<?php
/* 
 * Plugins Garbage Collector Lirary general staff
 * Author: Vladimir Garagulya vladimir@shinephp.com
 * 
 */


if (!function_exists("get_option")) {
  header('HTTP/1.0 403 Forbidden');
  die;  // Silence is golden, direct call is prohibited
}


function pgc_show_message($message) {

  if ($message) {
    echo '<div class="updated" style="margin:0;">'.$message.'</div><br style="clear: both;"/>';
  }

}
// end of pgc_showMessage()


function pgc_get_db_table_info( $table_name ) {
    global $wpdb;
    
    $query = "SHOW TABLE STATUS FROM `" . DB_NAME . "` LIKE '$table_name'";
    $result = $wpdb->get_results($query);

    $table = new stdClass;
    $table->name = $table_name;
    $table->name_without_prefix = substr_replace( $table_name, '', 0, strlen( $wpdb->prefix ) );
    $table->records = $result[0]->Rows; 
    $table->kbytes = ROUND( ($result[0]->Data_length + $result[0]->Index_length ) / 1024, 2 ); //$result[0]->kbytes;        
    if ( !PGC_Known_Plugins::fill_data( $table ) ) {
        $table->plugin_name = '';
        $table->plugin_file = '';
        $table->plugin_state = '';
    }
    
    
    return $table;
}
// end of pgc_get_db_table_info()


function pgc_update_hidden_tables_list( $tables ) {

    $pgc_settings = get_option('pgc_settings');
    if ( empty( $pgc_settings['hidden'] ) ) {
        return;
    }
    $update_needed = false;
    foreach ( $pgc_settings['hidden'] as $table_name ) {
        $found = false;
        foreach ( $tables as $table ) {
            if ($table->name == $table_name) {
                $found = true;
                break;
            }
        }
        if ( !$found ) {
            unset( $pgc_settings['hidden'][$table_name] );
            $update_needed = true;
        }
    }
    if ( $update_needed ) {
        update_option( 'pgc_settings', $pgc_settings );
    }
    
}
// end of pgc_update_hidden_tables_list()


function pgc_get_blog_ids() {
    global $wpdb;

    if ( !is_multisite() ) {
        return null;
    }

    $network = get_current_site();        
    $query = $wpdb->prepare(
                "SELECT blog_id FROM {$wpdb->blogs}
                    WHERE site_id=%d ORDER BY blog_id ASC",
                    array( $network->id ) );
    $blog_ids = $wpdb->get_col( $query );

    return $blog_ids;
}
// end of get_blog_ids()


function pgc_table_from_current_blog( $table_name, $blog_ids ) {
    global $wpdb;
    
    $current_blog_id = get_current_blog_id();
    $current_blog_prefix = $wpdb->get_blog_prefix();
    if ( substr( $table_name, 0, strlen( $current_blog_prefix ) )!==$current_blog_prefix ) {    //  wp_1 != $wp_2 
        return false;
    }
    
    // Exclude wp_11, wp_12 and similar to leave wp_1 only
    foreach( $blog_ids as $blog_id ) {
        if ( $blog_id==$current_blog_id ) {
            continue;
        }
        $prefix = $wpdb->base_prefix . $blog_id . '_';
        if ( substr( $table_name, 0, strlen( $prefix ) )===$prefix ) {  // table from other blog detected
            return false;
        }   
    }
    
    return true;
} 
// end of pgc_table_from_current_blog()


function pgc_get_not_wp_tables() {
    global $wpdb;

    $all_plugins = get_plugins();
    $blog_ids = pgc_get_blog_ids();
    $wp_tables = $wpdb->tables('all', true );
    $non_wp_tables = array();
    $query = 'SHOW TABLES';
    $db_tables = $wpdb->get_col( $query );
    foreach ( $db_tables as $table_name ) {
        if ( in_array( $table_name, $wp_tables ) || 
            strpos( $table_name, $wpdb->prefix, 0)===false ) {
            continue;
        }
        if ( is_multisite() && !pgc_table_from_current_blog( $table_name, $blog_ids ) ) {
            continue;
        }
                
        $table = pgc_get_db_table_info( $table_name );
        if ( !empty( $table->plugin_file ) && isset( $all_plugins[ $table->plugin_file ] ) ) {
            $plugin_data = $all_plugins[ $table->plugin_file ];
            $table->plugin_name .= ' '. $plugin_data['Version'];
        }
        $non_wp_tables[] = $table;
    }

    pgc_update_hidden_tables_list( $non_wp_tables );        

    return $non_wp_tables;
}
// end of pgc_get_not_wp_tables()


function pgc_get_active_plugins() {
    
    $list = (array) get_option('active_plugins', array() );
    if ( is_multisite() ) {
        $list2 = get_site_option('active_sitewide_plugins', array() );
        if ( !empty( $list2 ) ) {
            $list = array_merge( $list, array_keys( $list2 ) );
        }
    }
    
    return $list;
}
// end of pgc_get_active_plugins()


function pgc_get_plugin_state( $all_plugins,  $active_plugins, $plugin_file ) {
    
    $plugin_active = false;
    foreach ($active_plugins as $active_plugin) {
        if ($plugin_file == $active_plugin) {
            $plugin_active = true;
            break;
        }
    }
    if ($plugin_active) {
        $plugin_state = 'active';
    } else {
        if ( isset( $all_plugins[$plugin_file] ) ) {
            $plugin_state = 'inactive';
        } else {
            $plugin_state = 'unused';
        }
    }
    
    return $plugin_state;
}
// end of pgc_get_plugin_state()


function pgc_set_plugin_state_for_tables() {
    $all_plugins = get_plugins();
    $active_plugins = pgc_get_active_plugins();
    foreach ($_SESSION['plugins-garbage-collector']['tables'] as $table) {
        if ($table->plugin_file) {
            $table->plugin_state = pgc_get_plugin_state( $all_plugins, $active_plugins, $table->plugin_file );
        } else {
            $table->plugin_state = 'unused';
        }
    }
}

// end of pgc_set_plugin_state_for_tables()


function pgc_get_plugin_php_files( $plugin ) {
                    
    $all_files = get_plugin_files( $plugin['key'] );
    if ( empty( $all_files ) ) {
        $answer = array('result'=>'error', 'message'=>'Invalid request - unexisted plugin '. $plugin['key']);
        return $answer;
    }

    // Extract PHP files only
    $php_files = array();
    foreach ($all_files as $plugin_file) {
        $ext = pathinfo( $plugin_file, PATHINFO_EXTENSION );
        if ( strtolower( $ext )!='php' ) {
            continue;
        }
        $php_files[] = $plugin_file;
    }
    
    return $php_files;
}
// end of pgc_get_plugin_php_files()


function pgc_scan_file( $file, $plugin ) {
    
    $fh = fopen( WP_PLUGIN_DIR . '/' . $file, 'r' );
    if ( !$fh ) {
        return;
    }
    while ( !feof( $fh ) ) {
        $s = fgets( $fh );
        $s = strtolower( $s );
        foreach( $_SESSION['plugins-garbage-collector']['tables'] as $table ) {
            if ( !empty( $table->plugin_name ) ) {
                continue;
            }
            if ( strpos( $s, $table->name_without_prefix ) !== false ) {
                $table->plugin_name = $plugin['title'] . ' ' . $plugin['version'];
                $table->plugin_file = $plugin['key'];
            }
        } // foreach()
    }
    fclose($fh);
}


function pgc_scan_plugin_for_db_tables_use() {
            
    if ( !isset( $_POST['plugin'] ) || empty( $_POST['plugin'] ) ) {
        $answer = array('result'=>'error', 'message'=>'Invalid request - missed plugin parameter');
        echo json_encode( $answer );
        return;
    }
    
    $plugin = filter_var_array( $_POST['plugin'], FILTER_SANITIZE_STRING );
    if ( !isset( $plugin['key'] ) ) {
        $answer = array('result'=>'error', 'message'=>'Invalid request - wrong plugin parameter value');        
        return $answer;
    }
    
    $php_files = pgc_get_plugin_php_files( $plugin );
    if ( isset( $php_files['result'] ) ) {
        echo json_encode( $php_files );
        return;
    }
    
    $current_file = filter_var( $_POST['current_file'], FILTER_SANITIZE_NUMBER_INT );
    if ( empty( $current_file ) ) {
        $current_file = 0;
    }
        
    $files_to_process = 500;
    for ( $i=$current_file; $i<count( $php_files ); $i++ ) {
        pgc_scan_file( $php_files[$i], $plugin );                
        $files_to_process--;
        if ( $files_to_process<1 ) {
            break;
        }
    }
    
    $total_files = count( $php_files );
    $current_file = $i++;
    $answer = array(
        'result'=>'success', 
        'current_file'=>$current_file,
        'total_files'=>$total_files,
        'message'=> $plugin['title'] .' '. esc_html__(' checked', 'plugins-garbage-collector')
        );        
    echo json_encode( $answer );
}
// end of pgc_scan_plugin_for_db_tables_use()


function pgc_get_tables_to_delete() {
    
    $tables = array();
    foreach ( array_keys( $_POST ) as $key ) {
        if ( strpos( $key, 'delete_') !== false ) {
            $tables[] = substr( $key, 7 );
        }
    }
    
    return $tables;
}
// end of pgc_get_tables_to_delete()


function pgc_switch_off_fkc() {
    global $wpdb;
    
    $query = "SHOW VARIABLES LIKE 'FOREIGN_KEY_CHECKS'";
    $result = $wpdb->get_row( $query );
    $fkc_value = $result->Value;
    if ( $fkc_value=='ON' ) {
        $query = 'SET FOREIGN_KEY_CHECKS=0';
        $wpdb->query( $query );
    }
    
    return $fkc_value;
}
// end of pgc_switch_off_fkc()


function pgc_restore_fkc( $old_fkc_value ) {
    global $wpdb;
    
    if ( $old_fkc_value=='ON' || $old_fkc_value==1 ) {
        $query = 'SET FOREIGN_KEY_CHECKS=1';
        $wpdb->query( $query );
    }
    
}
// pgc_restore_fkc()


function pgc_delete_unused_db_tables() {
    global $wpdb;

    $tables = pgc_get_tables_to_delete();
    if ( empty( $tables ) ) {
        return;
    }
    
    $old_fkc_value = pgc_switch_off_fkc();          
    $db_name = DB_NAME;
    $action_result = '';
    foreach ( $tables as $table ) {
        if ($action_result) {
            $action_result .= ', ';
        }
        $query = "drop table `$db_name`.`$table`";
        $wpdb->query( $query );
        if ( $wpdb->last_error ) {
            if ( $action_result ) {
                $action_result = esc_html__('Tables are deleted: ', 'plugins-garbage-collector') . $action_result;
            }
            pgc_restore_fkc( $old_fkc_value );
            return $action_result . '<br/>' . $wpdb->last_error;
        }
        $action_result .= ' ' . $table;
    }

    pgc_restore_fkc( $old_fkc_value );
    
    return esc_html__('Tables are deleted successfully: ', 'plugins-garbage-collector') . $action_result;
}
// end of pgc_delete_unused_db_tables()


function pgc_display_box_start($title='', $style='') {
  $html = '<div class="postbox" '. (empty($style) ? '' : 'style="'.$style.'"') .'  >'. PHP_EOL;
  if (!empty($title)) {
      $html .= '<h3 style="cursor:default;"><span>'.$title.'</span></h3>'. PHP_EOL;
  }
		$html .= '<div class="inside">'. PHP_EOL;

  return $html;
}
// 	end of thanks_displayBoxStart()


function pgc_display_box_end() {
  $html = '
				</div>
			</div>';

  return $html;
}
// end of pgc_display_box_end()


function pgc_display_column_headers_none_wp() {
  $html = '<tr>
              <th>'. esc_html__('Hide', 'plugins-garbage-collector').'</th>
              <th>'. esc_html__('Table Name', 'plugins-garbage-collector').'</th>
              <th>'. esc_html__('Records #', 'plugins-garbage-collector').'</th>
              <th>'. esc_html__('KBytes #', 'plugins-garbage-collector').'</th>
              <th>'. esc_html__('Plugin Name' ,'plugins-garbage-collector').'</th>
              <th>'. esc_html__('State', 'plugins-garbage-collector').'</th>
            </tr>';
   return $html;
}
// pgc_display_column_headers_none_wp()


function pgc_translate_plugin_state( $state ) {
    
    if ( $state=='active' ) {
        $translated = esc_html('active', 'plugins-garbage-collector' );
    } else if ( $state=='inactive' ) {
        $translated = esc_html('inactive', 'plugins-garbage-collector' );
    } else if ( $state=='unused' ) {
        $translated = esc_html('unused', 'plugins-garbage-collector' );
    } else {
        $translated = $state;
    }
    
    return $translated;
}
// end of pgc_translate_plugin_state()


function pgc_show_tables() {
    
    $tables = $_SESSION['plugins-garbage-collector']['tables'];

    if ( count( $tables )>0 ) {
        $html = esc_html__('Let\'s see what tables in your database do not belong to the core WordPress installation:', 'plugins-garbage-collector');
        $pgc_settings = get_option('pgc_settings');
        $html .= '
       <table id="pgc_plugin_tables" class="widefat" style="clear:none;" cellpadding="0" cellspacing="0">
          <thead>';
        $html .= pgc_display_column_headers_none_wp();
        $html .= '
          </thead>
          <tbody>';

        $showHiddenTables = isset($_POST['show_hidden_tables']) && $_POST['show_hidden_tables'];
        $showDeleteTablesButton = false;
        $hiddenTableExists = false;
        $i = 0;
        foreach ($tables as $table) {
            if ($i & 1) {
                $rowClass = 'class="pgc_odd"';
            } else {
                $rowClass = 'class="pgc_even"';
            }
            $hiddenTable = isset($pgc_settings['hidden'][$table->name]);
            if ($hiddenTable && !$showHiddenTables) {  // skip this table
                $hiddenTableExists = true;
                continue;
            }
            $i++;
            $html .= '<tr ' . $rowClass . ' id="' . $table->name . '" >
                  <td style="width:50px;">';
            if ($hiddenTable) {
                $checked = 'checked="checked"';
            } else {
                $checked = '';
            }
            $html .= '<input type="checkbox" name="hidden_' . $table->name . '" id="hidden_' . $table->name . '" onclick="pgc_hide_table(this, \'' . $table->name . '\')" ' . $checked . ' />
              <img id="ajax_' . $table->name . '" class="ajax_processing" src="' . admin_url('images/loading.gif') . '" alt="ajax request processing..." title="AJAX request processing..."/>';
            $html .= '</td>
            <td style="vertical-align:top;width:300px;" >';
            $deleteCheckBox = '';
            if (empty($table->plugin_name) || $table->plugin_state == 'unused') {
                $color = 'red';
                $deleteCheckBox = '<input type="checkbox" name="delete_' . $table->name . '" />';
                $showDeleteTablesButton = true;
            } else if ($table->plugin_state == 'active') {
                $color = 'green';
            } else {
                $color = 'blue';
            }
            $html .= $deleteCheckBox . ' <span style="color:' . $color . ';">' . $table->name . '</span>';
            $html .= '
            </td>
            <td style="width:100px;text-align: right;">
              <span style="color:' . $color . ';">' . $table->records . '</span>
            </td>
            <td style="width:100px;text-align: right;">
              <span style="color:' . $color . ';">' . $table->kbytes . '</span>
            </td>
            <td>';
            if ($table->plugin_name) {
                $html .= '<span style="color:' . $color . ';">' . $table->plugin_name . '</span>';
            } else {
                $html .= '<span style="color:red;">Unknown</span>';
            }
            $plugin_state = pgc_translate_plugin_state( $table->plugin_state );
            $html .= '
            </td>
            <td>
              <span style="color:' . $color . ';">' . $plugin_state . '</span>
            </td>
          </tr>';
        }
        $html .= '
          </tbody>
          <tfoot>';

        $html .= pgc_display_column_headers_none_wp();
        $html .= '
          </tfoot>
      </table>';
        if ($hiddenTableExists) {
            $html .= '<span style="color: #bbb; font-size: 0.8em;">' . esc_html__('Some tables are hidden by you. Turn on "Show hidden DB tables" option and click "Scan" button again to show them.', 'plugins-garbage-collector') . '</span>';
        }
        if ($showDeleteTablesButton) {
            $html .= '
      <table>
        <tr>
          <td>
            <div class="submit">
              <input type="submit" name="drop_table_action" value="' . esc_html__('Delete Tables', 'plugins-garbage-collector') . '"/>
            </div>
          </td>
          <td>
            <div style="padding-left: 10px;"><span style="color: red; font-weight: bold;">' . esc_html__('Attention!', 'plugins-garbage-collector') . '</span> ' .
                    esc_html__('Operation rollback is not possible. Consider to make database backup first. Please double think before click "Delete Tables" button.', 'plugins-garbage-collector') . '
            </div>
          </td>
        </tr>
      </table>';
        }
    } else {
        $html = '<br><br><br><br><br>'. pgc_display_box_start() . '
    <span style="color: green; text-align: center; font-size: 1.2em;">' .
                esc_html__('Congratulations! It seems that your WordPress database is clean.', 'plugins-garbage-collector') . '
    </span>' .
                pgc_display_box_end();
    }

    unset($_SESSION['plugins-garbage-collector']['tables']);

    return $html;
}
// end of pgc_show_tables()


function pgc_display_column_headers_wp() {
  $html = '<tr>
              <th>'.esc_html__('Hide','plugins-garbage-collector').'</th>
              <th>'.esc_html__('Table Name','plugins-garbage-collector').'</th>
              <th>'.esc_html__('Extra Field','plugins-garbage-collector').'</th>
              <th>'.esc_html__('Plugin Name','plugins-garbage-collector').'</th>
              <th>'.esc_html__('Plugin State','plugins-garbage-collector').'</th>
            </tr>';
   return $html;
}
// end of pgc_display_column_headers_wp()


// Get all of the field names in the query from between the parens
function pgc_extract_field_names($query) {

  $columns = array(); 
  $match2 = array();
  preg_match("|\((.*)\)|ms", strtolower($query), $match2);
  $line = trim($match2[1]);
  // Separate field lines into an array
  $fields = explode("\n", $line);  
  // For every field line specified in the query
  foreach($fields as $field) {
    $validfield = true;
    $field = trim($field);
    // Extract the field name
    $fvalue = array();
    preg_match("|^([^ ]*)|", $field, $fvalue);
    $fieldname = strtolower(trim($fvalue[1], '`' ));
    // Verify the found field name
    switch ($fieldname) {
      case '':
      case 'primary':
      case 'index':
      case 'fulltext':
      case 'unique':
      case 'key':
        $validfield = false;
        break;
    }

    // If it's a valid field, add it to the field array
    if ($validfield) {
      $columns[$fieldname] = 1;
    }
  }

  return $columns;
}
// pgc_extract_field_names()


function pgc_check_wp_tables_structure() {

    global $wpdb;
    
    $admin_path = str_replace( get_bloginfo( 'url' ) . '/', ABSPATH, get_admin_url() );
    require_once($admin_path .'includes/schema.php');

    $wp_db_schema = wp_get_db_schema('all');
// Separate individual queries into an array
  $queries = explode(';', $wp_db_schema);
  if (''==$queries[count($queries)-1]) {
    array_pop($queries);
  }

  $wpTablesList = array();

  foreach ($queries as $query) {
    if (preg_match("|CREATE TABLE ([^ ]*)|", $query, $matches)) {
      $wpTablesList[trim( strtolower($matches[1]), '`' )] = $query;
    }
  }

  $changedTables = array();
  $i = 1;
  foreach ($wpTablesList as $table=>$createQuery) {
    update_option('pgc_scanprogress_current', $i);
    update_option('pgc_scanprogress_status', $table);

    // orginal structure columns list
    $origColumns = pgc_extract_field_names($createQuery);

    // fact structrue columns list
    $query = "describe $table";
    $factColumns = $wpdb->get_results($query);
    foreach ($factColumns as $factColumn) {
      if (!isset($origColumns[strtolower($factColumn->Field)])) {
        if (!isset($changedTables[$table])) {
          $changedTables[$table] = array();
        }        
        $changedTables[$table][$factColumn->Field] = new stdClass();
        $changedTables[$table][$factColumn->Field]->plugin_name = '';
        $changedTables[$table][$factColumn->Field]->plugin_state = '';
      }
    }
  } 

  if (count($changedTables)>0) {
    
    $html = '
       <table id="pgc_plugin_tables" class="widefat" style="clear:none;" cellpadding="0" cellspacing="0">
          <thead>'
      .pgc_display_column_headers_wp().
          '</thead>
          <tbody>';
    $pgc_settings = get_option('pgc_settings');
    $showHiddenTables = isset($_POST['show_hidden_tables']) && $_POST['show_hidden_tables'];
    $showDeleteButton = false; $hiddenTableExists  = false;
    $i = 0;
    foreach ($changedTables as $tableName=>$columnData) {
      foreach ($columnData as $column=>$plugin) {
      if ($i & 1) {
        $rowClass = 'class="pgc_odd"';
      } else {
        $rowClass = 'class="pgc_even"';
      }
      $hiddenTable = isset($pgc_settings['hidden'][$tableName]);
      if ($hiddenTable && !$showHiddenTables) {  // skip this table
        $hiddenTableExists  = true;
        continue;
      }
      $i++;
      $html .= '<tr '.$rowClass.' id="'.$tableName.'" >
                  <td>';
      if ($plugin->plugin_state=='active') {
        if ($hiddenTable) {
          $checked = 'checked="checked"';
        } else {
          $checked = '';
        }
        $html .= '<input type="checkbox" name="hidden_'.$tableName.'" id="hidden_'.$tableName.'" onclick="pgc_hide_table(this, \''.$tableName.'\')" '.$checked.' />
                  <img id="ajax_'.$tableName.'" class="ajax_processing" src="'. admin_url('images/loading.gif') .'" alt="ajax request processing..." title="AJAX request processing..."/>';
      }
      $html .= '</td>
            <td style="vertical-align:top;width:300px;" >';
      $deleteCheckBox = '';
      if (!$plugin->plugin_name) {
        $color = 'red';
        $deleteCheckBox = '<input type="checkbox" name="delete_'.$tableName.'" />';
        $showDeleteButton = true;
      } else if ($plugin->plugin_state=='active') {
        $color = 'green';
      } else {
        $color = 'blue';
      }
      $html .= $deleteCheckBox.' <span style="color:'.$color.';">'.$tableName.'</span>';
      $html .= '
            </td>
            <td><span style="color:'.$color.';">'.$column.'</span></td><td>';
      if ($plugin->plugin_name) {
        $html .= '<span style="color:'.$color.';">'.$plugin->plugin_name.'</span>';
      } else {
        $html .= '<span style="color:red;">unknown</span>';
      }
      $html .= '</td>
            <td><span style="color:'.$color.';">'.$plugin->plugin_state.'</span></td>
          </tr>';
      }
    }
    $html .= '</tbody>
          <tfoot>'
    .pgc_display_column_headers_wp().
          '</tfoot>
      </table>';
    if ($hiddenTableExists) {
      $html .= '<span style="color: #bbb; font-size: 0.8em;">'.esc_html__('Some tables are hidden by you. Turn on "Show hidden DB tables" option and click "Scan" button again to show them.', 'plugins-garbage-collector').'</span>';
    }
    if ($showDeleteButton) {
      $html .= '
      <table>
        <tr>
          <td>
            <div class="submit">
              <input type="submit" name="delete_extra_columns_action" value="'.esc_html__('Delete Extra Columns', 'plugins-garbage-collector').'"/>
            </div>
          </td>
          <td>
            <div style="padding-left: 10px;"><span style="color: red; font-weight: bold;">'.esc_html__('Attention!','plugins-garbage-collector').'</span> '.
              esc_html__('Operation rollback is not possible. Consider to make database backup first. Please double think before click <code>Delete Extra Columns</code> button.','plugins-garbage-collector').'
            </div>
          </td>
        </tr>
      </table>';
    }
  } else {
    $html = '
    <span style="color: green; text-align: center; font-size: 1.2em;">'.
      esc_html__('Congratulations! It seems that your WordPress database tables structure is not changed','plugins-garbage-collector').'
    </span>';
  }

  $result = array('result'=>'success', 'html'=>$html);
  
  echo json_encode($result);
}
// end of pgc_check_wp_tables_structure()



function pgc_delete_extra_columns_from_wp_tables() {

  $message = esc_html__('This feature is still under development and will be realized in the future version', 'plugins-garbage-collector');
  
  return $message;
}
// end of pgc_deleteExtraColumnsFromWPTables()



function pgc_get_plugins_list() {

    $_SESSION['plugins-garbage-collector'] = null;
    $_SESSION['plugins-garbage-collector']['tables'] = pgc_get_not_wp_tables();
    $plugins = get_plugins();
    $skip_list = PGC_Known_Plugins::get_skip_list();
    $plugins_list = array();
    foreach($plugins as $key=>$plugin) {
        $key_lc = strtolower( $key ); 
        if ( in_array( $key_lc, $skip_list ) ) {
            continue;
        }
        $plugin_short = new stdClass();
        $plugin_short->key = $key;
        $plugin_short->title = $plugin['Title'];
        $plugin_short->version = $plugin['Version'];
        $plugins_list[] = $plugin_short;
    }
    
    $answer = array('result'=>'success', 'plugins_list'=>$plugins_list);
    
    echo json_encode( $answer );
}


function pgc_get_plugins_scan_results() {
    
    pgc_set_plugin_state_for_tables();
    $html = pgc_show_tables();
    $result = array('result'=>'success', 'html'=>$html);
    
    echo json_encode($result);
}
// end of pgc_scan_db_tables()



function pgc_get_table_name_from_post() {
        
    $table_name = filter_input(INPUT_POST, 'table_name', FILTER_SANITIZE_STRING);
    if (empty($table_name)) {
        $answer = array('result'=>'error', 'message'=>'Wrong request - required parameter table_name is missed.');
        echo json_encode($answer);
        return false;
    }
        
    return $table_name;
}
// end of pgc_get_table_name_from_post()


function pgc_hide_table() {
    
    $table_name = pgc_get_table_name_from_post();
    if (empty($table_name)) {
        return;
    }
       
    $pgc_settings = get_option('pgc_settings');
    if (!$pgc_settings) {
        $pgc_settings = array();
        $pgc_settings['hidden'] = array();
    }
    $pgc_settings['hidden'][$table_name] = 1;
    update_option('pgc_settings', $pgc_settings);
    $answer = array('result'=>'success', 'message'=> esc_html__('Table was hidden', 'plugins-garbage-collector'));
    echo json_encode($answer);
}
// end of pgc_hide_table()


function pgc_show_table() {
    $table_name = pgc_get_table_name_from_post();
    if (empty($table_name)) {
        return;
    }
    
    $pgc_settings = get_option('pgc_settings');
    if (!$pgc_settings) {
        $pgc_settings = array();
        $pgc_settings['hidden'] = array();
    } else if (isset($pgc_settings['hidden'][$table_name])) {
        unset($pgc_settings['hidden'][$table_name]);
    }
    update_option('pgc_settings', $pgc_settings);
    $answer = array('result'=>'success', 'message'=>esc_html__('Table was shown', 'plugins-garbage-collector'));
    echo json_encode($answer);
}
// end of pgc_show_table()


function pgc_process_ajax_request() {
    
    $action = filter_input(INPUT_POST, 'subaction', FILTER_SANITIZE_STRING);
    switch ($action) {
        case 'get-plugins-list': {
            pgc_get_plugins_list();
            break;
        }
        case 'scan-plugin-for-db-tables-use': {
            pgc_scan_plugin_for_db_tables_use();
            break;
        }
        case 'get-plugins-scan-results': {
            pgc_get_plugins_scan_results();
            break;
        }
        case 'check-wp-tables-structure': {
            pgc_check_wp_tables_structure();            
            break;
        }
        case 'show-progress': {
            pgc_show_progress();
            break;
        }
        case 'hide-table': {
            pgc_hide_table();
            break;
        }
        case 'show-table': {
            pgc_show_table();
            break;
        }
        default: {
            echo json_encode(array('result'=>'error', 'message'=>'Unknown action'));
        }
                
    }   // end of switch
    
}
// end of pgc_process_ajax_request()


function plugins_garbage_collector_ajax() {
    if (!check_ajax_referer( "plugins-garbage-collector" )) {
        echo json_encode(array('result'=>false, 'message'=>'Error: wrong request, wp nonce value is not valid'));        
        return false;
    }
    
    if (!isset($_POST['subaction'])) {
        echo json_encode(array('result'=>false, 'message'=>'Error: wrong action'));
        return false;
    }
    
    if (!session_id()) {
        @session_start();
    }
    
    try {
        ini_set('max_execution_time', '90'); // 90 seconds
        pgc_process_ajax_request();            
    } finally {              
        wp_die();
    }
}
// end of plugins_garbage_collector_ajax()