<?php
/*
 +--------------------------------------------------------------------+
 | CiviCRM version 4.7                                                |
 +--------------------------------------------------------------------+
 | Copyright CiviCRM LLC (c) 2004-2017                                |
 +--------------------------------------------------------------------+
 | This file is a part of CiviCRM.                                    |
 |                                                                    |
 | CiviCRM is free software; you can copy, modify, and distribute it  |
 | under the terms of the GNU Affero General Public License           |
 | Version 3, 19 November 2007 and the CiviCRM Licensing Exception.   |
 |                                                                    |
 | CiviCRM 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 Affero General Public License for more details.        |
 |                                                                    |
 | You should have received a copy of the GNU Affero General Public   |
 | License and the CiviCRM Licensing Exception along                  |
 | with this program; if not, contact CiviCRM LLC                     |
 | at info[AT]civicrm[DOT]org. If you have questions about the        |
 | GNU Affero General Public License or the licensing of CiviCRM,     |
 | see the CiviCRM license FAQ at http://civicrm.org/licensing        |
 +--------------------------------------------------------------------+
 */

/**
 *
 * @package CRM
 * @copyright CiviCRM LLC (c) 2004-2017
 */
class CRM_Logging_Schema {
  private $logs = array();
  private $tables = array();

  private $db;
  private $useDBPrefix = TRUE;

  private $reports = array(
    'logging/contact/detail',
    'logging/contact/summary',
    'logging/contribute/detail',
    'logging/contribute/summary',
  );

  /**
   * Columns that should never be subject to logging.
   *
   * CRM-13028 / NYSS-6933 - table => array (cols) - to be excluded from the update statement
   *
   * @var array
   */
  private $exceptions = array(
    'civicrm_job' => array('last_run'),
    'civicrm_group' => array('cache_date', 'refresh_date'),
  );

  /**
   * Specifications of all log table including
   *  - engine (default is archive, if not set.)
   *  - engine_config, a string appended to the engine type.
   *    For INNODB  space can be saved with 'ROW_FORMAT=COMPRESSED KEY_BLOCK_SIZE=4'
   *  - indexes (default is none and they cannot be added unless engine is innodb. If they are added and
   *    engine is not set to innodb an exception will be thrown since quiet acquiescence is easier to miss).
   *  - exceptions (by default those stored in $this->exceptions are included). These are
   *    excluded from the triggers.
   *
   * @var array
   */
  private $logTableSpec = array();

  /**
   * Setting Callback - Validate.
   *
   * @param mixed $value
   * @param array $fieldSpec
   *
   * @return bool
   * @throws API_Exception
   */
  public static function checkLoggingSupport(&$value, $fieldSpec) {
    $domain = new CRM_Core_DAO_Domain();
    $domain->find(TRUE);
    if (!(CRM_Core_DAO::checkTriggerViewPermission(FALSE)) && $value) {
      throw new API_Exception("In order to use this functionality, the installation's database user must have privileges to create triggers (in MySQL 5.0 – and in MySQL 5.1 if binary logging is enabled – this means the SUPER privilege). This install either does not seem to have the required privilege enabled.");
    }
    return TRUE;
  }

  /**
   * Setting Callback - On Change.
   *
   * Respond to changes in the "logging" setting. Set up or destroy
   * triggers, etal.
   *
   * @param array $oldValue
   *   List of component names.
   * @param array $newValue
   *   List of component names.
   * @param array $metadata
   *   Specification of the setting (per *.settings.php).
   */
  public static function onToggle($oldValue, $newValue, $metadata) {
    if ($oldValue == $newValue) {
      return;
    }

    $logging = new CRM_Logging_Schema();
    if ($newValue) {
      $logging->enableLogging();
    }
    else {
      $logging->disableLogging();
    }
  }

  /**
   * Populate $this->tables and $this->logs with current db state.
   */
  public function __construct() {
    $dao = new CRM_Contact_DAO_Contact();
    $civiDBName = $dao->_database;

    $dao = CRM_Core_DAO::executeQuery("
SELECT TABLE_NAME
FROM   INFORMATION_SCHEMA.TABLES
WHERE  TABLE_SCHEMA = '{$civiDBName}'
AND    TABLE_TYPE = 'BASE TABLE'
AND    TABLE_NAME LIKE 'civicrm_%'
");
    while ($dao->fetch()) {
      $this->tables[] = $dao->TABLE_NAME;
    }

    // do not log temp import, cache, menu and log tables
    $this->tables = preg_grep('/^civicrm_import_job_/', $this->tables, PREG_GREP_INVERT);
    $this->tables = preg_grep('/_cache$/', $this->tables, PREG_GREP_INVERT);
    $this->tables = preg_grep('/_log/', $this->tables, PREG_GREP_INVERT);
    $this->tables = preg_grep('/^civicrm_queue_/', $this->tables, PREG_GREP_INVERT);
    //CRM-14672
    $this->tables = preg_grep('/^civicrm_menu/', $this->tables, PREG_GREP_INVERT);
    $this->tables = preg_grep('/_temp_/', $this->tables, PREG_GREP_INVERT);
    // CRM-18178
    $this->tables = preg_grep('/_bak$/', $this->tables, PREG_GREP_INVERT);
    $this->tables = preg_grep('/_backup$/', $this->tables, PREG_GREP_INVERT);

    // do not log civicrm_mailing_event* tables, CRM-12300
    $this->tables = preg_grep('/^civicrm_mailing_event_/', $this->tables, PREG_GREP_INVERT);

    // do not log civicrm_mailing_recipients table, CRM-16193
    $this->tables = array_diff($this->tables, array('civicrm_mailing_recipients'));
    $this->logTableSpec = array_fill_keys($this->tables, array());
    foreach ($this->exceptions as $tableName => $fields) {
      $this->logTableSpec[$tableName]['exceptions'] = $fields;
    }
    CRM_Utils_Hook::alterLogTables($this->logTableSpec);
    $this->tables = array_keys($this->logTableSpec);
    $nonStandardTableNameString = $this->getNonStandardTableNameFilterString();

    if (defined('CIVICRM_LOGGING_DSN')) {
      $dsn = DB::parseDSN(CIVICRM_LOGGING_DSN);
      $this->useDBPrefix = (CIVICRM_LOGGING_DSN != CIVICRM_DSN);
    }
    else {
      $dsn = DB::parseDSN(CIVICRM_DSN);
      $this->useDBPrefix = FALSE;
    }
    $this->db = $dsn['database'];

    $dao = CRM_Core_DAO::executeQuery("
SELECT TABLE_NAME
FROM   INFORMATION_SCHEMA.TABLES
WHERE  TABLE_SCHEMA = '{$this->db}'
AND    TABLE_TYPE = 'BASE TABLE'
AND    (TABLE_NAME LIKE 'log_civicrm_%' $nonStandardTableNameString )
");
    while ($dao->fetch()) {
      $log = $dao->TABLE_NAME;
      $this->logs[substr($log, 4)] = $log;
    }
  }

  /**
   * Return logging custom data tables.
   */
  public function customDataLogTables() {
    return preg_grep('/^log_civicrm_value_/', $this->logs);
  }

  /**
   * Return custom data tables for specified entity / extends.
   *
   * @param string $extends
   *
   * @return array
   */
  public function entityCustomDataLogTables($extends) {
    $customGroupTables = array();
    $customGroupDAO = CRM_Core_BAO_CustomGroup::getAllCustomGroupsByBaseEntity($extends);
    $customGroupDAO->find();
    while ($customGroupDAO->fetch()) {
      $customGroupTables[$customGroupDAO->table_name] = $this->logs[$customGroupDAO->table_name];
    }
    return $customGroupTables;
  }

  /**
   * Disable logging by dropping the triggers (but keep the log tables intact).
   */
  public function disableLogging() {
    $config = CRM_Core_Config::singleton();
    $config->logging = FALSE;

    $this->dropTriggers();

    // invoke the meta trigger creation call
    CRM_Core_DAO::triggerRebuild();

    $this->deleteReports();
  }

  /**
   * Drop triggers for all logged tables.
   *
   * @param string $tableName
   */
  public function dropTriggers($tableName = NULL) {
    /** @var \Civi\Core\SqlTriggers $sqlTriggers */
    $sqlTriggers = Civi::service('sql_triggers');
    $dao = new CRM_Core_DAO();

    if ($tableName) {
      $tableNames = array($tableName);
    }
    else {
      $tableNames = $this->tables;
    }

    foreach ($tableNames as $table) {
      $validName = CRM_Core_DAO::shortenSQLName($table, 48, TRUE);

      // before triggers
      $sqlTriggers->enqueueQuery("DROP TRIGGER IF EXISTS {$validName}_before_insert");
      $sqlTriggers->enqueueQuery("DROP TRIGGER IF EXISTS {$validName}_before_update");
      $sqlTriggers->enqueueQuery("DROP TRIGGER IF EXISTS {$validName}_before_delete");

      // after triggers
      $sqlTriggers->enqueueQuery("DROP TRIGGER IF EXISTS {$validName}_after_insert");
      $sqlTriggers->enqueueQuery("DROP TRIGGER IF EXISTS {$validName}_after_update");
      $sqlTriggers->enqueueQuery("DROP TRIGGER IF EXISTS {$validName}_after_delete");
    }

    // now lets also be safe and drop all triggers that start with
    // civicrm_ if we are dropping all triggers
    // we need to do this to capture all the leftover triggers since
    // we did the shortening trigger name for CRM-11794
    if ($tableName === NULL) {
      $triggers = $dao->executeQuery("SHOW TRIGGERS LIKE 'civicrm_%'");

      while ($triggers->fetch()) {
        $sqlTriggers->enqueueQuery("DROP TRIGGER IF EXISTS {$triggers->Trigger}");
      }
    }
  }

  /**
   * Enable site-wide logging.
   */
  public function enableLogging() {
    $this->fixSchemaDifferences(TRUE);
    $this->addReports();
  }

  /**
   * Sync log tables and rebuild triggers.
   *
   * @param bool $enableLogging : Ensure logging is enabled
   */
  public function fixSchemaDifferences($enableLogging = FALSE) {
    $config = CRM_Core_Config::singleton();
    if ($enableLogging) {
      $config->logging = TRUE;
    }
    if ($config->logging) {
      $this->fixSchemaDifferencesForALL();
    }
    // invoke the meta trigger creation call
    CRM_Core_DAO::triggerRebuild(NULL, TRUE);
  }

  /**
   * Update log tables structure.
   *
   * This function updates log tables to have the log_conn_id type of varchar
   * and also implements any engine change to INNODB defined by the hooks.
   *
   * Note changing engine & adding hook-defined indexes, but not changing back
   * to ARCHIVE if engine has not been deliberately set (by hook) and not dropping
   * indexes. Sysadmin will need to manually intervene to revert to defaults.
   */
  public function updateLogTableSchema() {
    $updateLogConn = FALSE;
    foreach ($this->logs as $mainTable => $logTable) {
      $alterSql = array();
      $tableSpec = $this->logTableSpec[$mainTable];
      if (isset($tableSpec['engine']) && strtoupper($tableSpec['engine']) != $this->getEngineForLogTable($logTable)) {
        $alterSql[] = "ENGINE=" . $tableSpec['engine'] . " " . CRM_Utils_Array::value('engine_config', $tableSpec);
        if (!empty($tableSpec['indexes'])) {
          $indexes = $this->getIndexesForTable($logTable);
          foreach ($tableSpec['indexes'] as $indexName => $indexSpec) {
            if (!in_array($indexName, $indexes)) {
              if (is_array($indexSpec)) {
                $indexSpec = implode(" , ", $indexSpec);
              }
              $alterSql[] = "ADD INDEX {$indexName}($indexSpec)";
            }
          }
        }
      }
      $columns = $this->columnSpecsOf($logTable);
      if (empty($columns['log_conn_id'])) {
        throw new Exception($logTable . print_r($columns, TRUE));
      }
      if ($columns['log_conn_id']['DATA_TYPE'] != 'varchar' || $columns['log_conn_id']['LENGTH'] != 17) {
        $alterSql[] = "MODIFY log_conn_id VARCHAR(17)";
        $updateLogConn = TRUE;
      }
      if (!empty($alterSql)) {
        CRM_Core_DAO::executeQuery("ALTER TABLE {$this->db}.{$logTable} " . implode(', ', $alterSql));
      }
    }
    if ($updateLogConn) {
      civicrm_api3('Setting', 'create', array('logging_uniqueid_date' => date('Y-m-d H:i:s')));
    }
  }

  /**
   * Get the engine for the given table.
   *
   * @param string $table
   *
   * @return string
   */
  public function getEngineForLogTable($table) {
    return strtoupper(CRM_Core_DAO::singleValueQuery("
      SELECT ENGINE FROM information_schema.tables WHERE TABLE_NAME = %1
      AND table_schema = %2
    ", array(1 => array($table, 'String'), 2 => array($this->db, 'String'))));
  }

  /**
   * Get all the indexes in the table.
   *
   * @param string $table
   *
   * @return array
   */
  public function getIndexesForTable($table) {
    return CRM_Core_DAO::executeQuery("
      SELECT constraint_name
      FROM information_schema.key_column_usage
      WHERE table_schema = %2 AND table_name = %1",
      array(1 => array($table, 'String'), 2 => array($this->db, 'String'))
    )->fetchAll();
  }

  /**
   * Add missing (potentially specified) log table columns for the given table.
   *
   * @param string $table
   *   name of the relevant table.
   * @param array $cols
   *   Mixed array of columns to add or null (to check for the missing columns).
   * @param bool $rebuildTrigger
   *   should we rebuild the triggers.
   *
   * @return bool
   */
  public function fixSchemaDifferencesFor($table, $cols = array(), $rebuildTrigger = FALSE) {
    if (empty($table)) {
      return FALSE;
    }
    if (empty($this->logs[$table])) {
      $this->createLogTableFor($table);
      return TRUE;
    }

    if (empty($cols)) {
      $cols = $this->columnsWithDiffSpecs($table, "log_$table");
    }

    // use the relevant lines from CREATE TABLE to add colums to the log table
    $create = $this->_getCreateQuery($table);
    foreach ((array('ADD', 'MODIFY')) as $alterType) {
      if (!empty($cols[$alterType])) {
        foreach ($cols[$alterType] as $col) {
          $line = $this->_getColumnQuery($col, $create);
          CRM_Core_DAO::executeQuery("ALTER TABLE `{$this->db}`.log_$table {$alterType} {$line}", array(), TRUE, NULL, FALSE, FALSE);
        }
      }
    }

    // for any obsolete columns (not null) we just make the column nullable.
    if (!empty($cols['OBSOLETE'])) {
      $create = $this->_getCreateQuery("`{$this->db}`.log_{$table}");
      foreach ($cols['OBSOLETE'] as $col) {
        $line = $this->_getColumnQuery($col, $create);
        // This is just going to make a not null column to nullable
        CRM_Core_DAO::executeQuery("ALTER TABLE `{$this->db}`.log_$table MODIFY {$line}", array(), TRUE, NULL, FALSE, FALSE);
      }
    }

    if ($rebuildTrigger) {
      // invoke the meta trigger creation call
      CRM_Core_DAO::triggerRebuild($table);
    }
    return TRUE;
  }

  /**
   * Get query table.
   *
   * @param string $table
   *
   * @return array
   */
  private function _getCreateQuery($table) {
    $dao = CRM_Core_DAO::executeQuery("SHOW CREATE TABLE {$table}", array(), TRUE, NULL, FALSE, FALSE);
    $dao->fetch();
    $create = explode("\n", $dao->Create_Table);
    return $create;
  }

  /**
   * Get column query.
   *
   * @param string $col
   * @param bool $createQuery
   *
   * @return array|mixed|string
   */
  private function _getColumnQuery($col, $createQuery) {
    $line = preg_grep("/^  `$col` /", $createQuery);
    $line = rtrim(array_pop($line), ',');
    // CRM-11179
    $line = $this->fixTimeStampAndNotNullSQL($line);
    return $line;
  }

  /**
   * Fix schema differences.
   *
   * @param bool $rebuildTrigger
   */
  public function fixSchemaDifferencesForAll($rebuildTrigger = FALSE) {
    $diffs = array();
    foreach ($this->tables as $table) {
      if (empty($this->logs[$table])) {
        $this->createLogTableFor($table);
      }
      else {
        $diffs[$table] = $this->columnsWithDiffSpecs($table, "log_$table");
      }
    }

    foreach ($diffs as $table => $cols) {
      $this->fixSchemaDifferencesFor($table, $cols, FALSE);
    }
    if ($rebuildTrigger) {
      // invoke the meta trigger creation call
      CRM_Core_DAO::triggerRebuild(NULL, TRUE);
    }
  }

  /**
   * Fix timestamp.
   *
   * Log_civicrm_contact.modified_date for example would always be copied from civicrm_contact.modified_date,
   * so there's no need for a default timestamp and therefore we remove such default timestamps
   * also eliminate the NOT NULL constraint, since we always copy and schema can change down the road)
   *
   * @param string $query
   *
   * @return mixed
   */
  public function fixTimeStampAndNotNullSQL($query) {
    $query = str_ireplace("TIMESTAMP NOT NULL", "TIMESTAMP NULL", $query);
    $query = str_ireplace("DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP", '', $query);
    $query = str_ireplace("DEFAULT CURRENT_TIMESTAMP", '', $query);
    $query = str_ireplace("NOT NULL", '', $query);
    return $query;
  }

  /**
   * Add reports.
   */
  private function addReports() {
    $titles = array(
      'logging/contact/detail' => ts('Logging Details'),
      'logging/contact/summary' => ts('Contact Logging Report (Summary)'),
      'logging/contribute/detail' => ts('Contribution Logging Report (Detail)'),
      'logging/contribute/summary' => ts('Contribution Logging Report (Summary)'),
    );
    // enable logging templates
    CRM_Core_DAO::executeQuery("
            UPDATE civicrm_option_value
            SET is_active = 1
            WHERE value IN ('" . implode("', '", $this->reports) . "')
        ");

    // add report instances
    $domain_id = CRM_Core_Config::domainID();
    foreach ($this->reports as $report) {
      $dao = new CRM_Report_DAO_ReportInstance();
      $dao->domain_id = $domain_id;
      $dao->report_id = $report;
      $dao->title = $titles[$report];
      $dao->permission = 'administer CiviCRM';
      if ($report == 'logging/contact/summary') {
        $dao->is_reserved = 1;
      }
      $dao->insert();
    }
  }

  /**
   * Get an array of column names of the given table.
   *
   * @param string $table
   * @param bool $force
   *
   * @return array
   */
  private function columnsOf($table, $force = FALSE) {
    if ($force || !isset(\Civi::$statics[__CLASS__]['columnsOf'][$table])) {
      $from = (substr($table, 0, 4) == 'log_') ? "`{$this->db}`.$table" : $table;
      CRM_Core_TemporaryErrorScope::ignoreException();
      $dao = CRM_Core_DAO::executeQuery("SHOW COLUMNS FROM $from", CRM_Core_DAO::$_nullArray, TRUE, NULL, FALSE, FALSE);
      if (is_a($dao, 'DB_Error')) {
        return array();
      }
      \Civi::$statics[__CLASS__]['columnsOf'][$table] = array();
      while ($dao->fetch()) {
        \Civi::$statics[__CLASS__]['columnsOf'][$table][] = CRM_Utils_type::escape($dao->Field, 'MysqlColumnNameOrAlias');
      }
    }
    return \Civi::$statics[__CLASS__]['columnsOf'][$table];
  }

  /**
   * Get an array of columns and their details like DATA_TYPE, IS_NULLABLE, COLUMN_DEFAULT for the given table.
   *
   * @param string $table
   *
   * @return array
   */
  private function columnSpecsOf($table) {
    static $civiDB = NULL;
    if (empty(\Civi::$statics[__CLASS__]['columnSpecs'])) {
      \Civi::$statics[__CLASS__]['columnSpecs'] = array();
    }
    if (empty(\Civi::$statics[__CLASS__]['columnSpecs']) || !isset(\Civi::$statics[__CLASS__]['columnSpecs'][$table])) {
      if (!$civiDB) {
        $dao = new CRM_Contact_DAO_Contact();
        $civiDB = $dao->_database;
      }
      CRM_Core_TemporaryErrorScope::ignoreException();
      // NOTE: W.r.t Performance using one query to find all details and storing in static array is much faster
      // than firing query for every given table.
      $query = "
SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, DATA_TYPE, IS_NULLABLE, COLUMN_DEFAULT, COLUMN_TYPE
FROM   INFORMATION_SCHEMA.COLUMNS
WHERE  table_schema IN ('{$this->db}', '{$civiDB}')";
      $dao = CRM_Core_DAO::executeQuery($query);
      if (is_a($dao, 'DB_Error')) {
        return array();
      }
      while ($dao->fetch()) {
        if (!array_key_exists($dao->TABLE_NAME, \Civi::$statics[__CLASS__]['columnSpecs'])) {
          \Civi::$statics[__CLASS__]['columnSpecs'][$dao->TABLE_NAME] = array();
        }
        \Civi::$statics[__CLASS__]['columnSpecs'][$dao->TABLE_NAME][$dao->COLUMN_NAME] = array(
          'COLUMN_NAME' => $dao->COLUMN_NAME,
          'DATA_TYPE' => $dao->DATA_TYPE,
          'IS_NULLABLE' => $dao->IS_NULLABLE,
          'COLUMN_DEFAULT' => $dao->COLUMN_DEFAULT,
        );
        if (($first = strpos($dao->COLUMN_TYPE, '(')) != 0) {
          \Civi::$statics[__CLASS__]['columnSpecs'][$dao->TABLE_NAME][$dao->COLUMN_NAME]['LENGTH'] = substr(
            $dao->COLUMN_TYPE, $first, strpos($dao->COLUMN_TYPE, ')')
          );
        }
      }
    }
    return \Civi::$statics[__CLASS__]['columnSpecs'][$table];
  }

  /**
   * Get columns that have changed.
   *
   * @param string $civiTable
   * @param string $logTable
   *
   * @return array
   */
  public function columnsWithDiffSpecs($civiTable, $logTable) {
    $civiTableSpecs = $this->columnSpecsOf($civiTable);
    $logTableSpecs = $this->columnSpecsOf($logTable);

    $diff = array('ADD' => array(), 'MODIFY' => array(), 'OBSOLETE' => array());

    // columns to be added
    $diff['ADD'] = array_diff(array_keys($civiTableSpecs), array_keys($logTableSpecs));

    // columns to be modified
    // NOTE: we consider only those columns for modifications where there is a spec change, and that the column definition
    // wasn't deliberately modified by fixTimeStampAndNotNullSQL() method.
    foreach ($civiTableSpecs as $col => $colSpecs) {
      if (!isset($logTableSpecs[$col]) || !is_array($logTableSpecs[$col])) {
        $logTableSpecs[$col] = array();
      }

      $specDiff = array_diff($civiTableSpecs[$col], $logTableSpecs[$col]);
      if (!empty($specDiff) && $col != 'id' && !array_key_exists($col, $diff['ADD'])) {
        // ignore 'id' column for any spec changes, to avoid any auto-increment mysql errors
        if ($civiTableSpecs[$col]['DATA_TYPE'] != CRM_Utils_Array::value('DATA_TYPE', $logTableSpecs[$col])
        // We won't alter the log if the length is decreased in case some of the existing data won't fit.
        || CRM_Utils_Array::value('LENGTH', $civiTableSpecs[$col]) > CRM_Utils_Array::value('LENGTH', $logTableSpecs[$col])
        ) {
          // if data-type is different, surely consider the column
          $diff['MODIFY'][] = $col;
        }
        elseif ($civiTableSpecs[$col]['IS_NULLABLE'] != CRM_Utils_Array::value('IS_NULLABLE', $logTableSpecs[$col]) &&
          $logTableSpecs[$col]['IS_NULLABLE'] == 'NO'
        ) {
          // if is-null property is different, and log table's column is NOT-NULL, surely consider the column
          $diff['MODIFY'][] = $col;
        }
        elseif ($civiTableSpecs[$col]['COLUMN_DEFAULT'] != CRM_Utils_Array::value('COLUMN_DEFAULT', $logTableSpecs[$col]) &&
          !strstr($civiTableSpecs[$col]['COLUMN_DEFAULT'], 'TIMESTAMP')
        ) {
          // if default property is different, and its not about a timestamp column, consider it
          $diff['MODIFY'][] = $col;
        }
      }
    }

    // columns to made obsolete by turning into not-null
    $oldCols = array_diff(array_keys($logTableSpecs), array_keys($civiTableSpecs));
    foreach ($oldCols as $col) {
      if (!in_array($col, array('log_date', 'log_conn_id', 'log_user_id', 'log_action')) &&
        $logTableSpecs[$col]['IS_NULLABLE'] == 'NO'
      ) {
        // if its a column present only in log table, not among those used by log tables for special purpose, and not-null
        $diff['OBSOLETE'][] = $col;
      }
    }

    return $diff;
  }

  /**
   * Getter for logTableSpec.
   *
   * @return array
   */
  public function getLogTableSpec() {
    return $this->logTableSpec;
  }

  /**
   * Create a log table with schema mirroring the given table’s structure and seeding it with the given table’s contents.
   *
   * @param string $table
   */
  private function createLogTableFor($table) {
    $dao = CRM_Core_DAO::executeQuery("SHOW CREATE TABLE $table", CRM_Core_DAO::$_nullArray, TRUE, NULL, FALSE, FALSE);
    $dao->fetch();
    $query = $dao->Create_Table;

    // rewrite the queries into CREATE TABLE queries for log tables:
    $cols = <<<COLS
            ,
            log_date    TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
            log_conn_id VARCHAR(17),
            log_user_id INTEGER,
            log_action  ENUM('Initialization', 'Insert', 'Update', 'Delete')
COLS;

    if (!empty($this->logTableSpec[$table]['indexes'])) {
      foreach ($this->logTableSpec[$table]['indexes'] as $indexName => $indexSpec) {
        if (is_array($indexSpec)) {
          $indexSpec = implode(" , ", $indexSpec);
        }
        $cols .= ", INDEX {$indexName}($indexSpec)";
      }
    }

    // - prepend the name with log_
    // - drop AUTO_INCREMENT columns
    // - drop non-column rows of the query (keys, constraints, etc.)
    // - set the ENGINE to the specified engine (default is archive)
    // - add log-specific columns (at the end of the table)
    $query = preg_replace("/^CREATE TABLE `$table`/i", "CREATE TABLE `{$this->db}`.log_$table", $query);
    $query = preg_replace("/ AUTO_INCREMENT/i", '', $query);
    $query = preg_replace("/^  [^`].*$/m", '', $query);
    $engine = strtoupper(CRM_Utils_Array::value('engine', $this->logTableSpec[$table], 'ARCHIVE'));
    $engine .= " " . CRM_Utils_Array::value('engine_config', $this->logTableSpec[$table]);
    $query = preg_replace("/^\) ENGINE=[^ ]+ /im", ') ENGINE=' . $engine . ' ', $query);

    // log_civicrm_contact.modified_date for example would always be copied from civicrm_contact.modified_date,
    // so there's no need for a default timestamp and therefore we remove such default timestamps
    // also eliminate the NOT NULL constraint, since we always copy and schema can change down the road)
    $query = self::fixTimeStampAndNotNullSQL($query);
    $query = preg_replace("/(,*\n*\) )ENGINE/m", "$cols\n) ENGINE", $query);

    CRM_Core_DAO::executeQuery($query, CRM_Core_DAO::$_nullArray, TRUE, NULL, FALSE, FALSE);

    $columns = implode(', ', $this->columnsOf($table));
    CRM_Core_DAO::executeQuery("INSERT INTO `{$this->db}`.log_$table ($columns, log_conn_id, log_user_id, log_action) SELECT $columns, @uniqueID, @civicrm_user_id, 'Initialization' FROM {$table}", CRM_Core_DAO::$_nullArray, TRUE, NULL, FALSE, FALSE);

    $this->tables[] = $table;
    if (empty($this->logs)) {
      civicrm_api3('Setting', 'create', array('logging_uniqueid_date' => date('Y-m-d H:i:s')));
      civicrm_api3('Setting', 'create', array('logging_all_tables_uniquid' => 1));
    }
    $this->logs[$table] = "log_$table";
  }

  /**
   * Delete reports.
   */
  private function deleteReports() {
    // disable logging templates
    CRM_Core_DAO::executeQuery("
            UPDATE civicrm_option_value
            SET is_active = 0
            WHERE value IN ('" . implode("', '", $this->reports) . "')
        ");

    // delete report instances
    $domain_id = CRM_Core_Config::domainID();
    foreach ($this->reports as $report) {
      $dao = new CRM_Report_DAO_ReportInstance();
      $dao->domain_id = $domain_id;
      $dao->report_id = $report;
      $dao->delete();
    }
  }

  /**
   * Predicate whether logging is enabled.
   */
  public function isEnabled() {
    if (\Civi::settings()->get('logging')) {
      return ($this->tablesExist() && (\Civi::settings()->get('logging_no_trigger_permission') || $this->triggersExist()));
    }
    return FALSE;
  }

  /**
   * Predicate whether any log tables exist.
   */
  private function tablesExist() {
    return !empty($this->logs);
  }

  /**
   * Drop all log tables.
   *
   * This does not currently have a usage outside the tests.
   */
  public function dropAllLogTables() {
    if ($this->tablesExist()) {
      foreach ($this->logs as $log_table) {
        CRM_Core_DAO::executeQuery("DROP TABLE $log_table");
      }
    }
  }

  /**
   * Get an sql clause to find the names of any log tables that do not match the normal pattern.
   *
   * Most tables are civicrm_xxx with the log table being log_civicrm_xxx
   * However, they don't have to match this pattern (e.g when defined by hook) so find the
   * anomalies and return a filter string to include them.
   *
   * @return string
   */
  public function getNonStandardTableNameFilterString() {
    $nonStandardTableNames = preg_grep('/^civicrm_/', $this->tables, PREG_GREP_INVERT);
    if (empty($nonStandardTableNames)) {
      return '';
    }
    $nonStandardTableLogs = array();
    foreach ($nonStandardTableNames as $nonStandardTableName) {
      $nonStandardTableLogs[] = "'log_{$nonStandardTableName}'";
    }
    return " OR TABLE_NAME IN (" . implode(',', $nonStandardTableLogs) . ")";
  }

  /**
   * Predicate whether the logging triggers are in place.
   */
  private function triggersExist() {
    // FIXME: probably should be a bit more thorough…
    // note that the LIKE parameter is TABLE NAME
    return (bool) CRM_Core_DAO::singleValueQuery("SHOW TRIGGERS LIKE 'civicrm_contact'");
  }

  /**
   * Get trigger info.
   *
   * @param array $info
   * @param null $tableName
   * @param bool $force
   */
  public function triggerInfo(&$info, $tableName = NULL, $force = FALSE) {
    if (!CRM_Core_Config::singleton()->logging) {
      return;
    }

    $insert = array('INSERT');
    $update = array('UPDATE');
    $delete = array('DELETE');

    if ($tableName) {
      $tableNames = array($tableName);
    }
    else {
      $tableNames = $this->tables;
    }

    // logging is enabled, so now lets create the trigger info tables
    foreach ($tableNames as $table) {
      $columns = $this->columnsOf($table, $force);

      // only do the change if any data has changed
      $cond = array();
      foreach ($columns as $column) {
        $tableExceptions = array_key_exists('exceptions', $this->logTableSpec[$table]) ? $this->logTableSpec[$table]['exceptions'] : array();
        // ignore modified_date changes
        if ($column != 'modified_date' && !in_array($column, $tableExceptions)) {
          $cond[] = "IFNULL(OLD.$column,'') <> IFNULL(NEW.$column,'')";
        }
      }
      $suppressLoggingCond = "@civicrm_disable_logging IS NULL OR @civicrm_disable_logging = 0";
      $updateSQL = "IF ( (" . implode(' OR ', $cond) . ") AND ( $suppressLoggingCond ) ) THEN ";

      if ($this->useDBPrefix) {
        $sqlStmt = "INSERT INTO `{$this->db}`.log_{tableName} (";
      }
      else {
        $sqlStmt = "INSERT INTO log_{tableName} (";
      }
      foreach ($columns as $column) {
        $sqlStmt .= "$column, ";
      }
      $sqlStmt .= "log_conn_id, log_user_id, log_action) VALUES (";

      $insertSQL = $deleteSQL = "IF ( $suppressLoggingCond ) THEN $sqlStmt ";
      $updateSQL .= $sqlStmt;

      $sqlStmt = '';
      foreach ($columns as $column) {
        $sqlStmt .= "NEW.$column, ";
        $deleteSQL .= "OLD.$column, ";
      }
      if (civicrm_api3('Setting', 'getvalue', array('name' => 'logging_uniqueid_date'))) {
        // Note that when connecting directly via mysql @uniqueID may not be set so a fallback is
        // 'c_' to identify a non-CRM connection + timestamp to the hour + connection_id
        // If the connection_id is longer than 6 chars it will be truncated.
        // We tried setting the @uniqueID in the trigger but it was unreliable.
        // An external interaction could split over 2 connections & it seems worth blocking the revert on
        // these reports & adding extra permissioning to the api for this.
        $connectionSQLString = "COALESCE(@uniqueID, LEFT(CONCAT('c_', unix_timestamp()/3600, CONNECTION_ID()), 17))";
      }
      else {
        // The log tables have not yet been converted to have varchar(17) fields for log_conn_id.
        // Continue to use the less reliable connection_id for al tables for now.
        $connectionSQLString = "CONNECTION_ID()";
      }
      $sqlStmt .= $connectionSQLString . ", @civicrm_user_id, '{eventName}'); END IF;";
      $deleteSQL .= $connectionSQLString . ", @civicrm_user_id, '{eventName}'); END IF;";

      $insertSQL .= $sqlStmt;
      $updateSQL .= $sqlStmt;

      $info[] = array(
        'table' => array($table),
        'when' => 'AFTER',
        'event' => $insert,
        'sql' => $insertSQL,
      );

      $info[] = array(
        'table' => array($table),
        'when' => 'AFTER',
        'event' => $update,
        'sql' => $updateSQL,
      );

      $info[] = array(
        'table' => array($table),
        'when' => 'AFTER',
        'event' => $delete,
        'sql' => $deleteSQL,
      );
    }
  }

  /**
   * Disable logging temporarily.
   *
   * This allow logging to be temporarily disabled for certain cases
   * where we want to do a mass cleanup but do not want to bother with
   * an audit trail.
   */
  public static function disableLoggingForThisConnection() {
    if (CRM_Core_Config::singleton()->logging) {
      CRM_Core_DAO::executeQuery('SET @civicrm_disable_logging = 1');
    }
  }

  /**
   * Get all the log tables that reference civicrm_contact.
   *
   * Note that it might make sense to wrap this in a getLogTablesForEntity
   * but this is the only entity currently available...
   */
  public function getLogTablesForContact() {
    $tables = array_keys(CRM_Dedupe_Merger::cidRefs());
    return array_intersect($tables, $this->tables);
  }

  /**
   * Retrieve missing log tables.
   *
   * @return array
   */
  public function getMissingLogTables() {
    if ($this->tablesExist()) {
      return array_diff($this->tables, array_keys($this->logs));
    }
    return array();
  }

}
