php-flarum/src/Core/Discussions/DiscussionRepository.php

<?php namespace Flarum\Core\Discussions;

use Illuminate\Database\Eloquent\Builder;
use Flarum\Core\Users\User;

class DiscussionRepository
{
    /**
     * Get a new query builder for the discussions table.
     *
     * @return Builder
     */
    public function query()
    {
        return Discussion::query();
    }

    /**
     * Find a discussion by ID, optionally making sure it is visible to a
     * certain user, or throw an exception.
     *
     * @param integer $id
     * @param \Flarum\Core\Users\User $user
     * @return \Flarum\Core\Discussions\Discussion
     */
    public function findOrFail($id, User $user = null)
    {
        $query = Discussion::where('id', $id);

        return $this->scopeVisibleTo($query, $user)->firstOrFail();
    }

    /**
     * Get the IDs of discussions which a user has read completely.
     *
     * @param \Flarum\Core\Users\User $user
     * @return array
     */
    public function getReadIds(User $user)
    {
        return Discussion::leftJoin('users_discussions', 'users_discussions.discussion_id', '=', 'discussions.id')
            ->where('user_id', $user->id)
            ->where('read_number', '<', 'last_post_number')
            ->lists('id');
    }

    /**
     * Scope a query to only include records that are visible to a user.
     *
     * @param Builder $query
     * @param \Flarum\Core\Users\User $user
     * @return Builder
     */
    protected function scopeVisibleTo(Builder $query, User $user = null)
    {
        if ($user !== null) {
            $query->whereVisibleTo($user);
        }

        return $query;
    }
}