<?php

namespace App\Database\Migrations;

use CodeIgniter\Database\Migration;

class RemoveClassAssignmentSemester extends Migration
{
    public function up()
    {
        // Keep the legacy semester columns in place. They may be ignored by newer
        // code, but dropping them during a post-restore migrate destroys data.
    }

    public function down()
    {
        if ($this->db->tableExists('teacher_class')) {
            $this->forge->addColumn('teacher_class', [
                'semester' => [
                    'type'       => 'VARCHAR',
                    'constraint' => 25,
                    'null'       => false,
                    'default'    => '',
                ],
            ]);
        }
        if ($this->db->tableExists('student_class')) {
            $this->forge->addColumn('student_class', [
                'semester' => [
                    'type'       => 'VARCHAR',
                    'constraint' => 255,
                    'null'       => false,
                    'default'    => '',
                ],
            ]);
        }
    }

    private function indexExists(string $table, string $index): bool
    {
        $result = $this->db->query(
            'SHOW INDEX FROM `' . str_replace('`', '``', $table) . '` WHERE Key_name = ' . $this->db->escape($index)
        );

        return $result->getNumRows() > 0;
    }
}