/*  Copyright (c) 2015, 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 */

/**
  @file
  Server session service implementation. For more information please check
  the function comments.
*/

#include <stddef.h>
#include <new>

#include "my_dbug.h"
/*
 service_srv_session.h should not be first to be included as it will include
 - include/mysql/service_srv_session.h
 - include/mysql/plugin.h
 - include/mysql/services.h
 - include/mysql/service_command.h
 which in turn will need MYSQL_SESSION but won't see it, as it will be
 declared after the includes.
 */
#include "mysql/service_srv_session.h"
#include "mysqld_error.h"
#include "sql/conn_handler/connection_handler_manager.h"
#include "sql/current_thd.h"                              // current_thd
#include "sql/derror.h"                                   // ER_DEFAULT
#include "sql/mysqld.h"                                   // SERVER_OPERATING
#include "sql/server_component/mysql_admin_session_imp.h" /* mysql_component_mysql_admin_session_imp */
#include "sql/sql_class.h"
#include "sql/srv_session.h"

/**
  Initializes physical thread to use with session service.

  @return
    0  success
    1  failure
*/
int srv_session_init_thread(const void *plugin) {
  return Srv_session::init_thread(plugin);
}

/**
  Deinitializes physical thread to use with session service
*/
void srv_session_deinit_thread() { Srv_session::deinit_thread(); }

/**
  Opens server session

  @param error_cb              Default completion callback
  @param plugin_ctx            Plugin's context, opaque pointer that would
                               be provided to callbacks. Might be NULL.
  @param ignore_max_connection_limit true if the session is exempted
  @return
    handler of session   on success
    NULL                 on failure
*/
Srv_session *srv_session_open_internal(srv_session_error_cb error_cb,
                                       void *plugin_ctx,
                                       bool ignore_max_connection_limit) {
  DBUG_TRACE;

  if (!srv_session_server_is_available()) {
    if (error_cb)
      error_cb(plugin_ctx, ER_SERVER_ISNT_AVAILABLE,
               ER_DEFAULT(ER_SERVER_ISNT_AVAILABLE));
    return nullptr;
  }

  bool simulate_reach_max_connections = false;
  DBUG_EXECUTE_IF("simulate_reach_max_connections",
                  simulate_reach_max_connections = true;);

  Connection_handler_manager *conn_manager =
      Connection_handler_manager::get_instance();

  if (simulate_reach_max_connections ||
      !conn_manager->check_and_incr_conn_count(ignore_max_connection_limit)) {
    if (error_cb)
      error_cb(plugin_ctx, ER_CON_COUNT_ERROR, ER_DEFAULT(ER_CON_COUNT_ERROR));
    return nullptr;
  }

  Srv_session *session =
      new (std::nothrow) class Srv_session(error_cb, plugin_ctx);

  if (!session) {
    DBUG_PRINT("error", ("Can't allocate a Srv_session object"));
    connection_errors_internal++;
    if (error_cb)
      error_cb(plugin_ctx, ER_OUT_OF_RESOURCES,
               ER_DEFAULT(ER_OUT_OF_RESOURCES));
  } else {
    THD *current = current_thd;
    THD *stack_thd = session->get_thd();

    session->get_thd()->thread_stack = reinterpret_cast<char *>(&stack_thd);
    session->get_thd()->store_globals();

    bool result = session->open();

    session->get_thd()->restore_globals();

    if (result) {
      delete session;
      session = nullptr;
    }

    if (current) current->store_globals();
  }
  return session;
}

Srv_session *srv_session_open(srv_session_error_cb error_cb, void *plugin_ctx) {
  DBUG_TRACE;
  return srv_session_open_internal(error_cb, plugin_ctx, false);
}

/**
  Opens server admin session

  @param error_cb              Default completion callback
  @param ctx            Plugin's context, opaque pointer that would
                               be provided to callbacks. Might be NULL.
  @sa srv_session_open_internal
  @return
    handler of session   on success
    NULL                 on failure
*/
DEFINE_METHOD(MYSQL_SESSION, mysql_component_mysql_admin_session_imp::open,
              (srv_session_error_cb error_cb, void *ctx)) {
  DBUG_TRACE;
  return srv_session_open_internal(error_cb, ctx, true);
}

/**
  Detaches a session from current physical thread.

  @param session  Session handle to detach

  @returns
    0  success
    1  failure
*/
int srv_session_detach(Srv_session *session) {
  DBUG_TRACE;

  if (!session || !Srv_session::is_valid(session)) {
    DBUG_PRINT("error", ("Session is not valid"));
    return true;
  }

  return session->detach();
}

/**
  Closes a session.

  @param session  Session handle to close

  @returns
    0  Session successfully closed
    1  Session wasn't found or key doesn't match
*/
int srv_session_close(Srv_session *session) {
  DBUG_TRACE;

  if (!session || !Srv_session::is_valid(session)) {
    DBUG_PRINT("error", ("Session is not valid"));
    return 1;
  }

  session->close();
  delete session;

  /*
    Here we don't need to reattach the previous session, as the next
    function (run_command() for example) will attach to whatever is needed.
  */
  return 0;
}

/**
  Returns if the server is available (not booting or shutting down)

  @return
    0  not available
    1  available
*/
int srv_session_server_is_available() {
  return get_server_state() == SERVER_OPERATING;
}

int srv_session_attach(MYSQL_SESSION session, MYSQL_THD *ret_previous_thd) {
  DBUG_TRACE;

  if (!Srv_session::is_srv_session_thread()) {
    DBUG_PRINT("error", ("Thread can't be used with srv_session API"));
    return 1;
  }

  if (!session || !Srv_session::is_valid(session)) {
    DBUG_PRINT("error", ("Session is not valid"));
    return 1;
  }

  if (ret_previous_thd) *ret_previous_thd = current_thd;

  return session->attach();
}
