Proyectos de Subversion Moodle

<?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/>.

/**

 * Provides {@link tool_policy\output\renderer} class.

 *

 * @package     tool_policy

 * @category    output

 * @copyright   2018 David Mudrák <david@moodle.com>

 * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

namespace tool_policy;

use coding_exception;

use context_helper;

use context_system;

use context_user;

use core\session\manager;

use stdClass;

use tool_policy\event\acceptance_created;

use tool_policy\event\acceptance_updated;

use user_picture;

defined('MOODLE_INTERNAL') || die();

/**

 * Provides the API of the policies plugin.

 *

 * @copyright 2018 David Mudrak <david@moodle.com>

 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

class api {

    /**

     * Return current (active) policies versions.

     *

     * @param array $audience If defined, filter against the given audience (AUDIENCE_ALL always included)

     * @return array of stdClass - exported {@link tool_policy\policy_version_exporter} instances

     */

    public static function list_current_versions($audience = null) {

        $current = [];

        foreach (static::list_policies() as $policy) {

            if (empty($policy->currentversion)) {

                continue;

            }

            if ($audience && !in_array($policy->currentversion->audience, [policy_version::AUDIENCE_ALL, $audience])) {

                continue;

            }

            $current[] = $policy->currentversion;

        }

        return $current;

    }

    /**

     * Checks if there are any current policies defined and returns their ids only

     *

     * @param array $audience If defined, filter against the given audience (AUDIENCE_ALL always included)

     * @return array of version ids indexed by policies ids

     */

    public static function get_current_versions_ids($audience = null) {

        global $DB;

        $sql = "SELECT v.policyid, v.id

             FROM {tool_policy} d

             LEFT JOIN {tool_policy_versions} v ON v.policyid = d.id

             WHERE d.currentversionid = v.id";

        $params = [];

        if ($audience) {

            $sql .= " AND v.audience IN (?, ?)";

            $params = [$audience, policy_version::AUDIENCE_ALL];

        }

        return $DB->get_records_sql_menu($sql . " ORDER BY d.sortorder", $params);

    }

    /**

     * Returns a list of all policy documents and their versions.

     *

     * @param array|int|null $ids Load only the given policies, defaults to all.

     * @param int $countacceptances return number of user acceptances for each version

     * @return array of stdClass - exported {@link tool_policy\policy_exporter} instances

     */

    public static function list_policies($ids = null, $countacceptances = false) {

        global $DB, $PAGE;

        $versionfields = policy_version::get_sql_fields('v', 'v_');

        $sql = "SELECT d.id, d.currentversionid, d.sortorder, $versionfields ";

        if ($countacceptances) {

            $sql .= ", COALESCE(ua.acceptancescount, 0) AS acceptancescount ";

        }

        $sql .= " FROM {tool_policy} d

             LEFT JOIN {tool_policy_versions} v ON v.policyid = d.id ";

        if ($countacceptances) {

            $sql .= " LEFT JOIN (

                            SELECT policyversionid, COUNT(*) AS acceptancescount

                            FROM {tool_policy_acceptances}

                            GROUP BY policyversionid

                        ) ua ON ua.policyversionid = v.id ";

        }

        $sql .= " WHERE v.id IS NOT NULL ";

        $params = [];

        if ($ids) {

            list($idsql, $idparams) = $DB->get_in_or_equal($ids, SQL_PARAMS_NAMED);

            $sql .= " AND d.id $idsql";

            $params = array_merge($params, $idparams);

        }

        $sql .= " ORDER BY d.sortorder ASC, v.timecreated DESC";

        $policies = [];

        $versions = [];

        $optcache = \cache::make('tool_policy', 'policy_optional');

        $rs = $DB->get_recordset_sql($sql, $params);

        foreach ($rs as $r) {

            if (!isset($policies[$r->id])) {

                $policies[$r->id] = (object) [

                    'id' => $r->id,

                    'currentversionid' => $r->currentversionid,

                    'sortorder' => $r->sortorder,

                ];

            }

            $versiondata = policy_version::extract_record($r, 'v_');

            if ($countacceptances && $versiondata->audience != policy_version::AUDIENCE_GUESTS) {

                $versiondata->acceptancescount = $r->acceptancescount;

            }

            $versions[$r->id][$versiondata->id] = $versiondata;

            $optcache->set($versiondata->id, $versiondata->optional);

        }

        $rs->close();

        foreach (array_keys($policies) as $policyid) {

            static::fix_revision_values($versions[$policyid]);

        }

        $return = [];

        $context = context_system::instance();

        $output = $PAGE->get_renderer('tool_policy');

        foreach ($policies as $policyid => $policydata) {

            $versionexporters = [];

            foreach ($versions[$policyid] as $versiondata) {

                if ($policydata->currentversionid == $versiondata->id) {

                    $versiondata->status = policy_version::STATUS_ACTIVE;

                } else if ($versiondata->archived) {

                    $versiondata->status = policy_version::STATUS_ARCHIVED;

                } else {

                    $versiondata->status = policy_version::STATUS_DRAFT;

                }

                $versionexporters[] = new policy_version_exporter($versiondata, [

                    'context' => $context,

                ]);

            }

            $policyexporter = new policy_exporter($policydata, [

                'versions' => $versionexporters,

            ]);

            $return[] = $policyexporter->export($output);

        }

        return $return;

    }

    /**

     * Returns total number of users who are expected to accept site policy

     *

     * @return int|null

     */

    public static function count_total_users() {

        global $DB, $CFG;

        static $cached = null;

        if ($cached === null) {

            $cached = $DB->count_records_select('user', 'deleted = 0 AND id <> ?', [$CFG->siteguest]);

        }

        return $cached;

    }

    /**

     * Load a particular policy document version.

     *

     * @param int $versionid ID of the policy document version.

     * @param array $policies cached result of self::list_policies() in case this function needs to be called in a loop

     * @return stdClass - exported {@link tool_policy\policy_exporter} instance

     */

    public static function get_policy_version($versionid, $policies = null) {

        if ($policies === null) {

            $policies = self::list_policies();

        }

        foreach ($policies as $policy) {

            if ($policy->currentversionid == $versionid) {

                return $policy->currentversion;

            } else {

                foreach ($policy->draftversions as $draft) {

                    if ($draft->id == $versionid) {

                        return $draft;

                    }

                }

                foreach ($policy->archivedversions as $archived) {

                    if ($archived->id == $versionid) {

                        return $archived;

                    }

                }

            }

        }

        throw new \moodle_exception('errorpolicyversionnotfound', 'tool_policy');

    }

    /**

     * Make sure that each version has a unique revision value.

     *

     * Empty value are replaced with a timecreated date. Duplicates are suffixed with v1, v2, v3, ... etc.

     *

     * @param array $versions List of objects with id, timecreated and revision properties

     */

    public static function fix_revision_values(array $versions) {

        $byrev = [];

        foreach ($versions as $version) {

            if ($version->revision === '') {

                $version->revision = userdate($version->timecreated, get_string('strftimedate', 'core_langconfig'));

            }

            $byrev[$version->revision][$version->id] = true;

        }

        foreach ($byrev as $origrevision => $versionids) {

            $cnt = count($byrev[$origrevision]);

            if ($cnt > 1) {

                foreach ($versionids as $versionid => $unused) {

                    foreach ($versions as $version) {

                        if ($version->id == $versionid) {

                            $version->revision = $version->revision.' - v'.$cnt;

                            $cnt--;

                            break;

                        }

                    }

                }

            }

        }

    }

    /**

     * Can the user view the given policy version document?

     *

     * @param stdClass $policy - exported {@link tool_policy\policy_exporter} instance

     * @param int $behalfid The id of user on whose behalf the user is viewing the policy

     * @param int $userid The user whom access is evaluated, defaults to the current one

     * @return bool

     */

    public static function can_user_view_policy_version($policy, $behalfid = null, $userid = null) {

        global $USER;

        if ($policy->status == policy_version::STATUS_ACTIVE) {

            return true;

        }

        if (empty($userid)) {

            $userid = $USER->id;

        }

        // Check if the user is viewing the policy on someone else's behalf.

        // Typical scenario is a parent viewing the policy on behalf of her child.

        if ($behalfid > 0) {

            $behalfcontext = context_user::instance($behalfid);

            if ($behalfid != $userid && !has_capability('tool/policy:acceptbehalf', $behalfcontext, $userid)) {

                return false;

            }

            // Check that the other user (e.g. the child) has access to the policy.

            // Pass a negative third parameter to avoid eventual endless loop.

            // We do not support grand-parent relations.

            return static::can_user_view_policy_version($policy, -1, $behalfid);

        }

        // Users who can manage policies, can see all versions.

        if (has_capability('tool/policy:managedocs', context_system::instance(), $userid)) {

            return true;

        }

        // User who can see all acceptances, must be also allowed to see what was accepted.

        if (has_capability('tool/policy:viewacceptances', context_system::instance(), $userid)) {

            return true;

        }

        // Users have access to all the policies they have ever accepted/declined.

        if (static::is_user_version_accepted($userid, $policy->id) !== null) {

            return true;

        }

        // Check if the user could get access through some of her minors.

        if ($behalfid === null) {

            foreach (static::get_user_minors($userid) as $minor) {

                if (static::can_user_view_policy_version($policy, $minor->id, $userid)) {

                    return true;

                }

            }

        }

        return false;

    }

    /**

     * Return the user's minors - other users on which behalf we can accept policies.

     *

     * Returned objects contain all the standard user name and picture fields as well as the context instanceid.

     *

     * @param int $userid The id if the user with parental responsibility

     * @param array $extrafields Extra fields to be included in result

     * @return array of objects

     */

    public static function get_user_minors($userid, array $extrafields = null) {

        global $DB;

        $ctxfields = context_helper::get_preload_record_columns_sql('c');

        $userfieldsapi = \core_user\fields::for_name()->with_userpic()->including(...($extrafields ?? []));

        $userfields = $userfieldsapi->get_sql('u')->selects;

        $sql = "SELECT $ctxfields $userfields

                  FROM {role_assignments} ra

                  JOIN {context} c ON c.contextlevel = ".CONTEXT_USER." AND ra.contextid = c.id

                  JOIN {user} u ON c.instanceid = u.id

                 WHERE ra.userid = ?

              ORDER BY u.lastname ASC, u.firstname ASC";

        $rs = $DB->get_recordset_sql($sql, [$userid]);

        $minors = [];

        foreach ($rs as $record) {

            context_helper::preload_from_record($record);

            $childcontext = context_user::instance($record->id);

            if (has_capability('tool/policy:acceptbehalf', $childcontext, $userid)) {

                $minors[$record->id] = $record;

            }

        }

        $rs->close();

        return $minors;

    }

    /**

     * Prepare data for the {@link \tool_policy\form\policydoc} form.

     *

     * @param \tool_policy\policy_version $version persistent representing the version.

     * @return stdClass form data

     */

    public static function form_policydoc_data(policy_version $version) {

        $data = $version->to_record();

        $summaryfieldoptions = static::policy_summary_field_options();

        $contentfieldoptions = static::policy_content_field_options();

        if (empty($data->id)) {

            // Adding a new version of a policy document.

            $data = file_prepare_standard_editor($data, 'summary', $summaryfieldoptions, $summaryfieldoptions['context']);

            $data = file_prepare_standard_editor($data, 'content', $contentfieldoptions, $contentfieldoptions['context']);

        } else {

            // Editing an existing policy document version.

            $data = file_prepare_standard_editor($data, 'summary', $summaryfieldoptions, $summaryfieldoptions['context'],

                'tool_policy', 'policydocumentsummary', $data->id);

            $data = file_prepare_standard_editor($data, 'content', $contentfieldoptions, $contentfieldoptions['context'],

                'tool_policy', 'policydocumentcontent', $data->id);

        }

        return $data;

    }

    /**

     * Save the data from the policydoc form as a new policy document.

     *

     * @param stdClass $form data submitted from the {@link \tool_policy\form\policydoc} form.

     * @return \tool_policy\policy_version persistent

     */

    public static function form_policydoc_add(stdClass $form) {

        global $DB;

        $form = clone($form);

        $form->policyid = $DB->insert_record('tool_policy', (object) [

            'sortorder' => 999,

        ]);

        static::distribute_policy_document_sortorder();

        return static::form_policydoc_update_new($form);

    }

    /**

     * Save the data from the policydoc form as a new policy document version.

     *

     * @param stdClass $form data submitted from the {@link \tool_policy\form\policydoc} form.

     * @return \tool_policy\policy_version persistent

     */

    public static function form_policydoc_update_new(stdClass $form) {

        global $DB;

        if (empty($form->policyid)) {

            throw new coding_exception('Invalid policy document ID');

        }

        $form = clone($form);

        $form->id = $DB->insert_record('tool_policy_versions', (new policy_version(0, (object) [

            'timecreated' => time(),

            'policyid' => $form->policyid,

        ]))->to_record());

        return static::form_policydoc_update_overwrite($form);

    }

    /**

     * Save the data from the policydoc form, overwriting the existing policy document version.

     *

     * @param stdClass $form data submitted from the {@link \tool_policy\form\policydoc} form.

     * @return \tool_policy\policy_version persistent

     */

    public static function form_policydoc_update_overwrite(stdClass $form) {

        $form = clone($form);

        unset($form->timecreated);

        $summaryfieldoptions = static::policy_summary_field_options();

        $form = file_postupdate_standard_editor($form, 'summary', $summaryfieldoptions, $summaryfieldoptions['context'],

            'tool_policy', 'policydocumentsummary', $form->id);

        unset($form->summary_editor);

        unset($form->summarytrust);

        $contentfieldoptions = static::policy_content_field_options();

        $form = file_postupdate_standard_editor($form, 'content', $contentfieldoptions, $contentfieldoptions['context'],

            'tool_policy', 'policydocumentcontent', $form->id);

        unset($form->content_editor);

        unset($form->contenttrust);

        unset($form->status);

        unset($form->save);

        unset($form->saveasdraft);

        unset($form->minorchange);

        $policyversion = new policy_version($form->id, $form);

        $policyversion->update();

        return $policyversion;

    }

    /**

     * Make the given version the current active one.

     *

     * @param int $versionid

     */

    public static function make_current($versionid) {

        global $DB, $USER;

        $policyversion = new policy_version($versionid);

        if (! $policyversion->get('id') || $policyversion->get('archived')) {

            throw new coding_exception('Version not found or is archived');

        }

        // Archive current version of this policy.

        if ($currentversionid = $DB->get_field('tool_policy', 'currentversionid', ['id' => $policyversion->get('policyid')])) {

            if ($currentversionid == $versionid) {

                // Already current, do not change anything.

                return;

            }

            $DB->set_field('tool_policy_versions', 'archived', 1, ['id' => $currentversionid]);

        }

        // Set given version as current.

        $DB->set_field('tool_policy', 'currentversionid', $policyversion->get('id'), ['id' => $policyversion->get('policyid')]);

        // Reset the policyagreed flag to force everybody re-accept the policies.

        $DB->set_field('user', 'policyagreed', 0);

        // Make sure that the current user is not immediately redirected to the policy acceptance page.

        if (isloggedin() && !isguestuser()) {

            $USER->policyagreed = 1;

        }

    }

    /**

     * Inactivate the policy document - no version marked as current and the document does not apply.

     *

     * @param int $policyid

     */

    public static function inactivate($policyid) {

        global $DB;

        if ($currentversionid = $DB->get_field('tool_policy', 'currentversionid', ['id' => $policyid])) {

            // Archive the current version.

            $DB->set_field('tool_policy_versions', 'archived', 1, ['id' => $currentversionid]);

            // Unset current version for the policy.

            $DB->set_field('tool_policy', 'currentversionid', null, ['id' => $policyid]);

        }

    }

    /**

     * Create a new draft policy document from an archived version.

     *

     * @param int $versionid

     * @return \tool_policy\policy_version persistent

     */

    public static function revert_to_draft($versionid) {

        $policyversion = new policy_version($versionid);

        if (!$policyversion->get('id') || !$policyversion->get('archived')) {

            throw new coding_exception('Version not found or is not archived');

        }

        $formdata = static::form_policydoc_data($policyversion);

        // Unarchived the new version.

        $formdata->archived = 0;

        return static::form_policydoc_update_new($formdata);

    }

    /**

     * Can the current version be deleted

     *

     * @param stdClass $version object describing version, contains fields policyid, id, status, archived, audience, ...

     */

    public static function can_delete_version($version) {

        // TODO MDL-61900 allow to delete not only draft versions.

        return has_capability('tool/policy:managedocs', context_system::instance()) &&

                $version->status == policy_version::STATUS_DRAFT;

    }

    /**

     * Delete the given version (if it is a draft). Also delete policy if this is the only version.

     *

     * @param int $versionid

     */

    public static function delete($versionid) {

        global $DB;

        $version = static::get_policy_version($versionid);

        if (!self::can_delete_version($version)) {

            // Current version can not be deleted.

            return;

        }

        $DB->delete_records('tool_policy_versions', ['id' => $versionid]);

        if (!$DB->record_exists('tool_policy_versions', ['policyid' => $version->policyid])) {

            // This is a single version in a policy. Delete the policy.

            $DB->delete_records('tool_policy', ['id' => $version->policyid]);

        }

    }

    /**

     * Editor field options for the policy summary text.

     *

     * @return array

     */

    public static function policy_summary_field_options() {

        global $CFG;

        require_once($CFG->libdir.'/formslib.php');

        return [

            'subdirs' => false,

            'maxfiles' => -1,

            'context' => context_system::instance(),

        ];

    }

    /**

     * Editor field options for the policy content text.

     *

     * @return array

     */

    public static function policy_content_field_options() {

        global $CFG;

        require_once($CFG->libdir.'/formslib.php');

        return [

            'subdirs' => false,

            'maxfiles' => -1,

            'context' => context_system::instance(),

        ];

    }

    /**

     * Re-sets the sortorder field of the policy documents to even values.

     */

    protected static function distribute_policy_document_sortorder() {

        global $DB;

        $sql = "SELECT p.id, p.sortorder, MAX(v.timecreated) AS timerecentcreated

                  FROM {tool_policy} p

             LEFT JOIN {tool_policy_versions} v ON v.policyid = p.id

              GROUP BY p.id, p.sortorder

              ORDER BY p.sortorder ASC, timerecentcreated ASC";

        $rs = $DB->get_recordset_sql($sql);

        $sortorder = 10;

        foreach ($rs as $record) {

            if ($record->sortorder != $sortorder) {

                $DB->set_field('tool_policy', 'sortorder', $sortorder, ['id' => $record->id]);

            }

            $sortorder = $sortorder + 2;

        }

        $rs->close();

    }

    /**

     * Change the policy document's sortorder.

     *

     * @param int $policyid

     * @param int $step

     */

    protected static function move_policy_document($policyid, $step) {

        global $DB;

        $sortorder = $DB->get_field('tool_policy', 'sortorder', ['id' => $policyid], MUST_EXIST);

        $DB->set_field('tool_policy', 'sortorder', $sortorder + $step, ['id' => $policyid]);

        static::distribute_policy_document_sortorder();

    }

    /**

     * Move the given policy document up in the list.

     *

     * @param id $policyid

     */

    public static function move_up($policyid) {

        static::move_policy_document($policyid, -3);

    }

    /**

     * Move the given policy document down in the list.

     *

     * @param id $policyid

     */

    public static function move_down($policyid) {

        static::move_policy_document($policyid, 3);

    }

    /**

     * Returns list of acceptances for this user.

     *

     * @param int $userid id of a user.

     * @param int|array $versions list of policy versions.

     * @return array list of acceptances indexed by versionid.

     */

    public static function get_user_acceptances($userid, $versions = null) {

        global $DB;

        list($vsql, $vparams) = ['', []];

        if (!empty($versions)) {

            list($vsql, $vparams) = $DB->get_in_or_equal($versions, SQL_PARAMS_NAMED, 'ver');

            $vsql = ' AND a.policyversionid ' . $vsql;

        }

        $userfieldsapi = \core_user\fields::for_name();

        $userfieldsmod = $userfieldsapi->get_sql('m', false, 'mod', '', false)->selects;

        $sql = "SELECT u.id AS mainuserid, a.policyversionid, a.status, a.lang, a.timemodified, a.usermodified, a.note,

                  u.policyagreed, $userfieldsmod

                  FROM {user} u

                  INNER JOIN {tool_policy_acceptances} a ON a.userid = u.id AND a.userid = :userid $vsql

                  LEFT JOIN {user} m ON m.id = a.usermodified";

        $params = ['userid' => $userid];

        $result = $DB->get_recordset_sql($sql, $params + $vparams);

        $acceptances = [];

        foreach ($result as $row) {

            if (!empty($row->policyversionid)) {

                $acceptances[$row->policyversionid] = $row;

            }

        }

        $result->close();

        return $acceptances;

    }

    /**

     * Returns version acceptance for this user.

     *

     * @param int $userid User identifier.

     * @param int $versionid Policy version identifier.

     * @param array|null $acceptances List of policy version acceptances indexed by versionid.

     * @return stdClass|null Acceptance object if the user has ever accepted this version or null if not.

     */

    public static function get_user_version_acceptance($userid, $versionid, $acceptances = null) {

        if (empty($acceptances)) {

            $acceptances = static::get_user_acceptances($userid, $versionid);

        }

        if (array_key_exists($versionid, $acceptances)) {

            // The policy version has ever been accepted.

            return $acceptances[$versionid];

        }

        return null;

    }

    /**

     * Did the user accept the given policy version?

     *

     * @param int $userid User identifier.

     * @param int $versionid Policy version identifier.

     * @param array|null $acceptances Pre-loaded list of policy version acceptances indexed by versionid.

     * @return bool|null True/false if this user accepted/declined the policy; null otherwise.

     */

    public static function is_user_version_accepted($userid, $versionid, $acceptances = null) {

        $acceptance = static::get_user_version_acceptance($userid, $versionid, $acceptances);

        if (!empty($acceptance)) {

            return (bool) $acceptance->status;

        }

        return null;

    }

    /**

     * Get the list of policies and versions that current user is able to see and the respective acceptance records for

     * the selected user.

     *

     * @param int $userid

     * @return array array with the same structure that list_policies() returns with additional attribute acceptance for versions

     */

    public static function get_policies_with_acceptances($userid) {

        // Get the list of policies and versions that current user is able to see

        // and the respective acceptance records for the selected user.

        $policies = static::list_policies();

        $acceptances = static::get_user_acceptances($userid);

        $ret = [];

        foreach ($policies as $policy) {

            $versions = [];

            if ($policy->currentversion && $policy->currentversion->audience != policy_version::AUDIENCE_GUESTS) {

                if (isset($acceptances[$policy->currentversion->id])) {

                    $policy->currentversion->acceptance = $acceptances[$policy->currentversion->id];

                } else {

                    $policy->currentversion->acceptance = null;

                }

                $versions[] = $policy->currentversion;

            }

            foreach ($policy->archivedversions as $version) {

                if ($version->audience != policy_version::AUDIENCE_GUESTS

                        && static::can_user_view_policy_version($version, $userid)) {

                    $version->acceptance = isset($acceptances[$version->id]) ? $acceptances[$version->id] : null;

                    $versions[] = $version;

                }

            }

            if ($versions) {

                $ret[] = (object)['id' => $policy->id, 'versions' => $versions];

            }

        }

        return $ret;

    }

    /**

     * Check if given policies can be accepted by the current user (eventually on behalf of the other user)

     *

     * Currently, the version ids are not relevant and the check is based on permissions only. In the future, additional

     * conditions can be added (such as policies applying to certain users only).

     *

     * @param array $versionids int[] List of policy version ids to check

     * @param int $userid Accepting policies on this user's behalf (defaults to accepting on self)

     * @param bool $throwexception Throw exception instead of returning false

     * @return bool

     */

    public static function can_accept_policies(array $versionids, $userid = null, $throwexception = false) {

        global $USER;

        if (!isloggedin() || isguestuser()) {

            if ($throwexception) {

                throw new \moodle_exception('noguest');

            } else {

                return false;

            }

        }

        if (!$userid) {

            $userid = $USER->id;

        }

        if ($userid == $USER->id && !manager::is_loggedinas()) {

            if ($throwexception) {

                require_capability('tool/policy:accept', context_system::instance());

                return;

            } else {

                return has_capability('tool/policy:accept', context_system::instance());

            }

        }

        // Check capability to accept on behalf as the real user.

        $realuser = manager::get_realuser();

        $usercontext = \context_user::instance($userid);

        if ($throwexception) {

            require_capability('tool/policy:acceptbehalf', $usercontext, $realuser);

            return;

        } else {

            return has_capability('tool/policy:acceptbehalf', $usercontext, $realuser);

        }

    }

    /**

     * Check if given policies can be declined by the current user (eventually on behalf of the other user)

     *

     * Only optional policies can be declined. Otherwise, the permissions are same as for accepting policies.

     *

     * @param array $versionids int[] List of policy version ids to check

     * @param int $userid Declining policies on this user's behalf (defaults to declining by self)

     * @param bool $throwexception Throw exception instead of returning false

     * @return bool

     */

    public static function can_decline_policies(array $versionids, $userid = null, $throwexception = false) {

        foreach ($versionids as $versionid) {

            if (static::get_agreement_optional($versionid) == policy_version::AGREEMENT_COMPULSORY) {

                // Compulsory policies can't be declined (that is what makes them compulsory).

                if ($throwexception) {

                    throw new \moodle_exception('errorpolicyversioncompulsory', 'tool_policy');

                } else {

                    return false;

                }

            }

        }

        return static::can_accept_policies($versionids, $userid, $throwexception);

    }

    /**

     * Check if acceptances to given policies can be revoked by the current user (eventually on behalf of the other user)

     *

     * Revoking optional policies is controlled by the same rules as declining them. Compulsory policies can be revoked

     * only by users with the permission to accept policies on other's behalf. The reasoning behind this is to make sure

     * the user communicates with the site's privacy officer and is well aware of all consequences of the decision (such

     * as losing right to access the site).

     *

     * @param array $versionids int[] List of policy version ids to check

     * @param int $userid Revoking policies on this user's behalf (defaults to revoking by self)

     * @param bool $throwexception Throw exception instead of returning false

     * @return bool

     */

    public static function can_revoke_policies(array $versionids, $userid = null, $throwexception = false) {

        global $USER;

        // Guests' acceptance is not stored so there is nothing to revoke.

        if (!isloggedin() || isguestuser()) {

            if ($throwexception) {

                throw new \moodle_exception('noguest');

            } else {

                return false;

            }

        }

        // Sort policies into two sets according the optional flag.

        $compulsory = [];

        $optional = [];

        foreach ($versionids as $versionid) {

            $agreementoptional = static::get_agreement_optional($versionid);

            if ($agreementoptional == policy_version::AGREEMENT_COMPULSORY) {

                $compulsory[] = $versionid;

            } else if ($agreementoptional == policy_version::AGREEMENT_OPTIONAL) {

                $optional[] = $versionid;

            } else {

                throw new \coding_exception('Unexpected optional flag value');

            }

        }

        // Check if the user can revoke the optional policies from the list.

        if ($optional) {

            if (!static::can_decline_policies($optional, $userid, $throwexception)) {

                return false;

            }

        }

        // Check if the user can revoke the compulsory policies from the list.

        if ($compulsory) {

            if (!$userid) {

                $userid = $USER->id;

            }

            $realuser = manager::get_realuser();

            $usercontext = \context_user::instance($userid);

            if ($throwexception) {

                require_capability('tool/policy:acceptbehalf', $usercontext, $realuser);

                return;

            } else {

                return has_capability('tool/policy:acceptbehalf', $usercontext, $realuser);

            }

        }

        return true;

    }

    /**

     * Mark the given policy versions as accepted by the user.

     *

     * @param array|int $policyversionid Policy version id(s) to set acceptance status for.

     * @param int|null $userid Id of the user accepting the policy version, defaults to the current one.

     * @param string|null $note Note to be recorded.

     * @param string|null $lang Language in which the policy was shown, defaults to the current one.

     */

    public static function accept_policies($policyversionid, $userid = null, $note = null, $lang = null) {

        static::set_acceptances_status($policyversionid, $userid, $note, $lang, 1);

    }

    /**

     * Mark the given policy versions as declined by the user.

     *

     * @param array|int $policyversionid Policy version id(s) to set acceptance status for.

     * @param int|null $userid Id of the user accepting the policy version, defaults to the current one.

     * @param string|null $note Note to be recorded.

     * @param string|null $lang Language in which the policy was shown, defaults to the current one.

     */

    public static function decline_policies($policyversionid, $userid = null, $note = null, $lang = null) {

        static::set_acceptances_status($policyversionid, $userid, $note, $lang, 0);

    }

    /**

     * Mark the given policy versions as accepted or declined by the user.

     *

     * @param array|int $policyversionid Policy version id(s) to set acceptance status for.

     * @param int|null $userid Id of the user accepting the policy version, defaults to the current one.

     * @param string|null $note Note to be recorded.

     * @param string|null $lang Language in which the policy was shown, defaults to the current one.

     * @param int $status The acceptance status, defaults to 1 = accepted

     */

    protected static function set_acceptances_status($policyversionid, $userid = null, $note = null, $lang = null, $status = 1) {

        global $DB, $USER;

        // Validate arguments and capabilities.

        if (empty($policyversionid)) {

            return;

        } else if (!is_array($policyversionid)) {

            $policyversionid = [$policyversionid];

        }

        if (!$userid) {

            $userid = $USER->id;

        }

        self::can_accept_policies([$policyversionid], $userid, true);

        // Retrieve the list of policy versions that need agreement (do not update existing agreements).

        list($sql, $params) = $DB->get_in_or_equal($policyversionid, SQL_PARAMS_NAMED);

        $sql = "SELECT v.id AS versionid, a.*

                  FROM {tool_policy_versions} v

             LEFT JOIN {tool_policy_acceptances} a ON a.userid = :userid AND a.policyversionid = v.id

                 WHERE v.id $sql AND (a.id IS NULL OR a.status <> :status)";

        $needacceptance = $DB->get_records_sql($sql, $params + [

            'userid' => $userid,

            'status' => $status,

        ]);

        $realuser = manager::get_realuser();

        $updatedata = ['status' => $status, 'lang' => $lang ?: current_language(),

            'timemodified' => time(), 'usermodified' => $realuser->id, 'note' => $note];

        foreach ($needacceptance as $versionid => $currentacceptance) {

            unset($currentacceptance->versionid);

            if ($currentacceptance->id) {

                $updatedata['id'] = $currentacceptance->id;

                $DB->update_record('tool_policy_acceptances', $updatedata);

                acceptance_updated::create_from_record((object)($updatedata + (array)$currentacceptance))->trigger();

            } else {

                $updatedata['timecreated'] = $updatedata['timemodified'];

                $updatedata['policyversionid'] = $versionid;

                $updatedata['userid'] = $userid;

                $updatedata['id'] = $DB->insert_record('tool_policy_acceptances', $updatedata);

                acceptance_created::create_from_record((object)($updatedata + (array)$currentacceptance))->trigger();

            }

        }

        static::update_policyagreed($userid);

    }

    /**

     * Make sure that $user->policyagreed matches the agreement to the policies

     *

     * @param int|stdClass|null $user user to check (null for current user)

     */

    public static function update_policyagreed($user = null) {