#ifndef SQL_ITEM_REGEXP_FUNC_H_
#define SQL_ITEM_REGEXP_FUNC_H_

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/**
  @file item_regexp_func.h

  The function classes for regular expression functions. They have a common
  base class Item_func_regexp, which is also the prefix of their class
  names. After the %Item_func prefix comes the name of the SQL function,
  e.g. Item_func_regexp_instr represents the SQL function `REGEXP_INSTR`.

  Type resolution
  ===============

  The type and name resolution procedure is hooked into by the
  Item_func_regexp class, which implement both
  Item_result_field::resolve_type() and Item::fix_fields().

  Collations
  ==========

  The regular expression library doesn't deal with collations at all, but we
  need them because the 'winning' collation of the pattern and the subject
  strings dictates case-sensitivity. The winning collation is defined by
  coercion rules, and we don't delve into that here. See
  Item_func::agg_arg_charsets_for_comparison(). The call to this function is
  done in resolve_type() as this appears to be an unwritten convention.

  Implementation
  ==============

  All communication with the regular expression library is done through a
  Regexp_facade object, instantiated in Item_func_regexp::fix_fields().

  @todo We now clean up ICU heap memory in Item_func_regexp::cleanup. Should
  it be done more rarely? On session close?
*/

#include <assert.h>
#include <unicode/uregex.h>

#include <optional>
#include <string>

// assert
#include "my_inttypes.h"  // MY_INT32_NUM_DECIMAL_DIGITS
#include "sql/item_cmpfunc.h"
#include "sql/item_strfunc.h"
#include "sql/mysqld.h"  // make_unique_destroy_only
#include "sql/regexp/regexp_facade.h"
#include "sql_string.h"  // String

// GCC bug 80635.
#if defined(__GNUC__) && !defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
#endif

/**
  Base class for all regular expression function classes. Is responsible for
  creating the Regexp_facade object.
*/
class Item_func_regexp : public Item_func {
 public:
  Item_func_regexp(const POS &pos, PT_item_list *opt_list)
      : Item_func(pos, opt_list) {}

  /**
    Resolves the collation to use for comparison. The type resolution is done
    in the subclass constructors.

    For all regular expression functions, i.e. REGEXP_INSTR, REGEXP_LIKE,
    REGEXP_REPLACE and REGEXP_SUBSTR, it goes that the first two arguments
    have to agree on a common collation. This collation is used to control
    case-sensitivity.

    @see fix_fields()
  */
  bool resolve_type(THD *) override;

  /// Decides on the mode for matching, case sensitivity etc.
  bool fix_fields(THD *thd, Item **) override;

  /// The expression for the subject string.
  Item *subject() const { return args[0]; }

  /// The expression for the pattern string.
  Item *pattern() const { return args[1]; }

  /// The value of the `position` argument, or its default if absent.
  std::optional<int> position() const {
    int the_index = pos_arg_pos();
    if (the_index != -1 && arg_count >= static_cast<uint>(the_index) + 1) {
      int value = args[the_index]->val_int();
      /*
        Note: Item::null_value() can't be trusted alone here; there are cases
        (for the DATE data type in particular) where we can have it set
        without Item::m_nullable being set! This really should be cleaned up,
        but until that happens, we need to have a more conservative check.
      */
      if (args[the_index]->is_nullable() && args[the_index]->null_value)
        return {};
      else
        return value;
    }
    return 1;
  }

  /// The value of the `occurrence` argument, or its default if absent.
  std::optional<int> occurrence() const {
    int the_index = occ_arg_pos();
    if (the_index != -1 && arg_count >= static_cast<uint>(the_index) + 1) {
      int value = args[the_index]->val_int();
      /*
        Note: Item::null_value() can't be trusted alone here; there are cases
        (for the DATE data type in particular) where we can have it set
        without Item::maybe_null being set! This really should be cleaned up,
        but until that happens, we need to have a more conservative check.
      */
      if (args[the_index]->is_nullable() && args[the_index]->null_value)
        return {};
      else
        return value;
    }
    return 0;
  }

  /// The value of the `match_parameter` argument, or an empty string if absent.
  std::optional<std::string> match_parameter() const {
    int the_index = match_arg_pos();
    if (the_index != -1 && arg_count >= static_cast<uint>(the_index) + 1) {
      StringBuffer<5> buf;  // Longer match_parameter doesn't make sense.
      String *s = args[the_index]->val_str(&buf);
      if (s != nullptr)
        return to_string(*s);
      else
        return {};
    }
    return std::string{};
  }

  void cleanup() override;

 protected:
  String *convert_int_to_str(String *str) {
    assert(fixed == 1);
    longlong nr = val_int();
    if (null_value) return nullptr;
    str->set_int(nr, unsigned_flag, collation.collation);
    return str;
  }

  my_decimal *convert_int_to_decimal(my_decimal *value) {
    assert(fixed == 1);
    longlong nr = val_int();
    if (null_value) return nullptr; /* purecov: inspected */
    int2my_decimal(E_DEC_FATAL_ERROR, nr, unsigned_flag, value);
    return value;
  }

  double convert_int_to_real() {
    assert(fixed == 1);
    return val_int();
  }

  double convert_str_to_real() {
    assert(fixed == 1);
    int err_not_used;
    const char *end_not_used;
    String *res = val_str(&str_value);
    if (res == nullptr) return 0.0;
    return my_strntod(res->charset(), res->ptr(), res->length(), &end_not_used,
                      &err_not_used);
  }

  longlong convert_str_to_int() {
    assert(fixed == 1);
    int err;
    String *res = val_str(&str_value);
    if (res == nullptr) return 0;
    return my_strntoll(res->charset(), res->ptr(), res->length(), 10, nullptr,
                       &err);
  }

  /**
    The position in the argument list of 'position'. -1 means that the default
    should be used.
  */
  virtual int pos_arg_pos() const = 0;

  /**
    The position in the argument list of 'occurrence'. -1 means that the default
    should be used.
  */
  virtual int occ_arg_pos() const = 0;

  /// The position in the argument list of match_parameter.
  virtual int match_arg_pos() const = 0;

  bool set_pattern();

  unique_ptr_destroy_only<regexp::Regexp_facade> m_facade;
};

class Item_func_regexp_instr : public Item_func_regexp {
 public:
  Item_func_regexp_instr(const POS &pos, PT_item_list *opt_list)
      : Item_func_regexp(pos, opt_list) {
    set_data_type_longlong();
  }

  Item_result result_type() const override { return INT_RESULT; }

  bool fix_fields(THD *thd, Item **arguments) override;

  String *val_str(String *str) override { return convert_int_to_str(str); }

  double val_real() override { return convert_int_to_real(); }

  longlong val_int() override;

  const char *func_name() const override { return "regexp_instr"; }

  /// The value of the `return_option` argument, or its default if absent.
  std::optional<int> return_option() const {
    int the_index = retopt_arg_pos();
    if (the_index != -1 && arg_count >= static_cast<uint>(the_index) + 1) {
      int value = args[the_index]->val_int();
      if (args[the_index]->null_value)
        return std::optional<int>();
      else
        return value;
    }
    return 0;
  }

  /**
    @{

    Copy-pasted from Item_int_func. Usually, an SQL function returning INTEGER
    just inherits Item_int_func and thus the implementation, but these classes
    need to have Item_func_regexp as base class because of fix_fields().
  */
  bool get_date(MYSQL_TIME *ltime, my_time_flags_t fuzzydate) override {
    return get_date_from_int(ltime, fuzzydate);
  }

  bool get_time(MYSQL_TIME *t) override { return get_time_from_int(t); }
  /// @}

 protected:
  int pos_arg_pos() const override { return 2; }
  int occ_arg_pos() const override { return 3; }
  /// The position in the argument list of `occurrence`.
  int retopt_arg_pos() const { return 4; }
  int match_arg_pos() const override { return 5; }

 private:
  bool resolve_type(THD *) final;
};

class Item_func_regexp_like : public Item_func_regexp {
 public:
  Item_func_regexp_like(const POS &pos, PT_item_list *opt_list)
      : Item_func_regexp(pos, opt_list) {
    set_data_type_bool();
  }

  Item_result result_type() const override { return INT_RESULT; }

  String *val_str(String *str) override { return convert_int_to_str(str); }

  double val_real() override { return convert_int_to_real(); }

  longlong val_int() override;

  const char *func_name() const override { return "regexp_like"; }

  bool is_bool_func() const override { return true; }

  /**
    @{

    Copy-pasted from Item_int_func. Usually, an SQL function returning INTEGER
    just inherits Item_int_func and thus the implementation, but these classes
    need to have Item_func_regexp as base class because of fix_fields().
  */
  bool get_date(MYSQL_TIME *ltime, my_time_flags_t fuzzydate) override {
    return get_date_from_int(ltime, fuzzydate);
  }

  bool get_time(MYSQL_TIME *t) override { return get_time_from_int(t); }
  /// @}

 protected:
  int pos_arg_pos() const override { return -1; }
  int occ_arg_pos() const override { return -1; }
  int match_arg_pos() const override { return 2; }

 private:
  bool resolve_type(THD *) final;
};

class Item_func_regexp_replace : public Item_func_regexp {
 public:
  Item_func_regexp_replace(const POS &pos, PT_item_list *item_list)
      : Item_func_regexp(pos, item_list) {}

  Item_result result_type() const override { return STRING_RESULT; }

  bool resolve_type(THD *) final;

  Item *replacement() { return args[2]; }

  longlong val_int() override { return convert_str_to_int(); }

  String *val_str(String *result) override;

  double val_real() override { return convert_str_to_real(); }

  const char *func_name() const override { return "regexp_replace"; }

  /**
    @{

    Copy-pasted from Item_str_func. Usually, an SQL function returning INTEGER
    just inherits Item_str_func and thus the implementation, but these classes
    need to have Item_func_regexp as base class because of fix_fields().
  */
  bool get_date(MYSQL_TIME *ltime, my_time_flags_t fuzzydate) override {
    return get_date_from_string(ltime, fuzzydate);
  }

  bool get_time(MYSQL_TIME *t) override { return get_time_from_string(t); }
  /// @}

 protected:
  int pos_arg_pos() const override { return 3; }
  int occ_arg_pos() const override { return 4; }
  int match_arg_pos() const override { return 5; }
};

class Item_func_regexp_substr : public Item_func_regexp {
 public:
  Item_func_regexp_substr(const POS &pos, PT_item_list *item_list)
      : Item_func_regexp(pos, item_list) {}

  Item_result result_type() const override { return STRING_RESULT; }

  bool resolve_type(THD *) final;

  longlong val_int() override { return convert_str_to_int(); }

  String *val_str(String *result) override;

  double val_real() override { return convert_str_to_real(); }

  const char *func_name() const override { return "regexp_substr"; }

  /**
    @{

    Copy-pasted from Item_str_func. Usually, an SQL function returning INTEGER
    just inherits Item_str_func and thus the implementation, but these classes
    need to have Item_func_regexp as base class because of fix_fields().
  */
  bool get_date(MYSQL_TIME *ltime, my_time_flags_t fuzzydate) override {
    return get_date_from_string(ltime, fuzzydate);
  }

  bool get_time(MYSQL_TIME *t) override { return get_time_from_string(t); }
  /// @}

 protected:
  int pos_arg_pos() const override { return 2; }
  int occ_arg_pos() const override { return 3; }
  int match_arg_pos() const override { return 4; }
};

class Item_func_icu_version final : public Item_static_string_func {
  using super = Item_static_string_func;

 public:
  explicit Item_func_icu_version(const POS &pos);

  bool itemize(Parse_context *pc, Item **res) override;
};

#if defined(__GNUC__) && !defined(__clang__)
#pragma GCC diagnostic pop
#endif

#endif  // SQL_ITEM_REGEXP_FUNC_H_