<?php

namespace App\Database\Migrations;

use CodeIgniter\Database\Migration;
use RuntimeException;

class BackfillAddedSchoolYearColumns extends Migration
{
    public function up(): void
    {
        $schoolYear = $this->configuredSchoolYear();

        foreach ($this->tablesWithSchoolYearColumn() as $table) {
            $this->db->query(
                sprintf(
                    'UPDATE %s SET `school_year` = ? WHERE `school_year` IS NULL OR TRIM(`school_year`) = \'\'',
                    $this->quoteIdentifier($table)
                ),
                [$schoolYear]
            );
        }
    }

    public function down(): void
    {
        // This is a data backfill. Do not erase school_year values on rollback.
    }

    private function configuredSchoolYear(): string
    {
        if (! $this->db->tableExists('configuration')) {
            throw new RuntimeException('Cannot backfill school_year columns: configuration table is missing.');
        }

        $row = $this->db->table('configuration')
            ->select('config_value')
            ->where('config_key', 'school_year')
            ->where('config_value IS NOT NULL', null, false)
            ->where('TRIM(config_value) <>', '')
            ->orderBy('id', 'DESC')
            ->get(1)
            ->getRowArray();

        $schoolYear = trim((string)($row['config_value'] ?? ''));
        if (preg_match('/^\d{4}-\d{4}$/', $schoolYear) !== 1) {
            throw new RuntimeException(
                'Cannot backfill school_year columns: configuration.school_year must be set as YYYY-YYYY.'
            );
        }

        return $schoolYear;
    }

    /**
     * @return list<string>
     */
    private function tablesWithSchoolYearColumn(): array
    {
        $rows = $this->db->query(
            "SELECT c.TABLE_NAME AS table_name
             FROM information_schema.COLUMNS c
             INNER JOIN information_schema.TABLES t
                ON t.TABLE_SCHEMA = c.TABLE_SCHEMA
               AND t.TABLE_NAME = c.TABLE_NAME
             WHERE c.TABLE_SCHEMA = DATABASE()
               AND c.COLUMN_NAME = 'school_year'
               AND t.TABLE_TYPE = 'BASE TABLE'
             ORDER BY c.TABLE_NAME"
        )->getResultArray();

        $tables = [];
        foreach ($rows as $row) {
            $table = trim((string)($row['table_name'] ?? ''));
            if ($table === '' || $table === 'school_years') {
                continue;
            }
            $tables[] = $table;
        }

        return $tables;
    }

    private function quoteIdentifier(string $identifier): string
    {
        return '`' . str_replace('`', '``', $identifier) . '`';
    }
}