/* Copyright (C) 2000-2006 MySQL AB

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   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 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

/* Functions to create an item. Used by sql/sql_yacc.yy */

#ifndef ITEM_CREATE_H
#define ITEM_CREATE_H

/**
  Public function builder interface.
  The parser (sql/sql_yacc.yy) uses a factory / builder pattern to
  construct an <code>Item</code> object for each function call.
  All the concrete function builders implements this interface,
  either directly or indirectly with some adapter helpers.
  Keeping the function creation separated from the bison grammar allows
  to simplify the parser, and avoid the need to introduce a new token
  for each function, which has undesirable side effects in the grammar.
*/

class Create_func
{
public:
  /**
    The builder create method.
    Given the function name and list or arguments, this method creates
    an <code>Item</code> that represents the function call.
    In case or errors, a NULL item is returned, and an error is reported.
    Note that the <code>thd</code> object may be modified by the builder.
    In particular, the following members/methods can be set/called,
    depending on the function called and the function possible side effects.
    <ul>
      <li><code>thd->lex->binlog_row_based_if_mixed</code></li>
      <li><code>thd->lex->current_context()</code></li>
      <li><code>thd->lex->safe_to_cache_query</code></li>
      <li><code>thd->lex->uncacheable(UNCACHEABLE_SIDEEFFECT)</code></li>
      <li><code>thd->lex->uncacheable(UNCACHEABLE_RAND)</code></li>
      <li><code>thd->lex->add_time_zone_tables_to_query_tables(thd)</code></li>
    </ul>
    @param thd The current thread
    @param name The function name
    @param item_list The list of arguments to the function, can be NULL
    @return An item representing the parsed function call, or NULL
  */
  virtual Item* create(THD *thd, LEX_STRING name, List<Item> *item_list) = 0;

protected:
  /** Constructor */
  Create_func() {}
  /** Destructor */
  virtual ~Create_func() {}
};


/**
  Function builder for qualified functions.
  This builder is used with functions call using a qualified function name
  syntax, as in <code>db.func(expr, expr, ...)</code>.
*/

class Create_qfunc : public Create_func
{
public:
  /**
    The builder create method, for unqualified functions.
    This builder will use the current database for the database name.
    @param thd The current thread
    @param name The function name
    @param item_list The list of arguments to the function, can be NULL
    @return An item representing the parsed function call
  */
  virtual Item* create(THD *thd, LEX_STRING name, List<Item> *item_list);

  /**
    The builder create method, for qualified functions.
    @param thd The current thread
    @param db The database name
    @param name The function name
    @param item_list The list of arguments to the function, can be NULL
    @return An item representing the parsed function call
  */
  virtual Item* create(THD *thd, LEX_STRING db, LEX_STRING name,
                       List<Item> *item_list) = 0;

protected:
  /** Constructor. */
  Create_qfunc() {}
  /** Destructor. */
  virtual ~Create_qfunc() {}
};


/**
  Find the native function builder associated with a given function name.
  @param thd The current thread
  @param name The native function name
  @return The native function builder associated with the name, or NULL
*/
extern Create_func * find_native_function_builder(THD *thd, LEX_STRING name);


/**
  Find the function builder for qualified functions.
  @param thd The current thread
  @return A function builder for qualified functions
*/
extern Create_qfunc * find_qualified_function_builder(THD *thd);


#ifdef HAVE_DLOPEN
/**
  Function builder for User Defined Functions.
*/

class Create_udf_func : public Create_func
{
public:
  virtual Item* create(THD *thd, LEX_STRING name, List<Item> *item_list);

  /**
    The builder create method, for User Defined Functions.
    @param thd The current thread
    @param fct The User Defined Function metadata
    @param item_list The list of arguments to the function, can be NULL
    @return An item representing the parsed function call
  */
  Item* create(THD *thd, udf_func *fct, List<Item> *item_list);

  /** Singleton. */
  static Create_udf_func s_singleton;

protected:
  /** Constructor. */
  Create_udf_func() {}
  /** Destructor. */
  virtual ~Create_udf_func() {}
};
#endif


/**
  Builder for cast expressions.
  @param thd The current thread
  @param a The item to cast
  @param cast_type the type casted into
  @param len TODO
  @param dec TODO
  @param cs The character set
*/
Item*
create_func_cast(THD *thd, Item *a, Cast_target cast_type, int len, int dec,
                 CHARSET_INFO *cs);

#endif

