Category.php

<?php

/** 
 * Laravel model for post Category.
 * Client wanted to set display rank for posts in a category list
 * Categories have a set minimum display number
 * $post->number is display rank + $category->post_number_start
 * i.e. category has number_start = 100, 1st post to display would have $post->number = 101
 * These are functions for changing order
 */

    public function movePostToTop($post)
    {
        //1,2,3,4,5 -> move 3 -> 3,1,2,4,5 - 1->2, 2->3
        $this->posts()->where('number', '<', $post->number)->each(function($p){
            $p->number = $p->number + 1;
            $p->save();
        });

        $post->number = $this->post_number_start;
        $post->save();
    }

    public function movePostToBottom($post)
    {
        //1,2,3,4,5 -> move 3 -> 1,2,4,5,3 - 4->3, 5->4
        $n = $this->posts()->max('number');
        $posts = $this->posts()->where('number', '>', $post->number)->get();

        foreach($posts as $p){
            // $n = $p->number;
            $p->number = $p->number - 1;
            $p->save();
        };

        $post->number = $n;
        $post->save();
    }

    public function movePostToNumber($post, $number)
    {
        if ($number <= $this->post_number_start){
            return $this->movePostToTop($post);
        }
        if ($number >= ($this->posts()->max('number'))){
            return $this->movePostToBottom($post);
        }

        if ($post->number > $number){
            //moving post up
            //1,2,3,4,5 -> move 4 to 2 -> 1,4,2,3,5 - 2->3, 3->4
            $this->posts()->where('number', '>=', $number)->where('number', '<', $post->number)->each(function($p){
                $p->number = $p->number + 1;
                $p->save();
            });
        }else if ($post->number < $number){
            //moving post down
            //1,2,3,4,5 -> move 2 to 4 -> 1,3,4,2,5 - 3->2, 4->3
            $this->posts()->where('number', '<=', $number)->where('number', '>', $post->number)->each(function($p){
                $p->number = $p->number - 1;
                $p->save();
            });
        }

        $post->number = $number;
        $post->save();
    }