<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateRevisionsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('revisions', function (Blueprint $table) {
            $table->increments('id');
            $table->timestamps();
            $table->unsignedInteger('refs'); // used for reference counting
            $table->unsignedInteger('ancestor_id')->index()->nullable(); // parent revision

            // a column that can be used as the primary key for a table; possibly a composite column if using a comma
            $table->string('index_column')->nullable();

            // author's note describing what has been changed
            $table->text('note');

            $table->foreign('ancestor_id')->references('id')->on('revisions')
                ->onDelete('set null');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('revisions');
    }
}