MDL-75349 group: implement groups datasource for custom reporting.

Create new entities for exposing report data on course groups and
groupings, joining to existing course/user entities to provide data
for the reportbuilder editor.

group/classes/reportbuilder/datasource/groups.php

@@ -0,0 +1,138 @@
+<?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/>.
+
+declare(strict_types=1);
+
+namespace core_group\reportbuilder\datasource;
+
+use core_group\reportbuilder\local\entities\{grouping, group, group_member};
+use core_reportbuilder\datasource;
+use core_reportbuilder\local\entities\{course, user};
+use core_reportbuilder\local\helpers\database;
+
+/**
+ * Groups datasource
+ *
+ * @package     core_group
+ * @copyright   2022 Paul Holden <paulh@moodle.com>
+ * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class groups extends datasource {
+
+    /**
+     * Return user friendly name of the datasource
+     *
+     * @return string
+     */
+    public static function get_name(): string {
+        return get_string('groups', 'core_group');
+    }
+
+    /**
+     * Initialise report
+     */
+    protected function initialise(): void {
+        $courseentity = new course();
+        $coursealias = $courseentity->get_table_alias('course');
+
+        $this->set_main_table('course', $coursealias);
+        $this->add_entity($courseentity);
+
+        $paramsiteid = database::generate_param_name();
+        $this->add_base_condition_sql("{$coursealias}.id != :{$paramsiteid}", [$paramsiteid => SITEID]);
+
+        // Re-use the context table alias/join from the course entity in subsequent entities.
+        $contextalias = $courseentity->get_table_alias('context');
+        $this->add_join($courseentity->get_context_join());
+
+        // Group entity.
+        $groupentity = (new group())
+            ->set_table_alias('context', $contextalias);
+        $groupsalias = $groupentity->get_table_alias('groups');
+        $this->add_entity($groupentity
+            ->add_join("LEFT JOIN {groups} {$groupsalias} ON {$groupsalias}.courseid = {$coursealias}.id"));
+
+        // Grouping entity.
+        $groupingentity = (new grouping())
+            ->set_table_alias('context', $contextalias);
+        $groupingsalias = $groupingentity->get_table_alias('groupings');
+
+        // Sub-select for all groupings groups.
+        $groupinginnerselect = "
+            SELECT gr.*, grg.groupid
+              FROM {groupings} gr
+              JOIN {groupings_groups} grg ON grg.groupingid = gr.id";
+
+        $this->add_entity($groupingentity
+            ->add_joins($groupentity->get_joins())
+            ->add_join("LEFT JOIN ({$groupinginnerselect}) {$groupingsalias}
+                ON {$groupingsalias}.courseid = {$coursealias}.id AND {$groupingsalias}.groupid = {$groupsalias}.id"));
+
+        // Group member entity.
+        $groupmemberentity = new group_member();
+        $groupsmembersalias = $groupmemberentity->get_table_alias('groups_members');
+        $this->add_entity($groupmemberentity
+            ->add_joins($groupentity->get_joins())
+            ->add_join("LEFT JOIN {groups_members} {$groupsmembersalias} ON {$groupsmembersalias}.groupid = {$groupsalias}.id"));
+
+        // User entity.
+        $userentity = new user();
+        $useralias = $userentity->get_table_alias('user');
+        $this->add_entity($userentity
+            ->add_joins($groupmemberentity->get_joins())
+            ->add_join("LEFT JOIN {user} {$useralias} ON {$useralias}.id = {$groupsmembersalias}.userid"));
+
+        // Add all elements from entities to be available in custom reports.
+        $this->add_all_from_entities();
+    }
+
+    /**
+     * Return the columns that will be added to the report as part of default setup
+     *
+     * @return string[]
+     */
+    public function get_default_columns(): array {
+        return [
+            'course:coursefullnamewithlink',
+            'group:name',
+            'user:fullname',
+        ];
+    }
+
+    /**
+     * Return the filters that will be added to the report as part of default setup
+     *
+     * @return string[]
+     */
+    public function get_default_filters(): array {
+        return [
+            'course:fullname',
+            'group:name',
+        ];
+    }
+
+    /**
+     * Return the conditions that will be added to the report as part of default setup
+     *
+     * @return string[]
+     */
+    public function get_default_conditions(): array {
+        return [
+            'course:fullname',
+            'group:name',
+        ];
+    }
+}