<?php

namespace Kirby\Cms;

/**
 * This trait is used by pages, files and users
 * to handle navigation through parent collections
 *
 * @package   Kirby Cms
 * @author    Bastian Allgeier <bastian@getkirby.com>
 * @link      https://getkirby.com
 * @copyright Bastian Allgeier GmbH
 * @license   https://getkirby.com/license
 */
trait HasSiblings
{
    /**
     * Returns the position / index in the collection
     *
     * @param \Kirby\Cms\Collection|null $collection
     *
     * @return int
     */
    public function indexOf($collection = null): int
    {
        if ($collection === null) {
            $collection = $this->siblingsCollection();
        }

        return $collection->indexOf($this);
    }

    /**
     * Returns the next item in the collection if available
     *
     * @param \Kirby\Cms\Collection|null $collection
     *
     * @return \Kirby\Cms\Model|null
     */
    public function next($collection = null)
    {
        if ($collection === null) {
            $collection = $this->siblingsCollection();
        }

        return $collection->nth($this->indexOf($collection) + 1);
    }

    /**
     * Returns the end of the collection starting after the current item
     *
     * @param \Kirby\Cms\Collection|null $collection
     *
     * @return \Kirby\Cms\Collection
     */
    public function nextAll($collection = null)
    {
        if ($collection === null) {
            $collection = $this->siblingsCollection();
        }

        return $collection->slice($this->indexOf($collection) + 1);
    }

    /**
     * Returns the previous item in the collection if available
     *
     * @param \Kirby\Cms\Collection|null $collection
     *
     * @return \Kirby\Cms\Model|null
     */
    public function prev($collection = null)
    {
        if ($collection === null) {
            $collection = $this->siblingsCollection();
        }

        return $collection->nth($this->indexOf($collection) - 1);
    }

    /**
     * Returns the beginning of the collection before the current item
     *
     * @param \Kirby\Cms\Collection|null $collection
     *
     * @return \Kirby\Cms\Collection
     */
    public function prevAll($collection = null)
    {
        if ($collection === null) {
            $collection = $this->siblingsCollection();
        }

        return $collection->slice(0, $this->indexOf($collection));
    }

    /**
     * Returns all sibling elements
     *
     * @param bool $self
     * @return \Kirby\Cms\Collection
     */
    public function siblings(bool $self = true)
    {
        $siblings = $this->siblingsCollection();

        if ($self === false) {
            return $siblings->not($this);
        }

        return $siblings;
    }

    /**
     * Checks if there's a next item in the collection
     *
     * @param \Kirby\Cms\Collection|null $collection
     *
     * @return bool
     */
    public function hasNext($collection = null): bool
    {
        return $this->next($collection) !== null;
    }

    /**
     * Checks if there's a previous item in the collection
     *
     * @param \Kirby\Cms\Collection|null $collection
     *
     * @return bool
     */
    public function hasPrev($collection = null): bool
    {
        return $this->prev($collection) !== null;
    }

    /**
     * Checks if the item is the first in the collection
     *
     * @param \Kirby\Cms\Collection|null $collection
     *
     * @return bool
     */
    public function isFirst($collection = null): bool
    {
        if ($collection === null) {
            $collection = $this->siblingsCollection();
        }

        return $collection->first()->is($this);
    }

    /**
     * Checks if the item is the last in the collection
     *
     * @param \Kirby\Cms\Collection|null $collection
     *
     * @return bool
     */
    public function isLast($collection = null): bool
    {
        if ($collection === null) {
            $collection = $this->siblingsCollection();
        }

        return $collection->last()->is($this);
    }

    /**
     * Checks if the item is at a certain position
     *
     * @param \Kirby\Cms\Collection|null $collection
     * @param int $n
     *
     * @return bool
     */
    public function isNth(int $n, $collection = null): bool
    {
        return $this->indexOf($collection) === $n;
    }
}
