first version

kirby/src/Cms/HasSiblings.php

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+<?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      http://getkirby.com
+ * @copyright Bastian Allgeier
+ */
+trait HasSiblings
+{
+
+    /**
+     * Returns the position / index in the collection
+     *
+     * @return int
+     */
+    public function indexOf(): int
+    {
+        return $this->siblingsCollection()->indexOf($this);
+    }
+
+    /**
+     * Returns the next item in the collection if available
+     *
+     * @return Model|null
+     */
+    public function next()
+    {
+        return $this->siblingsCollection()->nth($this->indexOf() + 1);
+    }
+
+    /**
+     * Returns the end of the collection starting after the current item
+     *
+     * @return Collection
+     */
+    public function nextAll()
+    {
+        return $this->siblingsCollection()->slice($this->indexOf() + 1);
+    }
+
+    /**
+     * Returns the previous item in the collection if available
+     *
+     * @return Model|null
+     */
+    public function prev()
+    {
+        return $this->siblingsCollection()->nth($this->indexOf() - 1);
+    }
+
+    /**
+     * Returns the beginning of the collection before the current item
+     *
+     * @return Collection
+     */
+    public function prevAll()
+    {
+        return $this->siblingsCollection()->slice(0, $this->indexOf());
+    }
+
+    /**
+     * Returns all sibling elements
+     *
+     * @param bool $self
+     * @return 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
+     *
+     * @return bool
+     */
+    public function hasNext(): bool
+    {
+        return $this->next() !== null;
+    }
+
+    /**
+     * Checks if there's a previous item in the collection
+     *
+     * @return bool
+     */
+    public function hasPrev(): bool
+    {
+        return $this->prev() !== null;
+    }
+
+    /**
+     * Checks if the item is the first in the collection
+     *
+     * @return bool
+     */
+    public function isFirst(): bool
+    {
+        return $this->siblingsCollection()->first()->is($this);
+    }
+
+    /**
+     * Checks if the item is the last in the collection
+     *
+     * @return bool
+     */
+    public function isLast(): bool
+    {
+        return $this->siblingsCollection()->last()->is($this);
+    }
+
+    /**
+     * Checks if the item is at a certain position
+     *
+     * @return bool
+     */
+    public function isNth(int $n): bool
+    {
+        return $this->indexOf() === $n;
+    }
+}