/* Copyright (c) 2015, 2020 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 */


#include "sql_show_status.h"
#include "sql_parse.h"
#include "sql_yacc.h"
#include "parse_tree_items.h"
#include "parse_tree_nodes.h"
#include "item_cmpfunc.h"

/**
  Build a replacement query for SHOW STATUS.
  When the parser accepts the following syntax:
    SHOW GLOBAL STATUS
  the parsed tree built for this query is in fact:
  SELECT * FROM
           (SELECT VARIABLE_NAME as Variable_name, VARIABLE_VALUE as Value
            FROM performance_schema.global_status) global_status

  Likewise, the query:
    SHOW GLOBAL STATUS LIKE "<value>"
  is built as:
  SELECT * FROM
           (SELECT VARIABLE_NAME as Variable_name, VARIABLE_VALUE as Value
            FROM performance_schema.global_status) global_status
            WHERE Variable_name LIKE "<value>"

  Likewise, the query:
    SHOW GLOBAL STATUS where <where_clause>
  is built as:
    SELECT * FROM
             (SELECT VARIABLE_NAME as Variable_name, VARIABLE_VALUE as Value
              FROM performance_schema.global_status) global_status
              WHERE <where_clause>
*/
SELECT_LEX*
build_query(const POS &pos,
            THD *thd,
            enum_sql_command command,
            const LEX_STRING& table_name,
            const String *wild,
            Item *where_cond)
{
  /*
    MAINTAINER:
    This code builds a parsed tree for a query.
    Write the query to build in SQL first,
    then see turn_parser_debug_on() in sql_yacc.yy
    to understand which grammar actions are needed to
    build a parsed tree for this SQL query.
  */
  static const LEX_STRING col_name= { C_STRING_WITH_LEN("VARIABLE_NAME")};
  static const LEX_STRING as_name= { C_STRING_WITH_LEN("Variable_name")};
  static const LEX_STRING col_value= { C_STRING_WITH_LEN("VARIABLE_VALUE")};
  static const LEX_STRING as_value= { C_STRING_WITH_LEN("Value")};
  static const LEX_STRING pfs= { C_STRING_WITH_LEN("performance_schema")};

  static const Query_options options=
  {
    0, /* query_spec_options */
    SELECT_LEX::SQL_CACHE_UNSPECIFIED /* sql_cache */
  };

  static const Select_lock_type lock_type=
  {
    false, /* is_set */
    TL_READ, /* lock_type */
    false /* is_safe_to_cache_query */
  };


  /* * */
  Item *star= new (thd->mem_root) Item_asterisk(pos, NULL, NULL);

  PT_select_item_list *item_list2;
  item_list2= new (thd->mem_root) PT_select_item_list();
  if (item_list2 == NULL)
    return NULL;
  item_list2->push_back(star);

  /* SELECT * ... */
  PT_select_options_and_item_list *options_and_item_list2;
  options_and_item_list2= new (thd->mem_root) PT_select_options_and_item_list(options, item_list2);
  if (options_and_item_list2 == NULL)
    return NULL;


 /*
    ... (SELECT VARIABLE_NAME as Variable_name, VARIABLE_VALUE as Value
           FROM performance_schema.<table_name>) ...
  */

  /* ... VARIABLE_NAME ... */
  PTI_simple_ident_ident *ident_name;
  ident_name= new (thd->mem_root) PTI_simple_ident_ident(pos, col_name);
  if (ident_name == NULL)
    return NULL;

  /* ... VARIABLE_NAME as Variable_name ... */
  PTI_expr_with_alias *expr_name;
  expr_name= new (thd->mem_root) PTI_expr_with_alias(pos, ident_name, pos.cpp, as_name);
  if (expr_name == NULL)
    return NULL;

  /* ... VARIABLE_VALUE ... */
  PTI_simple_ident_ident *ident_value;
  ident_value= new (thd->mem_root) PTI_simple_ident_ident(pos, col_value);
  if (ident_value == NULL)
    return NULL;

  /* ... VARIABLE_VALUE as Value ... */
  PTI_expr_with_alias *expr_value;
  expr_value= new (thd->mem_root) PTI_expr_with_alias(pos, ident_value, pos.cpp, as_value);
  if (expr_value == NULL)
    return NULL;

  /* ... VARIABLE_NAME as Variable_name, VARIABLE_VALUE as Value ... */
  PT_select_item_list *item_list;
  item_list= new (thd->mem_root) PT_select_item_list();
  if (item_list == NULL)
    return NULL;
  item_list->push_back(expr_name);
  item_list->push_back(expr_value);

  /* SELECT VARIABLE_NAME as Variable_name, VARIABLE_VALUE as Value ... */
  PT_select_options_and_item_list *options_and_item_list;
  options_and_item_list= new (thd->mem_root) PT_select_options_and_item_list(options, item_list);
  if (options_and_item_list == NULL)
    return NULL;

  /*
    make_table_list() might alter the database and table name strings. Create
    copies and leave the original values unaltered.
  */

  /* ... performance_schema ... */
  LEX_CSTRING tmp_db_name;
  if (!thd->make_lex_string(&tmp_db_name, pfs.str, pfs.length, false))
    return NULL;

  /* ... <table_name> ... */
  LEX_CSTRING tmp_table_name;
  if (!thd->make_lex_string(&tmp_table_name, table_name.str, table_name.length, false))
    return NULL;

  /* ... performance_schema.<table_name> ... */
  Table_ident *table_ident;
  table_ident= new (thd->mem_root) Table_ident(tmp_db_name, tmp_table_name);
  if (table_ident == NULL)
    return NULL;

  /* ... FROM performance_schema.<table_name> ... */
  PT_table_factor_table_ident *table_factor;
  table_factor= new (thd->mem_root) PT_table_factor_table_ident(table_ident, NULL, NULL, NULL);
  if (table_factor == NULL)
    return NULL;

  PT_join_table_list *join_table_list;
  join_table_list= new (thd->mem_root) PT_join_table_list(pos, table_factor);
  if (join_table_list == NULL)
    return NULL;

  PT_table_reference_list *table_reference_list;
  table_reference_list= new (thd->mem_root) PT_table_reference_list(join_table_list);
  if (table_reference_list == NULL)
    return NULL;

  PT_table_expression *table_expression;
  table_expression= new (thd->mem_root)PT_table_expression(table_reference_list,
                                                           NULL,
                                                           NULL,
                                                           NULL,
                                                           NULL,
                                                           NULL,
                                                           NULL,
                                                           lock_type);

  /* ... FROM (SELECT ...) ... */
  PT_table_factor_select_sym *table_factor_select_sym;
  table_factor_select_sym= new (thd->mem_root) PT_table_factor_select_sym(pos, NULL, options, item_list, table_expression);
  if (table_factor_select_sym == NULL)
    return NULL;

  PT_select_derived *select_derived;
  select_derived= new (thd->mem_root) PT_select_derived(pos, table_factor_select_sym);
  if (select_derived == NULL)
    return NULL;

  PT_select_derived_union_select *select_derived_union_select;
  select_derived_union_select= new (thd->mem_root) PT_select_derived_union_select(select_derived, NULL, pos);
  if (select_derived_union_select == NULL)
    return NULL;

  /* ... derived_table ... */
  LEX_STRING derived_table_name;
  if (!thd->make_lex_string(&derived_table_name, table_name.str, table_name.length, false))
    return NULL;

  PT_table_factor_parenthesis *table_factor_parenthesis;
  table_factor_parenthesis= new (thd->mem_root) PT_table_factor_parenthesis(select_derived_union_select, &derived_table_name, pos);
  if (table_factor_parenthesis == NULL)
    return NULL;

  PT_join_table_list *join_table_list2;
  join_table_list2= new (thd->mem_root) PT_join_table_list(pos, table_factor_parenthesis);
  if (join_table_list2 == NULL)
    return NULL;

  PT_table_reference_list *table_reference_list2;
  table_reference_list2= new (thd->mem_root) PT_table_reference_list(join_table_list2);
  if (table_reference_list2 == NULL)
    return NULL;

  /* where clause */
  Item *where_clause= NULL;

  if (wild != NULL)
  {
    /* ... Variable_name ... */
    PTI_simple_ident_ident *ident_name_where;
    ident_name_where= new (thd->mem_root) PTI_simple_ident_ident(pos, as_name);
    if (ident_name_where == NULL)
      return NULL;

    /* ... <value> ... */
    LEX_STRING *lex_string;
    lex_string= static_cast<LEX_STRING*> (thd->alloc(sizeof(LEX_STRING)));
    if (lex_string == NULL)
      return NULL;
    lex_string->length= wild->length();
    lex_string->str= thd->strmake(wild->ptr(), wild->length());
    if (lex_string->str == NULL)
      return NULL;

    PTI_text_literal_text_string *wild_string;
    wild_string= new (thd->mem_root) PTI_text_literal_text_string(pos, false, *lex_string); // TODO WL#6629 check is_7bit
    if (wild_string == NULL)
      return NULL;

    /* ... Variable_name LIKE <value> ... */
    Item_func_like *func_like;
    func_like= new (thd->mem_root) Item_func_like(pos, ident_name_where, wild_string, NULL);
    if (func_like == NULL)
      return NULL;

    /* ... WHERE Variable_name LIKE <value> ... */
    where_clause= new (thd->mem_root) PTI_context<CTX_WHERE>(pos, func_like);
    if (where_clause == NULL)
      return NULL;
  }
  else
  {
    where_clause= where_cond;
  }


  /* SELECT * FROM (SELECT ...) derived_table [ WHERE Variable_name LIKE <value> ] */
  /* SELECT * FROM (SELECT ...) derived_table [ WHERE <cond> ] */
  PT_select_part2 *select_part2;
  select_part2= new (thd->mem_root) PT_select_part2(options_and_item_list2,
                                                    NULL, /* opt_into */
                                                    table_reference_list2, /* from_clause */
                                                    where_clause, /* opt_where_clause */
                                                    NULL, /* opt_group_clause */
                                                    NULL, /* opt_having_clause */
                                                    NULL, /* opt_order_clause */
                                                    NULL, /* opt_limit_clause */
                                                    NULL, /* opt_procedure_analyse_clause */
                                                    NULL, /* opt_into */
                                                    lock_type /* opt_select_lock_type */);
  if (select_part2 == NULL)
    return NULL;

  PT_select_init2 *select_init2;
  select_init2= new (thd->mem_root) PT_select_init2(NULL, select_part2, NULL);
  if (select_init2 == NULL)
    return NULL;

  PT_select *select;
  select= new (thd->mem_root) PT_select(select_init2, SQLCOM_SELECT);
  if (select == NULL)
    return NULL;

  LEX *lex= thd->lex;
  SELECT_LEX *current_select= lex->current_select();
  Parse_context pc(thd, current_select);
  if (thd->is_error())
    return NULL;

  if (select->contextualize(&pc))
    return NULL;

  /* contextualize sets to COM_SELECT */
  lex->sql_command= command;

  return current_select;
}

SELECT_LEX*
build_show_session_status(const POS &pos, THD *thd, const String *wild, Item *where_cond)
{
  static const LEX_STRING table_name= { C_STRING_WITH_LEN("session_status")};

  return build_query(pos, thd, SQLCOM_SHOW_STATUS, table_name, wild, where_cond);
}

SELECT_LEX*
build_show_global_status(const POS &pos, THD *thd, const String *wild, Item *where_cond)
{
  static const LEX_STRING table_name= { C_STRING_WITH_LEN("global_status")};

  return build_query(pos, thd, SQLCOM_SHOW_STATUS, table_name, wild, where_cond);
}

SELECT_LEX*
build_show_session_variables(const POS &pos, THD *thd, const String *wild, Item *where_cond)
{
  static const LEX_STRING table_name= { C_STRING_WITH_LEN("session_variables")};

  return build_query(pos, thd, SQLCOM_SHOW_VARIABLES, table_name, wild, where_cond);
}

SELECT_LEX*
build_show_global_variables(const POS &pos, THD *thd, const String *wild, Item *where_cond)
{
  static const LEX_STRING table_name= { C_STRING_WITH_LEN("global_variables")};

  return build_query(pos, thd, SQLCOM_SHOW_VARIABLES, table_name, wild, where_cond);
}

