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<?php
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// This file is part of Moodle - http://moodle.org/
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//
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// Moodle is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Moodle is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
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namespace core_question\local\bank;
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use core\output\datafilter;
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/**
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 * An abstract class for filtering/searching questions.
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 *
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 * @package    core_question
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 * @copyright  2013 Ray Morris
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 * @author     Safat Shahin <safatshahin@catalyst-au.net>
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 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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 */
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abstract class condition {
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    /** @var int The default filter type */
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    const JOINTYPE_DEFAULT = datafilter::JOINTYPE_ANY;
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    /** @var ?array Filter properties for this condition. */
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    public ?array $filter;
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    /** @var string SQL fragment to add to the where clause. */
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    protected string $where = '';
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    /** @var array query param used in where. */
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    protected array $params = [];
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    /**
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     * Return title of the condition
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     *
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     * @return string title of the condition
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     */
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    abstract public function get_title();
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    /**
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     * Return the Javascript filter class to provide the UI for this condition.
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     *
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     * If left as null, this will use the default core/datafilter/filtertype class. Otherwise, override it to return
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     * the full path to the Javascript module path for the class.
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     *
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     * @return ?string filter class
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     */
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    public function get_filter_class() {
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        return null;
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    }
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    /**
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     * Extract the required filter from the provided question bank view and set the initial values.
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     *
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     * This will look for the filter matching {@see get_condition_key()} in the view's current filter parameter.
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     * If the filter is not being initialised to display the question bank UI (for example, to resolve a list of questions matching
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     * a set of filters), then the `$qbank` argument may be null, and any usage of it to set the initial filter state is skipped.
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     *
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     * @param ?view $qbank The question bank view the filter is being rendered for. This may only be used for setting the
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     *     initial state of the filter.
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     */
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    public function __construct(?view $qbank = null) {
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        if (is_null($qbank)) {
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            return;
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        }
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        $this->filter = static::get_filter_from_list($qbank->get_pagevars('filter'));
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        // Build where and params.
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        [$this->where, $this->params] = $this->filter ? static::build_query_from_filter($this->filter) : ['', []];
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    }
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    /**
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     * Whether customisation is allowed.
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     *
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     * @return bool
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     */
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    public function allow_custom() {
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        return true;
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    }
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    /**
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     * Whether multiple values are allowed .
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     *
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     * @return bool
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     */
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    public function allow_multiple() {
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        return true;
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    }
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    /**
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     * Initial values of the condition
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     *
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     * @return array
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     */
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    public function get_initial_values() {
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        return [];
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    }
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    /**
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     * Extra data specific to this condition.
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     *
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     * @return \stdClass
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     */
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    public function get_filteroptions(): \stdClass {
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        return (object)[];
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    }
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    /**
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     * Whether empty value is allowed
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     *
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     * @return bool
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     */
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    public function allow_empty() {
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        return true;
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    }
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    /**
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     * Whether this filter is required - if so it cannot be removed from the list of filters.
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     *
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     * @return bool
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     */
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    public function is_required(): bool {
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        return false;
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    }
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    /**
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     * Return this condition class
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     *
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     * @return string
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     */
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    public function get_condition_class() {
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        return get_class($this);
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    }
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    /**
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     * Each condition will need a unique key to be identified and sequenced by the api.
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     * Use a unique string for the condition identifier, use string directly, dont need to use language pack.
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     * Using language pack might break the filter object for multilingual support.
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     *
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     * @return string
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     */
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    abstract public static function get_condition_key();
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    /**
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     * Return an SQL fragment to be ANDed into the WHERE clause to filter which questions are shown.
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     *
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     * @return string SQL fragment. Must use named parameters.
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     */
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    public function where() {
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        return $this->where;
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    }
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    /**
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     * Return parameters to be bound to the above WHERE clause fragment.
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     * @return array parameter name => value.
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     */
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    public function params() {
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        return $this->params;
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    }
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    /**
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     * Display GUI for selecting criteria for this condition. Displayed when Show More is open.
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     *
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     * Compare display_options(), which displays always, whether Show More is open or not.
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     * @return bool|string HTML form fragment
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     * @deprecated since Moodle 4.0 MDL-72321 - please do not use this function any more.
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     * @todo Final deprecation on Moodle 4.1 MDL-72572
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     */
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    public function display_options_adv() {
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        debugging('Function display_options_adv() is deprecated, please use filtering objects', DEBUG_DEVELOPER);
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        return false;
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    }
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    /**
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     * Display GUI for selecting criteria for this condition. Displayed always, whether Show More is open or not.
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     *
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     * Compare display_options_adv(), which displays when Show More is open.
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     * @return bool|string HTML form fragment
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     * @deprecated since Moodle 4.0 MDL-72321 - please do not use this function any more.
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     * @todo Final deprecation on Moodle 4.1 MDL-72572
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     */
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    public function display_options() {
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        debugging('Function display_options() is deprecated, please use filtering objects', DEBUG_DEVELOPER);
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        return false;
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    }
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    /**
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     * Get the list of available joins for the filter.
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     *
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     * @return array
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     */
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    public function get_join_list(): array {
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        return [
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            datafilter::JOINTYPE_NONE,
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            datafilter::JOINTYPE_ANY,
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            datafilter::JOINTYPE_ALL,
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        ];
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    }
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    /**
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     * Method to be overridden in condition classes to filter out anything invalid from the filterconditions array.
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     *
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     * This can be applied anywhere where the $filterconditions array exists, to let condition plugins remove elements
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     *  from the array, based on their own internal logic/validation. For example, this is used on the
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     *  /mod/quiz/editrandom.php page to filter out question categories which no longer exist, which previously
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     *  broke the editrandom page.
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     *
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     * @param array $filterconditions
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     * @return array
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     */
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    public function filter_invalid_values(array $filterconditions): array {
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        return $filterconditions;
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    }
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    /**
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     * Given an array of filters, pick the entry that matches the condition key and return it.
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     *
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     * @param array $filters Array of filters, keyed by condition.
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     * @return ?array The filter that matches this condition
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     */
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    public static function get_filter_from_list(array $filters): ?array {
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        return $filters[static::get_condition_key()] ?? null;
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    }
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    /**
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     * Return the SQL WHERE condition and parameters to be ANDed with other filter conditions.
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     *
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     * The $filter parameter recieves an array with a 'values' key, containing an array of the filter values selected,
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     * and a 'jointype' key containing the selected join type.
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     *
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     * @param array $filter filter properties
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     * @return array ['SQL where condition', ['param1' => 'value1', 'param2' => 'value2', ...]]
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     */
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    abstract public static function build_query_from_filter(array $filter): array;
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}