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/>.

/**

 * Privacy Fetch Result Set.

 *

 * @package    core_privacy

 * @copyright  2018 Andrew Nicols <andrew@nicols.co.uk>

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

 */

namespace core_privacy\local\request;

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

/**

 * Privacy Fetch Result Set.

 *

 * @copyright  2018 Andrew Nicols <andrew@nicols.co.uk>

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

 */

class contextlist extends contextlist_base {

    /**

     * Add a set of contexts from  SQL.

     *

     * The SQL should only return a list of context IDs.

     *

     * @param   string  $sql    The SQL which will fetch the list of * context IDs

     * @param   array   $params The set of SQL parameters

     * @return  $this

     */

    public function add_from_sql(string $sql, array $params): contextlist {

        global $DB;

        $fields = \context_helper::get_preload_record_columns_sql('ctx');

        if ($fieldname = $this->guess_id_field_from_sql($sql)) {

            if (is_numeric($fieldname)) {

                $wrapper = "

                  SELECT {$fields}

                    FROM {context} ctx

                   WHERE ctx.id = :fieldvalue";

                $params = ['fieldvalue' => $fieldname];

            } else {

                // Able to guess a field name.

                $wrapper = "

                  SELECT {$fields}

                    FROM {context} ctx

                    JOIN ({$sql}) target ON ctx.id = target.{$fieldname}";

            }

        } else {

            // No field name available. Fall back on a potentially slower version.

            $wrapper = "

              SELECT {$fields}

                FROM {context} ctx

               WHERE ctx.id IN ({$sql})";

        }

        $contexts = $DB->get_recordset_sql($wrapper, $params);

        $contextids = [];

        foreach ($contexts as $context) {

            $contextids[] = $context->ctxid;

            \context_helper::preload_from_record($context);

        }

        $contexts->close();

        $this->set_contextids(array_merge($this->get_contextids(), $contextids));

        return $this;

    }

    /**

     * Adds the system context.

     *

     * @return $this

     */

    public function add_system_context(): contextlist {

        return $this->add_from_sql(SYSCONTEXTID, []);

    }

    /**

     * Adds the user context for a given user.

     *

     * @param int $userid

     * @return $this

     */

    public function add_user_context(int $userid): contextlist {

        $sql = "SELECT DISTINCT ctx.id

                  FROM {context} ctx

                 WHERE ctx.contextlevel = :contextlevel

                   AND ctx.instanceid = :instanceid";

        return $this->add_from_sql($sql, ['contextlevel' => CONTEXT_USER, 'instanceid' => $userid]);

    }

    /**

     * Adds the user contexts for given users.

     *

     * @param array $userids

     * @return $this

     */

    public function add_user_contexts(array $userids): contextlist {

        global $DB;

        list($useridsql, $useridparams) = $DB->get_in_or_equal($userids, SQL_PARAMS_NAMED);

        $sql = "SELECT DISTINCT ctx.id

                  FROM {context} ctx

                 WHERE ctx.contextlevel = :contextlevel

                   AND ctx.instanceid $useridsql";

        return $this->add_from_sql($sql, ['contextlevel' => CONTEXT_USER] + $useridparams);

    }

    /**

     * Sets the component for this contextlist.

     *

     * @param string $component the frankenstyle component name.

     */

    public function set_component($component) {

        parent::set_component($component);

    }

    /**

     * Guess the name of the contextid field from the supplied SQL.

     *

     * @param   string  $sql The SQL to guess from

     * @return  string  The field name or a numeric value representing the context id

     */

    protected function guess_id_field_from_sql(string $sql): string {

        // We are not interested in any subquery/view/conditions for the purpose of this method, so

        // let's reduce the query to the interesting parts by recursively cleaning all

        // contents within parenthesis. If there are problems (null), we keep the text unmodified.

        // So just top-level sql will remain after the reduction.

        $recursiveregexp = '/\((([^()]*|(?R))*)\)/';

        $sql = (preg_replace($recursiveregexp, '', $sql) ?: $sql);

        // Get the list of relevant words from the SQL Query.

        // We explode the SQL by the space character, then trim any extra whitespace (e.g. newlines), before we filter

        // empty value, and finally we re-index the array.

        $sql = rtrim($sql, ';');

        $words = array_map('trim', preg_split('/\s+/', $sql));

        $words = array_filter($words, function($word) {

            return $word !== '';

        });

        $words = array_values($words);

        $uwords = array_map('strtoupper', $words); // Uppercase all them.

        // If the query has boolean operators (UNION, it is the only one we support cross-db)

        // then we cannot guarantee whats coming after the first query, it can be anything.

        if (array_search('UNION', $uwords)) {

            return '';

        }

        if ($firstfrom = array_search('FROM', $uwords)) {

            // Found a FROM keyword.

            // Select the previous word.

            $fieldname = $words[$firstfrom - 1];

            if (is_numeric($fieldname)) {

                return $fieldname;

            }

            if ($hasdot = strpos($fieldname, '.')) {

                // This field is against a table alias. Take off the alias.

                $fieldname = substr($fieldname, $hasdot + 1);

            }

            return $fieldname;

        } else if ((count($words) == 1) && (is_numeric($words[0]))) {

            // Not a real SQL, just a single numerical value - such as one returned by {@link self::add_system_context()}.

            return $words[0];

        } else if ((count($words) == 2) && (strtoupper($words[0]) === 'SELECT') && (is_numeric($words[1]))) {

            // SQL returning a constant numerical value.

            return $words[1];

        }

        return '';

    }

}