BookStack/app/Entities/Tools/NextPreviousContentLocator.php

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2021-06-26 11:23:15 -04:00
<?php
namespace BookStack\Entities\Tools;
use BookStack\Entities\Models\BookChild;
use BookStack\Entities\Models\Entity;
use Illuminate\Support\Collection;
/**
* Finds the next or previous content of a book element (page or chapter).
*/
class NextPreviousContentLocator
{
protected $relativeBookItem;
protected $flatTree;
protected $currentIndex = null;
/**
* NextPreviousContentLocator constructor.
*/
public function __construct(BookChild $relativeBookItem, Collection $bookTree)
{
$this->relativeBookItem = $relativeBookItem;
$this->flatTree = $this->treeToFlatOrderedCollection($bookTree);
$this->currentIndex = $this->getCurrentIndex();
}
/**
* Get the next logical entity within the book hierarchy.
*/
public function getNext(): ?Entity
{
return $this->flatTree->get($this->currentIndex + 1);
}
/**
* Get the next logical entity within the book hierarchy.
*/
public function getPrevious(): ?Entity
{
return $this->flatTree->get($this->currentIndex - 1);
}
/**
* Get the index of the current relative item.
*/
protected function getCurrentIndex(): ?int
{
$index = $this->flatTree->search(function (Entity $entity) {
return get_class($entity) === get_class($this->relativeBookItem)
&& $entity->id === $this->relativeBookItem->id;
});
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return $index === false ? null : $index;
}
/**
* Convert a book tree collection to a flattened version
* where all items follow the expected order of user flow.
*/
protected function treeToFlatOrderedCollection(Collection $bookTree): Collection
{
$flatOrdered = collect();
/** @var Entity $item */
foreach ($bookTree->all() as $item) {
$flatOrdered->push($item);
$childPages = $item->getAttribute('visible_pages') ?? [];
$flatOrdered = $flatOrdered->concat($childPages);
}
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return $flatOrdered;
}
}