datatable.directory/app/Models/Revision.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Support\Collection;
use Riesjart\Relaquent\Model\Concerns\HasRelaquentRelationships;

/**
 * Table revision (a set of rows)
 *
 * @property int $id
 * @property \Carbon\Carbon $created_at
 * @property \Carbon\Carbon $updated_at
 * @property int $refs
 * @property int $ancestor_id
 * @property string $note
 * @property object $columns
 * @property Revision|null $parentRevision
 * @property Row[]|Collection $rows
 * @property Proposal|null $sourceProposal - proposal that was used to create this revision
 * @property Proposal[]|Collection $dependentProposals
 */
class Revision extends Model
{
    use HasRelaquentRelationships;
    protected $guarded = [];

    protected static function boot()
    {
        parent::boot();

        static::deleting(function(Revision $self) {
            // update refcounts
            $self->rows()->decrement('refs');

            $self->rows()->where('refs', '<=', 0)->delete();
        });
    }

    /** Included rows */
    public function rows()
    {
        return $this->belongsToMany(Row::class, 'revision_row_pivot');
    }

    /** Proposal that lead to this revision */
    public function sourceProposal()
    {
        return $this->hasOneThrough(Proposal::class, 'revision_proposal_pivot');
    }

    /** Proposals that depend on this revision */
    public function dependentProposals()
    {
        return $this->hasMany(Proposal::class);
    }

    /** Revision this orignates from */
    public function parentRevision()
    {
        return $this->belongsTo(Revision::class, 'ancestor_id');
    }

    /** Tables referencing this revision */
    public function tables()
    {
        return $this->belongsToMany(Table::class, 'table_revision_pivot');
    }
}