem_root, const Singleton<T> &other,
                        bool *error)
    : Histogram(mem_root, other, error), m_buckets(mem_root) {
  if (m_buckets.reserve(other.m_buckets.size())) {
    *error = true;
    return;  // OOM
  }
  for (const SingletonBucket<T> &other_bucket : other.m_buckets) {
    SingletonBucket<T> bucket(DeepCopy(other_bucket.value, mem_root, error),
                              other_bucket.cumulative_frequency);
    if (*error) return;
    m_buckets.push_back(bucket);
  }
}

template <class T>
bool Singleton<T>::build_histogram(const Value_map<T> &value_map,
                                   size_t num_buckets) {
  // Clear any existing data.
  m_buckets.clear();
  m_null_values_fraction = INVALID_NULL_VALUES_FRACTION;
  m_sampling_rate = value_map.get_sampling_rate();

  // Set the number of buckets that was specified/requested by the user.
  m_num_buckets_specified = num_buckets;

  // Set the character set for the histogram data.
  m_charset = value_map.get_character_set();

  // Get total frequency count.
  ha_rows num_non_null_values = 0;
  for (const auto &node : value_map) num_non_null_values += node.second;

  // No values, nothing to do.
  if (num_non_null_values == 0) {
    if (value_map.get_num_null_values() > 0)
      m_null_values_fraction = 1.0;
    else
      m_null_values_fraction = 0.0;

    return false;
  }

  const ha_rows total_count =
      value_map.get_num_null_values() + num_non_null_values;

  // Set the fractions of NULL values.
  m_null_values_fraction =
      value_map.get_num_null_values() / static_cast<double>(total_count);

  // Create buckets with relative frequency, and not absolute frequency.
  ha_rows cumulative_sum = 0;

  if (m_buckets.reserve(value_map.size())) return true;  // OOM

  for (const auto &node : value_map) {
    cumulative_sum += node.second;
    const double cumulative_frequency =
        cumulative_sum / static_cast<double>(total_count);
    bool value_copy_error = false;
    SingletonBucket<T> bucket(
        DeepCopy(node.first, get_mem_root(), &value_copy_error),
        cumulative_frequency);
    if (value_copy_error) return true;
    m_buckets.push_back(bucket);
  }

  return false;
}

template <class T>
bool Singleton<T>::histogram_to_json(Json_object *json_object) const {
  /*
    Call the base class implementation first. This will add the properties that
    are common among different histogram types, such as "last-updated" and
    "histogram-type".
  */
  if (Histogram::histogram_to_json(json_object))
    return true; /* purecov: inspected */

  // Add the Singleton buckets.
  Json_array json_buckets;
  for (const auto &bucket : m_buckets) {
    Json_array json_bucket;
    if (create_json_bucket(bucket, &json_bucket))
      return true; /* purecov: inspected */
    if (json_buckets.append_clone(&json_bucket))
      return true; /* purecov: inspected */
  }

  if (json_object->add_clone(buckets_str(), &json_buckets))
    return true; /* purecov: inspected */

  if (histogram_data_type_to_json(json_object))
    return true; /* purecov: inspected */
  return false;
}

template <class T>
bool Singleton<T>::create_json_bucket(const SingletonBucket<T> &bucket,
                                      Json_array *json_bucket) {
  // Value
  if (add_value_json_bucket(bucket.value, json_bucket))
    return true; /* purecov: inspected */

  // Cumulative frequency
  const Json_double frequency(bucket.cumulative_frequency);
  if (json_bucket->append_clone(&frequency))
    return true; /* purecov: inspected */
  return false;
}

template <>
bool Singleton<double>::add_value_json_bucket(const double &value,
                                              Json_array *json_bucket) {
  const Json_double json_value(value);
  if (json_bucket->append_clone(&json_value))
    return true; /* purecov: inspected */
  return false;
}

template <>
bool Singleton<String>::add_value_json_bucket(const String &value,
                                              Json_array *json_bucket) {
  const Json_opaque json_value(enum_field_types::MYSQL_TYPE_STRING, value.ptr(),
                               value.length());
  if (json_bucket->append_clone(&json_value))
    return true; /* purecov: inspected */
  return false;
}

template <>
bool Singleton<ulonglong>::add_value_json_bucket(const ulonglong &value,
                                                 Json_array *json_bucket) {
  const Json_uint json_value(value);
  if (json_bucket->append_clone(&json_value))
    return true; /* purecov: inspected */
  return false;
}

template <>
bool Singleton<longlong>::add_value_json_bucket(const longlong &value,
                                                Json_array *json_bucket) {
  const Json_int json_value(value);
  if (json_bucket->append_clone(&json_value))
    return true; /* purecov: inspected */
  return false;
}

template <>
bool Singleton<MYSQL_TIME>::add_value_json_bucket(const MYSQL_TIME &value,
                                                  Json_array *json_bucket) {
  enum_field_types field_type;
  switch (value.time_type) {
    case MYSQL_TIMESTAMP_DATE:
      field_type = MYSQL_TYPE_DATE;
      break;
    case MYSQL_TIMESTAMP_DATETIME:
      field_type = MYSQL_TYPE_DATETIME;
      break;
    case MYSQL_TIMESTAMP_TIME:
      field_type = MYSQL_TYPE_TIME;
      break;
    default:
      /* purecov: begin deadcode */
      assert(false);
      return true;
      /* purecov: end */
  }

  const Json_datetime json_value(value, field_type);
  if (json_bucket->append_clone(&json_value))
    return true; /* purecov: inspected */
  return false;
}

template <>
bool Singleton<my_decimal>::add_value_json_bucket(const my_decimal &value,
                                                  Json_array *json_bucket) {
  const Json_decimal json_value(value);
  if (json_bucket->append_clone(&json_value))
    return true; /* purecov: inspected */
  return false;
}

template <class T>
std::string Singleton<T>::histogram_type_to_str() const {
  return singleton_str();
}

template <class T>
bool Singleton<T>::json_to_histogram(const Json_object &json_object,
                                     Error_context *context) {
  if (Histogram::json_to_histogram(json_object, context)) return true;

  const Json_dom *buckets_dom = json_object.get(buckets_str());
  if (buckets_dom == nullptr) {
    context->report_missing_attribute(Histogram::buckets_str());
    return true;
  }
  if (buckets_dom->json_type() != enum_json_type::J_ARRAY) {
    context->report_node(buckets_dom, Message::JSON_WRONG_ATTRIBUTE_TYPE);
    return true;
  }

  const Json_array *buckets = down_cast<const Json_array *>(buckets_dom);
  if (m_buckets.reserve(buckets->size())) return true;  // OOM

  for (size_t i = 0; i < buckets->size(); ++i) {
    const Json_dom *bucket_dom = (*buckets)[i];
    if (buckets_dom == nullptr) {
      context->report_missing_attribute(Histogram::buckets_str());
      return true;
    }
    if (bucket_dom->json_type() != enum_json_type::J_ARRAY) {
      context->report_node(bucket_dom, Message::JSON_WRONG_ATTRIBUTE_TYPE);
      return true;
    }
    const Json_array *bucket = down_cast<const Json_array *>(bucket_dom);
    if (bucket->size() != 2) {
      context->report_node(bucket_dom, Message::JSON_WRONG_BUCKET_TYPE_2);
      return true;
    }

    // First item is the value, second is the cumulative frequency
    const Json_dom *cumulative_frequency_dom = (*bucket)[1];
    if (cumulative_frequency_dom->json_type() != enum_json_type::J_DOUBLE) {
      context->report_node(cumulative_frequency_dom,
                           Message::JSON_WRONG_ATTRIBUTE_TYPE);
      return true;
    }

    const Json_double *cumulative_frequency =
        down_cast<const Json_double *>(cumulative_frequency_dom);

    const Json_dom *value_dom = (*bucket)[0];
    T value;
    if (extract_json_dom_value(value_dom, &value, context)) return true;

    // Bucket extraction post-check
    {
      if ((cumulative_frequency->value() < 0.0) ||
          (cumulative_frequency->value() > 1.0)) {
        context->report_node(cumulative_frequency_dom,
                             Message::JSON_INVALID_FREQUENCY);
        return true;
      }
      if (context->check_value(&value)) {
        context->report_node(value_dom, Message::JSON_VALUE_OUT_OF_RANGE);
        return true;
      }
      // Check endpoint sequence and frequency sequence.
      if (!m_buckets.empty()) {
        SingletonBucket<T> *last_bucket = &m_buckets[m_buckets.size() - 1];
        if (!histograms::Histogram_comparator()(last_bucket->value, value)) {
          context->report_node(value_dom, Message::JSON_VALUE_NOT_ASCENDING_1);
          return true;
        }
        if (last_bucket->cumulative_frequency > cumulative_frequency->value()) {
          context->report_node(
              cumulative_frequency_dom,
              Message::JSON_CUMULATIVE_FREQUENCY_NOT_ASCENDING);
          return true;
        }
      }
    }

    assert(m_buckets.capacity() > m_buckets.size());
    m_buckets.push_back(
        SingletonBucket<T>(value, cumulative_frequency->value()));
  }
  bool histogram_buckets_sorted = std::is_sorted(
      m_buckets.begin(), m_buckets.end(), Histogram_comparator());
  bool already_validated [[maybe_unused]] = context->binary();
  assert(!already_validated || histogram_buckets_sorted);
  if (!histogram_buckets_sorted) {
    context->report_node(buckets_dom, Message::JSON_VALUE_NOT_ASCENDING_1);
    return true;
  }

  // Global post-check
  {
    /*
      Note that Singleton may be built on an empty table or an all-NULL
      column. In this case the buckets array is empty.
    */
    if (m_buckets.empty()) {
      if (get_null_values_fraction() != 1.0 &&
          get_null_values_fraction() != 0.0) {
        context->report_global(Message::JSON_INVALID_NULL_VALUES_FRACTION);
        return true;
      }
    } else {
      SingletonBucket<T> *last_bucket = &m_buckets[m_buckets.size() - 1];
      float sum =
          last_bucket->cumulative_frequency + get_null_values_fraction();
      if (std::abs(sum - 1.0) > 0) {
        context->report_global(Message::JSON_INVALID_TOTAL_FREQUENCY);
        return true;
      }
    }
  }
  return false;
}

template <class T>
Histogram *Singleton<T>::clone(MEM_ROOT *mem_root) const {
  DBUG_EXECUTE_IF("fail_histogram_clone", return nullptr;);
  bool error = false;
  Histogram *singleton = new (mem_root) Singleton<T>(mem_root, *this, &error);
  if (error) return nullptr;
  return singleton;
}

template <class T>
double Singleton<T>::get_equal_to_selectivity(const T &value) const {
  /*
    Find the first histogram bucket where the value is not less than the
    user-provided value.
  */
  const auto found = std::lower_bound(m_buckets.begin(), m_buckets.end(), value,
                                      Histogram_comparator());

  if (found == m_buckets.end()) return 0.0;

  if (Histogram_comparator()(value, found->value) == 0) {
    if (found == m_buckets.begin())
      return found->cumulative_frequency;
    else {
      const auto previous = std::prev(found, 1);
      return found->cumulative_frequency - previous->cumulative_frequency;
    }
  }

  return 0.0;
}

template <class T>
double Singleton<T>::get_less_than_selectivity(const T &value) const {
  /*
    Find the first histogram bucket where the value is not less than the
    user-provided value.
  */
  const auto found = std::lower_bound(m_buckets.begin(), m_buckets.end(), value,
                                      Histogram_comparator());
  if (found == m_buckets.begin())
    return 0.0;
  else {
    const auto previous = std::prev(found, 1);
    return previous->cumulative_frequency;
  }
}

template <class T>
double Singleton<T>::get_greater_than_selectivity(const T &value) const {
  /*
    Find the first histogram bucket where the value is greater than the
    user-provided value.
  */
  const auto found = std::upper_bound(m_buckets.begin(), m_buckets.end(), value,
                                      Histogram_comparator());

  if (found == m_buckets.begin())
    return get_non_null_values_fraction();
  else {
    const auto previous = std::prev(found, 1);
    return get_non_null_values_fraction() - previous->cumulative_frequency;
  }
}

// Explicit template instantiations.
template class Singleton<double>;
template class Singleton<String>;
template class Singleton<ulonglong>;
template class Singleton<longlong>;
template class Singleton<MYSQL_TIME>;
template class Singleton<my_decimal>;

}  // namespace histograms