MDL-46455 backup: Implement backup of standard logstore

Using standard subplugin support, this commit implements
the backup of logstore subplugins in general and the
standard logstore in particular. Notes:

- Uses a custom final element (base64_encode_final_element) to
  support the storage of serialized 'other' information in logs.
- Organization: Instead of directly extending backup_subplugin,
  every logstore extends backup_tool_log_logstore_subplugin just
  in case any shared code is needed in the future.
- Implements both course and activity logs, sharing the structure
  completely (both are based in contextid to pick the target
  information, from database or whatever other logstores use).

admin/tool/log/backup/moodle2/backup_tool_log_logstore_subplugin.class.php

@@ -0,0 +1,37 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle 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, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle 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 Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Backup support for tool_log logstore subplugins.
+ *
+ * @package    tool_log
+ * @category   backup
+ * @copyright  2015 onwards Eloy Lafuente (stronk7) {@link http://stronk7.com}
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Parent class of all the logstore subplugin implementations.
+ *
+ * Note: While this intermediate class is not strictly required and all the
+ * subplugin implementations can extend directly {@link backup_subplugin},
+ * it is always recommended to have it, both for better testing and also
+ * for sharing code between all subplugins.
+ */
+abstract class backup_tool_log_logstore_subplugin extends backup_subplugin {
+}

admin/tool/log/store/standard/backup/moodle2/backup_logstore_standard_subplugin.class.php

@@ -0,0 +1,55 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle 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, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle 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 Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Backup implementation for the (tool_log) logstore_standard subplugin.
+ *
+ * @package    logstore_standard
+ * @category   backup
+ * @copyright  2015 onwards Eloy Lafuente (stronk7) {@link http://stronk7.com}
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+class backup_logstore_standard_subplugin extends backup_tool_log_logstore_subplugin {
+
+    /**
+     * Returns the subplugin structure to attach to the 'logstore' XML element.
+     *
+     * @return backup_subplugin_element the subplugin structure to be attached.
+     */
+    protected function define_logstore_subplugin_structure() {
+
+        $subplugin = $this->get_subplugin_element();
+        $subpluginwrapper = new backup_nested_element($this->get_recommended_name());
+
+        // Create the custom (base64 encoded, xml safe) 'other' final element.
+        $otherelement = new base64_encode_final_element('other');
+
+        $subpluginlog = new backup_nested_element('logstore_standard_log', array('id'), array(
+            'eventname', 'component', 'action', 'target', 'objecttable',
+            'objectid', 'crud', 'edulevel', 'contextid', 'userid', 'relateduserid',
+            'anonymous', $otherelement, 'timecreated', 'ip', 'realuserid'));
+
+        $subplugin->add_child($subpluginwrapper);
+        $subpluginwrapper->add_child($subpluginlog);
+
+        $subpluginlog->set_source_table('logstore_standard_log', array('contextid' => backup::VAR_CONTEXTID));
+
+        return $subplugin;
+    }
+}

backup/moodle2/backup_activity_task.class.php

@@ -166,7 +166,10 @@ abstract class backup_activity_task extends backup_task {
 
         // Generate the logs file (conditionally)
         if ($this->get_setting_value('logs')) {
+            // Legacy logs.
             $this->add_step(new backup_activity_logs_structure_step('activity_logs', 'logs.xml'));
+            // New log stores.
+            $this->add_step(new backup_activity_logstores_structure_step('activity_logstores', 'logstores.xml'));
         }
 
         // Generate the calendar events file (conditionally)

backup/moodle2/backup_course_task.class.php

@@ -121,7 +121,10 @@ class backup_course_task extends backup_task {
 
         // Generate the logs file (conditionally)
         if ($this->get_setting_value('logs')) {
+            // Legacy logs.
             $this->add_step(new backup_course_logs_structure_step('course_logs', 'logs.xml'));
+            // New log stores.
+            $this->add_step(new backup_course_logstores_structure_step('course_logstores', 'logstores.xml'));
         }
 
         // Generate the inforef file (must be after ALL steps gathering annotations of ANY type)

backup/moodle2/backup_custom_fields.php

@@ -78,6 +78,25 @@ class mnethosturl_final_element extends backup_final_element {
     }
 }
 
+/**
+ * Implementation of {@link backup_final_element} that provides base64 encoding.
+ *
+ * This final element transparently encodes with base64_encode() contents that
+ * normally are not safe for being stored in utf-8 xml files (binaries, serialized
+ * data...).
+ */
+class base64_encode_final_element extends backup_final_element {
+
+    /**
+     * Set the value for the final element, encoding it as utf-8/xml safe base64.
+     *
+     * @param string $value Original value coming from backup step source, usually db.
+     */
+    public function set_value($value) {
+        parent::set_value(base64_encode($value));
+    }
+}
+
 /**
  * Implementation of backup_nested_element that provides special handling of files
  *

backup/moodle2/backup_stepslib.php

@@ -1485,6 +1485,36 @@ class backup_activity_logs_structure_step extends backup_structure_step {
     }
 }
 
+/**
+ * Structure step in charge of constructing the logstores.xml file for the course logs.
+ *
+ * This backup step will backup the logs for all the enabled logstore subplugins supporting
+ * it, for logs belonging to the course level.
+ */
+class backup_course_logstores_structure_step extends backup_structure_step {
+
+    protected function define_structure() {
+
+        // Define the structure of logstores container.
+        $logstores = new backup_nested_element('logstores');
+        $logstore = new backup_nested_element('logstore');
+        $logstores->add_child($logstore);
+
+        // Add the tool_log logstore subplugins information to the logstore element.
+        $this->add_subplugin_structure('logstore', $logstore, true, 'tool', 'log');
+
+        return $logstores;
+    }
+}
+
+/**
+ * Structure step in charge of constructing the logstores.xml file for the activity logs.
+ *
+ * Note: Activity structure is completely equivalent to the course one, so just extend it.
+ */
+class backup_activity_logstores_structure_step extends backup_course_logstores_structure_step {
+}
+
 /**
  * structure in charge of constructing the inforef.xml file for all the items we want
  * to have referenced there (users, roles, files...)