<?php

declare(strict_types=1);

/*
 * This file is part of the TYPO3 CMS project.
 *
 * It is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License, either version 2
 * of the License, or any later version.
 *
 * For the full copyright and license information, please read the
 * LICENSE.txt file that was distributed with this source code.
 *
 * The TYPO3 project - inspiring people to share!
 */

namespace TYPO3\CMS\Core\Authentication;

use Psr\EventDispatcher\EventDispatcherInterface;
use TYPO3\CMS\Core\Authentication\Event\AfterGroupsResolvedEvent;
use TYPO3\CMS\Core\Database\Connection;
use TYPO3\CMS\Core\Database\ConnectionPool;
use TYPO3\CMS\Core\Utility\GeneralUtility;

/**
 * A provider for resolving fe_groups / be_groups, including nested sub groups.
 *
 * When fetching subgroups, the current group (parent group) is handed in recursive.
 * Duplicates are suppressed: If a subgroup is including in multiple parent groups,
 * it will be resolved only once.
 *
 * @internal this is not part of TYPO3 Core API.
 */
class GroupResolver
{
    protected EventDispatcherInterface $eventDispatcher;
    protected string $sourceTable = '';
    protected string $sourceField = 'usergroup';
    protected string $recursiveSourceField = 'subgroup';

    public function __construct(EventDispatcherInterface $eventDispatcher)
    {
        $this->eventDispatcher = $eventDispatcher;
    }

    /**
     * Fetch all group records for a given user recursive.
     *
     * Note order is important: A user with main groups "1,2", where 1 has sub group 3,
     * results in "3,1,2" as record list array - sub groups are listed before the group
     * that includes the sub group.
     *
     * @param array $userRecord Used for context in PSR-14 event
     * @param string $sourceTable The database table to look up: be_groups / fe_groups depending on context
     * @return array List of group records. Note the ordering note above.
     */
    public function resolveGroupsForUser(array $userRecord, string $sourceTable): array
    {
        $this->sourceTable = $sourceTable;
        $originalGroupIds = GeneralUtility::intExplode(',', (string)($userRecord[$this->sourceField] ?? ''), true);
        $resolvedGroups = $this->fetchGroupsRecursive($originalGroupIds);
        $event = $this->eventDispatcher->dispatch(new AfterGroupsResolvedEvent($sourceTable, $resolvedGroups, $originalGroupIds, $userRecord));
        return $event->getGroups();
    }

    /**
     * Load a list of group uids, and take into account if groups have been loaded before.
     *
     * @param int[] $groupIds
     */
    protected function fetchGroupsRecursive(array $groupIds, array $processedGroupIds = []): array
    {
        if (empty($groupIds)) {
            return [];
        }
        $foundGroups = $this->fetchRowsFromDatabase($groupIds);
        $validGroups = [];
        foreach ($groupIds as $groupId) {
            // Database did not find the record
            if (!is_array($foundGroups[$groupId] ?? null)) {
                continue;
            }
            // Record was already processed, continue to avoid adding this group again
            if (in_array($groupId, $processedGroupIds, true)) {
                continue;
            }
            // Add sub groups first
            $subgroupIds = GeneralUtility::intExplode(',', (string)($foundGroups[$groupId][$this->recursiveSourceField] ?? ''), true);
            if (!empty($subgroupIds)) {
                $subgroups = $this->fetchGroupsRecursive($subgroupIds, array_merge($processedGroupIds, [$groupId]));
                $validGroups = array_merge($validGroups, $subgroups);
            }
            // Add main group after sub groups have been added
            $validGroups[] = $foundGroups[$groupId];
        }
        return $validGroups;
    }

    /**
     * Does the database query. Does not care about ordering, this is done by caller.
     *
     * @return array Full records with record uid as key
     */
    protected function fetchRowsFromDatabase(array $groupIds): array
    {
        $queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)->getQueryBuilderForTable($this->sourceTable);
        $result = $queryBuilder
            ->select('*')
            ->from($this->sourceTable)
            ->where(
                $queryBuilder->expr()->in(
                    'uid',
                    $queryBuilder->createNamedParameter(
                        $groupIds,
                        Connection::PARAM_INT_ARRAY
                    )
                )
            )
            ->executeQuery();
        $groups = [];
        while ($row = $result->fetchAssociative()) {
            $groups[(int)$row['uid']] = $row;
        }
        return $groups;
    }

    /**
     * This works the other way around: Find all users that belong to some groups. Because groups are nested,
     * we need to find all groups and subgroups first, because maybe a user is only part of a higher group,
     * instead of a "All editors" group.
     *
     * @param int[] $groupIds a list of IDs of groups
     * @param string $sourceTable e.g. be_groups or fe_groups
     * @param string $userSourceTable e.g. be_users or fe_users
     * @return array full user records
     */
    public function findAllUsersInGroups(array $groupIds, string $sourceTable, string $userSourceTable): array
    {
        $this->sourceTable = $sourceTable;

        // Ensure the given groups exist
        $mainGroups = $this->fetchRowsFromDatabase($groupIds);
        $groupIds = array_map('intval', array_column($mainGroups, 'uid'));
        if (empty($groupIds)) {
            return [];
        }
        $parentGroupIds = $this->fetchParentGroupsRecursive($groupIds, $groupIds);
        $queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)->getQueryBuilderForTable($userSourceTable);
        $queryBuilder
            ->select('*')
            ->from($userSourceTable);

        $constraints = [];
        foreach ($groupIds as $groupUid) {
            $constraints[] = $queryBuilder->expr()->inSet($this->sourceField, (string)$groupUid);
        }
        foreach ($parentGroupIds as $groupUid) {
            $constraints[] = $queryBuilder->expr()->inSet($this->sourceField, (string)$groupUid);
        }

        $users = $queryBuilder
            ->where(
                $queryBuilder->expr()->or(...$constraints)
            )
            ->executeQuery()
            ->fetchAllAssociative();
        return !empty($users) ? $users : [];
    }

    /**
     * Load a list of group uids, and take into account if groups have been loaded before as part of recursive detection.
     *
     * @param int[] $groupIds a list of groups to find THEIR ancestors
     * @param array $processedGroupIds helper function to avoid recursive detection
     * @return array a list of parent groups and thus, grand grand parent groups as well
     */
    protected function fetchParentGroupsRecursive(array $groupIds, array $processedGroupIds = []): array
    {
        if (empty($groupIds)) {
            return [];
        }
        $parentGroups = $this->fetchParentGroupsFromDatabase($groupIds);
        $validParentGroupIds = [];
        foreach ($parentGroups as $parentGroup) {
            $parentGroupId = (int)$parentGroup['uid'];
            // Record was already processed, continue to avoid adding this group again
            if (in_array($parentGroupId, $processedGroupIds, true)) {
                continue;
            }
            $processedGroupIds[] = $parentGroupId;
            $validParentGroupIds[] = $parentGroupId;
        }

        $grandParentGroups = $this->fetchParentGroupsRecursive($validParentGroupIds, $processedGroupIds);
        return array_merge($validParentGroupIds, $grandParentGroups);
    }

    /**
     * Find all groups that have a FIND_IN_SET(subgroups, [$subgroupIds]) => the parent groups
     * via one SQL query.
     */
    protected function fetchParentGroupsFromDatabase(array $subgroupIds): array
    {
        $queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)->getQueryBuilderForTable($this->sourceTable);
        $queryBuilder
            ->select('*')
            ->from($this->sourceTable);

        $constraints = [];
        foreach ($subgroupIds as $subgroupId) {
            $constraints[] = $queryBuilder->expr()->inSet($this->recursiveSourceField, (string)$subgroupId);
        }

        $result = $queryBuilder
            ->where(
                $queryBuilder->expr()->or(...$constraints)
            )
            ->executeQuery();

        $groups = [];
        while ($row = $result->fetchAssociative()) {
            $groups[(int)$row['uid']] = $row;
        }
        return $groups;
    }
}
