/* Copyright (C) 2010 Sergei Golubchik and Monty Program 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */

#include "feedback.h"
#include <sql_acl.h>
#include <sql_parse.h>
#include <sql_show.h>
#include <time.h>

namespace feedback {

static THD *thd= 0;                ///< background thread thd
static my_thread_id thd_thread_id; ///< its thread_id

static size_t needed_size= 20480;

ulong startup_interval= 60*5;     ///< in seconds (5 minutes)
ulong first_interval= 60*60*24;   ///< in seconds (one day)
ulong interval= 60*60*24*7;       ///< in seconds (one week)

/**
  reads the rows from a table and puts them, concatenated, in a String

  @note
  1. only supports two column tables - no less, no more.
  2. it emulates mysql -e "select * from..." and thus it separates
     columns with \t and starts the output with column names.
*/
static int table_to_string(TABLE *table, String *result)
{
  int res;
  char buff1[MAX_FIELD_WIDTH], buff2[MAX_FIELD_WIDTH];
  String str1(buff1, sizeof(buff1), system_charset_info);
  String str2(buff2, sizeof(buff2), system_charset_info);

  res= table->file->ha_rnd_init(1);

  dbug_tmp_use_all_columns(table, &table->read_set);

  while(!res && !table->file->ha_rnd_next(table->record[0]))
  {
    table->field[0]->val_str(&str1);
    table->field[1]->val_str(&str2);
    if (result->reserve(str1.length() + str2.length() + 3))
      res= 1;
    else
    {
      result->qs_append(str1.ptr(), str1.length());
      result->qs_append('\t');
      result->qs_append(str2.ptr(), str2.length());
      result->qs_append('\n');
    }
  }

  res = res || (int)result->append('\n');

  /*
    Note, "|=" and not "||" - because we want to call ha_rnd_end()
    even if res is already 1.
  */
  res |= table->file->ha_rnd_end();

  return res;
}

/**
  Initialize the THD and TABLE_LIST

  The structures must be sufficiently initialized for create_tmp_table()
  and fill_feedback() to work.
*/
static int prepare_for_fill(TABLE_LIST *tables)
{
  /*
    Add our thd to the list, for it to be visible in SHOW PROCESSLIST.
    But don't generate thread_id every time - use the saved value
    (every increment of global thread_id counts as a new connection
    in SHOW STATUS and we want to avoid skewing the statistics)
  */
  thd->variables.pseudo_thread_id= thd->thread_id;
  server_threads.insert(thd);
  thd->thread_stack= (char*) &tables;
  thd->store_globals();

  thd->mysys_var->current_cond= &sleep_condition;
  thd->mysys_var->current_mutex= &sleep_mutex;
  thd->proc_info="feedback";
  thd->set_command(COM_SLEEP);
  thd->system_thread= SYSTEM_THREAD_EVENT_WORKER; // whatever
  thd->set_time();
  thd->init_for_queries();
  thd->real_id= pthread_self();
  thd->db= null_clex_str;
  thd->security_ctx->host_or_ip= "";
  thd->security_ctx->db_access= DB_ACLS;
  thd->security_ctx->master_access= ALL_KNOWN_ACL;
  bzero((char*) &thd->net, sizeof(thd->net));
  lex_start(thd);
  thd->lex->init_select();

  LEX_CSTRING tbl_name= {i_s_feedback->table_name, strlen(i_s_feedback->table_name) };

  tables->init_one_table(&INFORMATION_SCHEMA_NAME, &tbl_name, 0, TL_READ);
  tables->schema_table= i_s_feedback;
  tables->schema_table_reformed= 1;
  tables->select_lex= thd->lex->first_select_lex();
  DBUG_ASSERT(tables->select_lex);
  tables->table= create_schema_table(thd, tables);
  if (!tables->table)
    return 1;

  tables->table->pos_in_table_list= tables;

  return 0;
}

/**
  Try to detect if this thread is going down

  which can happen for different reasons:
  * plugin is being unloaded
  * mysqld server is being shut down
  * the thread is being killed

*/
static bool going_down()
{
  return shutdown_plugin || abort_loop || (thd && thd->killed);
}

/**
  just like sleep, but waits on a condition and checks "plugin shutdown" status
*/
static int slept_ok(time_t sec)
{
  struct timespec abstime;
  int ret= 0;

  set_timespec(abstime, sec);

  mysql_mutex_lock(&sleep_mutex);
  while (!going_down() && ret != ETIMEDOUT)
    ret= mysql_cond_timedwait(&sleep_condition, &sleep_mutex, &abstime);
  mysql_mutex_unlock(&sleep_mutex);

  return !going_down();
}

/**
  create a feedback report and send it to all specified urls

  If "when" argument is not null, only it and the server uid are sent.
  Otherwise a full report is generated.
*/
static void send_report(const char *when)
{
  TABLE_LIST tables;
  String str;
  int i, last_todo;
  Url **todo= (Url**)alloca(url_count*sizeof(Url*));

  str.alloc(needed_size); // preallocate it to avoid many small mallocs

  /*
    on startup and shutdown the server may not be completely
    initialized, and full report won't work.
    We send a short status notice only.
  */
  if (when)
  {
    str.length(0);
    str.append(STRING_WITH_LEN("FEEDBACK_SERVER_UID"));
    str.append('\t');
    str.append(server_uid_buf, sizeof(server_uid_buf)-1);
    str.append('\n');
    str.append(STRING_WITH_LEN("FEEDBACK_WHEN"));
    str.append('\t');
    str.append(when, strlen(when));
    str.append('\n');
    str.append(STRING_WITH_LEN("FEEDBACK_USER_INFO"));
    str.append('\t');
    str.append(user_info, strlen(user_info));
    str.append('\n');
    str.append('\n');
  }
  else
  {
    /*
      otherwise, prepare the THD and TABLE_LIST,
      create and fill the temporary table with data just like
      SELECT * FROM INFORMATION_SCHEMA.FEEDBACK is doing,
      read and concatenate table data into a String.
    */
    if (!(thd= new THD(thd_thread_id)))
      return;

    if (prepare_for_fill(&tables))
      goto ret;

    if (fill_feedback(thd, &tables, NULL))
      goto ret;

    if (table_to_string(tables.table, &str))
      goto ret;

    needed_size= (size_t)(str.length() * 1.1);

    free_tmp_table(thd, tables.table);
    tables.table= 0;
  }

  /*
    Try to send the report on every url from the list, remove url on success,
    keep failed in the list. Repeat until the list is empty.
  */
  memcpy(todo, urls, url_count*sizeof(Url*));
  last_todo= url_count - 1;
  do
  {
    for (i= 0; i <= last_todo;)
    {
      Url *url= todo[i];

      if (thd) // for nicer SHOW PROCESSLIST
        thd->set_query(const_cast<char*>(url->url()), (uint) url->url_length());

      if (url->send(str.ptr(), str.length()))
        i++;
      else
        todo[i]= todo[last_todo--];
    }
    if (last_todo < 0)
      break;
  } while (slept_ok(send_retry_wait)); // wait a little bit before retrying

ret:
  if (thd)
  {
    if (tables.table)
      free_tmp_table(thd, tables.table);
    thd->cleanup_after_query();
    /*
      clean up, free the thd.
      reset all thread local status variables to minimize
      the effect of the background thread on SHOW STATUS.
    */
    server_threads.erase(thd);
    thd->set_status_var_init();
    thd->killed= KILL_CONNECTION;
    delete thd;
    thd= 0;
  }
}

/**
  background sending thread
*/
pthread_handler_t background_thread(void *arg __attribute__((unused)))
{
  if (my_thread_init())
    return 0;

  thd_thread_id= next_thread_id();

  if (slept_ok(startup_interval))
  {
    send_report("startup");

    if (slept_ok(first_interval))
    {
      send_report(NULL);

      while(slept_ok(interval))
        send_report(NULL);
    }

    send_report("shutdown");
  }

  my_thread_end();
  pthread_exit(0);
  return 0;
}

} // namespace feedback