<?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/>.

namespace mod_quiz\question\bank;

use context_module;
use core_question\local\bank\version_options;
use core_question\local\bank\question_version_status;
use core_question\local\bank\random_question_loader;
use core_question\question_reference_manager;
use qbank_tagquestion\tag_condition;
use qubaid_condition;
use stdClass;

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

require_once($CFG->dirroot . '/question/engine/bank.php');

/**
 * Helper class for question bank and its associated data.
 *
 * @package    mod_quiz
 * @category   question
 * @copyright  2021 Catalyst IT Australia Pty Ltd
 * @author     Safat Shahin <safatshahin@catalyst-au.net>
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class qbank_helper {

    /**
     * Get the available versions of a question where one of the version has the given question id.
     *
     * @param int $questionid id of a question.
     * @return stdClass[] other versions of this question. Each object has fields versionid,
     *       version and questionid. Array is returned most recent version first.
     */
    #[\core\attribute\deprecated(
        'core_question\local\bank::get_version_options',
        since: 5.0,
        mdl: 'MDL-77713')
    ]
    public static function get_version_options(int $questionid): array {
        \core\deprecation::emit_deprecation_if_present([self::class, __FUNCTION__]);
        return version_options::get_version_options($questionid);
    }

    /**
     * Get the information about which questions should be used to create a quiz attempt.
     *
     * Each element in the returned array is indexed by slot.slot (slot number) an each object hass:
     * - All the field of the slot table.
     * - contextid for where the question(s) come from.
     * - category id for where the questions come from.
     * - For non-random questions, All the fields of the question table (but id is in questionid).
     *   Also question version and question bankentryid.
     * - For random questions, filtercondition, which is also unpacked into category, randomrecurse,
     *   randomtags, and note that these also have a ->name set and ->qtype set to 'random'.
     *
     * @param int $quizid the id of the quiz to load the data for.
     * @param context_module $quizcontext the context of this quiz.
     * @param int|null $slotid optional, if passed only load the data for this one slot (if it is in this quiz).
     * @return array indexed by slot, with information about the content of each slot.
     */
    public static function get_question_structure(int $quizid, context_module $quizcontext,
            ?int $slotid = null): array {
        global $DB;

        $params = [
            'draft' => question_version_status::QUESTION_STATUS_DRAFT,
            'quizcontextid' => $quizcontext->id,
            'quizcontextid2' => $quizcontext->id,
            'quizcontextid3' => $quizcontext->id,
            'quizid' => $quizid,
            'quizid2' => $quizid,
        ];
        $slotidtest = '';
        $slotidtest2 = '';
        if ($slotid !== null) {
            $params['slotid'] = $slotid;
            $params['slotid2'] = $slotid;
            $slotidtest = ' AND slot.id = :slotid';
            $slotidtest2 = ' AND lslot.id = :slotid2';
        }

        // Load all the data about each slot.
        $slotdata = $DB->get_records_sql("
                SELECT slot.slot,
                       slot.id AS slotid,
                       slot.page,
                       slot.displaynumber,
                       slot.requireprevious,
                       slot.maxmark,
                       slot.quizgradeitemid,
                       qsr.filtercondition,
                       qsr.usingcontextid,
                       qv.status,
                       qv.id AS versionid,
                       qv.version,
                       qr.version AS requestedversion,
                       qv.questionbankentryid,
                       q.id AS questionid,
                       q.*,
                       qc.id AS category,
                       COALESCE(qc.contextid, qsr.questionscontextid) AS contextid

                  FROM {quiz_slots} slot

             -- case where a particular question has been added to the quiz.
             LEFT JOIN {question_references} qr ON qr.usingcontextid = :quizcontextid AND qr.component = 'mod_quiz'
                                        AND qr.questionarea = 'slot' AND qr.itemid = slot.id
             LEFT JOIN {question_bank_entries} qbe ON qbe.id = qr.questionbankentryid

             -- This way of getting the latest version for each slot is a bit more complicated
             -- than we would like, but the simpler SQL did not work in Oracle 11.2.
             -- (It did work fine in Oracle 19.x, so once we have updated our min supported
             -- version we could consider digging the old code out of git history from
             -- just before the commit that added this comment.
             -- For relevant question_bank_entries, this gets the latest non-draft slot number.
             -- TODO: Optimise the query, as Oracle-specific constraints no longer apply.
             LEFT JOIN (
                   SELECT lv.questionbankentryid,
                          MAX(CASE WHEN lv.status <> :draft THEN lv.version END) AS usableversion,
                          MAX(lv.version) AS anyversion
                     FROM {quiz_slots} lslot
                     JOIN {question_references} lqr ON lqr.usingcontextid = :quizcontextid2 AND lqr.component = 'mod_quiz'
                                        AND lqr.questionarea = 'slot' AND lqr.itemid = lslot.id
                     JOIN {question_versions} lv ON lv.questionbankentryid = lqr.questionbankentryid
                    WHERE lslot.quizid = :quizid2
                          $slotidtest2
                      AND lqr.version IS NULL
                 GROUP BY lv.questionbankentryid
             ) latestversions ON latestversions.questionbankentryid = qr.questionbankentryid

             LEFT JOIN {question_versions} qv ON qv.questionbankentryid = qbe.id
                                       -- Either specified version, or latest usable version, or a draft version.
                                       AND qv.version = COALESCE(qr.version,
                                           latestversions.usableversion,
                                           latestversions.anyversion)
             LEFT JOIN {question_categories} qc ON qc.id = qbe.questioncategoryid
             LEFT JOIN {question} q ON q.id = qv.questionid

             -- Case where a random question has been added.
             LEFT JOIN {question_set_references} qsr ON qsr.usingcontextid = :quizcontextid3 AND qsr.component = 'mod_quiz'
                                        AND qsr.questionarea = 'slot' AND qsr.itemid = slot.id

                 WHERE slot.quizid = :quizid
                       $slotidtest

              ORDER BY slot.slot
              ", $params);

        // Unpack the random info from question_set_reference.
        foreach ($slotdata as $slot) {
            // Ensure the right id is the id.
            $slot->id = $slot->slotid;

            if ($slot->filtercondition) {
                // Unpack the information about a random question.
                $slot->questionid = 's' . $slot->id; // Sometimes this is used as an array key, so needs to be unique.
                $filter = json_decode($slot->filtercondition, true);
                $slot->filtercondition = question_reference_manager::convert_legacy_set_reference_filter_condition($filter);

                $slot->category = $slot->filtercondition['filter']['category']['values'][0] ?? 0;

                $slot->qtype = 'random';
                $slot->name = get_string('random', 'quiz');
                $slot->length = 1;
            } else if ($slot->qtype === null) {
                // This question must have gone missing. Put in a placeholder.
                $slot->questionid = 's' . $slot->id; // Sometimes this is used as an array key, so needs to be unique.
                $slot->category = 0;
                $slot->qtype = 'missingtype';
                $slot->name = get_string('missingquestion', 'quiz');
                $slot->questiontext = ' ';
                $slot->questiontextformat = FORMAT_HTML;
                $slot->length = 1;
            } else if (!\question_bank::qtype_exists($slot->qtype)) {
                // Question of unknown type found in the database. Set to placeholder question types instead.
                $slot->originalqtype = $slot->qtype;
                $slot->qtype = 'missingtype';
            } else {
                $slot->_partiallyloaded = 1;
            }
        }

        return $slotdata;
    }

    /**
     * Get this list of random selection tag ids from one of the slots returned by get_question_structure.
     *
     * @param stdClass $slotdata one of the array elements returned by get_question_structure.
     * @return array list of tag ids.
     */
    public static function get_tag_ids_for_slot(stdClass $slotdata): array {
        $tagids = [];
        if (!isset($slotdata->filtercondition['filter'])) {
            return $tagids;
        }
        $filter = $slotdata->filtercondition['filter'];
        if (isset($filter['qtagids'])) {
            $tagids = $filter['qtagids']['values'];
        }
        return $tagids;
    }

    /**
     * Given a slot from the array returned by get_question_structure, describe the random question it represents.
     *
     * @param stdClass $slotdata one of the array elements returned by get_question_structure.
     * @return string that can be used to display the random slot.
     */
    public static function describe_random_question(stdClass $slotdata): string {
        $qtagids = self::get_tag_ids_for_slot($slotdata);

        if ($qtagids) {
            $tagnames = [];
            $tags = \core_tag_tag::get_bulk($qtagids, 'id, name');
            foreach ($tags as $tag) {
                $tagnames[] = $tag->name;
            }
            $description = get_string('randomqnametags', 'mod_quiz', implode(",", $tagnames));
        } else {
            $description = get_string('randomqname', 'mod_quiz');
        }
        return shorten_text($description, 255);
    }

    /**
     * Choose question for redo in a particular slot.
     *
     * @param int $quizid the id of the quiz to load the data for.
     * @param context_module $quizcontext the context of this quiz.
     * @param int $slotid optional, if passed only load the data for this one slot (if it is in this quiz).
     * @param qubaid_condition $qubaids attempts to consider when avoiding picking repeats of random questions.
     * @return int the id of the question to use.
     */
    public static function choose_question_for_redo(int $quizid, context_module $quizcontext,
            int $slotid, qubaid_condition $qubaids): int {
        $slotdata = self::get_question_structure($quizid, $quizcontext, $slotid);
        $slotdata = reset($slotdata);

        // Non-random question.
        if ($slotdata->qtype != 'random') {
            return $slotdata->questionid;
        }

        // Random question.
        $randomloader = new random_question_loader($qubaids, []);
        $fitlercondition = $slotdata->filtercondition;
        $filter = $fitlercondition['filter'] ?? [];
        $newqusetionid = $randomloader->get_next_filtered_question_id($filter);

        if ($newqusetionid === null) {
            throw new \moodle_exception('notenoughrandomquestions', 'quiz');
        }
        return $newqusetionid;
    }

    /**
     * Check all the questions in an attempt and return information about their versions.
     *
     * Once a quiz attempt has been started, it continues to use the version of each question
     * it was started with. This checks the version used for each question, against the
     * quiz settings for that slot, and returns which version would be used if the quiz
     * attempt was being started now.
     *
     * There are several cases for each slot:
     * - If this slot is currently set to use version 'Always latest' (which includes
     *   random slots) and if there is now a newer version than the one in the attempt,
     *   use that.
     * - If the slot is currently set to use a fixed version of the question, and that
     *   is different from the version currently in the attempt, use that.
     * - Otherwise, use the same version.
     *
     * This is used in places like the re-grade code.
     *
     * The returned data probably contains a bit more information than is strictly needed,
     * (see the SQL for details) but returning a few extra ints is fast, and this could
     * prove invaluable when debugging. The key information is probably:
     * - questionattemptslot <-- array key
     * - questionattemptid
     * - currentversion
     * - currentquestionid
     * - newversion
     * - newquestionid
     *
     * @param stdClass $attempt a quiz_attempt database row.
     * @param context_module $quizcontext the quiz context for the quiz the attempt belongs to.
     * @return array for each question_attempt in the quiz attempt, information about whether it is using
     *      the latest version of the question. Array indexed by questionattemptslot.
     */
    public static function get_version_information_for_questions_in_attempt(
        stdClass $attempt,
        context_module $quizcontext,
    ): array {
        global $DB;

        return $DB->get_records_sql("
            SELECT qa.slot AS questionattemptslot,
                   qa.id AS questionattemptid,
                   slot.slot AS quizslot,
                   slot.id AS quizslotid,
                   qr.id AS questionreferenceid,
                   currentqv.version AS currentversion,
                   currentqv.questionid AS currentquestionid,
                   newqv.version AS newversion,
                   newqv.questionid AS newquestionid

              -- Start with the question currently used in the attempt.
              FROM {question_attempts} qa
              JOIN {question_versions} currentqv ON currentqv.questionid = qa.questionid

              -- Join in the question metadata which says if this is a qa from a 'Try another question like this one'.
              JOIN {question_attempt_steps} firststep ON firststep.questionattemptid = qa.id
                           AND firststep.sequencenumber = 0
         LEFT JOIN {question_attempt_step_data} otherslotinfo ON otherslotinfo.attemptstepid = firststep.id
                           AND otherslotinfo.name = :otherslotmetadataname

              -- Join in the quiz slot information, and hence for non-random slots, the questino_reference.
              JOIN {quiz_slots} slot ON slot.quizid = :quizid
                           AND slot.slot = COALESCE({$DB->sql_cast_char2int('otherslotinfo.value', true)}, qa.slot)
         LEFT JOIN {question_references} qr ON qr.usingcontextid = :quizcontextid
                           AND qr.component = 'mod_quiz'
                           AND qr.questionarea = 'slot'
                           AND qr.itemid = slot.id

              -- Finally, get the new version for this slot.
              JOIN {question_versions} newqv ON newqv.questionbankentryid = currentqv.questionbankentryid
                           AND newqv.version = COALESCE(
                               -- If the quiz setting say use a particular version, use that.
                               qr.version,
                               -- Otherwise, we need the latest non-draft version of the current questions.
                               (SELECT MAX(version)
                                  FROM {question_versions}
                                 WHERE questionbankentryid = currentqv.questionbankentryid AND status <> :draft),
                                -- Otherwise, there is not a suitable other version, so stick with the current one.
                                currentqv.version
                            )

             -- We want this for questions in the current attempt.
             WHERE qa.questionusageid = :questionusageid

          -- Order not essential, but fast and good for debugging.
          ORDER BY qa.slot
        ", [
            'otherslotmetadataname' => ':_originalslot',
            'quizid' => $attempt->quiz,
            'quizcontextid' => $quizcontext->id,
            'draft' => question_version_status::QUESTION_STATUS_DRAFT,
            'questionusageid' => $attempt->uniqueid,
        ]);
    }
}
